Structural and functional changes in regenerating antennules in the crayfish Orconectes sanborni.

Crayfish rely on the chemosensory neurons in their antennules to help them find food and habitat and to mediate social interactions. These structures often sustain damage from aggressive interactions or from the environment, but they have the ability to regenerate. In this study, we examine whether the effects of antennule ablation and regeneration on odor-tracking ability correlate with structural changes in the antennule that occur during regeneration. We initiated the regeneration process by removing the right antennules from 55 individuals of Orconectes sanborni. We developed a method to nondestructively sample the regenerating antennules so that we could follow the growth of new antennular tissue in the same animals over time. We used dental epoxy to make molds of the regenerating antennule after each molt. We then made resin positives, which were visualized using scanning electron microscopy. Structural parameters including aesthetasc length, diameter, segment length, and number per row were measured from scanning electron micrographs using Image J software. Crayfish were tested in a tabletop water Y-maze before and after surgery and after each molt to assess their ability to track food odors. The structural and the behavioral data indicate that the antennules possessed many aspects of their original structure by the end of the second molt. Flicking of antennules, investigation of substrate, success rate at finding the odor-containing Y-maze branch, and time to completion of Y-maze regained pre-antennulectomy values by the end of the third molt.