SPERMATOPHORE FORMATION IN THE WHITE SHRIMPS PENAEUS SETIFERUS AND P. VANNAMEI

Abstract

The medial and distal vasa deferentia and terminal ampullae of Penaeus setiferus and P. vannamei were studied by light and electron microscopy to assess their roles in spermatophore formation. The ascending medial vas deferens of each species consisted of 2 parallel epitheliumlined ducts, referred to as the spermatophoric and accessory ducts, with the accessory duct fitting into a groove along the spermatophoric duct. In the spermatophoric duct, the sperm mass was surrounded by a thick primary spermatophore layer secreted by the epithelial lining. Two secretions forming accessory layers 1 and 2 were deposited by the epithelial cells of the accessory duct. The lumina of the two ducts partially merged at the flexure between the ascending and descending portions of the medial vas deferens. Upon confluence, accessory layer 1 flowed into the spermatophoric duct and formed an additional layer around the primary spermatophore layer. Additional spermatophore components were deposited in the terminal ampulla, which consisted of 5 interconnecting chambers or lumina in P. setiferus and 4 in P. vannamei, respectively. The spermatophoric and accessory ducts terminated in chambers I and II, respectively. New secretions from chamber I were a thick dorsal plate and a thin adhesive layer. In chamber II, structural alteration of accessory layer 2 into corky reticulate and collapsed or fibrous reticulate portions occurred. Chamber III was a branching duct and contained glutinous material. Chamber IV seemed to be an extension of chamber II, but formed a distinct large lumen located in the proximal to medial regions of the terminal ampulla. This chamber contained a large amount offibrous reticulate substance similar to that observed in chamber II. Chamber V of P. setiferus contained the wing portion of the spermatophore. The terminal ampulla of P. vannamei possessed neither this chamber nor wing material. Upon ejaculation, each spermatophore joined mesially along the adhesive layer and formed a compound spermatophore. Accessory layer 1 and the corky reticulate layer were hard and functioned as a sheath for the sperm mass. These layers also supported the structure of the compound spermatophore. The dorsal plate, glutinous material, fibrous reticulate layer, and wing served to attach the compound spermatophore to the open thelycum.