TEMPERATURE EFFECTS ON THE EMBRYONIC DEVELOPMENT AND HATCHING SUCCESS OF THE SQUID LOLIGO VULGAR1S REYNAUDII

摘要

The squid Loligo vulgaris reynaudii spawns in two environmentally different areas, shallow (<60 m) inshore bays and in deeper (60―120 m) waters on the mid-continental shelf off the south east coast of South Africa. The temperature regimes between these two spawning environments are variable. The effects of temperature on the embryonic development of L. v. reynaudii were investigated at both stable and fluctuating laboratory temperatures and natural fluctuating conditions. The relationship between embryonic development time and water temperature was defined by a polynomial regression function. Embryonic development time decreased with increasing temperature. An optimum temperature range for development was identified between 12℃ and ～17℃, at which development took 50.1 and ～26.6 d, respectively. Outside the optimal temperature range (9℃ and 21℃) abnormal embryonic development occurred. Fluctuating temperature experiments were based on inshore temperature data collected over 7 yrs. The early development stages were more sensitive to variable temperature regimes than later development stages. Embryonic development under laboratory and natural conditions was similar. Natural upwelling events in the inshore spawning areas had a negligible effect on the development success of eggs in these areas.