Histology of testis, sperm-reproducing pattern and season, and size at first maturation of Mystus albolineatus in Vietnamese Mekong Delta

Abstract

Mystus albolineatus is a common catfish distributed in tropical regions; however, its biological information is still limited, especially in the Mekong Delta in Vietnam, where it is caught for food supply. This study aimed to determine testicular morphology and histology, sperm-releasing season, and length at first maturation (L_m) of Mystus albolineatus based on a collection of 290 individuals from Can Tho and Soc Trang provinces. The results showed that Mystus albolineatus exhibited elongated testes with several small lobes. Histological observations included spermatogonia, primary and secondary spermatocytes, spermatids, and spermatozoa. The fish were found to be reproductively active throughout the study period, releasing sperm mainly in the wet season as the gonadosomatic index in this time (0.66 ± 0.04 SE) was significantly higher than in the dry season (0.44 ± 0.03 SE, Mann-Whitney U, Z = -2.88, p < 0.001). The sperm-releasing peak in Can Tho was slightly earlier (in July) than in Soc Trang (in August) due to the highest value of the gonadosomatic index in these months. The L_m was 9.02 ± 1.05 SE cm in Can Tho and 8.69 ± 0.41 SE cm in Soc Trang. Findings suggested environmental factors influencing reproductive timing and established important biological references valuable for managing this commercially exploited species.