Effects of changes in salinity and temperature on survival and development of larvae and juveniles of the crucifix crab Charybdis feriatus (Crustacea:Decapoda:Portunidae)

Abstract

An experiment was carried out to determine the effects of changes in temperature and salinity on the survival and development of the larvae (zoea, megalopa) and crab instar 1 (C1) juveniles of the crucifix crab, Charybdis feriatus. Larvae and juveniles in each stage of development were reared at various salinity and temperature combinations: four salinities of 15, 25, 35 and 45‰ for each of the 5 zoea stages, five salinities of 5, 15, 25, 35, 45‰ for the megalopa and six salinities of 0, 5, 15, 25, 35, 45‰ for the C1 juveniles, at temperatures of 20, 26 and 32 °C. Results showed that both salinity and temperature significantly affected survival of larvae and juveniles and there was a significant interaction between salinity and temperature. There was generally high survival of zoea and megalopa at 25, 35‰ in 26, 32 °C and of C1 at 25‰ in 20, 26, 32 °C. Salinity and temperature also affected onset of development and duration of molt. There was rapid and synchronous development at 25 and 35‰ but delayed and extended at 45‰. With decreasing temperature, there was a delay in the start of development and duration of molt was prolonged. Larvae and juveniles did not survive in 15‰ even with 6 h of acclimation while larvae survived at 45‰ during abrupt and gradual transfer. The optimum salinity–temperature combination recommended for the larval and nursery rearing of C. feriatus is 25–35‰ at 26–32 °C.