Ishrat Mohd Dar, Farooz A. Bhat, Tasaduq H. Shah, Bilal A. Bhat, Gohar B. Wani, Zaheer Abass

Seasonal reproductive dynamics in common carp (Cyprinus carpio): Variations in gonadosomatic index and hormonal profiles

Introduction

Seasonal reproductive dynamics in common carp (cyprinus carpio): variations in gonadosomatic index and hormonal profiles. Investigate common carp's seasonal reproductive cycle. This study analyzes GSI and hormonal profiles, revealing GtH-II's pivotal role in gonadal development and reproductive timing.

Abstract

This study investigated the seasonal reproductive cycle and hormonal dynamics in common carp (Cyprinus carpio var. communis), emphasising variations in the gonadosomatic index (GSI) and gonadotropin hormones (GtH-I and GtH-II). GSI remained low from late summer to December and peaked in May, reaching 9.5±0.46 in males and 16.3±0.12 in females. GtH-I levels showed minimal fluctuations throughout the year and had no significant correlation with GSI. In contrast, GtH-II exhibited marked seasonal variations, peaking in May (1.26±0.03 IUl-1 in females and 0.36±0.15 IUl-1 in males), with a strong positive correlation with GSI (females: r = 0.91, males: r = 0.84). These findings highlight the pivotal role of GtH-II in regulating gonadal development and reproductive timing in common carp, providing insights into its endocrine control mechanisms. Keywords: Endocrine control, Gonadotropins,GSI, Reproductive cycle,Seasonal variation

Review

This study effectively investigates the seasonal reproductive cycle and hormonal dynamics in common carp, a species of considerable ecological and aquacultural importance. By meticulously tracking variations in the gonadosomatic index (GSI) and gonadotropin hormones (GtH-I and GtH-II), the research provides a clear and concise overview of the endocrine control mechanisms governing reproduction. The stated objectives are well-defined, focusing on a critical aspect of fish biology with direct implications for aquaculture management and conservation efforts, making the contribution timely and relevant. The findings robustly demonstrate a clear seasonality in common carp reproduction, with GSI values peaking sharply in May for both sexes following a period of low activity from late summer to December. Crucially, the study differentiates the roles of the two gonadotropins: while GtH-I shows minimal fluctuations and no significant correlation with gonadal development, GtH-II exhibits striking seasonal variations that directly mirror the GSI peaks. This is powerfully underscored by strong positive correlations (r=0.91 for females, r=0.84 for males) between GtH-II levels and GSI. This compelling evidence strongly supports the conclusion that GtH-II plays a pivotal and dominant role in regulating gonadal maturation and the precise timing of reproduction in common carp, significantly advancing our understanding of its endocrine physiology. While the abstract provides a strong summary of the key findings, a full manuscript would undoubtedly benefit from a detailed discussion of the environmental cues (e.g., photoperiod, temperature) that likely influence these observed hormonal fluctuations, potentially establishing causal links. Furthermore, exploring the downstream molecular pathways activated by GtH-II would offer deeper insights into its mechanism of action. Overall, this study represents a significant contribution to the understanding of teleost reproductive endocrinology, particularly in common carp. The clear data and compelling conclusions make it a valuable resource for researchers and aquaculturists interested in optimizing breeding strategies and managing fish populations.

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