Meeting Abstract
P2.45 Friday, Jan. 4 Castles in the sand: Morphology, sediment profiles and the construction of sand collars by the naticid gastropod Euspira lewisii (Gould, 1847) NEWEL, M.S.*; BOURNE, G.B.; University of Calgary and the Bamfield Marine Sciences Centre; University of Calgary and the Bamfield Marine Sciences Centre bourne@ucalgary.ca
Naticid gastropods, including Euspira lewisii, typically deposit their eggs within elaborate masses aptly referred to as �sand collars�. In these collars, encapsulated eggs are sandwiched in a matrix of extruded mucus with embedded local sediment particles. This matrix, which was very resistant to chemical degradation, was composed of a homogeneous blend of acid and neutral mucosubstances and traces of protein. Sediment profiles from collars collected from Barkley Sound, Vancouver Island, as well as those deposited in the lab, indicated that egg masses were constructed using the finest grains available in local sediments. In further lab experiments, snails deposited collars in �fine�, �mixed� and �coarse� grained sediments. In each case, collars contained a significant shift to finer grained sediment but with a commensurate increase in the size of grains that mirrored the substrate. These results, along with observations of snails forming collars at or near the surface, provide a possible mechanism for sand collar construction. Once a snail has burrowed into the substrate, sediment captured on the ventral surface of the propodium is transported to the snail�s right mantle opening. The observed shift to finer grained sediments may simply represent the fraction of local sediment that is small enough to be captured and retained by the snails� mucociliary currents. At the excurrent mantle cavity opening, the mucus and entrained sediment coats the string of encapsulated eggs as they are extruded. Finally, this combined egg mass is molded, and possibly treated to initiate hardening, as it passes posteriorly out under the right dorsal flap of the propodium, ultimately leading to the production of a complete sand collar.
