Wentletrap Epitonium (Kanmacher, 1797)
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BASTERIA, 51: 95-108, 1987 Observations the clathratulum on wentletrap Epitonium (Kanmacher, 1797) (Prosobranchia, Epitoniidae) and the sea anemoneBunodosoma biscayensis (Fischer, 1874) (Actiniaria, Actiniidae) J.C. den Hartog Rijksmuseum van Natuurlijke Historie, P.O. Box 9517, 2300 RA Leiden, The Netherlands A review is of the literature given most important on parasite/host (or predator/prey) rela- modes of are mentioned. tions of Epitoniidae and Anthozoa, and various feeding An as yet association of unreported the wentletrap Epitonium clathratulum and the sea anemone is described. Both collected Bunodosoma biscayensis species were at Plage d’Ilbarritz,Côte Bas- SW. que, France. Field and aquarium observations suggest that E. clathratulum feeds on food in the ofits host-anemone. partly digested gastric cavity This is achieved in a way as yet unprecedented: the wentletrap climbs the oral disc of its host and introduces its proboscis the mouth slit into the feed. The through gastric cavity to sequence ofclimbingthe host and feeding is described and depicted. Key words: Gastropoda, Prosobranchia, Epitoniidae, Epitonium clathratulum, Actiniaria, Actiniidae, Bunodosoma France. biscayensis, nematocysts, parasite/host relation, INTRODUCTION of Associated occurrence a species of wentletrap (Epitonium tinctum Carpenter, 1864) and sea anemones was already incidentally mentioned in the literature by Strong in to 1930 (p. 186), whereas Ankel (1938: 8) seems have been the first to mention a feed species [E. clathrus (Linnaeus, 1758)] to upon these Cnidaria. He reported to have found both actinian nematocysts and zooxanthellae in specimens from Naples (Italy) and 1 few Kristineberg (Sweden) . A years later another species, Habea inazawaiKuroda, 1943, was described as "semi-parasitic" on the actinianDiadumene luciae(Verrill, 1898) (Habe, 1943). Thorson (1975), basing himselfon the above-mentionedreports and on observations also personal on Opalia crenimarginata (Dall, 1917), a wentletrap, thereupon suggested that the whole family Epitoniidae is "more or less adapted to a mode of life". Thorson's illustrated stimulated parasitic nicely paper further research, first of all Robertson, who, in a number of added more to our by elucidating papers, the knowledge on subject than any other single author. As aresult the Epitoniidae are now well-known as associates and temporary parasites/micropredators of Actinaria (sea anemonesproper), and to a lesser degree of Zoantharia (encrusting anemones) and Scleractinia(stony corals). A single species, viz., Epitonium indianorum(Carpenter, 1864), is known to appreciate Ceriantharia as food(Shimek, 1986: 173), although it is also found associated with Actinaria (cf. next page). 1 doubt Ankel's There is no reason to statementabout the nematocysts, but this author is almost certainly in the of zooxanthellaein from No actinian with error as concerns presence specimens Kristineberg. species zooxanthellae occurs in Swedish waters. 96 BASTERIA, Vol. 51, No. 4-6, 1987 mentioned that the number of Robertson (1963: 58) some 25 years ago already still species of Epitoniidae amounted to several hundred, and currently new species are as as 1985, added no less than 37 regularly described; Kilburn, e.g., recently species, added another 12. It is therefore not that whereas Bouchet & Waren (1986) surprising Fretter & Graham, 1982: new associations are also reported regularly (most recently: Robertson 387; Kilburn & Rippey, 1982: 78; Robertson, 1983a; & Schutt, 1984; 1985: Bouchet Waren, 1986: 523, Sabelli & Taviani, 1984; Kilburn, 295, 326, 331; & little is known about the and 532), but in spite of this nothing, or very only, biology it is ob- hosts of the great majority of species. However, from the available knowledge deal from one vious that the relation between snail and prey/host(s) may vary a good species to another. Epitionium albidum (d'Orbigny, 1842), in the Caribbean exclusively found associated 2 with the has been observed to large sea anemone Stichodactyla helianthus (Ellis, 1767) , the column off little of feed on the peripheral tentacles, on (by nipping pieces tissue), 1983b: A similar of and, less commonly, on mucus of its host (Robertson, 4). way 1963: and is feeding was observed in E. rupicola (Kurz, 1860) (Robertson, 55), possibly corals, such as also employed by species feeding upon the outer surface of solitary mille- E. ulu Pilsbry, 1921 (Bosch, 1965; Robertson, 1970: 45-46). Another species, E. feed on ectodermal mucus of its host, costatum (Pease, 1860-1861) seems to exclusively a colonial zoanthid 1981: 14). Other species, such as the Palythoa spec., (Robertson, Californian E. tinctum (Carpenter, 1864) [best known hosts: Anthopleura elegantissima (Brandt, 1835) and A. xanthogrammica (Brandt, 1835)] and E. indianorum (best known both 3 to feed hosts: Tealia crassicornis and T. lofotensis, sensu Hand, 1955) appear 4 the tentacles of their hosts and to a lesser on columnar ver- predominantly on , degree echinocostatum described to live rucae (Salo, 1977). The Carribean E. (d'Orbigny, 1842) 5 with the actinian (Duchassaing, 1850) on the leaves associated Bunodeopsis globulifera , to of turtle Thalassia testudinum ex has been observed feed grass (Banks Konig, 1805), of its exclusively on the tentacles quarry (Robertson, 1983 a). As mentioned above, the relation of Epitoniidae and their cnidarian associates is Some often referred to as parasitism (the snails being regarded as parasites). authors, whereas however, avoid this term and prefer to speak of predation (and predator), to others use both terms more or less indifferently, as if it is difficult decide which is most suitable. If anything, this indicates that the mode of feeding in Epitoniidae ap- case of if to be such. parently represents a marginal parasitism only, regarded as Speaking in general, the gamutof life-styles/feeding-strategies ranging from super- 2 is known it should Althoughthis species generally asStichodactyla ( = Stoichactis) helianthus (Ellis, 1767), in and later fact be referred to as S. anemone (Ellis, 1767). Both species were figured by Ellis (1767; 436, pi. 19) brief & 1786: Michelotti, 1866: on supplemented with a very description (Ellis Solander, 6). Duchassaing & and the first selected 122(28), already suggested this synonymy McMurrich (1889: 37), acting as reviser, McMurrich, 1905: anemone as the specific name (see also 10). 3 1986: I have discussed should be it is In a recentpaper (Den Hartog, 87) that this species re-named, as Ur- not identical with the Atlantic T. lofotensis (Danielssen, 1890) [presently regarded a junior synonym of ticina eques (Gosse, I860)]. * see Sisson For a beautiful picture ofE. tinctum in the act of feeding (1986: 255-256). 5 The is in need of revision. With the of it is dif- genusBunodeopsis Andres, 1880, present state knowledge ficult decide whether more of occur in the Caribbean. Robertson's to one, two, or species Bunodeopsis figure of the species (1983a: 100, fig. 1) conforms best to the form/species described as Bunodeopsis antilliensis Duerden, 1897 (pp. 7-11, pi. 1 figs. 1-2; cf. also Duerden, 1898: 455-456). Den Hartog: Epitonium clathratulum and Bunodosoma biscayensis 97 predator to the most advanced examples of obligate parasitism is so gradual and with it diverse, so many exceptional cases, that seems almost impossible and not always meaningful to delimit both phenomena (and indeed, what else is parasitism than a specialized form of predation). As a consequence it is practically impossible to give a definitionof and therefore will parasitism acceptable to everyone, marginal cases pro- bably always give rise to disputes. An interesting case illustrating the problems is presented by E. greenlandicum (Perry, 1811). This species has been observed in situ to small which are forage upon sea anemones, Gonactinia prolifera (M. Sars, 1835), swallowed whole, but underexperimental conditions it showed a preference for a much larger anemone species, viz., Metridium senile (Linnaeus, 1767), acting as an ec- toparasite/micropredator, and, like E. albidum, nipping off pieces of columnar tissue (Salo, 1977). If parasitism is simply defined, as often done in practice, as an association in which one component (the parasite) lives at the expense of another (the host), without killing in the in which it (or only doing so long term) [as opposed to predation sensu stricto, the other component (now called prey) is killed], many Epitoniidae may indeed be if the referred to as parasites, or more specifically: temporary ectoparasites, even association often more than diet. seems to represent hardly a monophagous However, in a number of species there is definitely a tendency to stick or to keep close to one and the host and least known attach their same specimen, at some species are to egg cap- sules to their host. The mode of feeding of the Californian Opalia crenimarginata seems to be of a different character than the examples mentioned above. Thorson (1957: 56-57) described this species to parasitize the anemone Anthopleura xanthogrammica, the snail piercing the body-wall of its host, introducing its long proboscis, and subsequently sitting "quietly sucking for hours or even days". In particular Thorson's statement that the whole pro- boscis is sometimes introduced, suggests strongly that it actually perforates the body- wall and enters the gastric cavity [and not that it is simply pushed into the body-wall, to that O. suck up body fluids (cf. Bandel, 1984: 63)]. Therefore, it seems quite possible in