Gonadal Histology and Reproductive Biology of African Lungfish (Protopterus annectens) in the Floodplains of Cross River State

The African lungfish (Protopterus annectens) is an evolutionarily ancient bimodal-breathing species whose reproductive biology in Nigerian floodplain systems remains poorly documented despite its ecological significance and local culinary importance. This study characterised the reproductive cycle, gonadal development, and spawning periodicity of P. annectens in the floodplain wetlands of Cross River State, South South Nigeria. Fish were collected monthly over twelve months using longlines, baited traps, and hand nets at three floodplain sites. Gonads were dissected, weighed, and processed for histological analysis using haematoxylin-eosin and periodic acid-Schiff staining. Gonadosomatic index and hepatosomatic index were calculated monthly. Oocyte developmental staging was performed for females. Histological examination of testicular tissue was used to determine spermatogenesis stages for males. A reproductive calendar was constructed based on gonadal activity patterns across seasons. Gonadosomatic index peaked in April and May for females, coinciding with rising floodplain water levels. Histological analysis confirmed five oocyte developmental stages, with vitellogenic and fully mature oocytes most abundant from February to April. Spermatogenic activity was highest from December to March. Batch fecundity estimates ranged from 204 to 1,847 ova per female, positively correlated with body weight. Aestivation period coincided with complete gonadal quiescence in both sexes. Estivating individuals showed significantly elevated hepatosomatic indices consistent with energy mobilisation from liver glycogen reserves. The study provides a comprehensive reproductive biological profile of P. annectens under natural Nigerian floodplain conditions. Keywords: Protopterus annectens, reproductive biology, gonadal histology, floodplain, Cross River State.