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

## TL;DR

This study shows how different light colors affect the growth, hormones, and gut bacteria of Rana dybowskii tadpoles, which could help improve aquaculture practices.

## Contribution

The study reveals specific effects of light spectrum on tadpole physiology and gut microbiota in Rana dybowskii.

## Key findings

- Green light increased testosterone levels in Rana dybowskii tadpoles.
- Blue light increased estradiol levels and the proportion of females.
- Yellow light maximized gut bacterial richness and diversity.

## Abstract

Light spectrum has a significant effect on the growth and health of aquaculture animals. In this study, we investigated how different light colors (white, red, yellow, blue, and green) affect the growth, sex ratio, hormone levels, and gut bacteria of the tadpoles of Rana dybowskii. The results indicate that green light increased testosterone levels, while blue light increased estradiol levels and female rate. The number of intestinal bacteria in yellow light was the highest. These results suggest that light color can affect many physiological parameters of tadpoles, which may help farmers optimize light conditions to improve tadpole health and growth in aquaculture systems.

Rana dybowskii, 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 R. dybowskii 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 R. dybowskii 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 R. dybowskii changed under different light colors. Our results advance R. dybowskii physiological knowledge and support aquaculture practices.