The Sharp-rib Drill
The Sharp-rib Drill, Eupleura sulcidentata Dall, 1890, was first featured in this column in March 2015. Its shell has a "flattened" appearance, thanks to the blade-like varices ("ribs") that occur alternately every 180 degrees (every half-whorl). Sharp-rib Drills use their ribbon of teeth, known as radula, to etch tiny holes into the shells of other mollusks. Part of the feeding process, the holes allow the drill to inject paralyzing compounds into the prey's tissues. As many marine snails do, Sharp-rib Drills manufacture egg cases to protect their offspring during their early development. The 3/16-inch-tall egg cases are produced by the foot gland, located under the anterior part of the snail's foot. Curiously enough, the egg cases resemble miniature champagne goblets. The images show, on left, a female Sharp-rib Drill laying egg cases on an aquarium wall, with the foot gland appearing as a circular pink area under the foot; on right, spent egg cases laid on a ponderous ark shell.
The Sharp-rib Drill, Eupleura suicidentata. Left, female laying egg cases (one case indicated by arrow) Photo by Amy Tripp; right, spent egg cases, photo by José H. Leal.