Gynandromorph of a Freshwater Crab, Geothelphusa dehaani (White)

Araki Akira, Matsuura Shuhei

doi:10.15017/23541

The morphology and gonad history of the gynandromorphic freshwater crab Geothelphusa dehaani (White) are described. About 200 specimens of females and 63 males of more than 10.9mm carapace width were collected from a natural population inhabiting the Taniyamagawa River, Fukuoka, Japan and dissection to study the gonadal maturation. External gynandromorphic individuals which have normal gonads were recognized in other specimens. (1) Externally like a female with female genital openings, but having partial masculinization of the first pleopods. (2) Externally like a female, but does not have female genital openings. (3) Externally like a male, but has female genital openings. As in type (1), 11 individuals are recognized. They appears comparatively frequently in the field and because we noted an individual carring eggs, they appear to function as a female. For type (2) and (3), for each only one individual was recognized. Gonadal gynandromorph was recognized in two specimens. Externally, the abdomen and gonopods exhibit male characteristics and secondary sexual characters appear in the right chelae. Male gonopores are open at the base of the fifth pereiopod and small incomplete female genital openings on the third thoracic sternite. Internally, the testes and vas deferens are present on both sides, but one specimen had eggs at the point of the gonad on the right side and the other specimen on both sides. It is necessary in the future to study about the apperance of gynandromorph in the life cycle and about the causes of gynandromorph by histological observations of gonad and the androgenic gland.

Gynandromorph of a Freshwater Crab, Geothelphusa dehaani (White)

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