Discipline: Biological Sciences
Harrison Wastson - Jackson State University
Co-Author(s): William Walton, Auburn University, Auburn, AL and Dauphin Island Sea Lab, Dauphin Island, AL; Charlotte Shade, University of Dayton, Dayton, OH
Larvae of the mud blister worm Polydora websteri (Annelida: Polychaeta: Spionidae: Mud Blister Worms) usually settle onto mud, rocks, and mollusk shells, but also the shells of the common eastern oyster (Crassostrea virginica). As these worms develop, they form burrows within the shell causing damage to the oyster shell, forcing the oyster to expend energy on shell repair and, as a result, infestation often impedes tissue and gonad growth. Furthermore, reduced shell quality often makes it more difficult for oyster famers to sell the oysters on the open market or forces sales well-below market value. Although the relationship between infestations of Polydora and reduced oyster quality has been known for decades, few studies explored the variables that impact infestation rates. For this study we examined the relationship between ploidy of oysters (triploid oysters, fast growing and lower reproduction rates vs. diploid oysters, slow growing and higher reproduction rates) and tidal height (subtidal vs. intertidal) to determine how these factors impact rates of infestation, oyster growth, and oyster recovery following infestation. We tested two hypotheses: 1) triploid oysters will recover faster from infestation than diploid oysters, and 2) oysters in the intertidal height will have a reduced rate of re-infestation compared to subtidal oysters. Six hundred adult oysters were deployed, with even distribution between ploidy and tidal height, at Point Aux Pins Oyster Farm May 18th, 2017. Beginning June 13th, 20 oysters were sampled each week over a seven-week period to determine: the number of Polydora specimens present per oyster, oyster shell dimensions and total mass, worm burrow density, and shell quality.
Due to the persistent rainy weather cycles, salinity levels were consistently lower than average and water levels were consistently higher. Despite these conditions, tidal height was found to significantly impact worm count with intertidal oysters demonstrating a lower worm count than subtidal oysters. While the cause is uncertain, we postulate that this may be a mechanism of intertidal oysters being exposed to the larval worms with less regularity than their subtidal counterparts. This data suggests that oysters kept at intertidal heights may have some protection from infestation and thus, may result in a higher oyster quality. In addition, the utilization of a pre-brine dip was successful in reducing worms counts to <1 worm/oyster and suggests a correlation between salinity and worm infestation densities. While our data support a correlation between infestation rates and salinity, the duration of the study, along with the confounding affects of the below average salinities, require additional studies over longer durations.
Funder Acknowledgement(s): The National Science Foundation (NSF)
Faculty Advisor: Dr. William Walton, firstname.lastname@example.org
Role: I conducted the sampling, data collection, and poster creation of the research.