Reproductive Biology of the Flattened Porcelain Crab, Petrolisthes Rufescens (Porcellanidae: Anomura: Crustacea) From Ain Sukhna, Gulf of Suez, Egypt

Abstract

The reproductive biology of the porcelain crab Petrolisthes rufescens (Heller, 1861) population at Ain Sukhna (62 km south Suez City) was studied during the period from April 2000 to May 2001. Sexual dimorphism was determined based on morphological differences between sexes. Abdomen is semi-circular with four pairs of biramous appendages in females, but tapering with only two pairs of unequal uniramous appendages (pleopds) in males. Size at first maturity was determined using allometric growth occurring at puberty from the relationships between male's 2 nd pleopodal length and chelae length against carapace length (C.L.) and by the appearance of distinctive ovaries in females. Overall sex ratio for this crab species was 1: 0.70 males to females, with highly significant Chi-square value (X 2 = 7.486, P< 0.05, df =1). It was not constant throughout the year particularly during breeding seasons, showing highly significant Chi-square value (X 2 = 20.185, df= 25, P < 0.05). Based on the appearance of ovigerous females, the breeding of P. rufescens is lengthy, start often at late winter and early spring and extends through summer to early autumn. Incubated eggs are oval or semi-oval, sometimes elliptical with polygonal surfaces, and varied in size from 400 to 1000 m with an average of 640 ± 105 m. These eggs are passed through five stages of maturation, and showed remarkably gradual decreasing in size throughout the period of incubation, reaching the minimum at last stages (stage V or the releasing larvae). The color of incubated eggs is also changed from bright yellow in newly laid eggs to grey at the last stage of development. The fecundity of ovigerous females was relatively low, varied from 35 to 450 with an average of 208 ± 92 eggs /female crab. It was correlated by a curvilinear relationship with carapace length only.