Bull. Tohoku Univ. Museum, No. 9, pp. 1–22, 2010
© by The Tohoku University Museum

A review of copepods associated with bivalves inJapan, with description of two new species (Crustacea,
Copepoda, Cyclopoida)
IL-HOI KIM1) and SHIN’ICHI SATO2)
1)

Department of Biology, Kangnung National University, Kangnung 210-702, Republic of Korea<ihkim@kangnung.ac.kr>
2)
The Tohoku University Museum, 6-3 Aoba, Aramaki, Aoba-ku, Sendai 980-8578, Japan<kurosato@mail.tains.tohoku.ac.jp>
Abstract. A taxonomical review is given for the copepods associated with bivalves from Japan. Two
new species Herrmannella macomae n. sp. associated with Macoma contabulata (Deshayes) andMyicola gamoensis n. sp. associated with Laternula (Exolaternula) marilina (Reeve) are describedfrom tidal flats in northern Japan. Herrmannella hiatellai Avdeev, H. longicaudata Avdeev, H.
longichaeta Avdeev, and H. soleni Kim and Ho are reported as new to Japan. H. longichaeta Avdeev
and Trochicola japonicus Shimura and Kuwabara are redescribed. Old scientific names of bivalve
hosts recorded previously are replaced to up-to-date ones.
Key words: Parasitic Copepoda, Cyclopoida, new species, new records, bivalves, Japan.

Introduction

Material and methods

Marine mollusks are well known as hosts of copepod
associates. Since Humes (1994) counted 431 species ofcopepods associated with mollusks, many more species
have been recorded. Among the mollusks, the class
Pelecypoda is the most preferred host taxon of the copepod
associates.
Although the marine bivalve fauna of Japan is well known,
knowledge of their copepod associates is quite insufficient(Kim et al., 2004). Mori (1935) probably is the first record inJapan of copepod associated with bivalves, who reported
Mytilicola orientalis as new species from Mytilus coruscus
Gould and Crassostrea gigas (Thunberg). More than 20
species of copepods associated with bivalves have since
been recorded from Japan. While the first author was visitingat the Tohoku University Museum for several months, theauthors made several field surveys to collect bivalves andtheir copepod parasites from tidal flats. The present reportdeals with the result of these surveys, with a review ofpreviously known copepod parasites of Japanese bivalves.
We believe that many more species of bivalve-parasitic
copepod are yet to be found and described from Japan. We
hope that this report will be helpful to marine biologists instudying this group of copepods.

Copepod specimens examined in this work were collected
in 2008 from bivalves caught mainly from several tidal flatsin Japan. On the tidal flats the bivalves were dug out with ashovel and collected in plastic bags, with different species
being placed in different bags and subsequently being fixed inalcohol. Some bivalves were also bought from fish markets
located near the tidal flats and examined for copepods.
Each bivalve was opened and washed, and the washings
were filtered through fine mesh net. The copepods were
picked from the sediments under a dissecting microscopeat a low magnification. Before microscopic observation anddissection, copepod specimens were immersed in lactic acidfor about an hour. Dissections were done using the reversed
slide method (Humes and Gooding, 1964). All drawings weremade with the aid of a camera lucida. In the formula for thearmature of legs 1-4 Roman numerals indicate spines andArabic numerals represent setae. The type specimens of
the new species described in the present paper have been
deposited in the Tohoku University Museum.

Systematic accountFamily Anthessiidae Humes, 1986
Genus Anthessius Della Valle, 1880

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IL-HOI KIM and SHIN'ICHI SATO

Anthessius graciliunguis Do and Kajihara, 1984
Previous record in Japan: From Mytilus galloprovincialis
Lamarck (as M. edulis galloprovincialis) at Himeji Harbor,
Hyogo Prefecture (Do and Kajihara, 1984); from plankton
samples collected in Miike Harbor, Ohmuta, Ariake Bay(Ueda et al., 2006).
Remarks. This species is also known from Korea as aparasite of the bivalves Patinopecten (Mizuchopecten)
yessoensis (Jay), Pecten (Notovola) albicans albicans(Schröter) (as P. albicans), Chlamys squamata (Gmelin) and
Solecurtus divaricatus (Lischke) (Kim, 1998, 2004). Ueda
et al. (2006) reported from plankton samples collected in
Ariake Bay and claimed that the specimens reported fromscallops in Korea belong to a different species becauseof differences in the caudal setae and ornamentation of
the male maxilliped. A careful examining of the Korean
specimens is needed to confirm the contention of Ueda etal.

Anthessius pectinis Tanaka, 1961

Previous record in Japan: From Pecten (Notovola) albicans
albicans (Schröter) (as Pecten laqueatus Sowerby) at
Sasebo Bay (type locality), Nagasaki Prefecture (Tanaka,1961); from Pecten (Notovola) albicans albicans at Sasebo
Bay (Ko et al., 1962).
Remarks. This species needs to be redescribed to make a
distinction between it and A. graciliunguis both recorded as
parasites of Pecten (Notovola) albicans albicans.
Family Clausidiidae Embleton, 1901
Genus Conchyliurus Bocquet and Stock, 1957

Conchyliurus quintus Tanaka, 1961
Previous records in Japan: From Paphia undulata (Born)
and Ruditapes philippinarum (Adams and Reeve) (asTapes japonica) at Sakibe (type locality) near Sasebo,
Nagasaki Prefecture (Tanaka, 1961); from Merisca (Pistris)
capsoides (Lamarck) (as Arcopagia diaphana) and Cyclina
sinensis (Gmelin) at Hiroshima (Ko et al., 1962); from
Ruditpaes philippinarum (as Tapes japonica) and Caecellachinensis Deshayes at Sasebo Bay (Ko et al., 1962); fromMactra veneriformis Reeve, Meretrix lusoria (Röding), andSinonovacula constricta (Lamarck) at Ariake Bay (Ko et al.,1962); from Nuttallia japonica (Deshayes) (as Soletellina
olivacea) at Hakata Bay (Ko et al., 1962); from Ruditapes
philippinarum (Adams and Reeve) (as Tapes philippinarum)
at Sasebo Bay (Ko et al., 1962; Ko, 1969c) and Nagasaki
City (Yoshikoshi and Ko, 1974).

Material examined. Four ♀♀ from 3 Macoma contabulata(Deshayes), west coast of Hiroura, Natori City, Miyagi
Prefecture, collected by S. Sato, 22 May 2008; 6 ♀♀
from 8 Nuttallia japonica (Deshayes), Uno-o, Souma City,
Fukushima Prefecture (Matsukawa-ura), collected by S.
Sato, 4 June 2008; 2 ♀♀ from 7 Nuttallia japonica, Gamo,
Sendai City, Miyagi Prefecture, collected by S. Sato, 23
May 2008; 8 ♀♀ 8 ♂♂ from more than 30 Nuttallia japonica,
Gamo, Sendai City, Miyagi Prefecture, collected by I.-H.
Kim, 13 Oct. 2008; 2 ♂♂, 8 copepodids from 36 Macoma
contabulata, Ashizaki, Mutsu City, Aomori Prefecture (Mutsu
Bay), collected by I.-H. Kim, 26 October 2008; 1 ♀, 1
copepodid from 3 Cyclina sinensis (Gmelin), Ashizaki, City,
Aomori Prefecture (Mutsu Bay), collected by S. Sato, 26
October 2008; 4 ♀♀, 1 ♂ from 30 Ruditapes philippinarum(Adams and Reeve), Kojiro, Shimabara City, Nagasaki
Prefecture, collected by S. Sato, 22 November 2008;14 ♀♀, 2 ♂♂ from 6 Mactra veneriformis Reeve, Kojiro,
Shimabara City, Nagasaki Prefecture, collected by S. Sato,
22 November 2008; 14 ♀♀, 19 ♂♂, and 21 copepodids fromTrapezium liratum (Reeve), mouth of Rokkaku River, Ogi
City, Saga Prefecture, collected by I.-H. Kim, 23 November
2008; 1 copepodid V from 5 Ruditapes philippinarum,
Minami-Arao, Arao City, Kumamoto Prefecture, collected by
S. Sato, 24 November 2008; 3 ♀♀, 1 ♂, and 4 copepodids,
from 13 Mactra veneriformis, Minami-Arao, Arao City,
Kumamoto Prefecture, collected by S. Sato, 24 November
2008;
Remarks. Kim (2004) reported 12 species of bivalves from
Korea as hosts of this species of copepod. Three speciesof bivalves are herein added newly as hosts: Macoma
contabulata (Deshayes), Nuttallia japonica (Deshayes), andTrapezium liratum (Reeve). Therefore, a total of 15 bivalve
species are known to be hosts of C. quintus.
Genus Hyphalion Humes, 1987

Hyphalion sagamiense Toda, Miura and Nemoto,
1992
Previous record in Japan: From Calyptogena soyoae
Okutani at a cold seep in the depth of 1170 m in Sagami Bay(Toda et al., 1992)
Family Lichomolgidae Kossmann, 1877
Genus Herrmannella Canu, 1891

Herrmannella macomae n. sp. (Figs. 1-3)
Material examined. Seven ♀♀ and 4 ♂♂ collected fromwashings of 15 Macoma contabulata (Deshayes), Ashizaki(41°15′02.3″N, 141°09′18.1″E) (Mutsu Bay), Mutsu City,

Copepods associated with bivalves in Japan
Aomori Prefecture, collected by S. Sato, 11 May 2008.
Holotype (♀, TUMC-85726), allotype (♂, TUMC-85727), andparatypes (3 ♀♀, 1 ♂, TUMC-85728) have been depositedin the Tohoku University Museum.
Female. Body (Fig. 1A) slender and 1.55 mm (1. 48-1.74mm) long, excluding caudal setae, based on 6 specimens.
Dissected specimen 1.66 mm long. Maximum width 414µm. Cephalosome demarcated from first pedigerous
somite by dorsal furrow, 293×414 μm. Urosome (Fig. 1B)
5-segmented, longer than prosome. Fifth pedigerous somite
160 μm wide. Genital double-somite distinctly longer thanwide, 316×182 μm, slightly broadened at portion anterior
to genital area. Genital area large and located dorsallyin position slightly anterior to midlength of somite. Threeabdominal somites longer than wide, 126×102, 105×83, and100×71 µm, respectively. Caudal ramus (Fig. 1C) 140×29
μm, 4.83 times as long as wide, armed with 1 minute outerproximal setule, 1 seta at place slightly anterior to midlengthof outer margin, 1 dorsodistal seta, 1 outer distal seta, and3 terminal setae; terminal margin ornamented with row offine spinules; all caudal setae smooth. Egg sac (Fig. 1D) 511
×195 µm.
Rostrum beak-like and extending to first segement ofantenna (Fig. 1E). Antennule (Fig. 1F) 254 µm long and7-segmented; armature formula 4, 13, 6, 3, 4+aesthetasc,
2+aesthetasc, and 7+aesthetasc; fourth segment thickened
subdistally; all setae smooth except for some setae on
3 distal segments. Antenna (Fig. 1G) 4-segmented, witharmature formula 1, 1, 3, and 4+claw; second segment
ornamented with small spinules on outer margin andproximal portion of inner margin; terminal claw massive andstrongly curved distally; terminal segment about 38×27 μm.
Labrum (Fig. 1H) short and broad, with wide medianincision; posterior lobes divergent. Mandible (Fig. 2A)
with shallow inner proximal notch; distal lash slender andelongate, with 1 row of spinules on both inner and outer(convex) margins and 1 subsidiary row of spinules on
proximal half of outer margin. Maxillule (Fig. 2B) armed
with 1 lateral setiform process and 2 apical pinnate setaeof unequal lengths. Maxilla (Fig. 2C) 2-segmented; robust
proximal segment (syncoxa) armed with minute spinules;
distal segment (allobasis) with weakly plumose anterior
seta (seta II), large inner seta (seta I) armed densely with
spinules on outer margin; distal lash heavily armed with
spinules. Maxilliped (Fig. 2D) 3-segmented; first segment
unarmed; second segment with 2 small, similar setae
subdistally; terminal segment small, terminated by nippleshaped knob, with 1 small subdistal seta.
Legs 1-4 with 3-segmented exopod and endopod. Legs
1-3 with row of spinules on posterior margin of basis (Fig.
2E, F). Outer seta on basis and inner seta on coxa of legs
1-4 plumose (Fig. 2E-G). Armature formula of legs 1-4 asfollows:
Leg 1: c oxa 0-1; basis 1-0; exp.
I-0; I-1; III,I,4;enp. 0-1; 0-1; I,2,3
Legs 2 & 3: coxa 0-1; basis 1-0; exp. I-0; I-1; III,I,5;
enp. 0-1; 0-2; II,I,3
Leg 4: coxa 0-1; basis 1-0; exp. I-0; I-1; II,I,5;
enp. 0-1; 0-1; II
Third endopodal segment of leg 4 (Fig. 2H) 62×22 μm, withsmall subdistal cusp on outer margin; two distal spines on
this segment 56 (outer) and 81 μm (inner).
Leg 5 represented by free segment and 1 small, naked
dorsal seta on fifth pedigerous somite; free segment (Fig. 2I)
41×24 μm, armed with smooth inner spine (75 μm long) andsmooth outer seta (41 μm). Leg 6 represented by 1 small
seta in genital area (Fig. 1B).
Male. Body (Fig. 3A) slender as in female. Body length ofdissected specimen 1.32 mm (other 2 specimens 1.28 and1.30 mm, respectively). Maximum width 346 µm acrosscephalothorax. Urosome (Fig. 3B) 6-segemented. Fifthpedigerous somite 117 μm wide. Genital somite 195×205
μm and anteriorly tapering; genital flap ornamented with 2
rows of small spinules (Fig. 3B). Four abdominal somites 94
×103, 96×88, 79×73, and 73×60 μm, respectively. Caudal
ramus 111×24 μm (ratio 4.63+1), with 6 setae.
Antennule different from that of female in bearing 3
additional aesthetascs, 2 on second and 1 on fourth
segments. Antenna (Fig. 3C) with scales on proximal half of
inner margin of second segment; third segment with 4 setae;
fourth segment with claw and 5 setae, two of latters being
bifurcated at tip.
Labrum, mandible, maxillule, and maxilla as in female.
Maxilliped (Fig. 3D) 4-segmented; first segment (syncoxa)
broadest but unarmed; second segment (basis) with pair ofsmall inner setae and longitudinal row of minute spinules onlateral surface; small third segment unarmed; fourth segment
forming long claw bearing 2 unequal setae proximally.
Leg 1 with pronounced inner distal process on terminal
segment of endopod (Fig. 3E). Legs 2-4 as in female. Free
segment of leg 5 (Fig. 3F) small, 26×13 μm (ratio 2.0+1),
armed with spear-shaped spine (34 μm) and simple seta (42μm), both elements naked. Leg 6 represented by 2 small
setae and 1 minute cusp on distal part of genital flap (Fig.
3B).
Etymology. The specific name of the new species
macomae is derived from the generic name of the bivalve
host Macoma.
Remarks. In the revision of the lichomolgid copepods,
Humes and Stock (1973) included 16 species in the key ofthe genus Herrmannella, including H. perplexa (Illg, 1949)

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IL-HOI KIM and SHIN'ICHI SATO

Fig. 1. Herrmannella macomae n. sp., female. A, habitus, dorsal; B, urosome, dorsal; C, caudal
rami, dorsal; D, egg sac; E, rostral area, ventral; F, antennule; G, antenna; H, labrum. Scales: A, D, 0.2mm; B, 0.1 mm; C, E, F, 0.05 mm; G, H, 0.02 mm.

Copepods associated with bivalves in Japan

Fig. 2. Herrmannella macomae n. sp., female. A, mandible; B, maxillule; C, maxilla; D, maxilliped; E,
leg 1; F, leg 2; G, leg 4; H, third endopodal segment of leg 4; I, free segment of leg 5. Scales: A-D, I, 0.02mm; E-H, 0.05 mm.

IL-HOI KIM and SHIN'ICHI SATO

Fig. 3. Herrmannella macomae n. sp., male. A, habitus, dorsal; B, urosome, ventral; C, antenna; D,maxilliped; E, endopod of leg 1; F, free segment of leg 5. Scales: A, 0.2 mm; B, 0.1 mm; C-F, 0.02 mm.

Copepods associated with bivalves in Japanand H. protothacae (Humes, 1967) both omitted in their
species list. Since then nine more species have been addedin the genus: H. longicaudata Avdeev, 1975; H. longichaeta
Avdeev, 1975; H. hiatellai Avdeev, 1975; H. dentata Avdeev,
1987; H. soleni Kim and Ho, 1991; H. duggani Holmes andMinchin, 1991; H. hoonsooi Kim, 1992; H. exigua Kim, 1993;
and H. kodiakensis Humes, 1995. Therefore, a total of 25
species are comparable with H. macomae n. sp.
The known species of Herrmannella may be grouped by
the following diagnostic features:
1) The third exopodal segment of leg 4 bears four spinesand five setae (armature formula III, I, 5, rather than II, I, 5):
H. caribaea (Humes, 1970), H. dentata, and H. dissidens(Humes, 1970).
2) The rostrum is simple, without beak-like process(es): H.
bullata Humes and Stock, 1973, H. inflatipes (Humes andCressey, 1958), H. perplexa, H. mesodesmatis (Humes,1967), H. duggani, H. protothacae, and H. kodiakensis.
3) T he free segment of leg 5 female bears a prominentproximal swelling: H. bullata, H. inflatipes, H. longicaudta,
H. perplexa, H. saxidomi (Illg, 1949), H. soleni, and H.
kodiakensis.
4) T he free segment of female leg 5 is armed with one
compound (serrate) spine and one seta: H. barneae(Pelseneer, 1929), H. inflatipes, H. mesodesmatis, H.
duggani, H. protothacae, H. haploceras (Bocquet andStock, 1959), H. hiatellai, H. pecteni (Sowinski, 1884),
and H. rostrata Canu, 1881.
Seven species of Herrmannella and H. macomae n. sp. do
not exhibit any of the above characteristics. H. macomae
can be distinguished from these seven species by thefollowing diagnostic features of its seven congeners.
In H. columbiae (Thompson, 1897) the proximal four
segments of antennules are markedly swollen, about threetimes thicker than the distal three segments and the antenna
and the free segment of female leg 5 are much more slenderthan those of H. macomae.
In H. exigua the caudal ramus is more than six times
longer than wide (4.83 times in H. macomae) and the third
endopodal segment of leg 4 bears two pointed processes onouter margin (one process in H. macomae).
In H. hoonsooi the prosome is broad and the margins of
cephalothorax and the anterior margin of antennules arecovered with a hyaline material.
In H. longichaeta which is redescribed in the following,
there is a claw on ventral surface posterior to the insertion ofantennules and the third endopodal segment of leg 4 bears
two pointed processes on outer margin.
In H. panopeae (Illg, 1949) the caudal ramus is about
seven times as long as wide and the third endopodalsegment of leg 4 bears three spines.
In H. tivelae (Illg, 1949) the caudal ramus is 7.9 times
longer than wide (Humes and Stock, 1973) and the antenna
is slender, with its second segment being about four times
as long as wide, according to Fig. 20g of Humes andStock (1973) (less than three times as long as wide in H.
macomae).
In H. valida Sars, 1918 the caudal ramus is relatively short,less than twice as long as wide and the third endopodal
segment of leg 4 bears no process on the outer margin,according to the illustrations of Sars (1918).

Herrmannella hiatellai Avdeev, 1975
Material examined. One ♀ from washings of 1 Panopea
japonica A. Adams bought at a fish market in Yanagawa City,
Fukuoka Prefecture, collected by I.-H. Kim, 23 November
2008.
Remarks. This species is new to Japan. The type host of
this copepod is Hiatella orientalis (Yokoyama) (as Hiatella
artica orientalis) reported from the Peter the Great Bay
in Russia (Avdeev, 1975). Kim (1998) also reported thiscopepod from Panopea japonica A. Adams on the Korean
coast of the Sea of Japan. As we collected this copepod
species in Ariake Bay, off Yanagawa City in Kyushu, it turned
out to be a species having a wide distribution from theSiberian coast to the west coast of Kyushu, Japan.

Herrmannella longicaudata Avdeev, 1975
Material examined. Four ♀♀ from 2 Chlamys(Azumapecten) farreri farreri (Jones and Preston), Ashizaki(Mutsu Bay), Mutsu City, Aomori Prefecture, collected by S.
Sato, 11 May 2008.
Remarks. Avdeev (1975) recorded originally this species
from Patinopecten (Mizuchopecten) yessoensis (Jay) (asMizuchopecten yessoensis) in the Russian coast of the Sea
of Japan. Ho and Kim (1991) and Kim (1998) reported thisspecies from Korea as a parasite of P. yessoensis, Chlamys
swifti (Bernardi) and C. squamata (Gmelin). H. longicaudata
is new to Japan and easily distinguishable by the elongate
urosome and the possession of several foliaceous setae on
the antennule.

Herrmannella longichaeta Avdeev, 1975
(Figs. 4, 5)Material examined. One ♀ and 874 copepodids (copepodid
III or IV stages) collected from one of 3 Spisula sachalinensis(Schrenck) bought at the Aomori fish market by I.-H. Kim, 27

IL-HOI KIM and SHIN'ICHI SATO

Fig. 4. Herrmannella longichaeta Avdeev, female. A, habitus, dorsal; B, urosome, dorsal; C, leftcaudal ramus, ventral; D, rostral area, ventral; E, rostrum, lateral; F, antennule; G, antenna; H, labrum; I,
mandible; J, maxillule. Scales: A, 0.2 mm; B, 0.1 mm; C-H, 0.05 mm; I, J, 0.02 mm.

Copepods associated with bivalves in Japan

Fig. 5. Herrmannella longichaeta Avdeev, female. A, maxilla; B, maxilliped; C, leg 1; D, leg 2; E,
third endopodal segment of leg 3; F, leg 4; G, free segment of leg 5. Scales: A, B, 0.02 mm; C-G, 0.05mm.

October 2008.
Female. Body (Fig. 4A) narrow. Body length 1.43mm, excluding caudal setae. Maximum width 414 μm.
Cephalosome 316 μm long, sub-triangular and clearly
demarcated from first pedigerous somite by dorsal furrow.
Urosome (Fig. 4B) 5-segmented, slightly shorter thanprosome. Fifth pedigerous somite 160 μm wide. Genital
double-somite distinctly longer than wide, 218×141 μm,
broadest across region of genital areas and gradually
narrowed posteriorly. Genital area large and locateddorsolaterally in position slightly anterior to midlength ofsomite. Three abdominal somites longer than wide, 94×
81, 71×68, and 75×60 µm, respectively. Caudal ramus (Fig.
4C) 128×25 μm, 5.12 times as long as wide, armed with 1
minute outer proximal setule, 1 seta at midlength of outermargin, 1 dorsodistal seta, and 4 terminal setae; terminal
margin ornamented with row of fine spinules; all caudal
setae smooth. Egg sac not seen.
Rostrum beak-like and extending to insertion of antenna(Fig. 4D, E). Antennule (Fig. 4F) 280 µm long and10

IL-HOI KIM and SHIN'ICHI SATO

7-segmented, but with incomplete segmentation between
third and fourth segments; armature formula 4, 13, 6, 3,
4+aesthetasc, 2+aesthetasc, and 7+aesthetasc; all setaesmooth except for some setae on 3 distal segments.
Postantennular hook locating between insertions ofantennule and antenna (Fig. 4D, E). Antenna (Fig. 4G)
4-segmented, with armature formula 1, 1, 3, and 5+claw;
second segment ornamented with small spinules on outermargin; fourth segment short, 41 μm long (average lengthof outer and inner margins) and 35 μm wide; terminal claw
massive; 2 of setae on terminal segment claw-like, weakly
bifurcate at tip.
Labrum (Fig. 4H) with rounded lobes and broad medianincision. Mandible (Fig. 4I) with shallow inner proximal notch;
distal lash slender and elongate, with row of spinules on bothmargins. Maxillule (Fig. 4J) armed with 1 lateral setiform
process and 2 apical setae of unequal lengths. Maxilla (Fig.
5A) 2-segmented; robust proximal segment ornamented
with 2 patches of minute spinules; distal segment withanterior seta (seta II) and inner seta (seta I), but proximal
seta lacking; distal lash elongate and armed with spinules on
proximal half of outer (convex) margin. Maxilliped (Fig. 5B)
3-segmented; first segment unarmed; second segment with
2 small setae subdistally; terminal segment small and blunt,
distally with 1 small seta and 1 minute spinule.
Legs 1-4 with 3-segmented exopod and endopod. Legs 1-3
with row of spinules on posterior margin of basis (Fig. 5C, D).
Armature formula of legs 1-4 as follows:
Leg 1: coxa 0-1; basis 1-0; exp. I-0; I-1; III,I,4;enp. 0-1; 0-1; I,2,3
Legs 2 & 3: coxa 0-1; basis 1-0; exp. I-0; I-1; III,I,5;
enp. 0-1; 0-2; I,II,3
Leg 4: coxa 0-1; basis 1-0; exp. I-0; I-1; II,I,5;
enp. 0-1; 0-1; II
Third endopodal segment of leg 4 (Fig. 5F) 52×23 μm, with
2 cusps on outer margin; two distal spines on this segment
63 (outer) and 84 μm (inner).
Leg 5 consisting of free segment and 1 small, naked dorsal
seta on fifth pedigerous somite (Fig. 4B); free segment(Fig. 5G) 66×22 μm (ratio 3.0 : 1), with smooth margins andarmed with spiniform inner seta (90 μm) and simple outerseta (67 μm). Leg 6 represented by 1 small seta in genitalarea (Fig. 4B).
Male. Not found in our collection.
Remarks. This species is new to Japan. Avdeev (1975)
originally recorded this species from the bivalves Mactrachinensis Philippi and Spisula sachalinensis (Schrenck)in the Russian coast of the Sea of Japan. Because hebriefly described and illustrated this species, the above
redescription may be helpful to understand the species
in detail. The most significant diagnostic features of thisspecies probably are the possession of the postantennular
hook between insertions of the antennule and antenna anda pair of cusp-like processes on the outer margin of the third
endopodal segment of leg 4. It is noted that the Avdeev’s
female specimens were 1.12-1.21 mm in lengths, but oursingle female was measured as 1.43 mm long.
Our finding of a single adult female with a vast number ofcopepodid larvae (874 individuals) of similar developmental
stages from one of 3 samples of the bivalve Spisulasachalinensis may inform the following interesting
phenomena: 1) the copepodid larvae are of a same litter; 2)
the adult female is the mother of the larvae; 3) and the adultfemale did a parental care for her offsprings.

Herrmannella soleni Kim and Ho, 1991
Material examined. One ♀, 1 ♂ from 13 Mactra veneriformis
Reeve, Minami-Arao, Arao City, Kumamoto Prefecture,collected by S. Sato, 24 November 2008; 1♀ from 6 Mactra
veneriformis, Kojiro, Shimabara City, Nagasaki Prefecture,collected by S. Sato, 22 November 2008.
Remarks: This species is a new record of Japan. In
addition to the above bivalve, three other bivalve species
Solen grandis Dunker, S. strictus Gould and Solecurtus
divaricatus (Lischke) were reported in Korea as hosts of thiscopepod (Kim and Ho, 1991; Kim, 2004).
Genus Lichomolgus Thorell, 1860

Lichomolgus bidentipes Ho, 1980
Previous records in Japan: From Septifer virgatus(Wiegmann) at Sirahama, Wakayama Prefecture (Ho, 1980);
from Mytilus galloprovincialis Lamarck (as Mytilus edulis
galloprovincialis) from Omura Bay, Nagasaki Prefecture (Doand Kajihara, 1986b).
Material examined. One ♀, 1 copepodid V female from
1 Modiolus metcalfei (Hanley), Kojiro, Shimabara City,
Nagasaki Prefecture, collected by S. Sato, 22 November
2008; 24 ♀♀, 65 ♂♂ from 30 Ruditapes philippinarum(Adams and Reeve), Kojiro, Shimabara City, Nagasaki
Prefecture, collected by S. Sato, 22 November 2008; 1 ♂
from 4 Corbicula japonica Prime, mouth of Okinohata River,Yanagawa City, Fukuoka Prefecture, collected by S. Sato,
23 November 2008; 1 ♀, 2 ♂♂, and 2 copepodid V from 5
Ruditapes philippinarum, Minami-Arao, Arao City, Kumamoto
Prefecture, collected by S. Sato, 24 November 2008; 3 ♀♀,3 ♂♂ from 13 Mactra veneriformis, Minami-Arao, Arao City,

Copepods associated with bivalves in Japan
Kumamoto Prefecture, collected by S. Sato, 24 November
2008; 15 ♀♀, 8 ♂♂ from 25 Musculista senhousia (Benson),
Minami-Arao, Arao City, Kumamoto Prefecture, collected by
S. Sato, 24 November 2008.
Remarks. Two species of bivalves were previously known
as hosts of Lichomolgus bidentipes: Septifer virgatus(Wiegmann) reported by Ho (1980) from Sado Island, thetype locality, and Mytilus galloprovincialis Lamarck (asMytilus edulis galloprovincialis) by Do and Kajihara (1986b)
from Omura Bay, Nagasaki Prefecture. With the additionin the present report of six more bivalve species as hosts,
L. bidentipes turned out to be a copepod showing very low
host specificity. It is notable that this species may infest to
small bivalves such as Musculista senhousia which seldom
exceeds 2 cm in length.

Lichomilgus inflatus Tanaka, 1961
Previous records in Japan: From Paphia sp. at Sasebo Bay(type locality), Nagasaki Prefecture (Tanaka, 1961); from
Pinctada fucata martensii (Dunker), Ruditapes philippinarum(Adams and Reeve) (as Tapes japonica) and Saxidomus
purpurata (Sowerby) at Sasebo Bay (Ko et al., 1962); from
Ruditapes philippinarum (as Tapes japonica) at Sasebo Bay(Ko, 1969c).
Remarks. Kim (2002) redescribed this species based ona single female found in Phacosoma japonicum (Reeve)(as Dosinorbis japonicus) from southern coast of Korea.
Ko et al. (1962) reported this species as a parasite of three
species of bivalves and briefly described their specimens.
We have examined a vast number of samples of Ruditapes
philippinarum from various localities in Japan and Korea,
but no specimen of L. inflatus has been obtained from theseclams. Kim (2002) was questionable to the identification of
L. inflatus by Ko et al., because their description is not for L.
inflatus but applicable generally to Herrmannella hoonsooi
Kim, 1992 and because two (Saxidomus purpurata and
Ruditapes philippinarum) of three bivalve species theyrecorded as hosts are the known hosts of H. hoonsooi.
Recently we have found that Tresus keenae (Kuroda andHabe) is the major bivalve host of L. inflatus in Korea.

Lichomolgus sadoensis Ho, 1980
Previous records in Japan: From Septifer virgatus(Wiegmann) at Sado Island, Niigata Prefecture (Ho,1980); from Mytilus galloprovincialis Lamarck (as M. edulis
galloprovincialis) at Sado Island (Do and Kajihara, 1986b).
Remarks. It is notable that Do and Kajihara (1986b)

11

examined more than six thousand samples of Mytilus
galloprovincialis taken from Kyushu to Hokkaido Islands
and extracted copepods from these blue mussels. They
found L. sadoensis only in the blue mussels collected from
Sado Island. This result reveals that L. sadoensis has a very
limited distribution.

Lichomolgus spondyli Yamaguti, 1936
Previous record: From Spondylus barbatus Reeve (asSpondylus japonicus Kuroda) from Wakayama Prefecture(exact locality is unknown) (Yamaguti, 1936).
Remarks. This species of copepod has never beenrediscovered since the original find. In general figure of bodyshown by the illustration of Yamaguti (1936), it appears
similar to L. inflatus.
Genus Modiolicola Aurivillius, 1882

Modiolicola bifidus Tanaka, 1961
Previous records in Japan: From Paphia sp. at Sasebo
Bay (type locality), Nagasaki Prefecture (Tanaka, 1961);
from Ruditapes philippinarum (Adams and Reeve) (asTapes japonica) at Sakibe, Sasebo Bay (Ko et al., 1962)
and Nagasaki City (Yoshikoshi and Ko, 1974); from Mactrachinensis Philippi (as M. sulcataria Reeve) at Matsubara,
Omura Bay (Ko et al., 1962); from Ruditapes philippinarum(as Tapes japonica) at Sasebo Bay (Ko, 1969c); from
Ruditapes philippinarum (as Tapes philippinarum) at
Nagasaki City (Yoshikoshi and Ko, 1974); from Mytilus
galloprovincialis Lamarck (as M. edulis galloprovincialis)
at Himeji Harbor, Hyogo Prefecture and Toyo, Ehime
Prefecture (Do and Kajihara, 1984, 1986b).
Material examined. One ♀ from 6 Cyclina sinensis (Gmelin),
Ashizaki (Mutsu Bay), Mutsu City, Aomori Prefecture,collected by S. Sato, 11 May 2008; 15 ♀♀, 8 ♂♂, from 30
Ruditapes philippinarum (Adams and Reeve), Ashizaki(Mutsu Bay), Mutsu City, Aomori Prefecture, collected by S.
Sato. 11 May 2008; 3 ♀♀ from 30 Ruditapes philippinarum,
Kojiro, Shimabara City, Nagasaki Prefecture, collected by
I.-H. Kim, 22 November 2008; 1 ♀, 4 ♂♂ from 13 Mactra
veneriformis Reeve, Minami-Arao, Arao City, Kumamoto
Prefecture, collected by S. Sato, 24 November 2008; 2 ♀
♀ from 25 Musculista senhousia (Benson), Minami-Arao,
Arao City, Kumamoto Prefecture, collected by S. Sato, 24
November 2008.
Remarks. This species is one of the copepods havingvery low host specificity. Kim (2004) recorded 11 speciesof bivalves as hosts of this copepod in Korea, not including

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IL-HOI KIM and SHIN'ICHI SATO

Mactra chinensis Philippi recorded by Ko et al. (1962) as
host in Japan. We add Cyclina sinensis (Gmelin) herein as a
new host record.

Modiolicola gracilicaudus Avdeev, 1977
Previous records in Japan: From Mytilus coruscus Gould
at Sado Island, Niigata Prefecture (Ho, 1980), Obama Bay,
Fukui Prefecture and Iwami, Tottori Prefecture (Do and
Kajihara, 1986b); Mytilus galloprovincialis Lamarck (as M.
edulis galloprovincialis) at Sado Island, Niigata Prefecture(Do and Kajihara, 1986b).
Remarks. This species infests to three species of mussels:
Crenomytilus grayanus (Dunker) in the Far Eastern coastof Russia (Avdeev, 1977), Mytilus coruscus in Japan and
Korea and M. gallopronicialis in Japan.
Genus Philoconcha Yamaguti, 1936

Philoconcha amygdalae Yamaguti, 1936
Previous record in Japan: From Ruditapes philippinarum(Adams and Reeve) (as Venerupis philippinarum) in Chiba
Prefecture (exact type locality is unknown) (Yamaguti, 1936).
Remarks. This species has not been rediscovered since
the original description. Yamaguti (1936) did not mention thesite of parasitism of this species, but it certainly lived in the
pericardium of the host clam.

Philoconcha paphiae Yamaguti, 1936
Previous record in Japan: From Paphia euglypta (Philippi)
at “Inland Sea” as type locality (probably Seto Inland Sea)
(Yamaguti, 1936).
Remarks. Kim (2002) redescribed this species found in
the pericardium of Phacosoma japonicum (Reeve) (asDosinorbis japonicas) from Korea.
Genus Paraphiloconcha Yamaguti, 1936

Paraphiloconcha meretricis Yamaguti, 1936
Previous records in Japan: From Meretrix lamarckii
Deshayes from the Sea of Japan (exact locality is unknown)(Yamaguti, 1936); from the same bivalve species at Oharai,
Ibaraki Prefecture (Kim et al., 2004).
Remarks. Kim et al. (2004) redescribed this species basedon three females and seven males found in the pericardiumof one individual of Meretrix lamarckii.
Family Myicolidae Yamaguti, 1936
Genus Myicola Wright, 1885

Myicola ostreae Hoshina and Sugiura, 1953
Previous records in Japan: From Crassostrea gigas(Thunberg) (as Ostrea gigas) at Yawata (type locality), Chiba
Prefecture (Hoshina and Sugiura, 1953); from the same
bivalve species at Tsushima Island, Nagasaki Prefecture(Tanaka, 1961).
Remarks. In Korea, this species was found also from
Sinonovacula constricta (Lamarck) (Kim, 2004).

Myicola gamoensis n. sp. (Figs. 6-8)
Material examined. Five ♀♀ from gut of about 60 Laternula(Exolaternula) marilina (Reeve), tidal flat in mouth of
Nanakita River (38°15′11.4″N, 141°00′36.6″E), Gamo,
Sendai City, Miyagi Prefecture, collected by I.-H. Kim, 13
November 2008. Holotype (♀, TUMC-85729) and paratypes(3 ♀♀, TUMC-85730) have been deposited in the Tohoku
University Museum. One dissected paratype (♀) is retainedin the collection of I.-H. Kim.
Other material examined. One ♀ (dissected) from gut of
3 Laternula (Exolaternula) marilina, west coast of Hiroura,
Natori City, Miyagi Prefecture, collected by S. Sato, 22
May 2008; 3 ♀♀ (1 ♀ dissected) from gut of 15 Laternula(Exolaternula) marilina, Gamo, Sendai City, Miyagi
Prefecture, collected by I.-H. Kim, 13 October 2008.
Female. Body (Fig. 6A) cyclopiform. Total length 1.35 mm,
excluding caudal seta, in dissected paratype. Prosome 808
μm long. Cephalothorax clearly divided in dorsal view into
cephalosome and first pedigerous somite. Cephalosome
271×402 μm. Second and third pedigerous somites withrudimentary dorsal tergite narrower than somite. Urosome(Fig. 6B) 5-segmented and occupying 40% of whole bodylength. Fifth pedigerous somite 145 μm wide. Genital
double-somite 179×160 μm, bearing 3 rows of spinules onventral surface (Fig. 6C). Genital areas located dorsally.
Three abdominal somites 75×98, 56×82, and 62×77 μm,
respectively. Proximal 2 abdominal somites with transverse
row of spinules on ventral surface near posterior border.
Anal somite with several spinules on posteroventral area
near base of caudal ramus. Caudal rami widely separated
from each other. Each ramus (Fig. 6D) 102×20 μm (ratio 5.10
: 1), tapering, with 6 naked setae; proximal seta located at
30% length of outer margin; 3 terminal setae much shorter
than caudal ramus, 57, 16, and 14 μm, respectively.

Copepods associated with bivalves in Japan

Fig. 6. Myicola gamoensis n. sp., female. A, habitus, dorsal; B, urosome, dorsal; C, genital doublesomite and abdomen, ventral; D, right caudal ramus, dorsal; E, egg sac; F, antennule; G, antenna; H,
maxillule. Scales: A, E, 0.2 mm; B, C, 0.1 mm; D, 0.05 mm; F-H, 0.02 mm.

13

14

IL-HOI KIM and SHIN'ICHI SATO

Fig. 7. Myicola gamoensis n. sp., female. A, rostral area, ventral; B, labrum; C, mandible; D,maxilla; E, leg 1; F, leg 2; G, leg 5. Scales: A, B, E, F, 0.05 mm; C, D, G, 0.02 mm.

Copepods associated with bivalves in Japan

15

Fig. 8. Myicola gamoensis n. sp., female. A, leg 3; B, leg 4. Scales: A, B, 0.05 mm.
Egg sac (Fig. 6E) with multiseriate eggs, containing about
25 eggs. Each egg about 150 μm in diameter.
Rostrum appearing as faint sclerotization (Fig. 7A).
Antennule (Fig. 6F) 212 μm long and 7-segmented,
with armature formula: 4, 14, 6, 3, 4+aesthetasc,
2+aesthetasc, and 7+aesthetasc. Several setae on distal
3 segments plumose, other setae naked. Antenna (Fig.
6G) 3-segmented. First segment massive, distally withtransverse row of spinules and 1 small inner distal seta.
Second segment with 1 small inner seta. Third segment 77
μm long (average length of inner and outer margins) and31 μm wide (ratio 2.48 : 1), with several spinules on outermargin and 4 small setae (1 near midway of inner margin, 1
inner distal, and 2 outer distal). Terminal claw stong and 55
μm long.
Labrum (Fig. 7A) broad, with wide but shallow posterior
incision. Mandible (Fig. 7C) terminated by long spiniferous
lash, with 2 plate-like elements and 1 elongate seta.
Maxillule (Fig. 6H) armed with 4 unequal setae. Maxilla (Fig.
7D) 2-segmented. First segment large, with 2 patches of
spinules on ventral surface. Second segment with small,
naked anterior seta, and inner seta bearing spinules on
distal margin. Distal lash spiniferous and distinctly shorter
than inner seta. Maxilliped lacking.

Legs 1-4 (Figs. 7E, F, 8A, B) biramous with 3-segmented
rami. Outer margin of both rami of legs 1-4 bearing spinules.
Armature formula of these legs as follows:
Leg 1: coxa 0-1; basis 1-I; exp. I-0; I-1; III,I,4;enp. 0-1; 0-1; I,2,3
Leg 2: coxa 0-1; basis 1-0; exp. I-0; I-1; III,I,5;
enp. 0-1; 0-2; I,II,3
Leg 3: coxa 0-1; basis 1-0; exp. I-0; I-1; II,I,5;
enp. 0-1; 0-2; I,II,I+2
Leg 4: coxa 0-1; basis 1-0; exp. I-0; I-1; II,I,5;
enp. 0-1; 0-2; I,II,I+1
Leg 5 (Fig. 7G) 2-segmented. Proximal segment with 1
outer naked seta. Distal segment 71×43 μm (ratio 1.65 : 1),with 2 spines and 2 naked setae and spinules on slightly
concave inner margin and convex outer margin. Longest
inner spine 45 μm, inner seta 27 μm, median terminal spine
30 μm, and outer seta 36 μm. Leg 6 not discernible.
Male. Unknown.
Etymology. This species is named after the type locality,
Gamo, a tidal flat located in Sendai City.

16

IL-HOI KIM and SHIN'ICHI SATO

Remarks. Four species are currently known in the genus
Myicola: M. formosanus Lin and Ho, 1999 from Taiwan, M.
intumidus Kim, 1997 from Korea, M. metisiensis Wright,
1885 from the Atlantic coast of North America, and M.
ostreae Hoshina and Sugiura, 1953 from Japan and Korea.
With an uninflated body in the female, the M. gamoensis
n. sp. is easily distinguishable from M. metisiensis and M.
ostreae both having an inflated, vermiform body. However, acareful comparison is needed to distinguish M. formosanus,
M. intumidus, and the new species.
To distinguish M. formosanus from M. intumidus, Lin andHo (1999) selected five characters, four of them are of thefemale as follows: 1) the female urosome occupies 0.29 ofbody length in M. intumidus and 0.42 in M. formosanus (0.40
in M. gamoensis), 2) the number of eggs in an egg sac isabout 30 in M. intumidus and less than 12 in M. formosanus(about 25 in M. gamoensis), 3) the median (inner) spineon the female leg 5 is distinctly shorter than ramus in M.
intumidus and about as long as ramus in M. formosanus(distinctly shorter than ramus in M. gamoensis), and 4)
the caudal ramus in the female is 3.91 times longer thanwide in M. intumidus and 4.92 times longer than wide in M.
formosanus (5.10 times in M. gamoensis).
Myicola gamoensis appears to be an intermediatemorphological state of M. intumidus and M. formosanus,
because, as above, in the first and last characters M.
gamogenesis is closer to M. formosanus, whereas in thesecond and third characters it is closer to M. intumidus.
However, M. gamoensis exhibits other obvious differencesfrom the two relatives: the maxillule is armed with four
setae (three in M. intumidus and M. formosanus) and thefree segment of female leg 5 bears spinules on both innerand outer margins (spinules only on inner margin in the two
species, as shown in the original descriptions by Kim, 1997
and Lin and Ho, 1999).
Genus Ostrincola Wilson, 1944

Ostrincola japonica Tanaka, 1961
Previous records in Japan: From Saccostrea kegaki
Torigoe and Inaba (as Ostrea echinata (Quoy and Gaimard))
at Sasebo, Nagasaki Prefecture (Tanaka, 1961); from
Crassostrea gigas (Thunberg) at Hiroshima and Saccostrea
kegaki (as S. echinata) at Sakibe, Sasebo Bay (Ko et al.,1962).
Material examined. One ♀ from 10 Crassostrea gigas,
Onagawa Port, Miyagi Prefecture, collected by I.-H. Kim, 30
November 2008.
Remarks. This species is an oyster parasite. In Korea, it
has been found only from Ostrea densellamellosa Lischke

which is considered to be the major host of this copepod.

Ostrincola koe Tanaka, 1961
Previous records in Japan: From Paphia undulata (Born)
at Sakibe (type locality) near Sasebo, Nagasaki Prefecture,and from Paphia sp. at Tsuyazaki, Fukutsu City, Fukuoka
Prefecture (Tanaka, 1961); from Merisca (Pistris) capsoides(Lamarck) (as Arcopagia diaphana), Cyclina sinensis(Gmelin) at Hiroshima (Ko et al., 1962); from Ruditapes
philippinarum (as Tapes japonica), Caecella chinensis
Deshayes and Claudiconcha japonica (Dunker) at Sasebo
Bay (Ko et al., 1962); from Mactra veneriformis Reeve andMeretrix lusoria (Röding) at Ariake Bay (Ko et al., 1962);
from Ruditapes philippinarum (as Tapes philippinarum) at
Nagasaki City (Yoshikoshi and Ko, 1974); from Ruditapes
philippinarum (as Tapes japonica) at Nagasaki City (Ko,1969a, 1969d, Ko et al., 1974) and at Sasebo Bay (Ko,1969b, 1969c); from Ruditapes philippinarum (as Tapes
philippinarum) at Nagasaki City (Ko and Yoshikoshi, 1974a,
1974b; Yoshikoshi and Ko, 1974).
Material examined. Six ♀♀, 2 ♂♂ from 5 Ruditapes
philippinarum (Adams and Reeve), Minami-Arao, Arao City,
Kumamoto Prefecture, collected by S. Sato, 24 November
2008; 7 ♀♀, 5 ♂♂ and 3 copepodids from 13 Mactra
veneriformis Reeve, Minami-Arao, Arao City, Kumamoto
Prefecture, collected by S. Sato, 24 November 2008; 1 ♀
from 1 small individual of Meretrix lusoria (Röding), MinamiArao, Arao City, Kumamoto Prefecture, collected by S. Sato,
24 November 2008.
Remarks. This species is one of the most prevalent
copepod parasites of bivalves in the Far East. It was
responsible for the mass mortality of the Meretrix meretrix(Linnaeus) cultured in the vicinity of Yangze River estuary,
China (Ho and Zheng, 1994). In 2002, the first author
learned from a Chinese fisheries biologist that the massmortality of the clams in Yangze River estuary had occurred
once in every four years. The known hosts of O. koe are 15
species of bivalves, as follows:
Barnea dilatata (Souleyet) in Korea; Barnea manilensis(Philippi) in Korea; Caecella chinensis Deshayes in Japan;
Claudiconcha japonica (Dunker) in Japan; Cryptomya
busoensis Yokoyama in Korea; Cyclina sinensis (Gmelin)in Korea; Mactra veneriformis Reeve in Japan and Korea;
Meretrix lusoria (Röding) in Japan and Korea; Meretrix
meretrix (Linnaeus) in China; Paphia undulata (Born) inJapan; Merisca (Pistris) capsoides (Lamarck) in Japan;
Ruditapes philippinarum (Adams and Reeve) in Japan and
Korea; Sinonovacula constricta (Lamarck) in Korea; Solen
grandis Dunker in Korea; and Solen strictus Gould in Korea.

Copepods associated with bivalves in Japan

Genus Pseudomyicola Yamaguti, 1936

Pseudomyicola spinosus(Rafaele and Monticelli, 1885)

Previous records in Japan: From Ostrea denselamellosa
Lischke at Hutami, Hyogo Prefecture (Yamaguti, 1936,
as Pseudomyicola ostreae n. gen. n. sp.); from Laternula(Exolaternula) marilina (Reeve) (as L. kamakurana
Pilsbry) at Kanazawa Bay (Hoshina and Sugiura, 1953,
as P. ostreae); from Mytilus galloprovincialis Lamarck (asM. edulis galloprovincialis) in Tokyo Bay (Nakamura and
Kajihara, 1979; Nakamura et al., 1979; Kajihara et al.,
1980; Do et al., 1984; Kajihara and Nakamura, 1985; Do
and Kajihara, 1986a); from the same bivalve species (asM. edulis) at Sado Island in Niigata Prefecture, Suzu City in
Ishikawa Prefecture, and Tokyo Bay near Yokohama (Ho,1980) and various localities from west coast of Hokkaido
to Kyushu (Do and Kajihara, 1986b); from Septifer virgatus(Wiegmann) at Sirahama, Wakayama Prefecture (Ho, 1980);
from Modiolus kurilensis Bernard (as M. difficilis (Kuroda
and Habe)) from Pacific coast of Aomori Prefecture (Do and
Kajihara, 1986b).
Material examined. Ten ♀♀, 4 ♂♂ from 3 Ostrea
denselamellosa Lischke, Ashizaki (Mutsu Bay), Mutsu City,
Aomori Prefecture, collected by S. Sato, 11 May 2008; 11 ♀
♀, 6 ♂♂ from 4 Mytilus galloprovincialis Lamarck, Ashizaki,
Mutsu City, Aomori Prefecture, collected by S. Sato, 11
May 2008; 2 ♀♀ from 5 Mytilus galloprovincialis Lamarck,
Uno-o (Matsukawa-ura), Souma City, Fukushima Prefecture,collected by S. Sato, 4 June 2008.
Remarks. Pseudomyicola spinosus is not a host specificparasite. Ho (1992) listed 51 species of bivalves in theworld as hosts of this copepod. Do et al. (1984) and Do and
Kajihara (1986b) studied very intensively about the biologyof this cosmopolitan species.
Family Mytilicolidae Bocquet and Stock,
1957Genus Mytilicola Steuer, 1902

Mytilicola orientalis Mori, 1935
Previous records in Japan: From Mytilus coruscus Gould(as Mytilus crassitesta Lischke) and Crassostrea gigas(Thunberg) (as Ostrea gigas Thunberg) at “Inland Sea”
(probably Seto Inland Sea) (Mori, 1935); from Mytilus
galloprovincialis Lamarck (as M. edulis galloprovincialis) at
Hiwasa, Tokushima Prefecture (Do and Kajihara, 1986b).
Remarks. Mytilicola orientalis has been accidently
introduced to Europe and the Pacific coast of North

17

Amereca, along with the oyster Crassostrea gigas
transplanted from Japan. It is considered a serious pest ofnative bivalves of received regions (Torchin et al, 2002).

Mytilicola mactrae Hoshina and Kuwabara, 1959
Previous record in Japan: From Mactra veneriformis Reeve
at Kisarazu, Chiba Prefecture (Hoshina and Kuwabara,1959).
Remarks. This species can be clearly separated by
the presence of a pair of dorsolateral processes on the
cephalothorax in the female (Do and Kajihara, 1986b).
Genus Pectenophilus Nagasawa, Bresciani and
Lützen, 1988

Pectenophilus ornatus Nagasawa, Bresciani and
Lützen, 1988
Previous records: From Patinopecten (Mizuchopecten)
yessoensis (Jay) from southern coast of Hokkaido andnorthern coast of Honshu (Nagasawa et al., 1988, 1991,
1993; Nagasawa and Nagata, 1992); from Chlamys farreri
nipponensis Kuroda from southern coast of Hokkaido(Nagasawa et al., 1993).
Remarks. The familial position of Pectenophilus had notbeen determined until Huys et al. (2006) have shown amolecular evidence that it belongs to the family Mytilicolidae.
This copepod species is a pest of the commercially
important bivalve Patinopecten (Mizuchopecten) yessoensis
in the northern coasts of Japan.
Genus Trochicola Dollfus, 1914

Trochicola japonica Shimura and Kuwabara,
1984 (Figs. 9, 10)
Previous record in Japan: From Ruditapes philippinarum(Adams and Reeve) (as Tapes phillipinarum) at Lake
Hamana (type locality), Shizuoka Prefecture (Shimura andKuwabara, 1984).
Material examined. One ♂ from gut of 30 Ruditapes
philippinarum, Ashizaki (Mutsu Bay), Mutsu City, Aomori
Prefecture, collected by S. Sato, 11 May 2008; 1 ♂ from 13
Ruditapes philippinarum, Hatsutsu-ura, Miyatojima, HigashiMatsushima City, Miyagi Prefecture, collected by S. Sato, 21
May 2008.
Male. Body (Fig. 9A) cylindrical and 1.36 mm long.
Prosome well-segmented, consisting of cephalosome
and first to fourth pedigerous somite. Prosomal somites

18

IL-HOI KIM and SHIN'ICHI SATO

Fig. 9. Trochicola japonicus Shimura and Kuwabara, male. A, habitus, dorsal; B, urosome, ventral;C, cephalosome, ventral; D, right caudal ramus, dorsal; E, antennule; F, antenna. Scales: A, B, 0.1 mm;
C, E, F, 0.02 mm; D, 0.05 mm.

Copepods associated with bivalves in Japan

19

Fig. 10. Trochicola japonicus Shimura and Kuwabara, male. A, leg 1; B, leg 2; C, leg 3; D, leg 4; E,
leg 5. Scales: A-D, 0.05 mm; E, 0.02 mm.
gradually shorter and narrower from anterior to posterior.
Cephalosome 274×271 μm. Rostral area pronounced
anteriorly. Urosome (Fig. 9B) 6-segmented; suture lines
indistinct, but each segments distinctly recognizable bylateral constrictions. Urosomal somites ornamented by manytransverse rows of minute spinules on all surfaces. Fifthpedigerous somite 169 μm wide. Genital somite 165×182
μm. Four abdominal somites 113×150, 86×138, 55×118, and70×100 μm, respectively. Caudal rami slightly divergent, 56
×32 μm (ratio 1.75 : 1), armed with 1 simple seta, 3 thick,spiniform setae, 2 membraneous flaps, and ornamented withrows of minute spinules (Fig. 9C).
Rostrum absent (Fig. 9D). Antennule (Fig. 9E) 147 μm
long and 5-segmented, with armature formula 2, 15,4+aesthetasc, 2+aesthetasc, and 7+aesthetasc. Aesthetascs
on third and fourth segments enlarged. Antenna (Fig. 9F)
3-segmented. First and third segments unarmed. Second
segment with small seta on inner margin. Terminal claw
strong and markedly curved.
Labrum with convex posterior margin (Fig. 9D). Mandible
absent. Maxillule lobate and armed with 2 apical setae.
Maxilla 2-segmented. Proximal segment large, with patch

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IL-HOI KIM and SHIN'ICHI SATO

of spinules on anteroventral surface. Distal segment small
and tapering, with serrated posterior margin. Maxilliped
rudimentary, consisting of 2 unarmed segments and terminal
claw. Proximal segment broadened distally. Distal segment
short. Terminal claw strongly curved, with membrane along
concave margin. Spermatophore 177×70 μm.
Legs 1-3 (Fig. 10A-C) with 3-segmented rami. Leg 4 (Fig.
10D) with 3-segmented exopod and 2-segmented endopod.
Exopod of legs 1-4 with membrane along outer margin.
Outer margin of endopodal segments also with membrane
except for second and third segments of leg 1 and distalsegment of leg 4. Armature formula of legs 1-4 as follows:
Leg 1: coxa 0-0; basis 1-0; exp. I-0; I-1; II,I,4;enp. 0-1; 0-1; 4
Leg 2: coxa 0-0; basis 1-0; exp. I-0; 0-1; II,I,5;
enp. 0-1; 0-2; I,5
Leg 3: coxa 0-0; basis 1-0; exp. I-0; 0-1; I,I,5;
enp. 0-1; 0-2; I,3
Leg 4: coxa 0-0; basis 1-0; exp. I-0; 0-1; I,I,4;enp. 0-1; I,4
Leg 5 obscurely 2-segmented. Proximal segment withouter seta. Distal segment armed with 2 short and 1 longer
setae. Leg 6 represented by 2 setae and 1 minute spinuleon posterior part of genital flap.
Female. Not discovered in our collection.
Remarks. Our male specimens exhibit some differencesfrom the original description of Shimura and Kuwabara(1984) as follows: 1) The third exopodal segment of leg 1
is armed with seven elements (armature formula II, I, 4)
instead of eight elements (III, 5); 2) the endopod of leg 4 is
two-segmented instead of three-segmented condition; 3) the
caudal ramus bears a pair of membranes in addition to thefour setae; and 4) leg 5 is indistinctly segmented.
Although Shimura and Kuwabara did not mentioned thevariability of Trochicola japonicus, we consider the above
differences are variations within a species or artifacts,
because the type specimens and our male specimens reveal
similarities in many important characters as follows: 1) legs
2-4 lack an outer spine on the second exopodal segment; 2)
the distal segment of leg 5 is armed with three setae; 3) the
shape and size of caudal ramus are same between the typespecimens and our specimens; 4) the body lengths are notdifferent between them; and finally 5) they were found fromthe same species of bivalve host.
Genus Piratasta Leigh-Sharpe, 1934

Piratasta brachidontis Yamaguti, 1939

Previous record: From Musculista senhousia (Benson)(as Brachiodontes senhausi (Reeve)) at Lake Hamana,
Shizuoka Prefecture (Yamaguti, 1939).
Remarks. The Lake Hamana is the type locality of both
Piratasta brachidontis Yamaguti, 1939 and Trochicola
japonica Shimura and Kuwabara, 1984. The genera of thefamily Mytilicolidae can barely be distinguishable by female
morphological traits. For example, the genera Myticlicola
and Trochicola can only be separated by morphologicaldifferences of male legs. The genus Piratasta is poorly
known, without a record for the male. Thus Boxshall andHalsey (2004) could not distinguish Piratasta from thetype genus Mytilicola. It is conceivable that Piratasta
brachiodontis is synonymous with Trochicola japonica, bothrecorded from the same place.

Acknowledgements
This study was made possible through financial support by
the Tohoku University Museum while the first author (IHK)
was staying for five months as a visiting professor of themuseum. We wish to thank Mr. Takeshi Igarashi, Mutsu City
Nature Center, for his aid and accompanying during the field
trip to Mutsu Bay in October 2008.

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