Triploid eastern oysters (Crassostrea virginica) display high susceptibility to microbial infections but only during early ontogenetic stages

Authors: BRIANIK, CHRISTOPHER - Stony Brook University; PALES ESPINOSA, EMANUELLE - Stony Brook University; LIU, MING - Morgan State University; RIVARRA, GREGG - Cornell University; GUO, XIMING - Rutgers University; Proestou, Dina; ALLAM, BASSEM - Stony Brook University

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/10/2024
Publication Date: 1/30/2025
Citation: Brianik, C., Pales Espinosa, E., Liu, M., Rivarra, G., Guo, X., Proestou, D.A., Allam, B. 2025. Triploid eastern oysters (Crassostrea virginica) display high susceptibility to microbial infections but only during early ontogenetic stages. Aquaculture. 595. Article 741613. https://doi.org/10.1016/j.aquaculture.2024.741613.
DOI: https://doi.org/10.1016/j.aquaculture.2024.741613

Interpretive Summary: Triploid oysters now constitute the predominant farm-raised oyster product in numerous regions with some hatcheries currently producing >90% triploid oyster spat. Triploid popularity is primarily driven by significant growth advantages and more consistent meat quality, with most prior work reporting comparable adult survivorship. Though adult performance is similar, some evidence suggests that triploids may be more susceptible to bacterial infections, particularly during earlier age classes. Anecdotal reports from local farmers endorse this view. To assess these claims, two cohorts of half-sibling diploid and triploid eastern oyster lines were produced in 2020 and 2021. A subset of larvae and juveniles from both spawns were then exposed to a cocktail of Vibrio pathogens and monitored for viability. Separate oysters from the same spawns were maintained at a hatchery for ~ 3 months before being deployed in either the Peconic Bay NY(2020), or Patuxent River MD (2021) and monitored for a year. Survivorship was significantly higher in diploids than triploids at both the larval and juvenile stages, however differential mortality decreased as oysters aged, with nearly identical adult performance after a year in the field. These trends were consistent across spawns and lines. Overall, the results support that triploids are frailer at younger age classes, but these differences decrease over time. Therefore, farmers may benefit from purchasing larger or older triploid seed, and hatcheries should have heightened biosecurity measures when raising triploids due to increased risk of bacteria-related mortalities.

Technical Abstract: Over the last two decades, oyster aquaculture has largely shifted from the use of diploids to the near-exclusive use of triploids in many regions, with some hatcheries now producing >90% triploid oyster spat. The increased demand for triploids is primarily driven by substantial growth advantages and more consistent meat quality associated with sterile triploid animals, with most data suggesting triploids and diploids display comparable adult survivorship. Although adult performance appears similar, anecdotal reports from farmers have suggested that triploids may exhibit greater frailty during earlier age classes, particularly in response to bacterial infections. Due to the extent of triploid production now taking place, the possibility of early ontogenetic frailty in triploids could pose a significant risk to oyster aquaculture production. To evaluate these claims, two cohorts of half-sibling diploid and triploid eastern oyster lines were generated in 2020 and 2021. A subset of larvae and juveniles from these lines were then exposed to a cocktail of bacterial pathogens and monitored for viability. The remaining oysters were then allowed to grow for another 2 months before being deployed in either Peconic Bay, New York (2020), or Patuxent River, Maryland (2021), where their survivorship was followed for another year. Results showed that triploids were at significantly greater risk of mortality during the larvae and juvenile stages, though differential mortality decreased with age. These trends were consistent across the two spawning events, and the extent of early ontogenetic triploid frailty was observed to vary between the lines tested. This work provides valuable data for hatchery managers and farmers alike and suggests areas where specific attention and further work are required.