Meeting Abstract

P1-123    From mud to meat: DNA metabarcoding of gut contents demystifies the evolution of carnivory in a genus of predatory annelids Mack, JM*; Bely, AE; University of Maryland, College Park; University of Maryland, College Park joemack@umd.edu https://belylab.weebly.com/

The transition into carnivory is a profound dietary shift that has evolved numerous times in animals, but underlying mechanisms for this transition are poorly understood. Lineages that have recently adopted predatory lifestyles are thus compelling models for understanding the evolution of animal carnivory. Within the phylum Annelida, ancient origins of carnivory have led to highly successful groups like leeches, while recent acquisitions of carnivory have also occurred. Chaetogaster, a genus of small freshwater oligochaetes, is one widespread example with at least two recent origins of carnivory. However, it is unknown how the predatory Chaetogaster species are descended from detritivorous ancestors. Do detritivores transition into carnivory through incremental shifts on intermediate diets? Or are diets on detritus sufficient to enable rapid shifts to carnivory? To understand how carnivory evolves from non-carnivorous diets, we employ a new metabarcoding gut-content analysis of eight Chaetogaster species. To identify gut contents, we sequenced 18S from ? 5 individuals of each species and inferred potential prey taxa from the reads. In preliminary findings, the species sampled show a high degree of trophic diversity. The two known predatory species yielded 18S reads from ciliates and metazoans like rotifers, crustaceans, or mollusks. Meanwhile, the remaining reportedly non-predatory species appear to be detritivorous and/or omnivorous, as varying mixtures of fungal, ciliate, and/or animal 18S reads were recovered. Preliminary sequencing results from six species, interpreted alongside a robust phylogeny of the genus, indicate that the two predatory Chaetogaster species are closely related to detritivorous Chaetogasters. This suggests that carnivory can rapidly evolve from a non-predatory detritivorous background. Overall, this work improves our understanding of the trophic steps involved in the evolution of carnivory in animals.