Ecology of Coxiella (Mollusca, Gastropoda, Prosobranchia), a snail endemic to Australian salt lakes

Abstract

Features of the taxonomy, physiology and ecology of Coxiella, a gastropod of Australian salt lakes, are discussed. It is concluded that the present taxonomic basis for species descriptions needs complete revision. The genus is widely distributed in southern Australian ephemeral and permanent salt lakes and is also known from central Australia and northern Queensland. Although an osmoconformer, active specimens have been recorded from lakes with salinities between 6 and 124 g l −1. With gradual acclimation, a population from Lake Tallinga, a South Australian ephemeral salt lake, had LD 50 limits for salinity of 2 and 95.5 g l −1; with direct transfer these limits narrowed to 6 and 83 g l −1. Animals from the same locality were moderately tolerant to high temperatures, desiccation and low oxygen concentrations. The life-cycle seems to involve iteroparous, intermittent reproduction, with rather few resources devoted to reproduction. Survival over the unfavourable season (lake dry or too saline) is as adults. It seems that Coxiella survives in ephemeral salt lakes because its behaviour meliorates environmental extremes and because it has an ecological strategy which can successfully overcome the risk of life in such environments.