Impact of Light Spectrum on Tadpole Physiology and Gut Microbiota in the Dybowski’s Frog (Rana dybowskii)

<i>Rana dybowskii</i>, widely distributed and extensively farmed in northeast China, holds significant economic value, particularly for its fallopian tubes, which are used as a traditional Chinese medicinal tonic known as "Oviductus Ranae." As the light spectrum is a cost-effective regulatory factor in aquaculture, understanding its effects on the tadpole stage of <i>R. dybowskii</i> is critical for optimizing cultivation practices. This study investigated the effects of five light colors (white, red, yellow, blue, and green) on steroid hormone levels and gut microbiota composition in <i>R. dybowskii</i> tadpoles. Steroid hormone levels were measured on days 15, 30, 45, and 60 using high-performance liquid chromatography (HPLC), while gut microbial communities were analyzed through high-throughput 16S rRNA sequencing. Results showed that the testosterone (T) level of frogs in green light (group G) peaked on day 60 (2.62 ± 3.70 ng/g). The estradiol (E2) level in blue light (group B) also peaked on day 60 (2.87 ± 0.71 ng/g). Importantly, sex ratio analysis revealed that the proportion of females was highest under blue light, reaching 61.11%. Meanwhile, the richness and diversity of the gut bacterial community of the tadpoles was highest under yellow light, followed by blue light. These data suggest that hormone levels fluctuated and the composition of the gut flora of <i>R. dybowskii</i> changed under different light colors. Our results advance <i>R. dybowskii</i> physiological knowledge and support aquaculture practices.