Alters Reproductive Hormones and Calcium Homeostasis in Cyprinus carpio Exposed to Varied Spectral Exposure

Abstract

Light spectra exert profound influence on fish physiology, behaviours, and development, shaping processes that extend from circadian regulation to growth and reproduction. The present study investigated the effects of chromatic light on the reproductive axis and calcium metabolism in the common carp (Cyprinus carpio). Following acclimatization, fish were divided into five groups: white light as control, and red, green, yellow, and blue light treatments, maintained under a 12:12 light–dark cycle for 120 days. Reproductive status was assessed through ovarian weight, gonadosomatic index (GSI), and follicular kinetics, while circulating reproductive hormones and serum Ca²⁺ levels were analyzed. Results demonstrated wavelength-specific modulation of endocrine and reproductive parameters. Yellow light significantly elevated FSH and induced maximal GSI, primarily due to previtellogenic follicle accumulation, suggesting enhanced follicle recruitment. Green light increased LH and progesterone, but produced the lowest GSI with maximal follicular atresia, indicating enhanced luteinization. Red light suppressed estradiol and vitellogenesis, reducing vitellogenic follicles. Blue light elevated progesterone while maintaining moderate GSI and balanced follicular development. Collectively, these findings highlight the profound role of spectral manipulation in regulating reproductive endocrinology and ovarian dynamics. Chromatic light regimes may serve as a practical, non-invasive strategy to optimize brood stock management and improve reproductive performance in aquaculture.