Bijdragen tot de Dierkunde, 53 (2): 218-226 — 1983 A new marine triclad ectoparasitic on Malaysian and Indonesian horseshoe crabs (Platyhelminthes, Turbellaria, Tricladida) by Ronald Sluys Institute of Taxonomie Zoology, University of Amsterdam, P.O. Box 20125, 1000 HC Amsterdam, The Netherlands been found Summary or, perhaps, even a fifth species, has on an American Horseshoe Crab from North A of undata new species marine triclad, Ectoplana n. sp., Carolina (Sluys & Ball, unpublished manu- ectoparasitic on the horseshoe crab Tachypleus gigas, is described. Cocoons of triclads found Kaburaki described the were on T. gigas as script). Ijima & (1916) well as on the horseshoe crab Carcinoscorpius rotundicauda; marine triclad Procerodes limuli which had been since from the latter species no triclads were collected, it obtained from specimens of the Chinese remains unknown whether these cocoons are those of E. Horseshoe Crab. One Kaburaki year later, undata The or of another species. genus Ectoplana, though transferred the the Ec- (1917) species to genus poorly defined, is here retained, for stated reasons, pend- is considered the Pro- ing a revision of the Procerodidae. toplana which to belong to cerodidae and to constitute the only memberof Résumé the subfamily Ectoplaninae (cf. Bresslau, Some later Kaburaki On décrit une nouvelle espèce de Triclades marins (Ec- 1933). years (1922) pro- vided detailed of toplana undata n. sp.), ectoparasite du Xyphosoure a more description Ectoplana Tachypleus gigas. Des cocons de Triclades ont été trouvés limuli. aussi bien T. le sur sur Xyphosoure Carcinoscor- gigas que In this of triclad is paper a new species n’a trouvé des Triclades pius rotundicauda; puisqu’on pas described, of which the were ob- dernière specimens sur cette espèce, la question de savoir si ces tained from a of horseshoe crab other cocons ceux de undata bien species sont E. ou d’une autre espèce, Le than mentioned above. In reste sans réponse. genre Ectoplana est retenu, en dépit the two already du fait qu’il est imparfaitement défini, en attendant une assessing the generic status of this species of révision des Procerodidae; les raisons de cette initiative triclad it will be necessary to examine critically sont expliquées. the defining characters of Ectoplana, as de- scribed in the literature. Planarian cocoons INTRODUCTION which found of another were on specimens still species of horseshoe crab from Malaysian and Marine triclads are known to live ec- Indonesian regions will also be described. toparasitically on the American Horseshoe Crab Limulus polyphemus (Linnaeus, 1758) and the Chinese Horseshoe Crab Tachypleus triden- MATERIAL AND METHODS tatus (Leach, 1819). These planarians live on the gills and legs of the crabs and profit from the The Zoological Museum in Amsterdam (ZMA) left houses small alcohol collection of food particles over from the meals of the lat- a horseshoe ter. crabs in which three species are represented, From L. polyphemus no less than four species viz. Limulus polyphemus, Carcinoscorpius rotun- of triclads have been described (cf. Wilhelmi, dicauda (Latreille, 1817), and Tachypleus gigas 1909). All these belong to the family (Müller, 1785). Specimens of the last two which contains searched for marine triclads Bdellouridae, also free-living species were and/or members. A different form of Bdelloura Candida their cocoons. These horseshoe crabs were BIJDRAGEN TOT DE DIERKUNDE, 53 (2) - 1983 219 either collected and preserved immediately, or Etymology. — The specific epithet undata (from the of Artis Zoo in shipped to Aquarium the Latin unda, wave) refers to the wavy course Amsterdam (NAM), where they lived for of the distal portion of the male atrium. several years before they died and were the collection of the External features — deposited in museum. (fig. 1). The holotype crab from which measured about 2.5 in and 1.25 Horseshoe specimens cocoons mm length mm and/or planarians were collected, are listed in diameter. The body is elongate-oval-shaped, collec- rounded. The below with their sample locality, date of whereas front and hind end are and collector. small lie considerable distance from tion, eyes at a the front end and close Both are together. ZMA Xi. 1007, Tachypleus gigas (mistakenly identified as paratypes were very much shrunken, due to Carcinoscorpius rotundicauda), Singapore, date ofcollection contraction, and of semi-circular shape. The unknown, died in Aquarium NAM 7.09.1965: one animals due lack of triclad and cocoons. are white, to pigment; T. ZMA no collection number, gigas. Belawan, Deli, ovaries, testicular follicles, intestinal rami, part died in Sumatra, 1931, leg. Capt. G.J. Terwiel, aqua- ventral of the copulatory apparatus and nerve rium at unknown date: two triclads and cocoons. visible the wall. cords are through body ZMA no collection number, T. gigas, Belawan, Deli, Sumatra, 1931, leg. Capt. G.J. Terwiel, died in Aqua- rium NAM unknown date: and dermal musculature.— Dorsal at cocoons. Epidermis ZMA ibid.: cocoons and ventral epithelium measure about 4.8 /tm ibid.: ZMA cocoons in thickness; both are packed with rhabdites. ZMA Xi.1004, 2 specimens of T. gigas, Java Sea, 1925, Ventral and dorsal body surface are covered leg. Capt. G. J. Terwiel: cocoons. which with numerous, cilia have ZMA Xi.1002, T. gigas, Java Sea at Pekalongan, Java, well-developed the cells. 1927: cocoons. about same height as the epidermal ZMA Xi. of further 1001, T. gigas, east coast Sumatra, no The basement membrane is well developed and information: cocoons. conspicuous. Dorsally and ventrally it is about ZMA Xi. 1003, Carcinoscorpius rotundicauda, Sabang, 2.4 /tm in diameter. The dermal musculature is Sumatra, no date of collection, leg. G. Herman: well developed. Immediately beneath the base- cocoons (there is a town Sabang on Celebes as well as a small N. but Van membrane there is of circular on island of Sumatra, according to ment a layer Benthem G. Herman stationed Jutting (1939) was on muscles, consisting of two rows of fibres. In- Sabang, Sumatra). of this there is teriorly layer a layer of ZMA 3 of C. rotundicauda, Xi.1006, specimens , Singapore, muscles which longitudinal measures dorsally died in Aquarium NAM in October 1964: cocoons from about 7.2 in diameter and about the gills of all three crabs. /im ventrally 12 /un. SYSTEMATIC SECTION — In the Alimentary system. the holotype TRICLADIDA MARICOLA between pharynx measures one-fifth and one- sixth of the It is constructed body-length. as Genus Ectoplana Kaburaki, 1917 follows: outer ciliated epithelium of about 2.4 undata (tm, outer longitudinal muscle layer of 2.5 /im, Ectoplana n. sp. circular muscle of 4.8 outer layer /tm, paren- Holotype: ZMA V.PI.603: sagittal sections on 2 slides, of 49 inner chymatous zone /tm, longitudinal stained in Mallory-Heidenhain; specimen collected from muscle of 4.8 inner circular muscle Tachypleus gigas from Singapore (ZMA Xi.1007). layer /im, of 24 inner ciliated of 2.4 Paratypes: ZMA V.PI.604.1: sagittal sections on 2 slides, layer /im, epithelium stained in Mallory-Heidenhain; specimen collected from /im. T. gigas from Deli, Sumatra; ZMA V.PI.604.2: sagittal The anterior ramus of the intestine does not sections stained in animal on 1 slide, Mallory-Heidenhain; extend in front of the but terminates collected eyes, from same specimen of T. gigas as paratype ZMA behind the brain. It off about 6 7 V.PI.604.1. gives or pairs All sections made intervals of 8 of lateral diverticula. Both rami are were at /im posterior 220 R. SLUYS - TRICLADS ON HORSESHOE CRABS 1. Dorsal view of of undata A: B: ZMA C: Fig. preserved specimens Ectoplana n. sp. holotype, paratype V.Pl.604.1, paratype ZMA V.Pl.604.2. confluent at the hind end of the This was the the deferentia into body. bulb, vasa open a large, difficult to observe in the holotype, whereas it rounded seminal vesicle. From the distal sur- in the vesicle could not be seen paratypes. Com- face of this a narrow ejaculatory duct missures between the rami be which into the blunt of the posterior may arises, opens tip The mouth situated the The seminal vesicle is lined present. opening is at penis papilla. with a hind end of the pharyngeal pocket. cuboidal, nucleate epithelium and is surround- ed by a layer of circular muscle fibres. — The consists of small bulb and Male reproductive system (figs. 2, 3). The penis a a very testicular follicles few in number: about 6-8 and blunt has are short papilla which a disposition either side of the the The on body. They occur more or more or less parallel to body surface. less in pairs between the intestinal branches (see nature of the lining epithelium of the papilla fig. 1A). In dorsal view the follicles are oval- could not be discerned and neither nuclei nor whereas in sections muscles A fine shaped, sagittal they appear subepithelial were seen. The secretion could be discerned in the as semi-circular or oval-shaped bodies. granular follicles and of the but the location of the are large occupy most space papilla, exact glandular between dorsal and ventral body surface. They cells remained obscure. The musculature of the extend from behind the ovaries up to the root of penis bulb is only weakly developed. the pharynx. The penis papilla projects into a rather In the pharyngeal region the vasa deferentia spacious dorsal portion of the male atrium form At first which distal enlarge to false seminal vesicles. narrows considerably into a narrow these of the ventral into the This run laterally nerve cords, part that opens common atrium. distal of the male atrium is but at the level of the mouth opening they turn narrow portion well and before rather and has less medially as as dorsally narrow long a more or undulated, In ZMA V.PI.604.1 the penetrating the penis bulb.