NOAA Technical Report NMFS 35

Synoptic Review of the

Literature on the

Southern Oyster Drill

Thais haemastoma floridana

Philip A. Butler

November 1985

U.S. DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

National Marine Fisheries Service
NOAA TECHNICAL REPORTS NMFS

The major responsibilities of the National Marine Fisheries Service (NMFS) are to monitor and assess the abundance and

geographic distribution of fishery resources, to understand and predict fluctuations in the quantity and distribution of these

resources, and to establish levels for their optimum use. NMFS is also charged with the development and implementation of

policies for managing national fishing grounds, development and enforcement of domestic fisheries regulations, surveillance of

foreign fishing off United States coastal waters, and the development and enforcement of international fishery agreements and

policies. NMFS also assists the fishing industry through marketing service and economic analysis programs, and mortgage insurance and vessel construction subsidies. It collects, analyzes, and publishes statistics on various phases of the industry.

The NOAA Technical Report NMFS series was established in 1983 to replace two subcategories of the Technical Reports

series: "Special Scientific Report-Fisheries" and "Circular." The series contains the following types of reports: Scientific

investigations that document long-term continuing programs of NMFS; intensive scientific reports on studies of restricted

scope; papers on applied fishery problems; technical reports of general interest intended to aid conservation and management;

reports thaI review in considerable detail and al a high technical level c.ertain broad areas of research; and technical papers

originating in economics studies and from management investigations. Since this is a formal series, all submitted papers receive

peer review and those accepted receive professional editing before publication.

Copies of NOAA Technical Reports NMFS are available free in limited numbers to governmental agencies, both federal

and State. They are also available in exchange for other scientific and technical publications in the marine sciences. Individual

copies may be obtained from: U.S. Department of Commerce, National Technical Information Service, 5285 Port Royal Road,

Springfield, VA 22161
NOAA Technical Report NMFS 35

Synoptic Review of the

Literature on the

Southern Oyster Drill

Thais haemastoma f10ridana

Philip A. Butler

November 1985

u.s. DEPARTMENT OF COMMERCE

Malcolm Baldrige, Secretary

National Oceanic and Atmospheric Administration

John V. Byrne, Administrator

National Marine Fisheries Service

William G. Gordon, Assistant Administrator for Fisheries
The National Marine Fisheries Service (NMFS) does not approve, recommend or endorse any proprietary product or proprietary material mentioned in this publication. No reference shall be made to NMFS, or to this

publication furnished by NMFS, in any advertising or sales promotion

which would indicate or imply thai NMFS approves, recommends or

endorses any proprietary product or proprietary material mentioned herein,

or which has as ,its purpose" an intent to cause directly or indirectly th~

advertised product to be used or purchased because of this NMFS

publication.

.' .

"

'.

,.
CONTENTS

Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1

Taxonomy...................................... 1

Distribution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2

Anatomy 2

Growth.. . . . .. . . . . . . . . .. . .. . .. . . . . .. . . . . . . . . .. . . . . . .. 3

Reproduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . .. 3

Behavior. . . . . . .. . . . . . .. . . .. .. .. . . 4

Population density 4

Drilling technique...................................................... 4

Feeding selectivity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5

Salinity tolerance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5

Predators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5

Parasites _. . . . . . . . . . . . . . . . . . . . .. 5

Economic importance................................................... 6

Control. . . . . . .. . . . . . ..... . .. .. . . .. ... . .. . . . ... . .. . . . . . .. . . . . . . . . . ... .. 6

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6

Literature cited. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 6

Synoptic Review

of the Literature on

the Southern Oyster Drill

Thais haemastoma

floridana 1

PHILIP A. BUTLER2

ABSTRACT

This literature search identifies a majority of the publications in the period

1880-1980 concerned with the marine gastropod, Thais haemastomafloridmul (Conrad). The southern oyster drill is an economically important oyster predator in

the western Atlantic and Gulf of Mexico littoral. Major contributions of each paper

to our knowledge ofthe drill's biology are briefly categorized. Hitherto unpublished

research by the author on the snail's biology is documented.

'Contribution No. 500 from the U.S. Environmental Protection Agency, Gulf Breeze,

FL 32561.

'106 Matamoros Drive, Gulf Breeze, FL 32561.

INTRODUCTION

The drill has been the subject of sporadic investigations for more

than 100 yr because of its association with the American oyster,

Crassostrea virginica (Gme1in). In the past, field surveys and

research in oyster biology were considered to be an appropriate part

of the Federal mandate for assistance to the States, and much of

the early work was conducted and published by Federal agencies.

Since 1950, however, perhaps in recognition of the nonmigratory

nature of oyster populations, Federal laboratories have been concerned only with the more generalized problems of oyster biology,

and State laboratories have strengthened their oyster research and

management programs.

Despite the long-continued efforts of oystermen and biologists alike

to control the depredations of this pest, the southern oyster drill still

prevents profitable oyster culture on about half of the estimated

3.6xl(f ha (1,400 mF) of otherwise suitable oyster bottoms in the

northern Gulf of Mexico. Interest in the drill's biology has increased

in recent years since the recognition of its suitability for laboratory

research on the osmoregulatory physiology of euryhaline species.

In view of the diverse interests in the drill, it seemed desirable to

gather and collate the available literature of the past century as an

aid to future research efforts, and to outline major aspects of the

biology of this gastropod.

Of the 173 publications cited, about 25 %are the result ofspecial

surveys and summary reports by Federal scientists. Another 18 %

represent research efforts at State laboratories charged with shellfish management responsibilities. Other than the few teehnic3.J. source

books listed, the remaining 25 % of the citations describe research

accomplished at university and museum laboratories.

TAXONOMY _

There has been continuing confusion on the nomenclature of New

World populations of snails belonging to the haemastoma complex

as described by Linne. Early workers in the Gulf of Mexico area

recognized that smaller drills tended to have smooth shells as opposed to the nodular large ones (Moore and Danglade 1915). Eventually, rugosity and large size as well as geographic restriction were

claimed as valid subspecies characters in separating T. haemastoma

haysae Clench (Clench 1930) from the smaller, smooth type of shell

of T. jloridana (Conrad 1837). More recently, a strongly indented

suture has been cited as critical in referring the nodulose shell tYpe

to T. haemastoma canaliculata (Gray) (Abbott 1lJ74). Curiously, the

apparent holotype for this most recently designated subspecies is

a single, entirely smooth shell of unknown provenance (Yen 1942;

Abbott 1lJ74).

It has been reported that the range of the nodulose shell type is

restricted geographically to the area from northwest Florida to Texas

(Abbott 1lJ74; Burkenroad 1931; Clench 1947; Moore and Danglade

1915), but more recently it has been reported from the Atlantic coast

(Haese 1969). In Mississippi, the two shell types have been considered to be only ecological variants (Moore 1961), and others have

rejected rugosity as a subspecific character (Butler 1954a; Gunter

1979). It appears that there are both smooth and knobby shells, with

and without the indented suture. The situation was perhaps best

summed up by Tryon (1880): "...the numerous species referred to

the haemastomoid group ...appear at best to be mere names for

geographical groups...which invariably connect with the parent

form ...."
In this bibliography, the termjloridana is recognized as valid in

separating New and Old World subspecies. References to T. h.

haemastoma (Linne) on the eastern Atlantic coast and in southern

Brazil are not included. In many of the citations a subspecific name

is not listed by the authors, and the appropriateness of their inclusion in this bibliography is dependent on the geographical locale

of the research.

DISTRIBUTION

The widespread distribution reported for the southern oyster drill

is a result of not only its economic importance but also of the obvious aphorism that the range of specific flora and fauna is coincident with the travels of observant naturalists. The following citations are not all-inclusive but rather identify only those papers that

are concerned primarily with the temporal and spatial aspects of

the drill's habitat.

The apparent focus of the drill's present-day distribution in the

mid-Gulf of Mexico littoral has ancient antecedents. Both smooth

and nodose shells are common in million-year-old Pleistocene

deposits east ofthe Mississippi Delta in Breton Sound (Parker 1956).

Oyster shell deposits in Mississippi Sound dating back about 5,000

yr contain numerous drill shells buried 5 m below the bottom level

(Butler 1954b; Demoran 1961), and shell deposits in nearby Lake

Pontchartrain show this area to have been a typical oyster and drill

biocoenose about 2,000 yr ago (Darnel 1962).

Drill populations have attracted attention since the close of the

19th century when declining oyster production became associated

with the predatory snail (Cary 1907; Moore 1898; Moore and Pope

1910; Swift 1898b). Early faunal inventories identified the drill in

Texas (Parker 1955), Louisiana (Cary 1906), and Mississippi and

Florida (Vanatta 1903). More recent faunal lists cite populations in

Texas (Gunter 1950; Hildebrand 1954; Pulley 1952; Strecker 1935;

Whitten et al. 1950), Louisiana (Behre 1950; Harry 1942), Mississippi (Walker 1953), and Florida (Menzel 1955b; Menzel et al. 1966;

Sykes and Hall 1970). The drill's range is most often given in shell

books as the littoral zone extending south from Cape Hatteras, NC,

about lat. 33oN, to the Gulf of Mexico, the Caribbean islands, and

the northeast coast of Brazil at about lat. 5 0 S (Abbott 1974; Aldrich

and Snyder 1936; Morris 1956; Perry and Schwengle 1955; Rehder

1954; Vilas and Vilas 1952; Warmke and Abbott 1961). Populations

ofthe knobbed shells have been restricted in shell books to the northern Gulf of Mexico (Abbott 1974; Clench 1947; Johnson 1934; Morris 1956). Field scientists have noted the presence of knobbed shells

in the coastal lagoons and offshore on the shrimping grounds in Texas

at depths <20 m (Breuer 1962; Hildebrand 1954; Strecker 1935;

Tunnell and Chaney 1970), and in Louisiana (Behre 1950;

Burkenroad 1931; Harry 1942; Perret 1971; St. Amant 1957). They

are reported also in Mississippi (Moore 1961), Alabama (Archer

1947), Florida (Butler 1954a), and, significantly, on the coast of

Georgia where knobbed shells approaching the maximum sizes

ascribed to Louisiana shells have been collected (Hoese 1969).

Drills with smooth shells are common in Texas bays (Gunter 1950;

Ladd 1951; Moffett 1975; Strecker 1935). In Louisiana, smooth shells

are much less common than the knobbed ones (Behre 1950; Harry

1942; Moore 1899; St. Amant 1938). The drill is only too prevalent

in Mississippi Sound in years of high salinity (Butler 1952; Engle

1948; Moore 1913a), in Alabama (Hoese et al. 1972; May 1968),

and on Florida's west coast (Butler 1954a; Dawson 1955: Finucane

and Campbell 1968; Higgins 1938a; Pearse and Wharton 1938;

Schecter 1943b). It has been found 8 km offshore on oil well platforms in the northern Gulf (Gunter and Geyer 1955). The drill is

2

less common on Florida's east coast (D'Asaro 1966; Ingle 1953).

In Georgia, the drill is rare (Walker et al. 1980), or only relatively

abundant in a few areas (Higgins 1938a; Hoose 1969); in South

Carolina it is uncommon but found occasionally in the subtidal

habitat (Zingmark 1978).

The earlier presumed northern extent of the drill was in the waters

of the barrier islands just south of Cape Hatteras (Chestnut 1956;

Wells 1961) and on the subtidal wrecks offshore in North Carolina

(Wells and Gray 1960). However, field studies in the 1950's identified living and long-buried shells in both the Virginia and Maryland

sections of Chincoteague Bay on the eastern shore at about lat. 37°N

(Sieling 1960). The scarcity of location records for the drill south

of Texas reflects the absence of economically important oyster

populations. However, intertidal collections have shown the drill to

be relatively common in Panama (Birkeland et al. 1976), the Antilles (Clench 1947; Dall and Simpson 1901; Lewis 1960), and in

Venezuela where dense populations were found at the entrance of

Lake Maricaibo (Rodriguez 1963).

The drill is abundant along the northern coast of Brazil, both intertidally and at depths down to 35 m. It is reported south to about

450 km below the Equator in which area it is sympatric with T.

h. haemastoma (Mathews 1968; Rios 1970; Rocha 1948). In view

of the drill's planktonic larval life, it is possible that field surveys

will fmd scattered populations of the subspecies further south in

the generally favorable climate along the Brazilian coast, perhaps

as far as Uruguay.

ANATOMY _

Apparently there is but a single description of the gross and microscopic anatomy of Thais. This is reasonably complete and accurate

but, unfortunately, only the abstract has been published (St. Amant

1938). Other than this Master's thesis, there are only minor contributions concerning the drill's adult structure and functions. The

accessory boring organ has been described as somewhat unusual

among muricids in its location atop the egg capsule gland (Carriker

1961). The dental conformation (Krutak 1977) and length of radula

in relation to shell length have been detailed (Radwin and Wells

1968). There is an absence of sexual differentiation in shell morphology, and the external reproductive verge is present in both sexes

but is either undeveloped or atrophied in the female (Morrison 1943).

Separation of copulating pairs revealed that the penis extends at least

40 mm in males about 55 mm in shell length. The proboscis is

relatively even longer (Menzel and Hopkins 1954). Chemical

methods for relaxing and fixing snail tissues to facilitate anatomical

studies are described (Carriker and Blake 1959).

The larval shell has been described and figured (Moore 1961).

There is a dramatic change in the character of the shell as the

definitive sinusigeral larva assumes the crawling habit. A thin,

knifelike varix is formed that separates the smooth larval shell from

the granulated adult shell. Presumably this change is the result of

the termination of the planktotrophic diet. We found that in monthold drills of about 10 mm length, the shell makes up about 75-80%

of the total body weight. This percentage declines to about 60 %

in drills >40 mm in shell length. Chemical studies of the shell identified nine amino acids in the organic matrix (Meenakshi et al. 1971).

Pharmacological studies of the secretions of the hypobranchial

gland revealed the presence of a newly identified choline ester (Keyl

et al. 1957; Whittaker 1957, 1960). Gland extracts were active

vasodilator and hypotensive agents (Huang and Mir 1972), stimulated

smooth muscle, and acted as a central nervous system depressant

(Mir 1971). Methanol and acetone extracts of the gland from both
shell types contained relatively large amounts ofseveral choline esters

(Roseghini and Fichman 1973). Aquaeous extracts of the gland had

an LDso of 215 mg/kg to mice (Huang and Mir 1971).

GROWTH

Thais h. jloridana is a moderately long-lived prosobranch in a taxonomic group whose life spans range from 1 to 20 yr. Early field

observations of drill growth showed that those passing through 6.4

mm mesh on oyster trays had grown a minimum of 45 % during the

following 2-mo period (Moore and Pope 1910). Juvenile snails captured in the northern Gulf of Mexico were >21 mm long in October of their first year (Higgins 1938b). Drills with a mean length

of 35 mm were captured, marked, and released in the field in south

Florida; when recaptured 82 d later, their mean length had increased

by about 12.2 mm (Ingle 1953). Field observations in Louisiana led

to the conclusion that most drills die when 2 yr old after spawning

only once (Menzel and Hopkins 1954). This was not corroborated

in our Florida studies in which data indicate a minimal normal life

span of 5 yr and a maximum perhaps twice as long. Six of 15 tagged

snails survived in a wire mesh cage or live-car for 6 yr and were

observed to deposit capsules of fertile eggs annually. During their

final 3 yr, these drills decreased 15 % in average shell length due

to erosion of the shell spire by the boring sponge CUona truitti Old.

When sacrificed during the breeding season, histological examination of the three male and three female survivors showed normal

gametogenic activity (Butler 1954a).

The mature larval shell or protoconch measures approximately

1.6 mm in length and has five whorls that are demarcated from the

new growth of the teleoconch shell by a thin varix (Moore 1961).

Veliger larvae may assume the crawling habit prior to metamorphosis

and we have found them occasionally on epifaunal study plates with

only three whorls and measuring about 0.7 mm in columnar length.

Drills showing the new demarcation between juvenile and adult shell

have been found frequently in suspended live-cars of oysters that

we examine at 30-d intervals during the summer months. Some of

these drills attain a length of 25 mm in a month's time and show

the larval shell persisting as the terminal three or four whorls of

the adult shell spire. These terminal whorls are solidified internally with shell deposits and may persist in very large or old shells.

In an extensive series of growth observations in west Florida, 600

drills of different size groups were maintained in large tanks with

flowing seawater and an abundance of food (Butler 1954a). The individually numbered drills were measured at monthly intervals for

3 yr. In this protected habitat, some drills reached a length of 55

mm at age 6 mo and were larger than other drills known to be 3

yr old. Annual growth increments in the drills were markedly affected by the severity of winter temperatures in the 3 yr, but the

mortality was about 12% per annum in all size groups. Length increases per annum declined from about 185 % in the smallest size

group, 10-19 mm, to about 10% in the largest size group that initially measured 50-59 mm in length. Male and female drills grew

at similar rates throughout the experiment.

Growth rate appears to be a direct response to food consumption

and ambient temperature, but individual variations under identical

conditions may be significant with some individuals not growing

at all seemingly under the best of conditions. Consequently, identification of individual snails is essential in experimental growth

studies. We marked drills with enamel paint but this needs frequent

renewing. Drills have been identified by notching the shells (Ingle

1953), and with plastic tags attached to the shells with fiber glass

resin (Fischer 1979).

3

REPRODUCTION

In the northern Gulf of Mexico, southern oyster drills usually attain sexual maturity at the age of 8-12 mo (Le., the first spring after

their metamorphosis) and spawn in the period April through August

(Engle 1945; Higgins 1938a; Hoese et al. 1972; Menzel and Hopkins

1954; Pearse and Wharton 1938). We have ,>bserved several instances, however, when 60-90 d-old drills were depositing capsules

in live-cars of experimental oysters. Spawning is temperature dependent and initiated at about 21°C. Depending on the severity of winter

weather in the northern Gulf, spawning may occur as early as

January (Butler 1954a; Little and Quick 1976) or February (Menzel

and Hopkins 1954) and continue sporadically through October. Eggs

laid in unseasonably warm winter months may be killed by subsequent cold weather (Menzel and Hopkins 1954) or have larval

development significantly delayed (Butler 1954a). In south Florida,

spawning typically occurs throughout the year (D'Asaro 1966).

Spawning usually occurs at salinity levels above 2Cfl/00 but a salinity

drop from 27 to 13°/00 for several days did not appear to damage

the embryos. However, a decline from 27 to 4°/00 killed embryos

in capsules within 20 min (Higgins 1938b).

Copulation may be observed in early spring when mass spawnings occur (Butler 1954a), but solitary females lay fertile eggs subsequently and dissection of oviducts in the summer reveals masses

of motile sperm (St. Amant 1938). Female drills that are held in

experimental aquaria in the absence of males may deposit normal

appearing capsules containing sterile eggs (Butler 1954a). Capsule

size is determined by female size; large female drills in the northern Gulf deposit capsules varying from 10 to 18 mm in length and

about 3 mm in width (Butler 1954a; Churchill 1920; St. Amant

1938). In warmer waters, capsules are reported to be smaller, about

6x2 mm (D'Asaro 1966). In one instance in Pensacola Bay we

observed 25-mm females, not more than 2 mo old, depositing capsules 4 mm long and containing about 500 viable embryos.

The creamy white capsules are deposited with the one concave

surface adjacent to the convex surface of the next capsule to form

a compact mass. Capsules are attached by a short stem to a hard

substrate, or in the case of mass spawnings they may be attached

in tiers to underlying capsules oftheir own or other species (DI\saro

1966). Capsules diagrammed as those of T. h. jloridana from Barbados are either incorrectly identified or markedly different from

jloridana capsules deposited in other areas (Lewis 1960). Under

field and laboratory conditions, capsules are deposited at the rate

of 2 to 4/h (Burkenroad 1931; Butler 1954a; Higgins 1938b; St.

Amant 1938) up to an observed maximum of 17 in 1 h (DJ\saro

1966). Clutches of capsules vary in number up to about 150, and

several clutches may be deposited by each female during the spawning period. The gregarious habit of spawning drills leads to the

deposition of thousands of capsules over a short period of time in

limited space (DJ\saro 1966; Galtsoff 1964; Glaser 1904; Higgins

1938b). The eggs are fertilized in the oviduct at some point near

the albumen gland before capsule formation (D'Asaro 1966). They

number from hundreds to more than 6,000 in each capsule depending on the size of the female (Butler 1954a, c; Di\saro 1966; Higgins 1938b; St. Amant 1938). The albumen gland has been described

as the best histological criterion ofspawning readiness (Belisle and

Stickle 1978). Capsules become brown as the embryos mature but

turn purple only when empty or when the developing embryos die

despite statements that capsules with developing embryos may be

purple (Churchill 1920; Galtsoff 1964; Moore 1913a). Under optimal conditions it would be possible for a female drill to produce

in excess of 10 million eggs during her lifetime.
The egg capsules are deposited about an hour before formation

of the first polar body, and larval development proceeds at rates controlled by ambient temperatures. At a mean temperature of 25°C,

development requires about 2 wk (D'Asaro 1966) but may be completed in 10 d or extended to at least 39 d (Butler 1954a; St. Amant

1938). We have found no evidence of larval mortality within the

capsule during the developmental period. The initial description of

Thais embryology was based entirely on external morphological

changes (St. Amant 1938), but a definitive description, based on

histological sections as well, traces the organogenesis ofthe developing larva until the planktotrophic stage is reached (D'Asaro 1.966).

Early investigators were unaware of the pelagic larval stage (Moore

and Pope 1.91.0), and it has been reported (without data) that T.

haemastoma has a pelagic stage in subtropical waters but not in

boreal areas (Thorson 1.950). Others conclude in a review of stenoglossan prosobranchs that the pelagic larval stage is a genetic rather

than a geographic attribute (Radwin and Chamberlin 1973). Duration of the pelagic stage is unknown. Clench (1954) believed that

it had to be short in order to explain the existence of clines, but

collection of pediveligers is rare until long after the onset of spawning; a free-swimming stage of not less than 2 mo seems likely (Moore

1961). Casual efforts to culture larvae through metamorphosis in vitro

have been unsuccessful (Butler 1954a; D'Asaro 1966; St. Amant

1938).

Young drills of both sexes have a clearly defined verge, and about

75 % initially develop a male gonad. Field surveys of drills <25 mm

in length and presumably <120 d old showed a preponderance of

4 ,or 5 males to 2 females. Shell size is not necessarily directly related

to sexual development since some of the smaller drills (16.5 mm)

of both sexes had well-developed gonads, while others measuring

as much as 42 mm could not be sexed either grossly or on the basis

of histology. We sexed a group of 300 snails estimated to be a year

old and maintained them in live-cars for 30 mo. During that period,

no sex reversals were detected; however, the snails were examined

only grossly.

A small verge usually persists in the adult female, and dissection

of 63 Louisiana drills showed them to be fundamentally hermaphroditic with male and female ducts present but with one set

undeveloped or degenerate (Morrison 1943). We randomly collected

532 presumably mature drills over a period of 3 yr in Santa Rosa

Sound, FL, and on the basis of gross examination 45 % were male,

49% were female, and 6% were of indeterminate sex.

BEHAVIOR

In the northern Gulf of Mexico, the activity of the southern oyster

drill is limited by the critical temperature of 12°C (St. Amant 1938).

Below this point, feeding stops and drills tend to disappear beneath

rocks and shells or bury themselves in the substrate (Butler 1954a).

The burying habit is well-established, and as much as 50% of a

drill population may be buried even when temperature and salinity

levels are suitable for feeding. When active, drills crawl easily on

very soft mud bottoms (Burkenroad 1~31); on hard surfaces, they

move at rates as fast as 9 m1h (Butler 1954a; St. Amant 1938). Drills

are occasionally taken from sandy bottoms in shrimp trawls

(Hildebrand 1954; Swingle 1971) and are reported hitchhiking on

a variety of floating objects as well as on the blue crab, Calinectes

sapidus (Rathbun), the horseshoe crab, Limulus polyphemus (Linne),

and sea grasses (Moore 1961). Drill larvae are effectively distributed

by water currents, and their presumably lengthy planktonic existence

facilitates dispersal ofthe species and repopulation of areas devastated

by periodic low salinities. In experimental studies, we found larval

-4

movement to be continuous and basically vertical. Monitored in flowthrough aquaria, larvae ascended at an observed rate of 20 cm/min.

POPULATION DENSITY _

The number of drills per unit area is of obvious interest and importance in assessing potential losses on oyster grounds due to this

predator. Drill populations fluctuate widely as a result of sudden

environmental changes. For example, the opening of the Bonnet

Carre Spillway in Louisiana appeared to have eliminated the drills

in western Mississippi Sound in 1950. Yet only 2 yr later in dredged

samples from this area, the volume ratio of drills to oysters was about

I to 150 (Gunter 1953). Density surveys are of only immediate value

and can cover but a limited area. Numbers in the following citations have been transposed to numbers of drills per square meter:

Apalachicola, FL, in 1955, 2.7 drills (Menzel et al. 1957); Santa

Rosa Sound, FL, in 1968, 222; lower Mobile Bay, AL, in 1967, 2.7

(May 1971); Mississippi Sound, MS, in 1956,27 (Chapman 1959);

west of the Mississippi River, LA, in 1936, 25 (St. Amant 1938);

and, remarkably, Lake Maracaibo, Venezuela, in 1956, 1,290

(Rodriguez 1963).

In 1968 when we found the drill population on the rocky shore

of the laboratory island in Santa Rosa Sound, FL, was 222/m2 , the

drills averaged 33 mm in length and 1.5 g in wet weight of tissues.

We estimated their biomass was the equivalent of about 3.3 t/ha.

DRILLING TECHNIQUE

The ability of Thais to prey on oysters has been a matter for discussion and some dissension since the turn of the century when perhaps

the first experimental observations of the drill were undertaken

(Moore and Pope 1910). Drills were placed in an enclosed live-car

with mixed-sized oysters, and apparently only oysters of <40 mm

length were killed. Oystermen as well as some biologists believed

that large oysters were immune to drill attack (Churchill 1920; Moore

1898; St. Amant 1938). Later studies showed that damage to large

oysters could be heavy but difficult to detect (Burkenroad 1931; Cary

1907; Moore 1899). Many oystermen failed to evaluate the importance of this pest (Baughman and Baker 1951; Burkenroad 1931;

Butler 1954a; Higgins 1938a; Moore 1899). We exposed a group

of 25-65 mm oysters in a live-car to 25-mm drills, and 83 oysters

were killed in a 7-d period. Ten of the oysters showed no evidence

of drill damage; in 65, the slitlike marginal hole was difficult to

find; and only in the remaining 8 was there an obvious circular hole

that was randomly located on the surface of the valves. Turn-ofthe-century oystennen believed that the drill secretes an acid to bore

the hole (Moore 19I3b); this has been affirmed more recently (Carriker 1961). Some suggested that there is a paralytic poison to make

the oyster gape (Baughman and Baker 1951; Gunter 1970; Higgins

1938a; McGraw and Gunter 1972; Moore 1898; St. Amant 1938),

but a more detailed study of drill feeding indicated oysters gaped

only after being three-quarters consumed (Chapman 1956).

The mechanics of radular movement during feeding are described

but present no evidence of an acid or paralytic secretion (Gunter

1952a). An accessory boring organ is assumed (Garton and Stickle

1980; Radwin and Wells 1968) and identified in Thais and related

species (Carriker 1961). The angle of the bore hole made by Thais

h. floridana is compared with that of other species of muricids (Gates

1910). Excision of the radula and odontophore is reported to be

followed by complete regeneration within 3 wk (Demoran and Gunter

1956). Early workers, unaware of the drill's planktonic stage, erroneously assumed that it was able to bore oysters as soon as it
emerged from the capsule like its northern counterparts (Moore

1913a), but its ability to drill as soon as it can crawl is well

documented (Butler 1953). Bore holes made by young drills gradually

increase in diameter from 0.1 to 0.2 mm and are as much as 10 times

as large in the adult. Some have assumed that mature drills, i.e.,

about 50 mm in length, no longer bore holes but simply rasp open

the oyster's valves (Gunter 1979).

FEEDING SELECTIVITY _

The importance of the drill as an oyster predator reflects essentially

the monocultural nature of oyster farming. Given a choice, drills

selectively feed on mussels, barnacles, small and then larger oysters,

presumably on the basis of ease in opening rather than flavor (Butler

1954a; Hedgpeth 1953; St. Amant 1938). In an evaluation of drill

attractants, we baited traps with four kinds of food. In a 2-wk period

of daily inspections, 190 drills (27-44 mm long) were captured. The

drills selected the different baits as follows: mussels, 35 %; barnacles,

30%; oysters <30 mm long, 27%; and large oysters, 8%. The drill

is an opportunist, however, and eats whatever is available including

Donax variabilis Say (Loesch 1957), Rangia cuneata Sowerby

(O'Heeron 1966), and Perna perna (Linne) (Urosa 1969). We have

also observed them feeding on Anomia simplex Orbigny, Crepidula

plana Say, and Mercenaria mercenaria (Linne). It apparently does

not feed naturally on scallops or blue crabs although it is occasionally

seen browsing on their epifauna.

Thais is attracted by shucked oyster meats in experimental trays

and as far as 3 m downstream from them (Gates 1910; Gunter et

al. 1957). It is readily attracted to oysters killed by other drills, and

as many as eight drills have been observed feeding on a single oyster

(McConnell 1954; Moore 1913a).

In the absence of a normal food supply, the drill readily feeds

on its companions. In an experimental group of mixed-size drills

that had been starved individually for a month, 26 were cannibalized in the following week when they were placed together. At the

end of the week, all of the remaining drills were approximately the

same size and the cannibalism stopped (Butler 1954a). Experimental data reveal that the drill stops feeding when the salinity declines

to 7.5°/00 (Garton and Stickle 1980). Field data indicate that feeding

and other activities terminate when the temperature drops to 12°C

or less (St. Amant 1938).

SALINITY TOLERANCE

The southern oyster drill tolerates a broad range of salinities but

typically flourishes only in the more saline parts of the estuary

(Cooley 1978). Adapted to tidal shifts in salinity patterns, it has no

narrowly defined, low-salinity death point. When acclimated to a

salinity of 35°/00, for example, drills became immobile when the

salinity declined to 15°/00; but when acclimated to a salinity of

20"/00, they were not harmed when the salinity declined to about

10%0 (Butler 1954a). Drills reportedly survived a gradual salinity

decline to about 5°/00 on Florida reefs (Higgins 1938a), although

mortalities were sustained at salinities of 8-100/00 in Mississippi

Sound (Gunter 1953). Experimentally, drills suffered higher mortality when suddenly exposed to a salinity of 7°/00 than to 3.5%0,

presumably because the lower salinity caused an immediate closure

of the operculum that sealed off the drill from the environment

(Schecter 1943a).

Low temperatures provide at least temporary protection for the

drill, as well as the oyster, from incursions of freshwater in the spring

months. Relict drill populations are preserved in pockets of more

5

saline benthic waters when spring freshets and floods result in a

superficial run-off of potentially lethal freshwater (Butler 1952).

Under experimental conditions, week-old encapsulated larvae acclimated to a salinity of about 25°/00 were killed after 48 h exposures to salinities of 15 and 100/00. When we exposed capsules

of veliger larvae to tap water and then returned them to salt water,

mortalities were as folJows: 2 min, 40%; 4-6 min, 75%; and 10 min

or longer resulted in a complete kill. Pelagic drill larvae reportedly

tolerate lower salinities than adults, but the planktonic stage is probably the limiting factor in the distribution of drills along the estuarine

salinity gradient (Gunter et al. 1974; Wells 1961).

Laboratory studies suggested that osmolality in the drill is controlJed by active rather than passive tissue processes (McRitchie

1968). The amplitude of osmolality fluctuates directly with ambient

salinity changes (Stickle and Howey 1975). Studies with artificial

tidal cycles showed that at lower salinities, drills contracted, their

oxygen consumption declined (Findley et aI. 1978), and their haemolymph osmolality tended to be hyperionic at low salinities and vice

versa (Hildreth and Stickle 1980).

PREDATORS

Thais must be judged an extremely successful animal in that it has

no documented natural predators in the adult stage. At least five

species of hermit crabs have been identified as inhabiting its shells

(Cooley 1978; Fotheringham 1976), but there is no evidence that such

acquisitions are other than accidental. In our studies of epifaunal

setting on artificial substrates, 2-mm anemones were found containing up to 10 snail shelJs but it is not certain that these were Thais,

although this snail was settling out of the plankton at the time.

In the laboratory, we found it possible to induce hermit crabs to

attack the drill only by forcing the crabs to occupy shells that were

too small for them. Starved drills in the laboratory will prey on each

other, and the crown snail, Melongena corona (Gmelin), will adapt

to a drill diet. Starved stone crabs, Menippe mercenaria (Say), will

feed on them (Powell and Gunter 1968), but not the banded tulip,

Fasciolaria lilium hunteria (G. Perry), which normally preys on other

gastropods (Wells 1958). Drills are damaged in nature by commensals residing in and gradually eroding their hosts' shells, especially

the boring sponge, Cliona truitti (Menzel and Hopkins 1954), the

boring clam, Diplothyra smithii Tryon (Harry 1976), and the blister

worm, Polydora spp. (Hyman 1967; Menzel and Hopkins 1954).

We found that experimental drills kept in live-cars were more damaged by boring sponge than by their benthic neighbors presumably

because the latter occasionally suffocate their commensals by burying

in bottom muds.

PARASITES

The southern oyster drill's rather limited diet has perhaps restricted

the variety of parasites which it serves as host (Cake 1975). Only

2 of 10 potential metacestode types were found in Thais when

surveyed with 35 other gastropod species (Cake 1976, 1978). This

was about the same level of infection of metacestodes found in oysters

(Cake and Menzel 1980). Larval cestodes are common gut parasites

in driJIs of both shelJ types examined in Texas (Wardle 1974). Only

one larval trematode type was found in thousands of drills examined

near Galveston, TX, although 14 others were observed in the 20

different gastropod species collected (Epstein 1972).

Cercariae of the digenetic trematode Parorchis acanthus (Nicoll)

were reported from snails in Florida and snails of both shell types

in Louisiana. The mass of cercariae effectively castrates the drill.
The adult trematode lives in the cloaca of gulls and other sea birds

(Hopkins 1957; Schecter 1943b). In the northern Gulf, the natural

infection rate of Parorchis is about 3%in Thais and can be increased

to only about 12% experimentally (Cooley 1958). The infection rate

in gulls is also low, and it was not possible to increase it experimentally (Cooley 1962). The adult polyclad Hoploplana inquilina

Wheeler is reported from the mantle cavity of Thais and other snails

from the western Atlantic littoral, and from Louisiana where the

specimens were larger than any collected from the type locality on

the Atlantic coast (Hyman 1967; Pearse and Wharton 1938; Schecter

1943b).

Of uncertain pathogenicity are protozoans we have observed frequently in sections of drill liver tissue, and a saprophytic Labyrinthula thaisii Cox and Mackin found on the gills of drills collected

near Galveston, TX (Cox and Mackin 1974).

ECONONUCIMPORTANCE

The extent of drill depredations on the oyster community is dependent naturally on salinity and temperature regimes. In more saline

areas, their damage varies inversely with the density of the associated

mussel and barnacle communities (St. Amant 1938). Under experimental conditions, a 50-mm drill ate about 85 2-wk-old spat

per day, and from 1 to 5 market-size oysters per month (Butler 1953,

1954a; Menzel and Hopkins 1956). A 15-mm drill ate its own volume

of oyster tissue in a 20-min period (St. Amant 1938). By extrapolation, an average drill can destroy 1,000 to 3,000 oysters during

its lifetime (Butler 1954a). Estimates of the damage caused by drills

in Texas varied from nil (Moore 1907) to about 90% or more in

some areas (Baker 1951; Baughman and Baker 1951; Gunter 1955;

Hofstetter 1959; Menzel 1955a). In Louisiana, the drill has been

recognized as the most serious oyster predator (Galtsoff et al. 1935;

Hopkins 1955; McConnell 1954; Pollard 1973; Van Sickle et al.

1976), and that its destructiv~ness increases as salinity levels increase

(Dugas 1977; Padgett 1960; St. Amant 1938). Similar observations

in Mississippi have been reported (Chapman 1959; Gunter 1953);

Gunter and Demoran 1971; MacKenzie 1977; Maghan 1967; May

and Bland 1m), and in Alabama (May 1968, 1971, 1972; Ritter 1896).

In Florida, reported damage varies from negligible (Menzel and

Nichy 1958) to extensive (Danglade 1917; Ingle and Whitfield 1968;

Swift 1898a, b). In Georgia, production of oysters subtidally is insignificant because of the drill (Harris 1980). It is generally recognized that there can be little extension of oyster grounds into more

saline areas until the development of efficient drill controls (Galtsoff

1950).

CONTROL

There is consensus that the southern oyster drill prevents profitable

oyster culture on thousands of hectares of otherwise suitable grounds

along the Gulf coast, but methods for controlling this predator are

essentially absent. Limited control may be obtained in some areas

by destruction of the drills culled when harvesting oysters (Gates

1910). So-called traps, however, permit drills to exit as well as enter

and so must be emptied at frequent intervals. They are prohibitive

in terms of required manpower (Butler 1954a, c). Use ofseed oysters

as bait in such traps is unsatisfactory because our experiments showed

that while this bait attracted about 75 % of the drills on a barren

bottom, only about 5 % were captured on an oyster reef. The oftensuggested use of palmetto or yucca branches to attract gregarious

drills during the breeding season is likewise too labor intensive to

be practical (Burkenroad 1931; Engle 1945; Menzel and Hopkins

1954).

6

Suggestions to make the harvest of drills more profitable by using

them for human food (Burkenroad 1931; Butler 1953; Gunter 1971)

were reflected in a small fishery in Louisiana in the early 1950's.

Special traps were constructed that harvested only the larger drills.

The processed drill meats had an acceptable flavor but became

discolored after being canned (George Seale3). Laboratory efforts

to increase the incidence of the trematode parasite PaTvrchis in hopes

of spreading this specific disease in the environment were also unsuccessful (Cooley 1962).

Inevitably, ideas for drill control have centered on the effects of

contrived fluctuations in salinity regimes. It has long been noted

that extensive spring freshets devastated drill populations (Breithaupt

and Dugas 1979; Burkenroad 1931; May 1972; Menzel et al. 1966)

as do flood waters from crevasses in the Mississippi River levee

system (Gunter 1952b; Viosca 1938). It has been suggested seriously

that regulated discharges from the Mississippi River could be used

to control the drill on Louisiana oyster grounds (Breithaupt and

Dugas 1979; St. Amant 1938). There is no question, however, that

drill problems are largely overcome by culturing oysters in less saline

areas (McConnell 1954).

ACKNOWLEDGMENTS

It is my pleasure to thank Henry Enos, Director of the EPA Environmental Research Laboratory at Gulf Breeze, FL, for providing

the physical amenities that made preparation ofthis manuscript possible. I am greatly indebted to librarians Andree Lowry and Alice

Pool of this laboratory for their diligence and cheerful efficiency

in helping locate many of the references.

LITERATURE CITED

ABBan, R. T.

1974. American seashells; the marine Mollusca of the Atlantic and Pacific coasts

of North America. 2d ed. Van Nostrand Reinhold, N.Y. 663 p.

ALDRICH, B., and E. SNYDER.

1936. Florida sea shells. Houghton Mifflin, N.Y., 122 p.

ARCHER,A. F.

1947. Oyster reefs in Alabama. Ala. Conserv., Dec. 7, 12.

BAKER, B. B., Jr.

1951. A brief report on the Texas oyster investigation. Proc. Natl. Shellfish.

Assoc. 41:50-52.

BAUGHMAN. J. L., and B. B. BAKER.

1951. Oysters in Texas. Tex. Game, Fish Oyster Comm. Bull. 29, 37 p.

BEHRE, E. H.

1950. Annotated list ofthe fuuna of the Grand Isle region. La. State Univ. Occas.

Pap. Mar. Lab. 6, 66 p.

BELISLE, B. w., and W. B. STICKLE.

1978. Seasonal patterns in the biochemical constituents and body component indexes of the muricid gastropod, Thais haemas/oma. BioI. Bull. (Woods Hole)

155 :259-272.

BIRKELAND, C., A. A. REIMER, and 1. R. YOUNG.

1976. Survey of marine communities in Panama and experiments with oil. EPA

Ecol. Res. Servo 600/3-76-028, 176 p.

BREITHAUPT, R. L., and R. 1. DUGAS.

1979. A study of the southern oyster drill (Thais haemas/oma) distribution and

density on the oyster seed grounds. La. Wl1dl. Fish. Comm. Tech. Bull. 30,

20 p.

BREUER, 1. P.

1962. An ecological study of the lower Laguna Madre of Texas, 1953-1959. Publ.

Inst. Mar. Sci., Univ. Tex. 8:153-183.

BURKENROAD, M. D.

1931. Notes on the Louisiana conch, Thais haemastoma Linne, and its relation

to the oyster, Os/rea virginica. Ecology 12:656-664.

'G. Seale, Golden Meadow Fisheries Co., Golden Meadow, LA 70357, pers. commun. 30 May 1955.
BUTLER, P. A.

1952. Effect of floodwaters on oysters in Mississippi Sound in 1950. U.S. Fish

Wildl. Serv., Res. Rep. 31, 20 p.

1953. The oyster predator problem. South. Fisherman, June, p. 35.

1954a. The southern oyster drill. Proc. Nat!. Shellfish. Assoc. 44:67-75.

1954b. Summary of our knowledge of the oyster in the Gulf of Mexico. In P.

S. Galtsoff (editor), Gulf of Mexico. Its origin, waters and marine life. p.479-489.

U.S. Fish Wildl. Servo Fish. Bull., Vol. 55.

1954c. Methods for controlling the southern oyster drill. Atl. Fisherman,

January, p. 17.

CAKE, E. w., Jr.

1975. Larval and postlarval cestode parasites of shallow-water benthic mollusks

of the Gulf of Mexico from the Florida Keys to the Mississippi Sound. Ph.D.

Thesis, Florida State Univ., Tallahassee, 434 p.

1976. A key to larval cestodes of shallow-water, benthic mollusks'of the northern

Gulf of Mexico. Proc. Helminthol. Soc. Wash. 43(2):160-171.

1978. Larval cestode parasites of edible mollusks of the northeastern Gulf of Mexico. Gulf Res. Rep. 6:1-8.

CAKE, E. w., Jr., and R. W. MENZEL.

1980. Infections of Tylocephalum metacestodes in commercial oysters and three

predaceous gastropods of the eastern Gulf of Mexico. Proc. Nat!. Shellfish.

Assoc. 70:94-104.

CARRIKER, M. R.

1961. Comparative functional morphology of boring mechanisms in gastropods.

Am. Zool. 1(2):263-266.

CARRJKER, M. R., and 1. W. BLAKE.

1959. A method for full relaxation of muricids. Nautilus 73(1):16-21.

CARY, L. R.

1906. A contribution to the fauna of the coast of Louisiana. Bull. Gulf BioI.

Sm. 6:50-59.

1907. A preliminary study of the conditions for oyster culture in the waters of

Terrebonne Parish, Louisiana. Bull. Gulf BioI. Stn. 9:1-62.

CHAPMAN, C. R.

1956. Feeding habits of the southern oyster drill, Thais haetnllStoma. Proc. Nat!.

Shellfish. Assoc. 46:169-176.

1959. Oyster drill (Thais haemastoma) predation in Mississippi Sound. Proc.

Nat!. Shellfish. Assoc. 49:87-97.

CHESTNUT, A. F.

1956. The distribution of oyster drills in NOr!h Carolina. Proc. Nat!. Shellfish.

Assoc. 46: 134-139.

CHURCHILL, E. P., Jr.

1920. The oyster and the oyster industry of the At!antic and Gulf coasts. Rep.

U.S. Comm. Fish., 1919. App. VIII (Doc. 890), 51 p.

CLENCH, W. 1.

1930. A new subspecies of Thais from Louisiana. Nautilus 41:6-8.

1947. The genera Purpura and Thais in the western Atlantic. Johnsonia

2(23):61-91.

1954. The occurrence of clines in molluscan populations. Syst. Zool. 3(3):

122-125.

CONRAD, T. A.

1837. Descriptions of new marine shells, from upper California. Collected by

Thomas Nuttal, Esq. 1. Acad. Nat. Sci., Phila. Ser. 1,7:227-268. (Not seen,

quoted by Clench.)

COOLEY, N. R.

1958. Incidence and life history of Parorchis acanthus, a digenetic trematode in

the southern oyster drill, Thais haetnllStoma. Proc. Natl. Shellfish. Assoc.

48: 174-188.

1962. Studies on Parorchis acanthus (Trematoda:Digenea) as a biological control for the southern oyster drill, Thais haetnllStoma. U.S. Fish Wildl. Servo

Bull. 62:77-91.

1978. An inventory of the estuarine fauna in the vicinity of Pensacola,

Florida. Fla. Mar. Res. Pub. 31, 119 p.

COX, B. A., and 1. G. MACKIN.

1974. Studies on a new species of Labyrinthula (Labyrinthulales) isolated from

the marine gastropod Thais haemastomafloridana. Trans. Am. Microsc. Soc.

93:62-70.

DALL, W. H., and C. T. SIMPSON.

1901. The Mollusca of Puerto Rico. Bull. U.S. Fish. Comm., 1900,20:351-524.

DANGLADE, E.

1917. Condition and extent of the natural oyster beds and barren bottoms in the

vicinity of Apalachicola, Fla. Rep. U.S. Comm. Fish., 1916, Doc. 841, 68 p.

DARNELL, R. M.

1962. Ecological history of Lake Pontchartrain, an estuarine community. Am.

MidI. Nat. 68(2):434-444.

D'ASARO, C. N.

1966. The egg capsules, embryogenesis and early organogenesis of a common

7

oyster predator, Thais haemastoma (Gastropoda: Prosobranchia). Bull. Mar.

Sci. 16(14):884-914.

DAWSON, C. E.

1955. A study of the oyster biology and hydrography at Crystal River,

Florida. Publ. Inst. Mar. Sci., Univ. Tex. 4:279-302.

DEMORAN, W. 1.

1961. Preliminary studies on the effect of the purple dye of the oyster drill Thais

haemastoma on the oyster. 1. Miss. Acad. Sci. 6:93-95.

DEMORAN, W. J., and G. GUNTER.

1956. Ability of Thais haemastoma to regenerate its drilling mechanism. Science

123(3208):1126.

DUGAS, R. 1.

1977. Oyster distribution and density on the productive portion of the State seed

grounds in southeastern Louisiana. La. Wildl. Fish. Comm. Tech. Bull. 23,

27 p.

ENGLE, 1. B.

1945. The condition of the natural oyster reefs and other public oyster bottoms

of Alabama in 1943 with suggestions for their improvement. U.S. Fish Wildl.

Servo Spec. Sci. Rep. 29, 42 p.

1948. Investigation of the oyster reefs of Mississippi, Louisiana and Alabama

following the hurricane of September 18, 1947. U.S. Fish Wildl. Servo Spec.

Sci. Rep. 59, 70 p.

EPSTEIN, R. A.

1972. Larval trematodies of marine gastropods from Galveston Island, Texas.

Tex. 1. Sci. 24(3):389.

FINDLEY, A. M., B. W. BELISLE, and W. B. STICKLE.

1978. Effects ofsalinity fluctuations on the respiration rate ofthe southern oyster

drill, Thais haemastoma, and the blue crab Callinectes sapidus. Mar. BioI.

(NY) 49:59-67.

FINUCANE, 1. H., and W. CAMPBELL, II.

1968. Ecology of American oysters in Old Thmpa Bay, Florida. Q. 1. Fla. Acad.

Sci. 31:37-46.

FISCHER, M.

1979. The results of a tag retention study utilizing various commercial adhesives

on the oyster drill, Thais haemastoma. La. Wildl. Fish. Comm. Tech. Bull.

28:29-34.

FarHERJNGHAM, N.

1976. Population consequences of shell utilization by hermit crabs. Ecology

57:570-578.

GALTSOFF, P. S.

1950. Latent oyster resources of Florida. Proc. Gulf Caribb. Fish. Inst. 2:15-16.

1964. The American oyster Crassostrea virginica Gmelin. U.S. Fish. Wildl.

Serv., Fish. Bull. 64, 480 p.

GALTSOFF, P. S., H. F. PRYTHERCH, R. 0. SMITH, and V. KOEHRING.

1935. Effects of crude oil pollution on oysters in Louisiana waters. U.S. Dep.

Commer, Bull. Bur. Fish., no. 18, vol. 48:143-210.

GARTON, D., AND W. B. STICKLE.

1980. Effects of salinity and temperature on the predation rate of Thais

haemastoma on Crassostrea virginica spat. BioI. Bull. (Woods Hole) 158:

49-57.

GATES, W. G.

1910. Oyster culture in Louisiana. Bull. Gulf BioI. Stn. 15:1-32.

GLASER,O. C.

1904. An incomplete list of the marine fauna ofCameron, Louisiana. Bull. Gulf

BioI. Stn. 2(II):40-42.

GUNTER, G.

1950. Seasonal population changes and distributions as related to salinity, of certain

invertebrates of the Texas coast, including the commercial shrimp. Publ. Inst.

Mar. Sci., Univ. Tex. 1(2):7-51.

1952a. Radu'la movement and boring efficiency of gastropods. Nature 169

(4302):630-631.

1952b. Historical changes in the Mississippi River and the adjacent marine environment. Publ. Inst. Mar. Sci., Univ. Tex. 2(2):119-139.

1953. The relationship of the Bonnet Carre Spillway to oyster beds in Mississippi Sound and the "Louisiana Marsh", with a report on the 1950 opening. Publ. Inst. Mar. Sci., Univ. Tex. 3(1):17-71.

1955. Mortality of oysters and abundance of certain associates as related to salinity. Ecology 36:601-605.

1970. Some factors concerning the drilling apparatus and the feeding and predation of the prosobranchiate gastropods especially on other molluscs. In:

Proceedings of symposium on Mollusca, p. 370-378. Mar. BioI. Assoc. India,

Mandapam Camp, India.

1971. The molluscan resources of the Gulf of Mexico. FAO Fish. Rep. 71.2(2):

111-115.

1979. Studies of the southern oyster borer, Thais haemastoma. Gulf Res. Rep.

6:249-260.
GUNTER, G., B. S. BALLARD, and A. VENKATARAMIAH.

1974. A review of salinity problems of organisms in United States coastal areas

subject to the effects of engineering works. Gulf Res. Rep. 4:380-475.

GUNTER, G., C. E. DAWSON, and W. 1. DEMORAN.

1957. Determination of how long oysters have been dead by studies of their

shells. Proc. Natl. Shellfish. Assoc. 47:31-33.

GUNTER, G., and W. J. DEMORAN.

1971. Mississippi oyster culture. Am. Fish Farm. 2(5):8-12.

GUNTER, G., and R. A. GEYER.

1955. Studies on fouling organisms of the northwest Gulf of Mexico on platform

and pile. Publ. Inst. Mar. Sci., Univ. Tex. 4(1):37-67.

HARRJS, C. D.

1980. Survey of intertidal and subtidal oyster resources of the Georgia coast. Ga.

Dep. Natl. Resour., Brunswick, GA, 44 p.

HARRY, H. W.

1942. List of Mollusca of Grand Isle, Louisiana, recorded from the Louisiana

State University Marine Laboratory, 1924-41. La. State Univ. Occas. Pap. No.

I, 13 p.

1976. Correlation of benthic Mollusca with substrate composition in lower

Galveston Bay, Texas. Veliger 19(2):135-152.

HEDGPETH, 1. W.

1953. An introduction to the zoogeography of the northwestern Gulf of Mexico

with reference to the invertebrate fauna. Publ. Inst. Mar. Sci., Univ. Tex.

3:107-224.

HIGGINS, E.

1938a. Progress in biological inquiries, 1935. Rep. U.S. Comm. Fish. 1936, App.

IV:381-452.

1938b. Progress in biological inquiries, 1936. Rep. U.S. Comm. Fish. 1938, App.

III:I-61.

HILDEBRAND, H. H.

1954. A study of the fauna of the brown shrimp (Penaeus azteeus Ives) grounds

in the western Gulf of Mexico. Publ. Inst. Mar. Sci., Univ. Tex. 3(2):229-366.

HILDRETH, J. E., and W. B. STICKLE.

1980. The effects of temperature and salinity on the osmotic composition of the

southern oyster drill, Thais haernastoma. BioI. Bull. (Woods Hole) 159:148-161.

HOESE, H. D.

1969. Population of large oyster drills (Urosa/pinx, Eup/eura, Thais) from the

southern United States salt marshes. In T. L. Linton (editor), Feasibility study

of methods for improving oyster production in Georgia. Ga. Game Fish Comm.

and Univ. Ga., 176 p.

HOESE, H. D., W. R. NELSON, and H. BECKERT.

1972. Seasonal and spatial setting of fouling organisms in Mobile Bay and

Mississippi Sound, Alabama. Ala. Mar. Resour. Bull. 8:9-17.

HOFSTETTER, R. P.

1959. The Texas oyster fishery. Tex. Game, Fish Oyster Comm. Bull. 40, 38 p.

HOPKINS, S. H.

1955. Oyster setting on the GulfCoast. Proc. Natl. Shellfish. Assoc. 45:52-55.

1957. Interrelationships of organisms. B. Parasitism. In: 1. W. Hedgpeth (editor),

Treatise on marine ecology and paleoecology. Geol. Soc. Am Mem. 67,

1:413-428.

HUANG, C. L., and G. N. MIR.

1971. Pharmacological properties of hypobranchial gland of Thais haemastoma

(Clench). 1. Pharm. Sci. 60:1842-1846.

1972. Pharmacological investigations of salivary gland of Thais haernastoma

(Clench). Toxicon 10(2):1ll-1I7.

HYMAN, L. H.

1967. The invertebrates: Mollusca I (Vol. VI). McGraw-Hili, N.Y., 792 p.

INGLE, R. M.

1953. Notes on growth of Thais haernastoma floridana and thais (Stramonita)

rustiea. Proc. Natl. Shellfish. Assoc. 42:12-14.

INGLE, R. M. and W. K. WHITFIELD.

1968. Oyster culture in Florida. Fla. Dep. Nat. Resour., &Iuc. Ser. 5, 1962 rev.,

25 p.

JOHNSON, C. W.

1934. List of marine Mollusca of the Atlantic Coast from Labrador to Texas.

Proc. Boston Soc. Nat. Hist. 40(1):1-204.

KEYL, M. 1., I. A. MICHAELSON, and V. P. WHITTAKER.

1957. Physiologically active choline esters in certain marine gastropods and other

invertebrates. 1. Physiol. (Lond.) 139:434-454.

KRUTAK, P. R.

1977. Gastropod radulae: their potential in the fossil record. Trans. Gulf Coast

Assoc. Geol. Soc. 27:314-322.

LADD, H. S.

1951. Brackish water and marine assemblages of the Texas coast with special

reference to mollusks. Publ. Inst. Mar. Sci., Univ. Tex. 2:125-164.

8

LEWIS, J. B.

1960. The fauna of rocky shores of Barbados, West Indies. Can. 1. Zool. 38:

391-535.

LITTLE, E. J., and 1. A. QUICK, Jr.

1976. Ecology, resource rehabilitation, and fungal parasitology of commercial

oysters, Crassostrea virginiea (Gmeiin), in Pensacola Estuary, Florida. Fla.

Mar. Res. Publ. 21, 89 p.

LOESCH, H. C.

1957. Studies of the ecology of two species of Donax on Mustang Island,

Texas. Publ. Inst. Mar. Sci., Univ. Tex. 4(2):201-227.

MacKENZIE, C. L., Jr.

1977. Development of an aquacultural program for rehabilitation of damaged oyster

reefs in Mississippi. Mar. Fish. Rev. 39(8):1-13.

MAGHAN,B. W.

1967. The Mississippi oyster industry. U.S. Fish Wildl. Servo Leafl. 607, 12 p.

MATTHEWS, H. R.

1968. Notas sobre 0 genero Thais Riiding, 1798, no nordeste Brasiliero. Arq.

Estac. BioI. Mar. Univ. Fed. Ceara 8:37-41.

MAY, E. B.

1968. Summer oyster mortalities in Alabama. Prog. Fish-Cult. 30(2):99.

1971. A survey of the oyster and the oyster shell resources of Alabama. Ala.

Mar. Resour. Bull. 4, 53 p.

1972. The effect of floodwater on oysters in Mobile Bay. Proc. Natl. Shellfish.

Assoc. 62:67-71.

MAY E. B., and D. G. BLAND.

1970. Survival of young oysters in areas of different salinity in Mobile Bay. Proc.

Southeast. Assoc. Game Fish Corom. 23:519-521.

McCONNELL, 1. H.

1954. The GulfCoast conch, Thais haemastoma. Proc. Natl. Shellfish. Assoc.

44:76-77.

McGRAW, K. A., and G. GUNTER.

1972. Observations on killing ofthe Virginia oyster by the Gulf oyster borer, Thais

haernastoma, with evidence for a paralytic secretion. Proc. Natl. Shellfish.

Assoc. 62:95-97.

McRITCHIE, R. G.

1968. Effects of thermal and osmotic acclimation on an estuarine gastropod.

Ph.D. Thesis, Rice University, Houston, TX, 71 p.

MEENAKSHI, V. R., P. E. HARE, and K. M. WILBUR.

1971. Amino acids ofthe organic matrix of neogastropod shells. Compo Biochem.

Physiol. B. Compo Biochem. 40(4):1037-1043.

MENZEL, R. W.

1955a. Some phases of the biology of Ostrea equestris Say and a comparison

with Crassostrea virginiea (Gmelin). Publ. Inst. Mar. Sci., Univ. Tex. 4:69-153.

1955b. Annotated check-list of the marine fauna of the St. George's SoundApalachee Bay region, Florida GulfCoast. Oceanogr. Inst. Florida State Univ.

Contrib. 61, 78 p.

MENZEL, R. w., and S. H. HOPKINS.

1954. Studies on oyster predators in Terrebonne Parish, Louisiana. Tex. A&M

Res. Found. Project 9, College Station, 155 p.

1956. Crabs as predators of oysters in Louisiana. Proc. Natl. Shellfish. Assoc.

46:177-184.

MENZEL, R. w., N. C. HULINGS, and R. R. HATHAWAY.

1958. Causes of depletion of oysters in St. Vincent Bar, Apalachicola Bay,

Florida. Proc. Natl. Shellfish. Assoc. 48:66-71.

1966. Oyster abundance in Apalachicola Bay, Florida, in relation to biotic associations influenced by salinity and other factors. Gulf Res. Rep. 2:73-96.

MENZEL, R. w., and F. E. NICHY.

1958. Studies of the distribution and feeding habits of some oyster predators

in Alligator Harbor, Florida. Bull. Mar. Sci. Gulf Caribb. 8:125-145.

MIR, G. N.

1971. Pharmacological investigations of some poisonous and venomous marine

animals of the Gulf of Mexico. Ph.D. Thesis, Univ. Miss., University, 110 p.

MOFFETT, A. W.

1975. The hydrography and macro-biota of the Chocolate Bayou estuary, Brazoria

County, Texas (1969-71). Tex. Parks Wildl. Dep. Tech. Ser. 14, 72 p.

MOORE, D. R.

1961. The marine and brackish water Mollusca of the State of Mississippi. Gulf

Res. Rep. 1:1-58.

MOORE, H. F.

1898. Some factors in the oyster problem. Bull. U.S. Fish Corom., 1897,

17:275-284.

1899. Report on the oyster beds of Louisiana. Rep. U.S. Comm. Fish., 1898,

24:45-100.

1907. Survey of oyster bottoms in Matagorda Bay, Texas. Rep. U.S. Comm. Fish.,

1905, Doc. 610, 86 p.

1913a. Condition and extent of the natural oyster beds and barren bottoms of

Mississippi Sound, Alabama. Rep. U.S. Comm. Fish., 1911, Doc. 769, 62 p.
1913b. Condition and extent of the natural oyster beds and barren bottoms of

Mississippi east of Biloxi. Rep. U.S. Comm. Fish., 1911, Doc. 774, 42 p.

MOORE, H. F., and E. DANGLADE.

1915. Condition and extent of the natural oyster beds and barren bottoms of Lavaca

Bay, Texas. Rep. U.S. Comm. Fish., 1914, Doc. 809. 45 p.

MOORE H. F., and T. E. B. POPE.

1910. Oyster culture experiments and investigations in Louisiana. Rep. U.S.

Comm. Fish., 1908, Doc, 731, 52 p.

MORRIS, P. A.

1956. A field guide to the shells of our Atlantic and Gulf coasts, 3d ed., W. 1.

Clench (editor). Houghton Mifflin Co., Boston, 236 p.

MORRISON, 1. P. E.

1943. Notes on the reproductive morphology of Thais. Nautilus 56(3):103-104.

O'HEERON, M. K., Jr.

1966. Some aspects of the ecology of Rangia cuneara (Gray). Masters Thesis,

Texas A&M Univ., College Station, 71 p.

PADGETT, H. R.

1960. The marine shellfisheries of Louisiana. Ph.D. Thesis, Louisiana State

University, Baton Rouge, 360 p.

PARKER, R. H.

1955. Changes in the invertebrate filuna, apparently attributable to salinity changes,

in the bays of central Texas. J. Paleontol. 29(2):193-211.

1956. Macro-invertebrate assemblages as indicators of sedimentary environments

in east Mississippi Delta region. Bull. Am. Assoc. Pet. Geol. 40:295-376.

PEARSE, A. S., and G. W. WHARTON.

1938. The oyster "leech" Sry/ochus inimicus Palombi, associated with oystcrs

on the coasts of Florida. Ecol. Monogr. 8:605-655.

PERRET, W. S.

1971. Cooperative Gulf of Mexico estuarine inventory and slUdy, Louisiana, Phase

IV, Biology Sect. I. La. Wildl. Fish. Comm., New Orleans, p. 29-105.

PERRY, L. M., and 1. S. SCHWENGLE.

1955. Marine shells of the western coast of Florida. Bull. Am. Paleontol.

26(96):1-318.

POLLARD, 1. F.

1973. Experimments to re-establish historical oyster seed grounds and to control

the southern oyster drill. La. Wildl. Fish. Comm. Tech. Bull. 6, 82 p.

POWELL, E. H., and G. GUNTER.

1968. Observations on the stone crab, Menippe mereenaria Say, in the vicinity

of Port Aransas, Texas. Gulf Res. Rep. 2:285-299.

PULLEY, T. E.

1952. An illustrated check list of the marine mollusks of Texas. Tex. 1. Sci.

4(2): 167-199.

RADWIN, G. E., and 1. L. CHAMBERLIN.

1973. Patterns of larval development in stenoglossan gastropods. Trans. San

Diego Soc. Nat. Hist. 17:107-117.

RADWIN, G. E., and H. W. WELLS.

1968. Comparative radular morphology and feeding habits of muricid gastropods

from the Gulf of Mexico. Bull. Mar. Sci. 18:72-85.

REHDER, H. A.

1954. Mollusks. U.S. Fish. Wildl. Serv., Fish. Bull. 55:469-474.

RIOS, E. C.

1m. Coastal Brazilian seashells. Fundaciio Cidade Rio Grande Mus. Oceanogr.

Rio Grande. XI, 82 p.

RITTER, H. P.

1896. Report of a reconnoissance of the oyster beds of Mobile Bay and Mississippi

Sound, Alabama. Bull. U.S. Fish Comm., 1895, 15:325-338.

ROCHA, D.

1948. Subsfdio para 0 estudo de fauna cearense. (Callilogo das especies animais

por mim coligidas e notadas). Rev. Inst. Ceara, Fortaleza 62:102-138.

RODRIGUEZ, G.

1963. The intertidal eslUarine communities in Maracaibo, Venezuela. Bull. Mar.

Sci. Gulf Caribb. 13:197-218.

ROSEGHINI, M., and M. FICHMAN.

1973. Choline esters and imidazole acids in extracts of the hypobranchial gland

of Thais haemaslOma. Compo Gen. Pharmacol. 4(15):251-257.

SCHECTER, V.

1943a. Tolerance of the snail 71IQis jloridana to waters of low salinity and the

effect of size. Ecology 24:493-499.

1943b. Two flatworms from the oyster-drilling snail Thais jloridana haysae

Clench. 1. Parisitol. 29:362.

SIELING, F. W.

1960. A notable range extension of the southern drill, Thai haemaslomajloridana,

into Chincoteague Bay. Chesapeake Sci. 1(3-4):212-215.

ST. AMANT, L. S.

1938. SlUdies on the biology of the Louisiana oyster drill, Thais jloridana haysae

Clench. Masters Thesis, Louisiana State Univ., Baton Rouge, 116 p.

9

1957. The southern oyster drill. In: Seventh Biennial Report, p. 81-84. La. Wildl.

Fish. Comm., New Orleans, LA.

STICKLE, W. B., and T. W. HOWEY.

1975. Effects of tidal fluclUations of salinity on hemolymph composition of the

southern oyster drill Thais haemaslOma. Mar. BioI. (NY) 33(4): 309-322.

STRECKER, 1. K.

1935. Notes on the marine shells of the Texas coast. Baylor Univ. Bull.

38(3):48-60.

SWIFT, F.

1898a. The oyster grounds of the west Florida coast: their extent, condition and

peculiarities. Bull. U.S. Fish. Comm. 17:285-296.

1898b. Report of a survey of the oyster regions of St. Vincent Sound, Apalachicola

Bay and St. George Sound, Florida. Rep. U.S. Comm. Fish., 1896,22:187-217.

SWINGLE, H. A.

1971. Biology of Alabama estuarine areas - cooperative Gulf of Mexico estuarine

inventory. Ala. Mar. Resour. Bull. 5, 123 p.

SYKES, 1. E., and 1. R. HALL.

1m. Comparative distribution of mollusks in dredged and undredged portions

of an estuary, with a systematic list of species. Fish. Bull., U.S. 68:299-306.

THORSON, G.

1950. Reproductive and larval ecology of marine bottom invertebrates. BioI. Rev.

Camb. Philos. Soc. 25:1-45.

TRYON, G. w., Jr.

1880. Manual of conchology, Vol. II, Muricinae, Purpuriniae. Published by

author, Phila., 289 p.

TUNNELL, 1. w., Jr., and A. H. CHANEY.

1m. A checklist of the mollusks of Seven and One-half Fathom Reef, northwestern Gulf of Mexico. Contrib. Mar. Sci. 15:193-203.

UROSA, L. 1.

1969. Identification of some predators of the mussel (Perna perna) under experimental conditions. FAO Fish. Rep. 71.1, 159 p.

VANATTA, E. G.

1903. A list of shells collected in western Florida and Hom Island, Mississippi. Proc. Acad. Nat. Sci. Phila. 55:756-759.

VAN SICKLE, V. R., B. B. BARRETT, T. B. FORD, and L. 1. GULICK.

1976. Barataria Basin: salinity changes and oyster distribution. La. Wildl. Fish.

Comm. Tech. Bull. 20, 22 p.

VILAS, C. N., and R. N. VILAS.

1952. Florida marine shells. Babbs-Merrill, Indianapolis, 170 p.

VIOSCA, P., Jr.

1938. Effect of Bonnet Carre Spillway on fisheries. La. Conserv. Rev. Winter

issue:51-53.

WALKER, 1. F.

1953. A check list of marine invertebrates collected at the Gulf Coast Research

Laboratory from 1947 through 1950. 1. Miss. Acad. Sci. 4:192-207.

WALKER, R. L., M. A. FLEETWOOD, and K. R. TENORE.

1980. The distribution of the hard clam Mercenaria mercenaria (Linne) and the

clam predators in Wassaw Sound, Georgia. Ga. Mar. Sci. Cen. Tech. Rep.

80-8, 59 p.

WARDLE, W. J.

1974. A survey of the occurrence, distribution and incidence of infection of

helminth parasites of marine and estuarine Mollusca from Galveston,

Texas. Ph.D. Thesis, Texas A&M Univ., College Station, 346 p.

WARMKE, G. L., and R. T. ABBOTT.

1961. Caribbean seashells. Livingston Publ., Narberth, PA., 346 p.

WELLS, H. W.

1958. Predation on pelecypods and gastropods by Fascia/aria hunteria

(Perry). Bull. Mar. Sci. Gulf Caribb. 8:152-166.

1961. The filuna of oyster beds, with special reference to the salinity filctor. Ecol.

Monogr. 31(3):239-266.

WELLS, H. w., and I. E. GRAY.

1960. Some oceanic sub-tidal oyster populations. Nautilus 73(4):139-147.

WHITTAKER, V. P.

1957. {3{3-Dimethylacrylycholine, a new naturally occurring, physiologically active ester of choline. Biochem. 1. 66:35.

1960. Pharmacologically active choline esters in marine gastropods. Ann. N.Y.

Acad. Sci. 90:695-705.

WHITTEN, H. L., H. F. ROSENE, and 1. W. HEDGPETH.

1950. The invertebrate fauna of Texas coast jetties; a preliminary survey. Publ.

Inst. Mar. Sci., Univ. Tex. 1(2):53-87.

YEN, T-C.

1942. A review of Chinese gastropods in the British Museum. Proc. Malac.

Soc. Lond. 24(V):J70-289.

ZINGMARK, R. G.

1978. An annotated checklist of the biota of the coastal zone of South Carolina.

Univ. S. Carolina Press, Columbia, 364 p.