Reproductive biology of Mithrax forceps (A. Milne-Edwards, 1875) (Crustacea: Decapoda: Majidae)

Abstract

Some aspects of the reproductive biology of Mithrax forceps were studied based on 580 specimens (380 males and 200 females) collected at Chacachacare, Margarita Island, Venezuela, from April 1984 to March 1985 and from July to November 1991. During the sampling period, males outnumbered females in the catch by almost two to one. Sex ratio was different from 1:1 in May, June, October, December, February and March. Male and female crabs attained sexual maturity at a size of 7.15 and 11.20 mm carapace length, respectively. Size at maturity for 50% of the population was 19.28 and 16.64 mm carapace length for males and females, respectively. As indicated by the presence of ovigerous females during the whole sampling period, the population can reproduce continuously during the year. Fecundity estimates of ovigerous females ranged from 34 to 4777 eggs (average = 1024 ± 93). Relative fecundity was 1.90 to 207.00 (average = 58.96 ± 4.54) eggs/mm carapace length, 1.82 to 200.29 (average = 56.32 ± 4.37) eggs/mm carapace width, and 12.19 to 1656.07 eggs/g (average = 465.16 ± 36.67). Fecundity was linear and positively related to carapace length and width, total weight and ovigerous mass weight. Embryonic development was divided into three stages according to the color of the ovigerous mass and the characteristics of the embryo.