Exploring the Effects of Rearing Densities on Epigenetic Modifications in the Zebrafish Gonads

18 pages, 5 figures, 1 tables, supplementary materials https://www.mdpi.com/article/10.3390/ijms242116002/s1.-- Data Availability Statement: Raw sequencing data were submitted to the Gene Expression Omnibus, with accession number GSE134646

Rearing density directly impacts fish welfare, which, in turn, affects productivity in aquaculture. Previous studies have indicated that high-density rearing during sexual development in fish can induce stress, resulting in a tendency towards male-biased sex ratios in the populations. In recent years, research has defined the relevance of the interactions between the environment and epigenetics playing a key role in the final phenotype. However, the underlying epigenetic mechanisms of individuals exposed to confinement remain elucidated. By using zebrafish (Danio rerio), the DNA methylation promotor region and the gene expression patterns of six genes, namely dnmt1, cyp19a1a, dmrt1, cyp11c1, hsd17b1, and hsd11b2, involved in the DNA maintenance methylation, reproduction, and stress were assessed. Zebrafish larvae were subjected to two high-density conditions (9 and 66 fish/L) during two periods of overlapping sex differentiation of this species (7 to 18 and 18 to 45 days post-fertilization, dpf). Results showed a significant masculinization in the populations of fish subjected to high densities from 18 to 45 dpf. In adulthood, the dnmt1 gene was differentially hypomethylated in ovaries and its expression was significantly downregulated in the testes of fish exposed to high-density. Further, the cyp19a1a gene showed downregulation of gene expression in the ovaries of fish subjected to elevated density, as previously observed in other studies. We proposed dnmt1 as a potential testicular epimarker and the expression of ovarian cyp19a1a as a potential biomarker for predicting stress originated from high densities during the early stages of development. These findings highlight the importance of rearing densities by long-lasting effects in adulthood conveying cautions for stocking protocols in fish hatcheries.

This study was supported by the Spanish Ministry of Science and Innovation grants AGL2015-73864-JIN ‘Ambisex’ and 2 PID2020-113781RB-I00 ‘MicroMet’ to LR and grant PID2019-108888RB-I00 to FP. Also was supported by the Consejo Superior de Investigaciones Científicas (CSIC) grant 02030E004 ‘Interomics’ to LR We thank the lab technician Sílvia Joly for her essential assistance to our team and Gemma Fusté for her assistance in the fish facilities. This study was supported by funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence accreditation (CEX2019-000928-S)’.

With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S).

Peer reviewed