Embryonic development and hatching rate of blue swimming crab, Portunus pelagicus at different salinity regimes

Abstract

The effect of salinity (5, 15, 25, 30, 35, 45 ppt) on spawning success, egg size and hatching succes the blue swimming crab, Portunus pelagicus were studied. The morphology of embryo were observed classified into 10 embryonic stages. Berried females of blue swimming crab, sampled from Gelang Patah, Johor. This study is important to expand the knowledge on P. pelagicus embryo and it's hatching mechanism. Berried female incubated in 5 ppt did not survive thus any further study in this treatment was not conducted. Female incubated 15 ppt did not spawn and those incubated in 45 ppt had retarded development and eventually released thus the study on egg size was not conducted. The Prehatch stage mean egg diameter that incubated in 25 ppt was largest (380.24 ± l.78μm) compared to ones incubated in 30 ppt (365.23 ± 0.64μm) and 35 ppt (357.34 ± l .04μm). Higher percentage increase in egg size occurred mostly at stage near hatching. Total incubation period for berried female incubated in 25, 30 and 35 ppt was 10 days. In this study, berried females of P. pelagicus tend to have unsynchronised hatching. The morphological characteristic of P. pelagicus embryo was almost the same as other brachyuran crab in which, the appendage will form followed by eye formation, present of chromatophore, heartbeat and then ready to hatch.