In this project, we will test the utility of epigenetic markers for determining chronological age in the European lobster.
In this project we investigated the utility of methylation state at ribosomal DNA (rDNA) sites for ageing European lobsters (Homarus gammarus). Methylation status was quantified across a total of 6212bp of ribosomal DNA sequence, resulting in 355 CpG sites that passed quality control in cohorts of known age lobsters that ranged from 1 day post-hatching to 2 years old. Percentage methylation was significantly correlated (Bonferroni–Holm corrected) to age at 71% of filtered CpGs (n = 252). Ten loci were selected to construct an ageing model using lasso regression that explained 91% of the variation in chronological age (R2 = 0.911).
To assess the precision of the ageing tool for known-age lobsters, the multiple regression analysis was re-run using leave-one-out cross validation (LOOCV) which estimated the precision of the ageing model to be 2.02 months. The selected makers were then used to estimate age in a sample of wild lobsters with unknown age. The mean age was estimated as 25 months with a range of 15.0 – 41.5 months. This is lower than we expected based on mark-recapture studies from the 1980s. Potential explanations for this lower than expected estimated age include differences in methylation accumulation in different tissues (known age samples used claw and wild samples used antennae); the small age range of known age samples used to calibrate the model (0-2 years); non-linear changes in methylation accumulation with age.
We plan to investigate these unknown factors in a follow-on project.
University of East Anglia