NOTES

A Gastropod Parasite of Solitary Corals in Hawaii'

H. F.BoSCH2

OF THE SPECIES of wentletraps (marine gas­ aquaria eventually became infested with them tropods of the family Epitoniidae) that live during the course of several separate experi ­ with or feed upon anthozoan coelenterates, ments carried out at the Hawaii Marine Lab­ most are associated with sea anemones . Rob­ oratory. Thirty Fungia, in one instance, became ertson (1963) lists four species of these snails infested within three weeks after having been that are known to be either pred ators or ecto­ placed in a large holding tank in order to test parasites of sea anemones, as well as two oth­ their ability to survive in an artificial environ­ ers that are assumed to be so. A seventh wen­ ment. These corals had been routinely inspected tletrap, however, associates itself with a for damages due to collecting prior to being scleractinian, rather than with an actinian, placed in the freshly cleaned tank, and seemed Found attached to solitary corals of the genus free of Epitonium eggs or adults. Yet each Fungia in the Philippine Islands (Root, 1958), coral harbored from one to six snails, with this wentletrap has been tentatively identified attendant egg masses, at the end of the three . as Epitonium aff. costulatum by Robertson, who week period. The increase in the snail popula­ considered it likely that the snail was feeding tion escaped notice during the interim as upon the coral. Thorson (1957) suggested that neither the snails nor their eggs ever appeared perhaps all members of the Epitoniidae were on the upper, feeding surface of the corals. adapted for a parasitic mode of life. Evidence Rather they restricted themselves to the un­ supporting both these ideas comes from a sim-' tentacled areas of their host : the periphery or ilar Epitonium-Fungia relationship recently undersurface. By what means the snails were noted in Hawaii. introduced into the tank is not known. Pos­ Specimens of the solitary coral, Fungia scu­ sibly a few eggs had escaped notice when the taria Lamarck, collected in Kaneohe Bay, Oahu, corals were inspected, or larvae had entered during the summer and fall of 1963, occasion­ with the sea water when the tank was initially ally had masses of small white eggs attached to filled. In either instance, it is clear that a num­ them. Usually one or two fragile white snails ber of larvae had rapidly matured and had also clung to the corals or to the egg masses. subsequently produced large clutches of new These snails were identified as Epitonium ulu eggs. Although the sea water in the tank was Pilsbry, a wentletrap previously reported only not filtered or renewed during the three weeks, from Hilo, Hawaii (Pilsbry, 1921:376; Ed­ conditions seemed favorable for larval viability mondson, 1946:138 ). While only a small per­ and growth, as many active veligers were prom­ centage of the corals taken in the field had inent whenever egg masses were examined adherent eggs or snails, all corals kept in under the microscope. This seemingly rapid development of sexually mature wentletraps, the largest of which attained a length of 16.5 1 Contribution No. 221, Hawaii Marine Labrat ory, mm, provides an index of maximal growth for This study was in part supported by a N ational Science Epitonium ulu. Found ation Summer Fellowship for Graduate Teach­ ing Assistants. Manuscript received May 26, 1964. Tissue lesions on the undersurfaces of some

2 Present address : Department of Oceanography, of the corals (F ig. 1) may have been caused The Johns Hopkins University, Baltimore, Maryland. by Epitonium, but this was difficult to prove

267 268 PACIFIC SCIENCE, Vol. XIX, April 1965

FIG. 1. The undersurface of the solitary coral Fungia scutaria Lamarck with the wentletrap Epitonium ulu Pilsbry and egg masses (arrows). Th e wentle trap is 16.5 mm long. W hite area to the right of the snail is a lesion in the coral's tissue. inasmuch as the snails avoided the light. While ACKNOWLEDGMENTS no direct observations of wentletraps feeding I thank the various members of the Uni ver­ on the corals were made, indirect evidence for sity of Hawaii faculty and of the B. P. Bishop this behavior was furnished by dissection. Vis­ Museum staff who have so kindly contributed cera of snails taken from a coral invariably helpful suggestions and criticism. I am particu­ contained copious amounts of pink tissue in larly indebted to Dr. Alison Kay for identifying which were imbedded symbiotic algal cells the specimens of Bpitonium ulu as well as for ( zooxanthellae) and nematocysts, all charac­ her interes t in this note. teristic of the corals. Moreover, wentletraps placed near corals which had been stained with a vital dye (n eutral red ) soon became suffused REFERENCES with the same color due to the ingestion of EDMONDSON, C. H. 1946. Reef and shore fauna dyed coral tissue. ( For such feeding to occur, of Hawaii. B. P. Bishop Museum Spec. Pub. it was necessary to keep the corals and the 22:138. snails in the dark. ) PILSBRY, H. A. 1921. The marine molluscs of W entletraps in the absence of their egg Hawaii. Proc. Acad. N at. Sci. Philadelphia masses were never found on Fungia. Thus the 72 (3) :376. relationship between these two animals may be correlated with the breeding cycle of the ROBERTSON, R. 1963. Wentletraps ( Epitonii­ snails and may be only intermittent or tempo­ dae) feeding on sea anemones and corals. rary. Th e foregoing observations, however, Proc. Malacological Soc. London 35 (2 and show that Bpitonium ulu is at least an occa­ 3): 51- 63. sional ectoparasite of Fungia seutaria. Th is evi­ ROOT, ]. 1958. Rapa rapa in the Sulu Sea. Ha­ dence supports Th orson's contention that the waiian Shell News 7 (l) :7-8. Epitoniidae in general are adapted to parasit­ THORSON, G. 1957. Parasitism in the marine ism and also Robertson's view of the parasitic gastropod family Scalidae. Vide nsk, Meddel. nature of Bpitonium aff. eostulatum. fra Dansk naturhisr, Foren. 119:55-58.