Reproductive biology and relative growth in the spider crab Maja crispata (Crustacea: Brachyura: Majidae)

Abstract

A series of life-history traits in the spider crab Maja crispata were studied on the island of Ischia (Italy) during four sampling periods in 1982: sex ratio, relative growth, sexual maturity, reproductive season, number of eggs per female, copulation and brood sequence. A total of 104 males and 86 females were captured. Mature animals were present year around. The greatest relative abundance of mature animals in both sexes was found in the warmer season. Three post-larval growth stages were distinguishable in males: crabs with juvenile morphological characteristics and immature gonads (between 1.69 and 5.03 cm carapace length), crabs with juvenile morphological characteristics and mature gonads (between 3.59 and 6.11) and crabs with adult morphological characteristics and mature gonads (between 4.98 and 7.16). In females, only two postlarval stages were detected: juveniles (between 1.87 and 4.62) and adults (between 3.56 and 6.11). Mature females with full seminal receptacles were always present. Breeding period extends from May to September. Mean number of eggs was 11473 per female. Breeding sequences in two females kept in the laboratory varied between 5 and 7 broods per year, at intervals of between 21 and 32 days.