Investigations on Gonadosomatic Index and Gonad Histology of Barred Spiny eel Macrognathus pancalus Hamilton, 1822 from Upper Assam, India

Abstract

Background: Macrognathus pancalus or barred spiny eel is a highly valued ornamental and food fish found in the Indian subcontinent. Due to the burgeoning population and their associated impacts, the population of the species is in rapid decline that necessitates time-bound intervention to conserve the species. The current investigation was undertaken to study the gonadosomatic index and gonad histology of Macrognathus pancalus collected from upper Assam, India.Methods: 500 samples of Macrognathus pancalus were collected from different water bodies such as wetlands, ponds, paddy fields, etc. from upper Assam, India during 2018-2019. Monthly samplings were carried out to evaluate the gonadosomatic index. The gonads were dissected out, measured and subsequently preserved for histological studies. Histological sections of preserved samples were prepared by employing accepted methodologies. The sections were then photographed using Leica DM 750 and gonadal staging was ascertained. Result: Gonadosomatic index studies revealed that it peaked in August in both males (3.45±0.18) and females (8.85±0.35), thereby indicating its spawning season. Minimum GSI values were observed during January in males (0.39±0.04) and in December in females (1.04±0.15) indicating the culmination of the breeding period and the advent of the preparatory phase. Macroscopic and microscopic examination unearthed five different phases of gonadal maturation. Gonadal staging through microscopic and macroscopic technique showed synchronicity with GSI values.