Artificial insemination of mud crab, Scylla olivacea

Aiming at solving the problem of crablet production for mud crab commercial farming, an artificial insemination (AI) method in the mud crab, Scylla olivacea, was described. Placing a pair of cathodes to the inner coxa of both sides of the swimming paddles and an anode to the inner abdominal flab upon the hind gut of sexually mature S. olivacea males and applying 5–6 V of DC current for 3–5 s induced sperm mass expulsion. The sperm mass, comprising several spermatophores containing > 10⁸ sperm/mL, was inserted into the vagina of the newly molted S. olivacea female. Out of 50 female trials, 10 of them developed ovarian maturation within 45 days, and 3 of these 10 crabs spawned. At full maturation of the ovary, needle aspiration of the ovarian tissue examined under light microscopy revealed approximately 50% mature oocytes with elevated fertilization membrane, indicating successful fertilization. Histological and ultrastructural studies of the seminal receptacle revealed numerous sperm with acrosome reaction (AR) within its lumen, revealing fertilization potential of the artificially inseminated sperm. Histologically, the mature ovary at 45 days following AI was composed of mature oocytes surrounded by numerous sperm with AR, suggesting sperm migration from the seminal receptacle into the ovarian tissue. This study reveals a high possibility of using AI for S. olivacea that could lead to the commercial supply of the crablets and a new insight into the internal fertilization of this economic species.