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| Author(s): |
Adriana Moriguchi Jeckel
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB) |
| Defense date: | 2015-06-26 |
| Examining board members: |
Taran Grant;
Glauco Machado;
Daniel Carvalho Pimenta
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| Advisor: | Taran Grant |
| Abstract | |
Amphibians have a great diversity of toxins in their skin to defend them against predators and pathogens. These compounds can be either produced or sequestrated from an arthropod diet. Independently of origin, these chemical compounds vary in composition between different species, between populations of the same species and even individuals of the same species. Differences between species and populations could be explained by differences in production or sequestration capacity, ecological pressures and alkaloid-containing arthropods availability. Variations among individuals of the same population are common, but the cause of this variation is not very well understood. We hypothesize that part of this variation is explained by differences in age of the individuals. The diversity of toxins in the skin is represents the balance between lifespan, production and/or sequestration of compounds and their use for protection. To test our hypothesis we used the species Melanophryniscus moreirae, a bufonid toad, and endemic from Serra da Mantiqueira, Brazil. This species belongs to the only genus of this family that has the ability to sequester alkaloids from the diet, and other studies had also detected biossynthesized compuonds. The Gas-Chromatography/Mass Spectrometry analysis resulted in high amounts of alkaloids and bufotenine, a biogenic amine, with high variance among individuals. We determined the age structure of this population by skeletochronology. By determining their age, we could find differences in maturation age between the sexes, and assume possible explanations for the size sexual dimorphism. We applied three multiple regression analysis to test our age hypothesis, with age, sex and skin mass as explanatory variables, and number of alkaloids, quantity of alkaloids and quantity of bufotenine as response variable of each regression. Age explained number of alkaloids, showing that the older the animal is, more it ate and the probability of eating from different alkaloid source is higher. Our study explains part of the chemical compound variation, but more study is needed to understand this complex system of chemical defense. (AU) | |
| FAPESP's process: | 13/14061-1 - Evaluation of the relation between age and diversity of defensive alkaloids in Melanophryniscus simplex (Anura: Bufonidae) |
| Grantee: | Adriana Moriguchi Jeckel |
| Support Opportunities: | Scholarships in Brazil - Master |