Sulfur in lucinid bivalves inhibits intake rates of a molluscivore shorebird

Abstract

A forager's energy intake rate is usually constrained by a combination of handling time, encounter rate and digestion rate. On top of that, food intake may be constrained when a forager can only process a maximum amount of certain toxic compounds. The latter constraint is well described for herbivores with a limited tolerance to plant secondary metabolites. In sulfidic marine ecosystems, many animals host chemoautotrophic endosymbionts, which store sulfur compounds as an energy resource, potentially making their hosts toxic to predators. The red knot Calidris canutus canutus is a molluscivore shorebird that winters on the mudflats of Banc d'Arguin, where the most abundant bivalve prey Loripes orbiculatus hosts sulfide-oxidizing bacteria. In this system, we studied the potential effect of sulfur on the red knots' intake rates, by offering Loripes with various sulfur content to captive birds. To manipulate toxicity, we starved Loripes for 10 days by removing them from their symbiont's energy source sulfide. As predicted, we found lower sulfur concentrations in starved Loripes. We also included natural variation in sulfur concentrations by offering Loripes collected at two different locations. In both cases lower sulfur levels in Loripes resulted in higher consumption rates in red knots. Over time the red knots increased their intake rates on Loripes, showing their ability to adjust to a higher intake of sulfur.

Food preferences in a generalist pollen feeder: A nutritional strategy mainly driven by plant carbohydrates

“…These strategies have been extensively studied in vertebrates, where generalism at the individual scale is the rule (Bernays and Minkenberg, 1997). Indeed, examples of such generalist feeding strategies at the individual scale can be found in mammals (Wiggins et al, 2006;Cui et al, 2018;Takahashi et al, 2021;Windley et al, 2022), birds (Fargallo et al, 2020;Cady et al, 2021;Oortwijn et al, 2022), reptiles (Figueras et al, 2021), and fishes (Yeager et al, 2014;Laske et al, 2018). In herbivorous insects, however, where most species are specialists (Bernays and Graham, 1988), feeding strategies of generalist species have received much less attention.…”