Temperature-dependent development and growth of Calanus chilensis Brodsky from Northern Chile

Development and growth of Calanus chilensis Brodsky were studied under laboratory conditions to establish the temperature-dependent rate function of embryonic development, to analyze potential maternal effects on development rates, and to study development and growth from egg to adult. As in previous studies, embryonic duration estimated at 9, 12, 15, 18 and 20 degrees C, was described by the Belehradek model of development and the fitted equation was D = 947.7 (T + 11.0)(-2.05), where D is embryonic duration (days) and T is temperature (degrees C). The parameter values, a = 947.7 and t(0) = 11.0, were comparable to those published for C. marshallae. At a constant temperature of 15 degrees C the embryonic duration depended on females, indicating a significant maternal effect and increasing variance within temperatures. When reared with excess of food at 15 degrees C, individual copepodites grew exponentially, with a generation time of 38 days. The weight-specific growth rate was 0.114 day(-1), and changes in body length were linear through time. Our results show that temperature-dependent predictions of generation time, number of generations per year, and female body size are not consistent with field data, suggesting that food shortage during the annual cycle may retard development and affect adult body size. An untested alternative hypothesis involves the potential vertical migration and permanency of individuals in deep waters. Development under low temperatures would give rise to larger animals and to fewer generations a year, consistent with the temperature-dependent prediction. (C) 1998 Elsevier Science BN. All rights reserved.