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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

The relationship between poison frog chemical defenses and age, body size, and sex

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Jeckel, Adriana M. [1] ; Saporito, Ralph A. [2] ; Grant, Taran [1]
Total Authors: 3
[1] Univ Sao Paulo, Inst Biosci, Dept Zool, BR-05508090 Sao Paulo, SP - Brazil
[2] John Carroll Univ, Dept Biol, University Hts, OH 44118 - USA
Total Affiliations: 2
Document type: Journal article
Source: Frontiers in Zoology; v. 12, OCT 1 2015.
Web of Science Citations: 11

Introduction: Amphibians secrete a wide diversity of chemicals from skin glands as defense against predators, parasites, and pathogens. Most defensive chemicals are produced endogenously through biosynthesis, but poison frogs sequester lipophilic alkaloids from dietary arthropods. Alkaloid composition varies greatly, even among conspecific individuals collected at the same time and place, with some individuals having only a few micrograms of one or a few alkaloids and others possessing > 1 mg of > 30 alkaloids. The paucity of alkaloids in juveniles and their abundance in adults suggests that alkaloids accumulate over time; however, alkaloid diversity is highly variable among adult poison frogs and has never been studied in relation to individual age. Using skeletochronology to infer individual ages and gas chromatography-mass spectrometry and vapor phase Fourier-transform infrared spectral analysis to identify the defensive chemicals of 63 individuals, we tested the relationship between defensive chemicals and age, size, and sex in the Brazilian red-belly toad, Melanophryniscus moreirae, a poison frog that possesses both sequestered alkaloids and the biosynthesized indolealkylamine bufotenine. Results: Adult females were, on average, older and larger than adult males. Juveniles were smaller but not necessarily younger than adults and possessed bufotenine and 18 of the 37 alkaloids found in adults. Alkaloid richness was positively related to age, but not size, whereas the quantities of sequestered alkaloids and bufotenine were positively related to size, but not age. Defensive chemicals were unrelated to sex, independent of size. Conclusions: The relationship between alkaloid richness and age appears to result from the gradual accumulation of alkaloids over a frog's lifetime, whereas the relationship between the quantity of defensive chemicals and size appears to be due to the greater storage capacity of larger individuals. The decoupling of age and size effects increases the amount of individual variation that can occur within a population, thereby possibly enhancing anti-predator efficacy. Further, given that both richness and quantity contribute to the overall chemical defense of individual frogs, our results suggest that older, larger individuals are better defended than younger, smaller ones. These considerations underscore the importance of including age in studies of the causes and consequences of variation in poison frog chemical defenses. (AU)

FAPESP's process: 12/10000-5 - A multi-disciplinary approach to the study of amphibian diversification
Grantee:Taran Grant
Support type: Research Grants - Young Investigators Grants
FAPESP's process: 13/23715-5 - Poison frog chemical defense: does alkaloid diversity increase as individuals grow older?
Grantee:Adriana Moriguchi Jeckel
Support type: Scholarships abroad - Research Internship - Master's degree
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 type: Scholarships in Brazil - Master
FAPESP's process: 14/15730-7 - Variation in sequestered chemical defenses in red belly toads (Melanophryniscus, Bufonidae)
Grantee:Taran Grant
Support type: Research Grants - Visiting Researcher Grant - International