Gonad Maturation Stages of Auchenoglanis occidentalis (Valenciennes 1840) in River Rima, North-Western Nigeria

摘要

The aim of this study was to gain knowledge on the gonad morphology and to determine the stages of gonad maturation in Auchenoglanis occidentalis (Cuvier and Valenciennes), based on macroscopic and histological procedures. A total of 800 samples, of which 398 were females, 399 males and 3 with unidentified sex were examined between November 2005 and December 2008. The samples ranged in total length from 6.60 to 33.00 cm with a mean of 19.51±4.50SD and from 2.26 to 462.90 g total weight with a mean of 100.05±70.09 SD. In females, mean ovary weight was 2.74±0.23 SE, mean left ovary length 3.70±0.08 SE, mean left ovary width 0.59±0.03 SE, mean right ovary length 3.65±0.08 SE and mean right ovary width 0.57±0.02 SE. In males, mean testis weight was 0.17±0.03 SE, mean left testis length 2.75±0.06 SE, mean left testis width 0.20±0.01 SE, mean right testis length 2.74±0.06 SE and mean testis width 0.19±0.01SE. This shows that in both sexes, the left gonads were slightly larger than the right ones. Six stages of gonad maturation were established for the females and males namely, immature (I), maturing (II), mature (III), ripe and running (IV), spent (V) and resting (VI). Based on macroscopy, eggs of various sizes and colours were found in each ovary, while histologically, various stages of oocytes and spermatocytes developed in each ovary and testis, respectively, indicating multiple spawning in both sexes. Spawning of the species occurs during the peak of rainy season in River Rima, which is between July and September.