The effect of salinity and temperature on the larval development of Mithrax caribbaeus Rathbun, 1920 (Brachyura: Majidae) reared in the laboratory

Larvae of Mithrax caribbaeus were reared in the laboratory in a factorial experiment employing three temperatures (22, 25 and 28 degrees C) and three salinities (32, 35 and 38 parts per thousand). Survival and duration of larval stages were recorded. Ovigerous females of M.caribbaeus were collected from the south-eastern coast of Margarita Island, Venezuela, and maintained in individual aquaria until hatching. Eggs from three of the females hatched in the laboratory. Larvae from each hatching were subdivided into groups of 10 and reared in plastic bowls containing 200 ml filtered and UV-irradiated sea water at different temperature-salinity combinations. Larvae were transferred daily to clean bowls with newly hatched Artemia nauplii, and the number of molts and mortality within each bowl was recorded. Complete larval development of M.caribbaeus occurred under all experimental conditions. Salinity had the greatest effect on percentage survival of each larval stage and complete development up to the first crab stage. The first zoeal stage exhibited the highest survival rate. Maximum survival for this stage occurred at 20 degrees C, 32-35 parts per thousand. Survival in the second zoeal stage and the megalopa was affected only by salinity. Effects of temperature and salinity on survival decreased with advance in development. The duration of the two zoeal stages, the megalopa, and development to the first crab stage showed a gradual reduction with increasing temperature. Salinity showed an effect on the duration of zoeal stages but not on the megalopal stage. Development from hatching to the first crab stage required 8-18 days, depending on the temperature-salinity combination, and was inversely related to temperature, averaging 14.3 days at 22 degrees C, 11.8 days at 25 degrees C and 9.2 days at 28 degrees C.