Morphofunctional organization of the male reproductive system of the catfish Iheringichthys labrosus (Lutken, 1874) (Siluriformes : Pimelodidae)

An anatomical, histological and ultrastructural study was made of the repro ductive system and spermatogenesis of Iheringichthys labrosus. The testis E ire digitiform and consist of a spermatogenic cranial region, a spermatogen ic/secretory medial (transition) region, and a strictly secretory caudal re gion. The cranial region represents 66% of the total length of the maturing testis and its fringes or lobes have a length of 5.59 +/- 0.73 mm. The med ial and caudal regions represent each 17% of the testicular length and thei r fringes have a length of 5.37 +/- 0.69 mm and 3.12 +/- 0.38 mm, respectiv ely. Histologically, the cranial region of the testis is made up of seminif erous tubules with spermatogenic cells contained in cysts. These cells unde rgo synchronous development, inside the cysts where spermatogenesis is comp leted. The secretory caudal region does not constitute an individualized gl and. Ultrastructurally, its secretory cells have a vesiculous nucleus and a cytoplasm with abundant dilated cisternae of rough endoplasmic reticulum. The caudal region produces a glycoproteic secretion and exhibits variable e lectron density during maturation. During the resting:period, these cells a re poor in synthesis organelles. The spermatozoa are of the primitive type, with a round head (1.56 +/- 0.11 mum), a rudimentary middle piece, and a l ong flagellum with a 9+2 axonemal arrangement. (C) 2001 Harcourt Publishers Ltd.