Effects of temperature on the egg incubation period, survival and developmental period of larvae of the mud crab Scylla serrata (Forskål) (Brachyura: Portunidae) reared in the laboratory

Abstract

This study examined effects of temperature on the egg incubation period, survival and developmental period of larvae of the mud crab Scylla serrata reared in the laboratory. Pre-mated females were held in tanks in which temperature varied seasonally; their spawning and hatching were recorded daily. The number of days from spawning to hatching and mean rearing temperature were determined for 92 females. The egg incubation period decreased exponentially from 30 to 10 days with increasing mean temperature in the range 20.3–30.0 °C. Larvae were reared in 1-l beakers at seven temperatures (17, 20, 23, 26, 29, 32 and 35 °C) and fed with rotifers and Artemia nauplii. Survival to the first crab stage occurred when larvae were reared at 23–32 °C: the best survival rate was obtained at 29 °C. Also, the number of days from hatching to attainment of each larval stage decreased with increasing temperature. Relationships between mean temperature ( T) and egg incubation period and larval developmental period from hatching to reach the megalopal stage ( D) were analyzed using the following three equation models: power function, D= aT b ; Bělehrádek's equation, D= a( T− α) b ; and from heat summation theory, D= a/( T− α). For both egg and larval development, the equation of heat summation theory was the best model to characterize the relationship between temperature and the number of days required for development. The biological lower critical temperature represented by parameter α was similar for eggs and larvae: 13.93 and 13.82 °C, respectively, for Bělehrádek's equation and 15.70 and 15.08 °C for heat summation theory.