Evolution of coprophagy and nutrient absorption in a Cave Salamander

Daphne Soares,Rachel Adams,Danté B Fenolio,Michael E Slay,Shea Hammond,Matthew L Niemiller

doi:10.3897/subtbiol.24.15013

Abstract

The transition from carnivory to omnivory is poorly understood. The ability to feed at more than one trophic level theoretically increases an animals fitness in a novel environment. Because of the absence of light and photosynthesis, most subterranean ecosystems are characterized by very few trophic levels, such that food scarcity is a challenge in many subterranean habitats. One strategy against starvation is to expand diet breadth. Grotto salamanders (Eurycea spelaea) are known to ingest bat guano deliberately, challenging the general understanding that salamanders are strictly carnivorous. Here we tested the hypothesis that grotto salamanders have broadened their diet related to cave adaptation and found that, although coprophagous behavior is present, salamanders are unable to acquire sufficient nutrition from bat guano alone. Our results suggest that the coprophagic behavior has emerged prior to physiological or gut biome adaptations.

Highlights

Coprophagy is a feeding strategy commonly found in invertebrates (Weiss 2006), but much less so in vertebrates
Salamanders fed 2.5% of initial body mass (IBM) lost an average of 31.3% (±14.3%) body mass eating guano compared to an average of 9.6% (±36.0%) eating amphipods
Body mass loss was least for salamanders fed 10% IBM, and guano-fed salamanders lost 28.3% (±4.4%) body mass compared to 7.6% (±11.5%) for the amphipod group

Summary

Introduction

Coprophagy is a feeding strategy commonly found in invertebrates (Weiss 2006), but much less so in vertebrates. Herbivorous tadpoles regularly feed on feces of conspecifics in captivity (Gromko et al 1973; Steinwascher 1978; Pryor and Bjorndal 2005), even when other food sources are available ad libitum (Pryor and Bjorndal 2005). Growth rates are slower when feces are removed from the diet (Steinwascher 1978) suggesting that herbivorous tadpoles benefit nutritionally from coprophagy even though feces are lower in energy (Gromko et al 1973)

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Results

Conclusion