Male reproductive system of the fish ectoparasite Argulus bengalensis (Crustacea: Branchiura).

Abstract

The male reproductive system of the fish ectoparasite Argulus bengalensis was reconstructed with serial histological sections through longitudinal and transverse planes and the description was re-evaluated after the discovery of spermatophore. The study revealed that the testis of A. bengalensis consists of two lobes, each comprised the two enclaves. The outer enclaves from both lobes are connected proximally with an isthmus. The inner enclave is covered with two layers of chromatophores which are presumably involved in androgenic hormone production. At the proximal end of the inner enclaves a pair of vasa efferentia originates and ascends into thorax where it leads into vesicula seminalis. Like Dolops ranarum, a pair of spermatophoric glands is found in the thorax just behind the second maxilla. Glandular cells of the spermatophoric glands are columnar with a large nucleus at their basal side. A pair of spermatophoric canals carries the secretion of the glands into the vesicula seminalis through vasa efferentia. Spermatophores are delivered to the female through a median vas deference originating from the vesicula seminalis. In addition to the spermatophoric glands, a pair of accessory glands is located in the coxa of the fourth thoracic legs. At the region dorsal to the isthmus both the spermatophoric canal and accessory gland ducts unite with the vas efferens of the respective side. The secretion of the accessory gland presumably contributes to semen composition of the parasite.