On this blog, we've had all kinds of blood-suckers - leeches, bats, ticks, and lice. But when it comes to vampirism, a snail doesn't usually come to mind, but that's exactly what today's parasite is - a blood-sucking snail. Cancellaria cooperi is a snail that appears to have specialised to feed on the blood of the Californian Torpedo Ray, Torpedo californica. These snails spend most of their time inactive, buried in the sand and waiting for the next potential victim. But when a torpedo ray comes along, this mollusc springs into action. Equipped with an extremely keen sense of smell, C. cooperi is capable of detecting the slightest trace of ray mucus, and observations of trails left by these blood-thirsty snails indicate that they can sniff out a ray from as much as 24 metres (about 80 feet) away. Upon making contact, the snail begin touching and exploring the dorsal surface of the ray with extended tentacles, before extending its proboscis and making a small incision with its scalpel-like radular teeth. It then insert its proboscis into the wound and begin its blood-sucking session, which can last for up to 40 minutes. This snail appears to be a specialised parasite of the California torpedo ray, and has no interest in approaching other benthic fishes which are common in its local area, though they have been observed to feed on the Angel Shark (Squantina californica) in laboratory settings. Surprisingly, the torpedo ray seems unperturbed by the experience of being felt up by a snail before getting cut and probed and having its blood-sucked by the vampiric mollusc. But then, torpedo rays seems to be generally unresponsive to most forms of prodding and mechanical stimuli.
Source: O'Sullivan, J.B., McConnaughey, R.R. and Huber, M.E. (1987) A blood-sucking snail: the Cooper's Nutmeg, Cancellaria cooperi Gabb, parasitizes the California Electric Ray, Torpedo californica Ayre. Biological Bulletin 172: 362-366.
Post by Tommy Leung and photo by Lovell & Libby Langstroth.