Effects of Temperature and Salinity on Postembryonic Growth in Mytilocypris Henricae (Chapman) (Crustacea, Ostracoda)

Effects of temperature and salinity on growth in the ostracode Mytilocypris henricae were studied both experimentally and in the field. In the experiments, individual growth during postembryonic development was monitored at 4 different temperatures (10°C, 15°C, 20°C, and 25°C, all at a salinity of 8 x 10-3) and at 3 salinities (S = 4 x 10-3, S = 8 x 10-3 and S = 16 x 10-3, all at 20°C). One hundred animals were subjected to each of 6 different treatments. Length and height of valves and the intermolt periods were measured. Growth was significantly affected by temperature, with animals growing more slowly at lower temperatures, but eventually attaining a larger size, except at 10°C where animals grew at the slowest rate of all but remained smaller than those at 15°C. Calculated length-height ratios (parameters for valve shape) were significantly different among the 4 investigated temperatures, but no clear pattern could be detected. No obvious effect of salinity on growth was observed. The length-height ratio, however, was significantly affected by salinity, and from stage 5 onward animals became more elongated at lower salinities. Measurements of valve length and height of the 8 larval stages and of the adult stage in 8 samples taken at different times of the year from Lake Bathurst (New South Wales, Australia), show that significant size differences exist in different seasons among animals in the same life stage.