# Fins as a reliable surrogate tissue for age-related changes of telomeres and DNA methylation in gonads of a short-lived fish

## TL;DR

This study shows that fish fins can be used to study aging markers like telomere length and DNA methylation in gonads without harming the fish.

## Contribution

The study demonstrates that fin tissue reliably reflects gonadal aging markers in a short-lived fish species.

## Key findings

- Telomere length in fin tissue corresponds with that in gonadal tissue.
- DNA methylation patterns in fins match those in gonads across different ages.
- Fin biopsies offer a non-lethal method to study aging in small fish.

## Abstract

Senescence is a multifactorial and individualised process of age-related physiological decline. Cellular markers, such as telomere length and DNA methylation, can reveal subtle changes associated with chronological age or expected lifespan. In this study, we evaluated the utility of fin tissue as a surrogate for assessing telomere length and proportion of DNA methylation in the gonads of a small, short-lived laboratory fish, the turquoise killifish (Nothobranchius furzeri). We collected fin and gonadal tissues from both females and males at three different ages. We extracted DNA to measure telomere length via terminal restriction fragment (TRF) analysis and global DNA methylation levels using double-digest restriction-associated DNA sequencing (ddRADseq). Our results show a notable correspondence between telomere length and DNA methylation patterns in fin and gonadal tissues. These findings support the use of fin biopsies as a non-lethal method for assessing ageing biomarkers in the gonads of small freshwater fish.

The online version contains supplementary material available at 10.1007/s10522-025-10338-4.