Morphology of the Gonads of Synodontis eupterus (Boulenger) from River Rima, North-western Nigeria

摘要

This study was carried out to gain knowledge on some aspects of reproduction of S. eupterus from River Rima which includes sexual dimorphism, size at first maturity, morphology of the gonads, gonad maturation stages and reproductive cycle. The study was conducted between November 2005 and December 2008. 1,610 samples, comprising of 781 females, 816 males and 13 samples whose sexes could not be identified were examined, giving a female: male ratio of almost 1:1. Means of total length and total weight for females was 10.66±1.61 cm and 18.04±6.39 g, respectively. For males, means of total length and total weight were 10.13±1.29 cm and 13.21±6.02 g, respectively. Sexual dimorphism was observed with the females larger than males and males possessing genital papilla. Size at first maturity for females 7.20 cm total length and 5.70 g total weight and 7.00 cm and 5.10 g in males. Female gonads were larger than those of males. In both sexes, the left gonads were slightly larger than the right ones. Based on macroscopic examination of gonads, six stages of gonad maturation were established in both sexes. Multiple spawning was confirmed for the species, with the peak spawning period between July and September in River Rima.