Effects of food concentration and temperature on development, growth, reproduction and survival of the copepod Pseudodiaptomus euryhalinus

Abstract

A series of experiments were conducted to evaluate the effect of temperature and the microalgae Isochrysis sp. concentration on the copepod Pseudodiaptomus euryhalinus cultured in laboratory conditions. First, the ingestion rate of P. euryhalinus was evaluated with different concentrations of Isochrysis sp. [2.74, 5.47, 8.21, 10.94 and 16.41 µg mL⁻¹ organic dry weight (ODW)] during 24 h, at a temperature of 24.3 ± 0.3 °C. The ingestion rate increased in direct proportion to microalgae concentration, reaching an asymptotic point at 16.41 µg mL⁻¹. P. euryhalinus was then cultured for 11 days at 24.4 ± 0.3 °C with different concentrations of Isochrysis sp. (5.47, 8.21, 10.94 and 16.41 µg mL⁻¹ ODW) in order to quantify the optimal food density. It was observed that food concentration did not have a significant effect on the development, growth, maturity, fecundity and survival of P. euryhalinus. The effect of different temperatures (19.4 ± 0.5, 21.9 ± 1.0, 24.2 ± 0.3, 27.8 ± 0.5 and 30.1 ± 0.8 °C) on the development, growth, survival and sex ratio of P. euryhalinus fed with Isochrysis sp. at 5.47 µg mL⁻¹ ODW was evaluated for 11 days of culture. The temperature had an inversely proportional effect on the time of development, and highest survival and growth were observed at 24.2 ± 0.3 °C. Finally, the effects of different temperatures (21.7 ± 0.5, 24.2 ± 0.3, 27.2 ± 0.3 and 30.7 ± 0.6 °C) in nauplii production of adult copepods were evaluated during 11 days. Nauplii production increased in direct proportion with the temperature. These results suggest that the optimum temperature and food concentration for P. euryhalinus culture are 24.2 ± 0.3 °C and 5.47 µg mL⁻¹ ODW of Isochrysis sp., respectively.