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Spermatogenesis |
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Spermatogenesis begins in the peripheral germinative layer of the testicular tubules, when spermatogonia enter into the prophase of meiosis. Spermatophores are formed during the passage of spermatozoa down the vase deferentia. The proximal and expanded part of the vas deferens is lined with a secretory epithelium and divided internally into two ducts. One contains clumps of spermatozoa, which are compacted into a spermatophoric matrix; the other, smaller duct secretes the wing matrix of the spermatophore, which does not contain spermatozoa. The separation of the two ducts is incomplete further down the vas deferens, but a partial septum persists to the terminal ampoule, where the spermatophore is compacted and a hyaline layer is secreted around the spermatophoric matrix (Dall et al., 1990). Spermatophores are liberated as pairs, one from each side of the reproductive system. The spermatophoric mass emerges first, followed by the wing matrix, and the two spermatophores are pressed together to form a twin spermatophoric complex (Dall et al., 1990). In species of Penaeus with closed thelyca, implantation occurs when the female has just moulted and the wing matrix breaks off after the cuticle hardens, leaving a plug which indicates that she has mated recently (Dall et al., 1990). |
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