Triviidae

Abstract: The marginellid gastropod Hydroginella caledonica (Jousseaume, 1876) has been observed parasitizing sleeping fishes of the families Scaridae, Serranidae and Pomacentridae at coral reefs in New Caledonia during the night, The snail inserts its proboscis in the fish tissues and probably pumps some body fluids. Fish parasitism is also exhibited by another species in the genus Tateshia Kosuge, 1986, here transferred from the Olividae to the Marginellidae. Several Indo-Pacific marginellids conchologically resemble H. caledonica, and it is anticipated that more species in the family will prove to have a similar feeding biology. Gastropods are known to parasitize or to be associated with many phyla of marine invertebrates. The most successful parasitic prosobranch radiation is certainly the eulimid radiation, parasitic on the five classes of echinoderms (Waren, 1984), but there are also significant gastropod radiations parasitizing various groups of Cnidaria (Architectonicidae, Epitoniidae, Coralliophilidae, Ovulidae and Pediculariidae). Species in the gastropod family Pyramidellidae parasitize other gastropods, bivalves, crustaceans, polychaetes or sipunculans. Other specialized host/prey associations include radiation of the families Triphoridae, Cerithiopsidae, and Fissurellidae (in part) on Demosponges; of the families Lamellariidae and Triviidae on tunicates; and many Opisthobranch radiations on Demosponges, Cnidaria and Bryozoa. The association reported here between a prosobranch gastropod and a fish occurs only at night, and appears to be parasitism. In this paper, I will (a) describe the occurrence and nature of the association; (b) discuss the taxonomy of the gastropod involved in the association; (c) discuss the taxonomic position of the recently described fish parasite genus Tateshia, and (d) finally discuss the marginellid radiation in the light of this new finding. Parasitism of the ray Torpedo califarnica Ayres by the cancellarid gastropod Cancellaria cooperi Gabb has recently been reported both in the field and in aquarium (O'Sullivan et al., 1987). The snails penetrate the fish tissues by their proboscis and appear to suck blood from the ray. DESCRIPTION OF THE ASSOCIAnON Fishes of the families Serranidae, Scaridae and Pomacentridae were first casually observed to carry small gastropods (Fig. 1)when sleeping in small cavities in coral reefs offNoumea, New Caledonia. Those fishes usually hide in cavities from dusk approximately 1800, until early in the morning, at sunrise. In the cavities, they lie in contact with the bottom by the ventral or lateral sides, sometimes protecting themselves by producing a mucus cocoon (Casimir, 1971; Winn, 1955; Winn and Bardach, 1959; Fourmanoir and Laboute, 1976). After this initial observation, several night dives were conducted specifically to look for such associations. Dives were made by J. C. Estival at 110t Crouy (22°21'S, 166°20.5'E) in November 1981, and 110tGoeIand (22°22'S, 166°22'E) in May 1982; by myself at 110tGoeland in October 1985. P. Laboute and J. L. Menou also supplied observations made during their dives in the area between 1980 and 1985.