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be


Page 6

Table 5. Prevalence of shell disease among Smithsonian Institu-

0
tion red crab specimens
60 Te moe
Severity Toms- TS eee
Rating © Hudson = Spencer Lindenkohl Scotia s0
3
1 9 0 4 0 i
Sw
2 7 0 4 0 *
» |
3 15 4 3 2
10
4 0 1 2 3
° 1 z 3 . 5
5 0 2 0 0 severly Reting
Totals 48 7 B 5 Figure 11. Shell disease prevalence and severity from Toms to
Spencer Canyon, 1884.
0 100
« load . 12 A
3 remote Sel aowseaoe
50 £ 70
5 ©
2 g *
2 x4 z
® 4
x» 4 ix
2»
° 10
° °
7 7 5 T H ove ee sen
Severity Reting Corepace wth (em)

Figure 9. Shell disease prevalence and severity in Hudson

Figure 12. Size-percent frequency distribution from Toms to

Canyon, 1884. Spencer Canyon, 1884.
10 50
ating
so 12 3 4 os vor
Sw Sac od Sremote
8
2 7
g © Ex
£ 3
:* u
z © Z 2
8 ®
g 8
g 24 0
10
° °
a 78 BOOT 7 i 3 H 3

Corapace Width (em)

Figure 10. Size-percent frequency distribution in Hudson Can-
yon, 1884.

Severity Rating

Figure 13. Shell disease prevalence and severity in Lindenkohl
Canyon.


NOAA Technical Memorandum NMFS-F/NEC-77

This TM series is used for documentation and timely communication of preliminary results,
interim reports, or special purpose information, and has not received complete formal review,
editorial control, or detailed editing.

Shell Disease among Red Crabs
Inhabiting Submarine Canyons
of the New York Bight

Randall R. Young
Waste Mgt. Inst, State Univ. of New York at Stony Brook, Stony Brook, NY 11794

U. S. DEPARTMENT OF COMMERCE
Robert A. Mosbacher, Secretary

National Oceanic and Atmospheric Administration
John A. Knauss, Administrator

National Marine Fisheries Service
James E. Douglas, Jr., Acting Assistant Administrator for Fisheries

Northeast Fisheries Center
Woods Hole, Massachusetts

December 1989




Page 2

into it (Rosen 1967) although Young and Pearce (1975)
found that epidermal tissues of American lobster speci-
mens were also necrotic. Regardless of the depth that the
original lesions attain, however, they may provide an entry
point for other organisms to invade the epidermal layer.

Many investigators have reported that the condition is
definitely contagious. Both Rosen (1970) and Fisher
(1988) have affirmed that shell disease is contagious among
lobsters (H. americanus and H. vulgaris), Gopalan and
Young (1975) demonstrated that it is communicable among
seven-spine bay shrimp (Crangon septemspinosa Say), and
Sindermann (1988) contended that it is infectious among
blue crabs.

Mortalities in adults due directly to shell disease are
infrequent (Rosen 1970; Fisher et al. 1978). Death may
occur in extremely diseased individuals at ecdysis resulting
from cohesion of the exoskeleton and the subskeleton at the
sites of infection. Melanization, occurring due to a normal
defensive response to block the progress of the infection,
causes the shell layers to bind together, sometimes trapping
the animal in its own exuvium. Infection of the gills may
also increase mortality by reducing the effective respira-
tory surface area. Furthermore, shell disease may indi-
rectly increase mortality by providing a portal of entry to
other pathogens.

MATERIALS AND METHODS

Samples were collected aboard the NOAA ship Alba-
tross IV on June 29 and 30, 1988, from the vicinities of three
submarine canyons (Figure 1) along the continental shelf
edge near the New York Bight. Table 1 gives the exact
sampling locations and depths. Thirty-minuté bottom
trawls were made at 2-2.5 knots (3.7-4.6 km/hr) using a 3/
4-size try-net apparatus. As many specimens as possible
were examined immediately upon capture for signs of shell
disease. A sketch of each animal was made, indicating the
affected areas of the body, and a disease severity rating was
assigned to each individual using the criteria listed in Table
2. The severity ratings range from one to five, with a “1”
indicating that no shell disease was visible to the naked eye,
and a “5” signifying a severely diseased individual. A zero
rating was not used to describe individuals lacking apparent
signs of shell disease because the initial stages of shell
disease are visible only through a microscope, and a zero
rating might give the erroneous impression that the animal
is absolutely free of any shell disease. Carapace width, sex,
and shell texture were also recorded. All crabs that could
not be inspected promptly were bagged and placed ina deep
freezer aboard ship for later examination. The total num-
bers of crabs examined from Hudson, Block, and Atlantis
Canyons were 202, 77, and 110, respectively.

Several diseased specimens from each collection site
were kept alive in fiberglass holding tanks for the duration
of the cruise. A separate, covered tank was maintained for

@ = Albatross IV samples

a = Smithsonian Institution samples

~ ff @ Allantis Canyon
Block 4
Canyon®@

Hudson ‘Hudson Canyon -
canyon - 1988 @' yon - 1884
Toms Canyon
NEW
YORK

* o6-mite site
BIGHT Lindenkohl Canyon

Spencer Canyon

Figure 1. Location map (darkened circles denote sites of Alba-
tross IV samples; darkened triangles denote sites of
Smithsonian Institution samples).

each site to eliminate transmission of pathogens among
members of different populations. To reduce stress to the
animals, the water was aerated and the temperature kept
between 15°and 20°C by floating sealed bags of ice on the


Table of Contents

Abstract...
Introduction
Scope of Project ...
Nature of Shell Disease
Materials and Methods ..
Results ....
Discussion
Appearance and Location of Disease
Symmetry of Shell Disease .
Molting and Size Considerations ..
Conclusion ....
Acknowledgements
References Cited ...

WOMIUNMNWNPEEE

List of Tables

Table 1. Trawl locations and depth ...

Table 2. Criteria for disease severity ratings .....

Table 3. Collection information for Smithsonian Institution specimens ..

Table 4. Prevalence of shell disease among red crabs from canyons adjacent to the
New York Bight--June 1988 .

Table 5. Prevalence of shell disease among Smithsonian Institution red crab specimens.

List of Figures

Figure 1, Location map ....
Figure 2. Size distribution of individuals from each canyon site ...
Figure 3. Shell disease prevalence and severity in Hudson Canyo
Figure 4. Size-percent frequency distribution in Hudson Canyon .
Figure 5. Shell disease prevalence and severity in Block Canyon .
Figure 6. Size-percent frequency distribution in Block Canyon
Figure 7. Shell disease prevalence and severity in Atlantis Canyon
Figure 8. Size-percent frequency distribution in Atlantis Canyon ..
Figure 9. Shell disease prevalence and severity in Hudson Canyon, 1884
Figure 10. Size-percent frequency distribution in Hudson Canyon, 1884 .
Figure 11. Shell disease prevalence and severity from Toms to Spencer Canyon, 1884 ..
Figure 12. Size-percent frequency distribution from Toms to Spencer Canyon, 1884
Figure 13. Shell disease prevalence and severity in Lindenkohl Canyon .
Figure 14. Size-percent frequency distribution in Lindenkoh! Canyot
Figure 15. Shell disease prevalence and severity from the Scotian Shelf .
Figure 16. Size-percent frequency distribution from the Scotian Shel!
Figure 17. Disease prevalence and severity among hard-shelled crab:
Figure 18. Disease prevalence and severity among soft-shelled crabs

MBAIAANDAAAUUUNADR HAN




(continued from inside front cover)

55. A Plan for Study: Response of the Habitat and Biota of the Inner New York Bight to Abatement of Sewage
Sludge Dumping. By Environmental Processes Division, Northeast Fisheries Center. June 1988. iii + 34 p., S figs.,
3 tables, 4 app. NTIS Access, No. PB89-100903/AS

56. Characterization of the Middle Atlantic Water Management Unit of the Northeast Regional Action Plan. By
Anthony L. Pacheco, ed. July 1988. v + 322 p., 136 figs., 21 tables. NTIS Access. No. PB89-145262/AS.

57. An Analysis and Evaluation of Ichthyoplankton Survey Data from the Northeast Continental Shelf
Ecosystem. By Wallace G. Smith, ed. August 1988. xiii + 132 p., 53 figs., 12 tables, 1 app. NTIS Access. No. PB89-
122501/AS.

58. An Indexed Bibliography of Northeast Fisheries Center Publications and Reports for 1987. By Jon A. Gibson.
August 1988. iii + 20 p. NTIS Access. No. PB89-113013/AS.

59. Surveys of Breeding Penguins and Other Seabirds in the South Shetland Islands, Antarctica, January-
February 1987. By W. David Shuford and Larry B. Spear. September 1988. vii + 27 p., 14 figs., 1 table. NTIS Access.
No. PB89-141311/AS.

60. Survey of Antarctic Fur Seals in the South Shetland Islands, Antarctica, during the 1986-1987 Austral
Summer. By John L. Bengtson, Lisa M. Ferm, Tero J. Harkonen, Everett G, Schaner, and Brent S. Stewart. September
1988. vii + 8 p., 1 fig., 3 tables. NTIS Access. No. PB89-141303/AS.

61. Fish as Sentinels of Environmental Health. By Robert A. Murchelano. September 1988. iii + 16 p., 4 figs. NTIS
Access. No. PB89-139737/AS.

62. The Effects of Density Dependent Population Mechanisms on Assessment Advice for the Northwest Atlantic
Mackerel Stock. By W. J. Overholtz, S.A. Murawski, W.L. Michaels, and L.M. Dery. October 1988. v + 49 p., 7 figs.,
20 tables. NTIS Access. No. PB89-151948/AS.

63. Status of the Fishery Resources Off the Northeastern United States for 1988. By Conservation and Utilization
Division. October 1988. iii + 135 p., 51 figs., 52 tables. NTIS Access. No. PB89-130819/AS.

64. The Shell Disease Syndrome in Marine Crustaceans. By Carl J. Sindermann. February 1989. v + 43 p., 5 figs.,
2 tables. NTIS Access, No. PB89-162523/AS.

65. Stock Assessment Information for Pollock, Pollachius virens (L.), in the Scotian Shelf, Georges Bank, and
Gulf of Maine Regions. By Ralph K. Mayo, Stephen H. Clark, and M. Christina Annand. April 1989, vi + 14 p., 6
figs., 14 tables. NTIS Access. No. PB90-120676/AS.

66. Guidelines for Estimating Lengths at Age for 18 Northwest Atlantic Finfish and Shellfish Species. By Judith
A. Pentilla, Gary A. Nelson, and John M. Burnett, III. May 1989. iii + 39 p., 18 figs., 19 tables.

67. Response of the Habitat and Biota of the Inner New York Bight to Abatement of Sewage Sludge Dumping.
Second Annual Progress Report -- 1988. By Environmental Processes Division, Northeast Fisheries Center. July
1989. vii + 47 p., 39 figs., 11 tables, 3 app. NTIS Access, No. PB90-160656/AS.

68. MARMAP Surveys of the Continental Shelf from Cape Hatteras, North Carolina, to Cape Sable, Nova Scotia
(1984-87). Atlas No. 3. Summary of Operations. By John D. Sibunka and Myron J. Silverman. July 1989. iv + 197
P., 36 figs., 2 tables. NTIS Access. No. PB90-125444/AS.

69. The 1988 Experimental Whiting Fishery: A NMFS/Industry Cooperative Program. By Frank P. Almeida,
Thurston S. Burns, and Sukwoo Chang. August 1989. v + 16 p., 9 figs., 11 tables, 1 app. NTIS Access. No. PB90-
160664/AS.


Page 1

ABSTRACT

issstady was undertaken to assess the extent and severity of shell disease among New York Bight deepsea red
crabs (Geryon quinquedens). The shell disease syndrome is a contagious condition which occurs among many
crustacean species and habitats, and is caused by a variety of chitinoclastic bacteria and fungi.

The severity of shell disease among red crab samples collected from ihrée Submarine canyons was assessed by
numerically rating each individual according to predetermined criteria~ Some live specimens were maintained in
aquaria aboard ship for subsequent bacterial culture experiments. Additional East Coast specimens dating back as far
as 1884 and maintained in the Smithsonian Institution crustacean collection were also examined and rated in the same
manner.

ras from the three canyons sampled, Hudson, Block, and Atlantis, had overall disease prevalences of 92, 92, and
86 percent, respectively. Of the Hudson Canyon specimens, 13 percent were rated as moderately to severely diseased:.
Thirty percent of the Block Canyon crabs and 19 percent of Atlantis Canyon crabs were moderately to severely diseased.
Disease prevalences among Smithsonian Institution specimens ranged from 69 to 100 percent. The shell disease among
the 1884 Hudson Canyon sample was significantly less severe than the modern samples.

>The appearance of the shell disease ranged from very small black spots to large grey to black patches covering a
substantial portion of the carapace... The disease was often found in a bilaterally symmetric arrangement Two expla-
nations are offered to explain how shell diseasé | might spread in this mafinét: (1) the protective epicuticle covering
corresponding body parts on each side of the animal are equally abraded by sediment, rocks, or other body parts,
exposing the chitinous layers beneath to chitinoclastic microorganisms; and (2) these mitroorganisms may gain access

to the underlying chitinous layers of the integument through pores which are arranged bilaterally. . - id

Affected animals can rid themselves of shell disease by molting. There seems to be a positive correlation between
animal size and disease severity.’ This may be because longer intermolt periods among older individuals allow more
time for chitinoclastic organisms to spread through the integument of their host.

INTRODUCTION
SCOPE OF PROJECT

Shellfishermen working the waters off the continental
shelf near the New York Bight have complained recently
that an unreasonably high percentage of their crab and
lobster catches was afflicted with shell disease which they
attribute to the disposal of municipal sewage sludge at the
106-Mile Dumpsite. The New York Bight, shown in Figure
1, is the area extending from Cape May, New Jersey, to
Montauk Point, Long Island, and seaward about 190 km to
the continental shelf break. This study was undertaken to
quantify the prevalence and severity of shell disease among
deepsea red crabs, Geryon quinquedens, inhabiting this
region and to begin a data base that can be used in further
study of this phenomenon in relation to ocean waste dis-

posal.

NATURE OF SHELL DISEASE

The condition has' been known variously as spot dis-
ease, burned spot disease, rust disease, or, most commonly,
shell disease. Rosen (1970) included an informative review
on the subject in his study. It is characterized by “a
Progressive chitinolysis and necrosis of the exoskeleton of
aquatic crustaceans.” Although no single organism has
been universally regarded as the causative agent, investiga-
tors have isolated a variety of chitinoclastic bacteria and

fungi in shell lesions of numerous crustacean species (Cook
and Lofton 1973; Fisher et al. 1978; Murchelano 1982).

That more than one agent causes shell disease is further
suggested by the fact that there are reports of the occurrence
of the malady in a wide variety of environments. It has been
found in habitats including bog ponds, lakes, rivers, estuar-
ies, and oceanic littorals, and in climatic conditions ranging
from ice-covered lakes in winter to semitropical estuaries
in summer (Rosen 1970). Furthermore, two independent
investigations have implicated the same three genera of
chitinoclastic bacteria in shell-diseased crustaceans. Cook
and Lofton (1973) isolated several species of bacteria
belonging to the genera Beneckea, Pseudomonas, and
Vibrio in lesions of Penaeus shrimp and blue crabs
(Callinectes sapidus). Malloy (1978) found the same
bacteria present among afflicted American lobsters (Ho-
marus americanus). It should be noted that the species
belonging to the genus Beneckea have since been included
in the genus Vibrio. Other bacterial isolates implicated as
being responsible for shell disease include those from the
genera Aeromonas, Spirillum, and Flavobacterium (Light-
ner 1988).

Chitinoclastic bacteria of this type are ubiquitous in the
marine environment. However, crustaceans are not de-
fenseless against attack. Their integument is composed of
four layers, only the bottom three of which are chitinous.
The topmost layer, the epicuticle, is made up largely of
lipoproteins rather than chitin (Warner 1977) and offers
some protection from these pathogens.

The syndrome is generally restricted to the exoskele-
ton only, and tends to spread parallel to the shell rather than


Shell Disease among Red Crabs

Inhabiting Submarine Canyons

of the New York Bight

U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Marine Fisheries Service
Northeast Fisheries Center
Woods Hole, Massachusetts

December 1989

1
{ReeRoDucED BY
i U.S. DEPARTMENT OF COMMERCE
NATIONAL TECHNICAL INFORMATION SERVICE
SPRINGFIELD, VA. 22161


Page 4

10 so
8 Site 2 wole
Soe See
ry em
30 BRB Bock
28 $04
3 3
3 7 2
x z x
as >
1.
| <4
: S N
°
°
severly Rating

Coropace Wicth (em)

Figure 2. Size distribution of individuals from each canyon site.

50

awe
© CS remot
je
»
‘ N

Hi 2 3 Hi H
Severity Rating

Figure 3. Shell disease prevalence and severity in Hudson

Canyon.
100
9 ating
. 12 3 4 os
go 4 aww oe
&
2 70
g 6
£90
F 6
2»
2
j »
w 4
ot
pe re oT >i

‘Corapace Width (em)

Figure 4, Size-percent frequency distribution in Hudson Canyon.

or “3”, 17 percent assigned a “4” rating, and 13 percent
given a “S” rating. All of the crabs rated moderately or
severely affected measured 9.0 cm wide or more. Bottom
temperature at this site was 6°C.

Ninety-one percent (100/110) of the Atlantis Canyon

Figure 5. Shell disease prevalence and severity in Block Canyon.

specimens showed signs of shell disease (Figures 7 and 8).
Seventy-two percent of the individuals received a “2” or
“3” rating, 15 percent a “4”, and 5 percent a “5” rating. Of
the Atlantis population that was moderately or severely
affected, 86 percent were 9.0 cm or larger. Bottom tem-
perature at Atlantis Canyon was 5°C.

Cultures of bacteria from the lesions of diseased crabs
resulted in the identification of several species (Bullis et al.
1988), including Vibrio aiginolyticus, V. campbellii, V.
fluvialis, Flavobacter meningosepticum, F. breve, and Es-
cherichia coli. Several fungi also isolated remain uniden-
tified. Attempts to promote chitinolytic or lipolytic activity
among these cultures have not been successful (Bullis,
personal communication).

The prevalence and severity of shell disease among the
Smithsonian Institution samples are presented in Table 5.
Eighty-one (39/48) percent of the 1884 Hudson Canyon
specimens showed at least some signs of shell disease.
However, none of the crabs was assigned a severity rating
greater than “3” (Figure 9). The 1884-Hudson Canyon crabs
were significantly less severely diseased (P <0.01) than
were the modern Hudson Canyon specimens. In general,
the disease severity increased with animal size (Figure 10).
Ninety-three percent of the individuals assigned a “3”
tating, the highest ascribed among this sample, were 9 cm
or larger.

The Toms-Spencer sample had a 100 percent disease
prevalence (7/7), with 57 percent slightly affected and 43
percent moderately to severely affected (Figure 11). The
size-frequency distribution for this sample is given in
Figure 12. All of the individuals in this sample had a
carapace width of 9 cm or greater.

Sixty-nine percent (9/13) of the Lindenkohl Canyon
specimens exhibited shell disease (Figure 13). Of these, 54
percent fell into either the very slightly or the slightly
affected categories. The other 15 percent were moderately
affected. Figure 14 displays the size-frequency distribution
for these specimens. All of the specimens rated moderately
affected were larger than 9 cm.


Table 1. Trawl locations and depth

Page 3

Table 2. Criteria for disease severity ratings

Average
Date Location Latitude Longitude Depth

(m)
6-29-88 Hudson Canyon 39°28’N 72°07’W_ 450
6-30-88 Block Canyon © 39°S4’N_71°19"W 542.
6-30-88 Atlantis Canyon 39°S8’N 70°14’W 640

water surface. These specimens were delivered to the
Marine Biological Laboratory in Woods Hole, Massachu-
setts, for pathological examinations and culture experi-
ments.

Because this initial cruise did not afford the opportu-
nity to collect samples from any other areas, additional
specimens from the crustacean collection at the Smith-
sonian Institution in Washington, D.C., were subsequently
examined. These specimens were inspected and rated in
the same manner as described above. Forty-eight speci-
mens collected near the Hudson Canyon (Figure 1) during
the summer of 1884 aboard the Albatross were examined.
Seven additional specimens collected from Toms Canyon
to Spencer Canyon aboard the same vessel in the autumn of
that year were also inspected. Two more recent small
samples were also included in the investigation. The first
of these was a sample of 13 collected in 1976 and 1977 near
the Lindenkohl Canyon. The other sample consisted of five
individuals caught south of Nova Scotia, Canada, in 1981
and 1985S, Information concerning the collection of these
specimens is contained in Table 3.

RESULTS

Although shell disease was present in each of the three
populations sampled from the canyons, most of the indi-
viduals were only slightly affected. Comparatively few
were moderately affected and fewer still showed signs of
advanced disease. Disease prevalences in these samples
are presented in Table 4 and the size distribution among the
three sites is illustrated in Figure 2.

At the Hudson Canyon site, 92 percent (185/202) of the
red crabs examined exhibited at least some degree of shell
disease. This is displayed graphically in Figure 3. Of these,
78 percent were very slightly or slightly affected, 8 percent
moderately affected, and 5 percent severely diseased. Of
the individuals assigned a disease severity rating of “4” or
“5,” 85 percent had a carapace width of 9.0 cm or greater.
Figure 4 indicates the percentage of individuals within
given size classes belonging to each assigned severity
rating. Bottom temperature near the Hudson Canyon
station was 12°C.

The prevalence at the Block Canyon location (Figures
Sand 6) was 92 percent (71/77), with 62 percent rated a “2”

Rating
Number

Disease

Severity Criteria

1 Imperceptible Absence of visible spots

2 Very slight <10 small spots or only
small light grey patches
3 Slight >10 small spots,

but <10% of body blackened
4 Moderate. Large areas affected,
10-50% of body

5 Severe Blackening over >50% of body;
or open lesions present; or old,
blackened amputation sites

Table 3. Collection information for Smithsonian Institution

specimens
Catalog Collection Location Average
Number Date Latitude Longitude Depth
(m)
Hudson Canyon
08000 7-23-1884  39°30’N TV°S0W 944
Toms Canyon-Spencer Canyon
14369 9-12-1884 38°36’N 73°06'W = 1152
14370 9-13-1884  39°09°N 72°03°W 1481
14371 9-13-1884 39°12’N 72°03"W 1292
Lindenkoh] Canyon
185424" 6-20-1976 38°55’N 73°00'W = 400
185433 9-12-1977
Scotian Shelf

Acc. No. 7-15-1981  42°50’N 63°S0’W = S50
364842 & 1-1985

Table 4. Prevalence of shell disease among red crabs from
canyons adjacent to the New York Bight -- June 1988

Severity Hudson Block Atlantis
Rating Canyon Canyon Canyon
1 7 6 10
2 oe 15 31
3 81 33 48
4 16 2B 16
5 11 10 5

Totals 202 77 110







instance, where the merus of the first walking leg comes
into contact with the cheliped, or where the merus of the
cheliped rubs against the subhepatic region of the carapace,
grey or black areas were often found. Less often, small
lesions were observed at the point on the cheliped propodus
where the carpus spur sometimes comes into contact.

Other examples of bilateral symmetry cannot be ex-
plained by abrasion of the epicuticle. Areas of the branchial
or hepatic regions, or the points along the edge of the
carapace, are often symmetrically blackened, but are not
continually in contact with the sea floor or other body parts.
Small spots are also common on the carapace where the
branchial lobe meets the cervical groove. All of these
examples suggest a second means of infection in addition
to the abrasion of the epicuticle. One possibility previously
discussed (Fisher et al. 1978) is that chitinolytic microor-
ganisms may invade the chitinous layers of the exoskeleton
through hypodermal ducts or setal pores.

Shell erosion was not, however, always bilaterally
symmetrical. The infection of some nonsymmetric areas of
the exoskeleton can easily be explained by abrasion or
partial crushing of the shell, thus allowing access to the
inner layers by chitinoclastic organisms. Other regions that
had been affected nonsymmetrically had either become
infected before their bilateral counterpart or the epicuticu-
lar defense was breached by another route. The chitinoclas-
tic microorganisms may gain access to the chitinous layers
with the aid of lipolytic bacteria. Non-chitinolytic bacteria
which exhibited lipolytic properties were consistently iso-
lated from shell lesions of the West Coast’s true Tanner
crab (Chionoecetes tanneri) (Fisher et al, 1978).

In general, bacterial genera isolated from the shell
lesions agreed with several previous studies in which Vibrio
and Flavobacter species were isolated. The‘ other species
identified, E. coli, was limited to only one specimen. As
this species does not thrive under marine conditions, its
presence is probably an anomaly that can be attributed to
the less than ideal sampling conditions aboard ship (Bullis,
personal communication).

These observations all lend support to the often raised
supposition that shell disease may be initiated by more than
one means and more than one pathogen (Rosen 1970;
Murchelano 1982; Malloy 1978; Lightner 1988).

MOLTING AND SIZE CONSIDERATIONS

Crustaceans suffering from shell disease may over-
come the affliction by achieving ecdysis, thus forming a
new, uninfected shell (McLeese 1965; Rosen 1970). A
comparison between hard-shelled (Figure 17) and soft-
shelled (Figure 18) Albatross IV specimens clearly demon-
strates the red crab’s ability to rid itself of a diseased
exoskeleton and start fresh with a new one. Nearly all of the
soft-shelled individuals examined were either totally free
of signs of shell disease or only very slightly affected, with
only a few small spots visible. The few exceptions were

Page 7

K Individuals within Each Size Closs

@ "6 corr tr
Corapace Wisth (cm)

Figure 14, Size-percent frequency distribution in Lindenkoh!

Canyon.
70
‘o woe
CS remate
so
z«
=
z 9
®
» 4
10
°
7 z 3 7 3
Severity Reting
Figure 15. Shell disease prevalence and severity from the Scotian
Shelf.
100
20
° ating
Be ys 2 3 4 os
o amen mm
£ 04
B
& 0
£0
3
3%
= 2»
®
10
°

o a8 e9 eto wont)?

Corapace Width (em)

Figure 16. Size-percent frequency distribution from the Scotian
Shelf.

almost all individuals which had suffered physical damage
to the new shell, such as a crushed or torn area, which
allowed entry of the disease-causing agents into the chiti-
nous layers of the shell. This is not surprising, as newly
molted individuals are vulnerable to damage without the
protection of a hardened shell.


ACKNOWLEDGEMENTS

I would like to thank Henry A. Walker of the U.S.
Environmental Protection Agency for making space avail-
able to me aboard the NOAA ship Albatross IV, Drs. Louis
Leibovitz and Robert Bullis of the Marine Biological
Laboratory for their helpful suggestions and culture work,
and the officers and crew of the Albatross IV for their
assistance and professionalism. I am especially thankful to
Mr. Manny Botelho for making a net at the Jast minute when
problems arose with the original. I would also like to
express my thanks to the National Marine Fisheries Service
for providing the ship for this endeavor.

I would like to thank Dr. Peter M. J. Woodhead for his
review of this manuscript and for providing freezer and lab
space and Dr. Sarah G. Horrigan for additional freezer
space. I am grateful to Drs. R.L. Swanson and Joel S.
O’Connor of the Waste Management Institute at the Marine
Sciences Research Center, and Drs. Joho B. Pearce and Carl
J. Sindermann of the National Marine Fisheries Service for
their critical reading of the manuscript and many valuable
suggestions.

I am grateful to Dr. Raymond Manning, Mr. Gary
Pettit, and the rest of the staff of the Smithsonian Institution
crustacean collection for their cooperation and assistance
in this endeavor, Also, though I never knew them, I would
like express my gratitude to the officers and crew of the R/
V Albatross for their part in this study.

Finally, I would like to thank the Waste Management
Institute and the Living Marine Resources Institute of the
Marine Sciences Research Center at the State University of
New York at Stony Brook for funding this project.

Page 9
REFERENCES CITED

Bullis, R., L. Leibovitz, L. Swanson, and R. Young. 1988.
Bacteriologic investigation of shell disease in the deep
sea red crab, Geryon quinquedens. Biol. Bull. 175:
304.

Cook, D.W., and S.R. Lofton. 1973. Chitinoclastic bacte-
tia associated with shell disease in Penaeus shrimp and
the blue crab (Callinectes sapidus). J. Wildl. Dis.
9:154-159.

Fisher, W.S., E.H. Nilson, J.F. Steenbergen, and D.V.
Lightner. 1978. Microbial diseases of cultured lob-
sters: a review. Aquaculture 14: 115-140.

Fisher, W.S. 1988. Shell disease of lobsters. Pages 236-239
in C.J. Sindermann and D.V. Lightner. eds. Disease
diagnosis and control in North American marine aq-
uaculture. Elsevier, New York.

Gopalan, U.K., and J.S. Young. 1975. Incidence of shell
disease in shrimp in the New York Bight. Mar. Pollut.
Bull. 6: 149-153.

Lightner, D.V. 1988. Bacterial shell (brown spot) disease
of penaeid shrimp. Pages 48-51 in C.J. Sindermann and
D.V. Lightner, eds. Disease diagnosis and control in
North American marine aquaculture. Elsevier, New
York.

Malloy, S.C. 1978. Bacteria induced shell disease of
lobsters (Homarus americanus). J. Wildl. Dis. 14: 2-
10. .

McLeese, D.W., and D.G. Wilder. 1964. Lobster storage
and shipment. Bull. Fish. Res. Bd. Can. 147.

McLeese, D.W. 1965. Lesions on the abdominal mem-
brane of lobsters. J. Fish. Res. Bd. Can. 22: 639-641.

Murchelano, R.A. 1982. Some pollution-associated dis-
eases and abnormalities of marine fishes and shell-
fishes: a perspective for the New York Bight. Pages
327-346 in G.F. Mayer, ed. Ecological stress and the
New York Bight: science and management. Estuarine
Research Federation, Columbia, S.C.

Rosen, B. 1967. Shell disease of the blue crab, Callinectes
sapidus. J. Invertebr. Pathol. 9: 348-353.

Rosen, B. 1970. Shell disease of aquatic crustaceans.
Pages 409-415 in S. Snieszko, ed. A symposium on
diseases of fishes and shellfishes. American Fisheries
Society, Bethesda, Md.

Sindermann, C.J, 1988, Shell disease of blue crabs. Pages
194-196 in C.J. Sindermann and D.V. Lightner, eds.
Disease diagnosis and control in North American
marine aquaculture. Elsevier, New York.

Warner, G.F. 1977. The biology of crabs. Van Nostrand
Reinhold Co., New York. 202 pp.

Young, J.S., and J.B. Pearce. 1975. Shell disease in crabs
and lobsters from New York Bight. Mar. Pollut. Bull.
6: 101-105.


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(continued on inside back cover)


At the Scotian Shelf site, 100 percent (5/5) of the crabs
examined exhibited signs of shell disease (Figures 15 and
16). All of the crabs examined were slightly to moderately
diseased.

DISCUSSION

APPEARANCE AND LOCATION
OF DISEASE

A wide variation in the extent and appearance of shell
disease was found among the red crab specimens examined.
Among the Albatross IV samples, the appearance ranged
from small black spots less than 1 mm in diameter to large
patches of grey or black areas covering most of the cara-
pace. Large grey to black patches were usually found in
either the hepatic regions or the branchial regions of the
carapace, but rarely in both. Scratches received from
brushes with predators or rocks were always blackened.
The points on the edge of the carapace as well as the spurs
on the carpi were also commonly affected areas. Walking
legs exhibited primarily small spots except at the joints,
where larger areas of necrosis commonly occurred. Also,
the sites of amputated legs seemed very susceptible to
infection, with the entire basis often reduced entirely to
very black necrotic tissue.

Contrary to earlier studies on blue crabs (Rosen 1967),
early stages of the disease are most easily observed on the
dorsal side of the red crab. The ventral side is only
occasionally affected, with. the most common occurrences
being grey patches on the sub-hepatic or sub-branchial
sections of the carapace and, less commonly, small black
necrotic lesions on the abdomen or outer maxilliped.

The appearance of the crab sample collected in 1884
near the Hudson Canyon differed from any other set exam-
ined. Sixty-eight percent of the crabs either exhibited no
visible sign of shell disease or were limited to only a few
small spots. Those that had more than 10 spots almost
always had them arranged in rows along the pores in their
walking legs. Only one male specimen exhibited any of the
patch-type blackening. Overall, this sample was by far the
least affected and may be an example of an essentially non-
impacted population.

The overall appearance of the other Smithsonian Insti-
tution specimens, including the second 1884 sample, re-
sembled those taken aboard the Albatross IV in the summer
of 1988,

SYMMETRY OF SHELL DISEASE

Very often, signs of shell erosion were found to be
bilaterally symmetrical. This can sometimes be explained
as regions receiving equal amounts of abrasion, thus equally
wearing away the epicuticle and allowing infection by

Page 5

90 Rating
12 3 4 os
80 mae

% Individusls Within Each Size Class

Pa a ee
Corapece width (em)

Figure 6. Size-percent frequency distribution in Block Canyon.

so
Dwoe
© 53 female
zx
3
:
= 2
me
w 4
Z
° h

H 2 3 H 3
Severity Rating

Figure 7. Shell disease prevalence and severity in Atlantis

Canyon.
100
so
7 ating
£ a oz 3 4 os
o mS sco a
£7
& «4
§ 9
=
5s «
2 » ff
2
®
10
°
a rr ne ta

Carapace wieth (em)

Figure 8. Size-percent frequency distribution in Atlantis Can-
yon.

chitinoclastic organisms. For example, necrosis of the shell
tissue is sometimes observed where the ventral side of the
coxae rub along the sea floor. More commonly, body parts
of the anima} itself which rub together were affected. For


20

% Individuals

2

Site YZ Site
so ESI Husson 50 ZZA Mudton
‘ OH Bek

SSS Atortis
rr
3

we
20
°
3 H >

Severity Roting

Figure 17. Disease prevalence and severity among hard-shelled
crabs.

There seems to be a direct correlation between animal
size and shell disease severity. Of the modern samples, the
Hudson Canyon population was comprised of the smallest
individuals on average, and also had the lowest mean
severity rating. Block Canyon, on the other hand, had the
highest percentage of larger individuals and also the highest
prevalence of “4” and “5” ratings. Upon examination of the
“3”-rated individuals in Figure 10, even the 1884 Hudson
Canyon reference specimens show a trend of increasing
disease severity among larger sized animals. This correla-
tion is probably related to molting, since the frequency of
molting decreases among larger individuals (Warner 1977).
Longer intermolt periods allow more time for the chitino-
clastic microorganisms to spread throughout the shell of
their host.

CONCLUSION

The occurrence of shell erosion among crustaceans has
been shown to be affected by many environmental factors.
High population density greatly enhances the spread of the
condition (McLeese and Wilder 1964; Rosen 1967). The
rate at which the disease progresses is dependent upon
temperature (Rosen 1970; Sindermann 1988); progression
below 1°-2°C being slow and above 4°-5°C more rapid. A
higher prevalence of shell disease has been shown to occur
in individuals fed an inadequate diet (Fisher et al. 1976).
Also, lobsters and crabs exposed in aquaria to sewage
sludge and dredge spoils by Young and Pearce (1975)
exhibited signs of shell disease. They also suggest that
fouling or low oxygen levels may contribute additional,
synergistic stresses to the animals. An overall degradation
of the environment may possibly furnish some common
chitinoclastic microorganisms the potential to become
pathogenic by reducing the abilities of crustaceans to ward
off infection (Rosen 1967; Young and Pearce 1975).

Itis not possible to ascertain from the data provided by
this study alone whether there is any connection between
the ocean disposal activities at the 106-Mile Dumpsite and
the incidence of shell disease among red crabs inhabiting

Severity Rating

Figure 18. Disease prevalence and severity among soft-shelled
crabs.

submarine canyons along the continental slope. Further
studies are needed to answer questions concerning preva-
lences of shell disease in red crabs from other areas, the
identification of the pathogens responsible for the disease,
population densities of the crabs, the degree of infectious-
ness of the syndrome, temperature trends and their implica-
tions, and sediment characteristics. Also, further analysis
of sewage sludge transport may determine whether any
sludge even reaches the submarine canyons northeast of the
106-Mile Dumpsite.

However, the prevailing presence of severe shell dis-
ease among individuals captured from other areas and times
suggests that the dumping of sewage sludge does not alone
promote the condition. While the 1884 autumn sample
collected from Toms Canyon to Spencer Canyon is unfor-
tunately small, it nevertheless indicates the presence of
shell disease near the vicinity of the present deep-water
dumpsite years before the dumping of sewage sludge was
initiated. The fact that these crabs were collected only a few
months after the 1884 Hudson Canyon specimens suggests
that either they were part of a separate population, that there
are distinct seasonal differences in the prevalence of the
disease, or that shell disease among red crabs may spread
rapidly under certain conditions. Furthermore, the more
recent specimens caught south of Nova Scotia indicate that
shell disease occurs in other, distant waters as well.

A better understanding of the cause or causes of shell
disease is essential. The disease may increase adult mortal-
ity enough to reduce the stock size, thus reducing the size
of crab landings. In addition, although the condition may
affect only the exoskeleton of crustaceans, leaving the
edible tissue completely safe to consume, it nevertheless
detracts from the visual appeal of the animal. Because
successful marketing of both crabs and lobsters is depend-
ent upon being able to visually attract buyers, there is the
potential for a severe economic impact on the shellfisheries
industry. Although red crabs are most commonly marketed
as a processed meat product rather than whole, consumers
may nonetheless tum away from them and other seafood
products that they perceive to be unsafe.