Taste for pollen comes in different shapes: Consumption by tadpoles from three divergent ecomorphotypes

Abstract

Pollen is a nutritive resource, but its role in aquatic food webs is little studied. Successful pollen acquisition may require behavioral adaptations for tadpoles with certain morphologies; however, pollen coats are hard to break to enable content assimilation. We investigated the consumption of pollen by tadpoles from three ecomorphotypes adapted to feed on the surface (neustonic), the water column (nektonic) and the bottom (benthic). We sampled three developmental stage ranges at both wet and dry seasons at a site in southeastern Brazil. We analyzed the pollen content and coat-breaking level in three sections of tadpole guts and in their feces. We compared pollen composition in tadpole guts among groups based on species and developmental stages and between seasons. We also compared the total number of pollen grains and proportion of broken grains (as a surrogate for digestion capacity) in the guts among species, developmental stages, and between seasons. Ecomorphotype, developmental stage, and season influenced both composition and quantity of pollen consumed. Neustonic tadpoles in general consumed a greater amount of pollen grains and broke them faster, compared to the other ecomorphotypes. Tadpoles showed some variation in the amount of pollen consumed among developmental stages, which interacted with species, but developmental stages of the same species did not differ. Pollen consumption only varied between seasons for the nektonic tadpoles, being greater in the dry season. The high nutritive value of pollen is likely to make consumption by tadpoles rewarding and has an important effect in aquatic food webs, reinforcing the importance of conserving riparian habitats and their vegetation.