Abstract

The neogastropod Amphissa columbiana is found abundantly in subtidal areas of the San Juan Archipelago. Two populations studied were composed of distinct age classes of sexually immature and mature specimens. Reproduction appears to take place in the fall by snails at least two years old. Amphissa is a chemoreceptive scavenger that usually feeds on carrion and on dead and injured animals. Feeding behavior is mediated by chemical attractants from dead and traumatized tissue. An unusual feeding association is formed where Amphissa congregate around feeding predators to share their meals. A specific defense mechanism is deployed by Amphissa especially in response to aggressive sea stars. In addition to using common shell twisting gyrations etc., seen in many gastropods, the proboscis of an Amphissa is inserted into the ambulacral groove of a sea star. The star responds by retracting its tube feet, lifting its ray and releasing the captured Amphissa. The radial nerve of the star may be involved in the pr[o]boscis attack.

Degree

College and Department

Life Sciences; Plant and Wildlife Sciences

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