Feeding preferences and digestion of talitrids in a Bay of Fundy, Canada salt marsh

The function of detritivores in salt marsh ecology still presents many unknowns. We experimentally investigate the food preferences of two talitrids found in Bay of Fundy salt marshes: Orchestia grillus (Bosc, 1802) (= Speziorchestia grillus Bosc, 1802) and Platorchestia exter Myers & Lowry, 2023 Food preferences were found to depend on (1) the availability of marsh plant litter at the supralittoral level where the talitrids live; (2) the degree of physical/microbiological decay of the plants present in marsh litter; (3) the talitrid ecotype that is doing the consuming. Our food preference experiments with different plant foods in culture conditions confirm that O. grillus is a palustral specialist limited to a single plant food class that contains structural lignocelluloses. Platorchestia exter is a wrack generalist able to acclimate in experimental cultures to a range of decaying plant foods including those containing structural celluloses (Phaeophyta) and lignocelluloses (Angiosperms). These results confirm the applicability of the generalist/specialist continuum within the Talitridae. Cellulolytic microbiological culture methods applied to dissected gut parts of O. grillus are consistent with the hypothesis that the midgut is where endosymbiotic enzyme activity occurs. The digestive enzymes originate from both resident hepatopancreatic and ingested microbes.