Ecology of hydrothermal vent gastropods

Pendlebury, Sophie Jane Dakin (2004) Ecology of hydrothermal vent gastropods. University of Southampton, Doctoral Thesis.

Abstract

The physical, chemical and biological processes of deep-sea hydrothermal vents undergo many large- and small-scale temporal and spatial variations.  The ecology of several species of hydrothermal vent gastropod, the majority of which are limpets, is examined, with particular emphasis on spatio-temporal variations.

Gastropods were collected from vents at 9°N (EPR), the Galapagos Rift and Menez Gwen (MAR) using submersibles and acoustically released cages.

The gametogenesis, fecundity and sperm storage of hydrothermal limpets was investigated using histology.  A simple method allowing estimates of actual fecundity is developed.  In general the maximum oocyte sizes observed for all species are less than those cited in literature.  No episodicity in terms of space or time is observed in the gametogenesis or fecundity of the species examined.  Early maturity and a low “brood” number is found in Lepetodrilus elevatus.  Continuous reproduction coupled with lecithotrophic larvae is suggested for all species.

The feeding behaviour of Lepetodrilus atlanticus is examined and the condition and fatty acid content of other vent gastropods is examined.  It is suggested that L. atlanticus is capable of suspension feeding as well as grazing.  No spatial or temporal variation in the condition indices or fatty acid analysis is evident.  No difference in the diets of the seven vent gastropod species was evident.

The radula composition of four species of vent limpet is examined;  using SEM coupled with energy dispersive X-ray analysis (EDS) and histology.  The radulae of two species, Eulepetopsis vitrea and Lepetodrilus elevatus contain elevated levels of iron and silica.

Oxygen and Carbon stable isotopes are used to investigate the microecologies of eight species of vent gastropod.  A method is developed to allow the analysis of shells containing both aragonite and calcite.  The fractionation of both carbon and oxygen is species dependent, with the δ¹³C values generally high, when compared to those of intertidal gastropods.  It is suggested that although the results may be impaired by factors such as pH variation, Rhyncopelta concentrica and Cyathermia naticoides have a higher temperature tolerance than the remaining species.

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