The reproductive cycle of crustaceans is a complex seasonal process with several transitional stages from moulting and mating to the hatching of larvae. A correct determination of the different gonad developmental stages is therefore essential when studying the reproductive cycle or when assessing the onset of sexual maturity in these species. The maturity cycle of female brown crabs (Cancer pagurus) was studied on the basis of a total of 524 female crabs (size range 100-150 mm) which were collected from three geographical locations in Norway.
Maturity classification was based on existing maturity scales (Edwards 1979). The crabs were allocated to different maturity stages based on visual gonad appearance, involving the colour of the gonads classified using Roche Salmofan and gonad somatic indices. Through microscopic examination, a description of identified cell types was made and maturity stages were defined based on the presence (prevalence), size and relative number of cell structures. Comparison between macroscopic and microscopic results showed good correlation between the gonad developmental stages.
The microscopic study identified a separate immature puberty stage which deviated from a strict immature gonad where half of the lobe was filled with primary oocytes. The registration of berried crabs clearly indicates that 50% maturity occurs at a shell width of more than 13 cm (minimum legal size). A detailed description of the different macroscopic and microscopic developmental stages is provided as a reference for future studies of gonad development in C. pagurus.
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