Histological assessment of gonad maturation in Labeo parvus (Teleostei: Cyprinidae) in Benin

Abstract

A histological analysis was undertaken on the gonad development of Labeo parvus Boulenger 1902, a medium-sized cyprinid from the Ouémé River, Benin. Samples were collected monthly between April 2006 and March 2007 and were examined using routine macroscopic and histological techniques. Five macroscopic stages of gonad maturation were identified in the ovaries and testes and described histologically. Oocyte development was subdivided into five stages, based on the presence of chromatin nucleolus oocytes, perinucleolus oocytes, yolk vesicle oocytes, vitellogenic oocytes and mature oocytes. Four stages of spermatogenesis (spermatogonia, spermatocytes, spermatids and spermatozoa) were observed. Comparisons of macroscopic and histological observations revealed that the temporal patterns of maturation activity obtained from visual examination closely reflected the seasonal histological trend in gonad development. Histological characteristics of spent ovaries and testes were similar to those of immature fish, indicating that L. parvus were synchronous iteroparous spawners.