Chemical signaling is critical in predator-prey relationships in marine systems. Not only do chemical cues elicit behavioral responses that aid in prey detection and predator avoidance, but they can also induce morphological changes during early development. For instance, prior research has shown that the eastern oyster, Crassostrea virginica, responds to chemical cues from crab predators with stronger shell development. This project aimed to induce this morphological response in a hatchery setting to create more predator-resistant oyster seed stock.
Several thousand newly single-set juvenile oysters were reared in setting trays within closed recirculating systems and exposed to chemicals released by live blue crabs, Callinectes Sapidus, for 16 weeks. The crabs were isolated in separate mesh cages to avoid predation and fed
shucked oysters daily to enhance chemical release. A control group of unexposed juvenile oysters was also reared in setting trays in separate closed recirculating systems. Samples of exposed and unexposed oysters were collected at 12, 14, and 16 weeks, respectively, and underwent scanning electron microscope imaging analyses to assess shell thickness. Results showed that at 12 weeks, the exposed oysters were thicker than the unexposed (p=0.05). At 14 and 16 weeks, all exposed oysters were shorter than unexposed oysters (p<0.001). These results suggest that the presence of crab chemical cues may lead to shifts in the energetic budgeting of oysters, with exposed oysters prioritizing thicker shell development and unexposed oysters prioritizing traditional shell growth (length). To determine if increased shell thickness results in greater predator resistance in a natural setting, the remaining oysters will be deployed to field sites with and without predator exclusion, and survivorship and growth will be compared between treatments. Field sites with known crab and or oyster drill presence will be purposely selected. The development of predator resistance in seed oysters through chemical-induced morphological change may have significant implications for both aquaculture and restoration efforts.