Bijdragen tot de Dierkunde, 63 (IJ 61-64 (1993)

SPB Academie Publishing bv, The Hague

Short notes and reviews

Copepoda (Crustacea) associated with commercial and non-commercial

Bivalvia in the East Scheldt, The Netherlands

Jan H. Stock

c/o Institute of Taxonomie Zoology, University of Amsterdam, P.O. Box 4766, 1009 AT Amsterdam,

The Netherlands

Keywords: Bivalvia, parasitic Copepoda, Netherlands

Abstract The shells were opened and the 's soft parts were taken

out and placed for some 12 hours in a mixture of 95% seawater

and 5% ethyl alcohol. The fluid was then filtered through a 300 Six species of CopepodaPoecilostomatoida ofthe families Myi- fim sieve and the were picked from the retained sedi- colidae, Sabelliphilidae, Lichomolgidae, and are

ment under a dissecting microscope. Specimens were studied in recorded from six different species of intertidal bivalves in the

glycerine or lactophenol and dissections were stored as perma- East Scheldt (The Netherlands), a branch of the southern bight nent mounts in Reyne's modification of Faure's medium. of the North Sea. One bivalve harbour species may more than Representative sets of each species have been placed in the onespecies of , and one copepod species may use more Zoölogisch Museum of the University of Amsterdam. than one species of bivalves as host.

Mytilicola orientalis and Myicolaostreae are new to the North

Sea, both being undoubtedlycarried in accidentally with oriental

introduced for mariculture. the of , successfully In light Results

the damage that was caused by Mytilicola intestinalis to Dutch

mussel cultures in the the acclimatization of past, M. orientalis The following copepods and host molluscs were is a matter of concern, the more so since it infests not only its found: original oriental host, Crassostrea gigas, but also the native

European species, Ostrea edulis and Mytilusedulis, both impor-

tant fisheries resources in the East Scheldt region. Family MYICOLIDAE

Material and methods Myicola ostreae Hoshina & Sugiura, 1953

During the period May to September 1992, bivalves were regu-

larly (3 times a week) collected in the East Scheldt, on the south Material. — Nine specimens from Crassostrea gigas and two

coast of the island of Schouwen, at a locality called Schelphoek. specimens from Ostrea edulis (collected overthe entire period of

The centre of the area bears the coordinates 45.500 x 413.000 observation).

on the topographic map of the Netherlands, sheet 42, scale

1:50,000 (Topographical Service, Emmen, 1986), which cor- This copepod has no doubt been accidentally in- responds roughly with 51°33'N 03°36'E. The area is semi- troduced into Dutch waters with oriental oysters. It enclosed by two dams, fully marine,but protected against rough

is uncommon, though actively reproducing, both in seas. The tidal difference during spring tides may amount to 3

m or more. Its western part consists of gravel and boulders; the C. gigas and O. edulis (the latter being a new host

central and eastern are intertidal flats of sandy mud and parts for the species). These are the first records for Myi-

fine sand. At low spring tides, extensive beds are exposed, cola in the North the ostreae Sea; species comes mainlyinhabited by wild specimens of the acclimatized oriental originally from Japanese and Korean waters. oyster, Crassostrea gigas. The generic status of this copepod has been dis- The bivalve species encountered, and their copepod asso- ciates, are shown in Table 1. cussed by Humes (1986), who suggested to remove

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M. ostreae to the genus Ostrincola, but for the mo- The real host of this copepod is somewhat of a mys-

consider it is live brown al- ment I follow Ho & Kim (1991) and the tery; supposed to on (feed on?)

multiseriate ovisac a key character for Myicola. gae.At any rate only two specimens of this copepod

were found in Crassostrea gigas, which seems to

indicate that this occurrence must be considered

Family SABELLIPHILIDAE accidental.

The species was already known from The Nether-

Herrmannella rostrata Canu, 1891 lands (Stock, 1957: 380; Stock & De Vos, 1960:

206).

Material. - Five specimens in branchial chamber of Mya arena-

ria, many specimens in branchial chamber of Scrobicularia plana, and many specimens in branchial chamber ofCerastoder- Family MYTILICOLIDAE

ma (formerly Cardium) edule.

Mytilicola intestinalis Steuer, 1902 Although this copepod is known from at least 11

different bivalve hosts (Humes & Stock, 1973), it Material. - Many specimens from the guts of Mytilus edulis. before from was not recorded Mya arenaria and

Scrobicularia Avdeev records plana. (1987) a spe- This copepod has been known from The Nether- cies of Herrmannella, H. dentata, from Mya japo- lands since the early fifties (Korringa, 1950; 1951), nica in the Sea of Japan, but I contented myself that when it caused considerable damage to mussel fish- the Dutch material from Mya belongs to H. rostra- eries and cultures. In the course of the years, the in-

ta and not to H. dentata. tensity of the infestations declined to such a level Herrmannelladuggani Holmes & Minchin, 1991, that no serious harm occurs anymore. At the maxi- recently described from Ostrea edulis from Ireland mum of the epidemic, M. intestinalis was sparingly

and Brittany, has not been encountered during our encountered in other mollusc hosts as well (Ostrea study. edulis and the gastropod Crepidula fornicata (Lin- In The Netherlands, H. rostrata occurs predom- naeus, 1758); Stock, 1965). During our 1992 sur- inantly in the Cockle, Cerastoderma edule but , intestinalis found in these vey no Mytilicola was has also been found (Stock, 1965) in Macoma two hosts. In Mytilus edulis from Schelphoek, M. balthica (Linnaeus, 1758) and Spisuta subtruncata intestinalis is more common than the following spe- (Da Costa, 1778). cies, M. orientalis.

Steuer published the combination Mytilicola in- Modiolicola insignis Aurivillius, 1882 testinalis first n. gen., n. sp. twice (1902, 1905); the

year takes priority of course.

Material. - Many specimens from the gills of Mytilus edulis.

Mytilicola orientalis Mori, 1935 This small copepod, with its distinctive pink colour, is common in the Boreal region of Europe, and is Material. - Many specimens from the gut of Grassostrea gigas; already known from The Netherlands (Stock & De many specimens from the gut of Ostrea edulis; some specimens

Vos, 1960: 206; Stock, 1965: 67). from the gut of Mytilus edulis.

No doubt this species, like Myicola ostreae, has

Family LICHOMOLGIDAE been introducedaccidentally into Europe (and else-

Pacific where, e.g., on the coast of the U.S.A.,

Macrochironfucicolum Brady, 1872 where it was at first considered a different species,

M. ostreae Wilson, 1938) with oriental oysters,

Material. — Two females from the gills of Crassostrea gigas. Crassostrea gigas. In Schelphoek, C. gigas nowa-

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is the fact that much of its Table I. Commercial (marked with *) and non-commercial spe- respect waters never

cies of Bivalvia encountered at Schelphoek (East Scheldt) and leave the embayment. The water moves seaward

their associates, if Note that the clam, arena- copepod any. Mya low inland during tide, again during high tide, go- ria, is a commercial species along the North American East ing forth and back in a kind of shuttle movement. in Netherlands. coast, but is not exploited The Infesting larval stages of parasitic or associated

Host Copepod copepods thus stay inside the East Scheldt, increas-

ing the chance of finding a suitable host. This *

makes the East Scheldt vulnerable to booms in in- (Thunberg, 1793) Mori, 1935

Myicola ostreae Hoshina

Sugiura, 1953 whose lar- for mariculture, in particular of oysters,

Macrochiron fucicolum vae settle in the area in which they were produced. Brady, 1872 In the early fifties, an epidemic caused by the *1Ostrea edulis Linnaeus, Mytilicola orientalis tilicola intestinalis caused 1758 Myicola ostreae copepod My great

*¡Mytilus edulis (Linnaeus, Mytilicola intestinalis damage to the commercial activities around the

1758) Steuer, 1902 catch and production of the , Mytilus Mytilicola orientalis edulis (see Korringa, 1950; 1951). The discovery, Modiolicola insignis of of during the present study, the presence an Aurivillius, 1882 acclimatized population of the copepod Mytilicola (*)'Mya arenaria Linnaeus, Herrmannella rostrata

1758 Canu, 1891 orientalis in the East Scheldt therefore is alarming.

*

gas, which "escaped" from mariculture and now Angulus tenuis (Da Costa, 1778) no copepods forms banks in wild. its Teredo navalis Linnaeus, 1758 no copepods large the Not only original

oriental host is infested, but the copepod invaded

also the indigenous bivalves, Ostrea edulis and

days outnumbers the indigenous oyster, Ostrea Mytilus edulis. It remains to be seen if Mytilicola edulis. Both infested orientalis will noxious its oyster species are heavily by turn out to be as as con-

M. orientalis; lower infestation percentages occur gener, M. intestinalis. At any rate, cautious obser-

in the blue mussel, Mytilus edulis. Both Ostrea edu- vations of the development of Mytilicola infesta-

lis and edulis hosts for tions Mytilus are new M. orienta- seem justified.

lis. Moreover, these are the first records of M. Of the other alien copepod introduced with orientalis for the North Sea area; the species oriental oysters, Myicola ostreae, no harmful

originates from Japan and Korea. effects are known, but this associate should be fol-

The distinctions between M. intestinalis and lowed since it has infest M. as well, especially proved to

orien talis are best shown by Ho & Kim (1992). M. not only its original host, Crassostrea gigas, but

intestinalis has strongly diverging caudal rami, also indigenous oysters, Ostrea edulis. At present,

shorter ovisacs, and less pointed, less divergent, it occurs in numbers too low to form an economic

lateral body processes. risk.

The remaining copepod associates are endemic to

not to the Boreal region, and are known cause any

Discussion noticeable damage.

The East Scheldt is a branch of the southern North Acknowledgments Sea with several peculiar ecological characteristics.

The area is fully marine, with little inflow of very The author is indebted to Mr. R.G. Moolenbeek, keeper of

fresh water, but more important in parasitological Malacology at the Zoölogisch Museum Amsterdam, for the

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identification of the material of Crassostrea gigas, and for Lichomolgidae Kossmann, 1877, cyclopoid copepods mainly

of the bivalve Smithson. nomenclatorial advice on the actual names hosts. associated with marine invertebrates. Contr.

Zool., 127: i-v, 1-368.

Korringa, P., 1950. De aanval van de parasiet Mytilicola intes-

tinalis op de Zeeuwse mosselcultuur. Visserij-Nieuws, 7 References (Suppl.): 1-7.

Korringa, P., 1951. Over Mytilicola intestinalis (Copepoda

Avdeev, G.V., 1987. [Two new copepod species (Sabelliphili- parasitica) en enkele andere ongewenste vreemdelingen in

Peter dae, ) from bivalvian molluscs in the onze wateren. Vakbl. Biol., 31(4): 63-74.

of the Zool. 608-613 intestinalis the Great Bay Japan Sea], Zh., 66(4): Steuer, A., 1902. Mytilicola n. gen. n. sp. aus dem

[in Russian, English summary]. Darm von Mytilus galloprovincialis Lam. Zool. Anz., 25:

Ho, J.-S. & I.H. Kim, 1991. Copepod parasites of commercial 635-637.

bivalves in Korea, II. Copepods from cultured bivalves. Bull. Steuer, A., 1905. Mytilicolaintestinalisn. gen. n. sp. Arb. zool.

Korean Fish. Soc., 24(6): 369-396. Inst. Univ. Wien, 15(1): 1-46, Pis. I-V.

Macrochiron Ho, J.-S. & I.H. Kim, 1992. Copepod parasites of gastropods Stock, J.H., 1957. Some notes on the genus Brady,

from Korea. Korean J. Zool., 35: 240-255. 1872 (Copepoda,). Ann. Mag. nat. Hist., (12)10:

1991. A Herr- Holmes, J.M.C. & D. Minchin, new species of 378-382.

mannella (Copepoda, Poecilostomatoida,Sabelliphilidae) as- Stock, J.H., 1965. On Copepoda associated with Dutch mol-

sociated with the oyster Ostrea edulis L. Crustaceana, 60(3): luscs. Basteria, 29: 65-71.

258-269. Stock, J.H. & A.P.C. de Vos, 1960. Einige wirbellose Tiergrup-

Humes, A.G., 1986. Myicola metisiensis (Copepoda: Poecilo- pen des Dollard-Ems-Estuariums. Verh. K. ned. geol. mijnb.

stomatoida),a parasiteof the bivalve Mya arenaria in eastern Genoot., (Geol.) 19: 203-220.

Canada, redefinition ofthe Myicolidae, and diagnosis of the

J. 64: Anthessidae n. fam. Can. Zool., 1021-1033.

Humes, A.G. & J.H. Stock, 1973. A revision of the family Received: 31 January 1993

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