Sperm Production and the Effects of Electrically Induced Spermatophore Expulsion in the Prawn Macrobrachium rosenbergii (de Man)

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Abstract
The effects of electroejaculation techniques upon sperm cell and spermatophore production in the giant prawn Macrobrachium rosenbergii were investigated extensively. Animals received electrical stimuli according to various regimes: fixed 24-h interval between stimuli; decreasing interval between stimuli; increasing interval between stimuli; stimulation postmolt only; daily abdominal stimulation; and no electrical stimulation. The mean percentages of successful electroejaculation attempts for the 29-day period ranged from 81.1-100%. Of the individuals tested, 45% were capable of extruding some portion of a spermatophore after as little as 3 h postejaculation. While mean ejaculum size decreased significantly over the experimental period, no structural or ultrastructural abnormalities were observed in either sperm cell or spermatophore morphology. The spawns of 4 female prawns artificially inseminated with study-group ejacula exhibited normal percentages of fertilization. Several undesirable conditions resulted from the use of electroejaculation, including coxal ulcerations, limited muscle necrosis, and melanization of reproductive tissues. The relevance of these results for increased profitability in and feasibility of commercial aquaculture and selective breeding programs is considered.