Temperature effects on embryo and early larval development of the spiny lobster Jasus edwardsii, and description of a method to predict larval hatch times

Ovigerous spiny lobsters (Jasus edwardsii) with known egg extrusion dates w ere held at four temperatures and embryo development was monitored at weekl y intervals. Times to hatch were approximately 65 days, 95 days, 155 days a nd 163 days at 18 degrees C, 15 degrees C, 12 degrees C and ambient tempera tures (9-14 degrees C) respectively. For the embryos, the appearance of the median eye, the eyes and the chromatophores, and an eye index, were used t o calculate the biological zero, i.e. the theoretical temperature at which development ceases, which, for J. edwardsii, was 7.53 degrees C. A formula based on the eye index was then derived to predict time to hatch at a range of temperatures using the cumulative difference between the rearing temper ature and the biological zero. Data were also collected on the time between females moulting and mating, the total number of larvae successfully hatch ed for a range of female sizes and Stage I phyllosoma larval size in relati on to the embryo-rearing temperature.