Reference: Bio/. Bull. 172: 362-366. (June, 1987) A BLOOD-SUCKING SNAIL: THE COOPER'S NUTMEG, CANCELLARIA COOPERI GABB, PARASITIZES THE CALIFORNIA ELECTRIC RAY, TORPEDO CALIFORNICA AYRES J. B. O'SULLIVAN 1 , R. R. McCONNAUGHEY 2 , AND M. E. HUBER 2 1 Monterey Bay Aquarium, Monterey, CA 93940-1085, and 2 Scripps Institution of Oceanography, A-007, LaJolla, California 92093 ABSTRACT Feeding habits of the over 200 living species of Cancellariidae are largely un-known. The Cooper's nutmeg, Cancellaria cooperi, was seen by divers on the dorsal surface of Pacific electric rays. Torpedo californica. C. cooperi was observed to parasit-ize electric rays in the laboratory. The snails made small cuts on the ray's ventral surface and inserted their proboscises into the wounds. Snails were also observed to insert their proboscises into the mouth, gill slits, and anus, as well as previously exist-ing wounds. After insertion of the proboscis, the snails appeared to suck blood from the ray. In Y-maze experiments, the snails actively sought out electric rays, but not other common California bottom fishes. Host location appeared to be by chemosen-sory means. In the absence of electric rays, snails remained buried in the sand without moving for at least 1 2 days. Field observations indicate that snails may travel as much as 24 meters in search of rays. INTRODUCTION The family Cancellariidae comprises over 200 species of marine neogastropod mollusks inhabiting subtidal and bathyal sand and mud bottoms (Harasewych and Petit, 1982, 1984). Mechanisms of feeding in the Cancellariidae are almost entirely unknown (Harasewych and Petit, 1982, 1984; Petit and Harasewych, 1986). Early workers suggested that the snails feed on "soft-bodied microorganisms" (Graham, 1966; Olsson, 1970), but the snails' radular structure, relatively simple digestive sys-tem, long extensile proboscis, and accessory salivary glands are associated with a car-nivorous diet (Harasewych and Petit, 1982, 1984). These and other features suggest that they are piercing fluid feeders (Harasewych and Petit, 1982; Petit and Harase-wych, 1986). The snails also possess organs associated with distance chemoreception (Harasewych and Petit, 1982, 1984; Kohn, 1983). Previous reports of feeding are limited to single observations of cancellariids found on a bivalve mollusk, a gastro-pod, and pieces offish and squid eggs in an aquarium (Cernohorsky, 1 972; Talmadge, 1972; Garrard, 1975). Here we report that Cancellaria cooperi GABB, the Cooper's nutmeg, parasitizes the Pacific electric ray, Torpedo californica AYRES, by sucking the ray's blood. This is the first known report of gastropod mollusks parasitic upon fishes. MATERIALS AND METHODS Field observations and collections were made during scuba dives at depths of 20-22 m at an artificial reef ("Torrey Pines # 1 " Lat 3253'12"N Long 1 1 7 5ff5(TW; Call-Received 21 November 1986; accepted 20 March 1987. 362
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