Genetic parameters for dermo challenge survival in a Viriginia, U.S. eastern oyster breeding population

Authors: Proestou, Dina; Delomas, Thomas; SMALL, JESSICA - Virginia Institute Of Marine Science

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2025
Publication Date: 6/12/2025
Citation: Proestou, D.A., Delomas, T.A., Small, J.M. 2025. Genetic parameters for dermo challenge survival in a Viriginia, U.S. eastern oyster breeding population. Aquaculture. 609.. https://doi.org/10.1016/j.aquaculture.2025.742816.
DOI: https://doi.org/10.1016/j.aquaculture.2025.742816

Interpretive Summary: Disease significantly limits eastern oyster aquaculture production in the U.S. Genetic improvement for disease resistance is a common strategy used in aquaculture species for long-term management of disease and laboratory disease challenges have proven more effective than natural exposures in finfish. The most prominent disease affecting eastern oysters in the U.S. is dermo disease, and the current industry practice is to select for general survival in oysters exposed to disease in the field. However, the intensity of field exposures is unpredictable and often confounded by other environmental factors, slowing the rate of genetic improvement for this trait. Here, we applied an optimized laboratory disease challenge protocol to oysters from a Virginia U.S. breeding population to more accurately measure survival in response to dermo exposure. Siblings of the challenged oysters were also monitored for survival at a field site where dermo prevalence is historically high. Quantitative genetic analysis estimated moderate standing genetic variation for both challenge survival and field survival suggesting ample potential for genetic improvement of both traits. Surprisingly, the two traits were not correlated. More work needs to be done to understand the lack of correlation between challenge and field survival before incorporating challenge survival into a multi-trait selection index.

Technical Abstract: Dermo, a chronic condition caused by the protozoan parasite Perkinsus marinus, is the most prominent disease affecting eastern oysters in Virginia, U.S. Genetic improvement for well-defined, dermo-resistance phenotypes could offer a viable long-term strategy for managing the disease if ample genetic variation exists in aquaculture populations. Here we report results from controlled laboratory disease challenge experiments that enabled direct measurement of disease response phenotypes and estimation of genetic parameters for Dermo resistance. Nearly 6000 individual one year old pedigreed oysters representing three year classes (2019, 2020, and 2021) and 109 unique full-sibling families from the Aquaculture Genetics and Breeding Technology Center (ABC) breeding program at the Virginia Institute of Marine Science were injected with a consistent concentration of cultured parasite and monitored for survival for 42 days. Parasite load of each oyster was quantified at either the time of death or the end of the experiment. Siblings of the challenged oysters were also evaluated for survival at a grow-out site with historically high disease pressure. Challenge survival was estimated to be moderately heritable (0.14 ± 0.03 on the observed scale, 0.24 ± 0.05 underlying liability scale). Field performance traits (growth, shape, and survival) were not correlated with challenge survival. Our results indicate good potential for genetic gains through selection for dermo challenge survival. More work needs to be done to understand the lack of correlation between challenge and field survival before incorporating challenge survival into a multi-trait selection index.