Copulatory system of the spider crab Libinia spinosa (Crustacea: Brachyura: Majoidea)

Abstract

Functional morphology of Libinia spinosa male gonopods, female holding systems and gonopores were described through scanning electron microscopy and histological sections, establishing differences between immature and mature individuals. The first gonopod of mature males, larger than 35.1 mm of carapace width (CW), is long, slender, and ended in two wing-like processes: abdominal, characterized by the presence of a sub-terminal ejaculatory duct, and sternal, closed and where the cuticle bulges holding setae. In immature males, smaller than 29.9 mm CW, both processes were shorter, and the tip of the abdominal process was closed. Six different types of setae were described for both gonopods. Internally, both gonopods have rosette glands in immature and mature individuals. The presence of secretions which may be involved in the molting process was observed in immature males towards the external cuticle corresponding to the rosette glands. In mature males the rosette glands could be related to reproduction. Bacterial colonies were present inside the ejaculatory opening of mature males. Females presented a typical press-button holding system and a biconcave gonopore. In immature females, smaller than 36.1 mm CW, the gonopore aperture was closed by integument bulging to the outside. In mature females, larger than 42.6 mm CW, the locking system was almost fused to the cuticle, and the gonopore showed an open biconcave form with a more inner flexible membrane. Morphological characteristics shown by the gonopods of mature males develop synchronously with the acquisition of physiological maturity, not with morphometricall maturity. In females the mature holding systems and gonopores are developed synchronously with physiological and morphometrical maturity.