Seasonal fauna of some ephemeral saline waters in westren Victoria with particular reference to Parartemia zietziana Sayce (Crustacea: Anostraca)

Abstract

Seasonal changes in physical, chemical and biological aspects of 16 ephemeral saline lakes in the Lake Corangamite district of western Victoria were studied. High temperatures, high salinities and low dissolved oxygen levels were recorded in the summer months. The less saline lakes contained a halophilic fauna which included Branchinella compacta, Daphniopsis pusilla, Boeckella triarticulata and Mesochra sp. In the more saline lakes, where salinity did not fall below 40%, at any time during the year, a truly halobiont fauna was present consisting of Parartemia zietziana, Calamoecia salina, C. clitellata, Microcyclops arnaudi, Australocypris robusta, Diacypris sp, and Platycypris sp. The occurrence of these halobiont species appeared to be controlled by salinity, new upper salinity records showing that all these species tolerate salinities well in excess of 100‰. Autecological studies on P. zietziana showed that development proceeded through 15 juvenile stages. Both subitaneous and resting eggs were produced with salinity being the controlling factor. Resting eggs hatched in response to a salinity drop over an approximate range of salinities of 50-200‰. In many populations development of the juveniles was retarded in stages 12-14. The length of adults was found to vary inversely with salinity. The occurrence of P. zietziana is discussed and it is concluded that the species occurs only in highly saline, astatic localities.