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Alternate Title

Population Size Structure and Feeding Biology of Bathynerita naticoidea Clarke 1989 (Gastropoda: Neritacea) from Gulf of Mexico Hydrocarbon Seeps

Abstract

Bathynerita naticoidea is a numerically dominant gastropod in upper continental slope chemosynthetic communities of the northern Gulf of Mexico. A comparison of population size structure at four sites off Louisiana revealed site-specific differences in mean shell size consistent with different recruitment histories and growth rates. Where individuals grow to the largest size, population numbers are low and recruitment seems to be limited. Where individuals grow to the smallest size, populations are high and recruitment seems to be high. These patterns appear to parallel the population size pattern of the beds of Bathymodiolus childressi Gustafson et. al. 1998 inhabited by the snail, which suggests a link between the control of the two. Analysis of gut contents and fecal matter of B. naticoidea and the organic film on the shell surface of B. childressi confirmed initial assumptions that the snail feeds by radular browsing. Free-living bacteria are abundant on mussel surfaces and are ingested by the snail. The presence of bacteria in the gut and feces was, however, lower, possibly because of dilution by mucus and digestion. It is proposed that B. childressi provides more than a passive surface for organic film development. The mussel may control the organic film development, thus controlling availability of food to the snail.

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