Venomics analyses of the skin secretion of Dermatonotus muelleri: Preliminary proteomic and metabolomic profiling.

Dermatonotus muelleri is the sole species of the Dermatonotus genus and inhabits Argentina, Bolivia, Brazil and Paraguay. This animal exhibits an explosive reproductive behavior during the Southern spring months, which lasts only for five days. Moreover, this animal displays specific adaptations to the habitat resulting in the energy conservation needed during either the intense reproduction period or times of estivation. During dry seasons and/or food shortages D. muelleri can survive because its food specialization and ability to dig an underground chamber for protection. Few literature is available on this amphibian and no biochemical characterization has ever been performed on the animal's skin secretion. This work, on the other hand, presents for the first time a venomic analysis of the major components present in the skin secretion of this microhylid. The crude skin secretion was obtained my mechanical stimulation and was analyzed according to one major criterion: >10 kDa or <10 kDa. The high molecular mass fraction was subjected to typical gel-based proteomic processing whereas the low molecular mass fraction was analyzed by liquid chromatography, mass spectrometry and nuclear magnetic resonance (NMR), yielding an overall 'venomics' approach. No classical/evident toxin was detected, but peptidases (metallo and serino) and structural proteins could be identified. In the low molecular mass fraction no peptides were detected, as well as no typical alkaloid or steroid. On the other hand, the amino acid tryptophan could be identified and a typical sugar spectrum was obtained in the NMR analyses. Altogether these findings point out to the fact that D. muelleri skin secretion is unique and the molecular arsenal present herein is yet to be explored; therefore, this venomics study is only the beginning.