Seasonal and spatial patterns of mudblister worm Polydora websteri infestation of farmed oysters in the northern Gulf of Mexico

Abstract

Mudblister worms Polydora websteri bore holes into oyster shells, and oysters respond by secreting extra layers of shell, creating a mudblister. When shucked, mudblisters can burst and release anoxic mud. Thus, infestation devalues oysters, particularly on the half-shell market. This study quantified oyster condition index and worm abundances over 2 full growing seasons at commercial oyster farms on the US Gulf of Mexico coast, and our results indicate that oyster growth rate, manipulated through ploidy and stocking densities, had little effect on worm infestation. Larval spionid worms were found year-round. Larval abundances were slightly higher within than away from farms, and larval size distributions were skewed toward smaller larvae within the farms, suggesting that farms may be a source of larvae. Triploid oysters had higher or comparable condition index values to diploids, but during summer months, when worm infestation was high, worm infestation was not correlated with condition index. Previously infested shells deployed at farms became more infested than uninfested shells at moderate infestation levels, but re-infestation was influenced more by farm location than by previous infestation condition. Higher infestation at a farm with more variable salinity as well as higher infestation in 2017 when salinity was lower suggest that salinity may be a potential driver of mudblister worm infestation. Results indicate that oyster farmers on this coast should use desiccation to treat oysters for mudblister worms frequently during the summer, but that manipulating stocking density or ploidy is unlikely to be effective in preventing mudblister worm infestation.

Climate Change and Shell-Boring Polychaetes (Annelida: Spionidae): Current State of Knowledge and the Need for More Experimental Research

“…Similar range expansions have also been recently recorded in Europe's Wadden Sea (Waser et al, 2020). Meanwhile, a two-year CLIMATE CHANGE AND POLYCHAETES survey of P. websteri infestation in the Gulf of Mexico found that the species reproduced year-round and exhibited the highest infestation rates during summer months (Cole et al, 2020), while de Souza et al (2017 found that in northeastern Brazil host size and age were the crucial factors driving infestation rates of P. websteri and Boccardiella ligerica.…”

“…Riascos et al hypothesized that the increased infestation rates were likely due to faster growth rates of offspring, earlier release of larvae from egg capsules, and activation of asexual reproduction. Other field studies by Mackin and Cauthron (1952), Blake (1969), Zajac (1991), and Cole et al (2020) have also shown that higher summer temperatures are positively correlated with infestation rates. Pertinent to host-parasite dynamics, these authors also found that warmer waters resulted in more physiologically stressed clams and, in turn, may also have contributed to the observably high rates of infestation.…”

“…Under heavy infestation, the structural integrity of the shell can become weakened; this makes the animal vulnerable to predation in its natural environment (Zottoli and Carriker, 1974;Riascos et al, 2008). Some studies have shown that, in some cases, tissue quality is also compromised, resulting in lowquality shellfish meat (Mackin and Cauthron, 1952;Wargo and Ford, 1993;Spencer et al, 2021), although this has been contested by other researchers who found no effect on meat quality (Loosanoff and Engle, 1943;Caceres-Martinez et al, 1998;Cole et al, 2020). The pathology associated with polydorids is most notably observed on aquaculture farms, and recent studies have shown that their ranges are expanding, with reports of increased infestation.…”

Evaluation of Mud Worm (Polydora spp.) Infestation in Cupped (Crassostrea gigas) and Flat Oyster (Ostrea edulis) Broodstocks: Comparison between Magnetic Resonance Imaging and Computed Tomography

“…For this reason, during the summer, oyster farmers along the coast of the northern Gulf of Mexico use desiccation to treat oysters for mud blister worms. Nevertheless, stocking density or ploidy was considered unlikely to be effective in preventing mud blister worm infestation [24].…”

Assessing Cumulative Stressors, State Shift, and the Current Outlook for Oyster Habitat in Apalachicola Bay, Florida

“…Population expansion of organisms that parasitize oyster shells is favored under high and variable salinity conditions (Mackin 1962, Curtin 1986, Handley & Bergquist 1997, Duckworth & Peterson 2013, Cole et al 2020). Endolithic shell-boring parasites historically observed in Apalachicola Bay, including boring sponges ( Cliona spp.…”