Variation in pigmentation gene expression is associated with distinct aposematic color morphs in the poison frog, Dendrobates auratus

Color and pattern phenotypes have clear implications for survival and reproduction in many species. However, the mechanisms that produce this coloration are still poorly characterized, especially at the genomic level. Here we have taken a transcriptomics-based approach to elucidate the underlying genetic mechanisms affecting color and pattern in a highly polytypic poison frog. We sequenced RNA from the skin from four different color morphs during the final stage of metamorphosis and assembled a de novo transcriptome. We then investigated differential gene expression, with an emphasis on examining candidate color genes from other taxa. Overall, we found differential expression of a suite of genes that control melanogenesis, melanocyte differentiation, and melanocyte proliferation (e.g., tyrpl, lefl, leol, and mitf) as well as several differentially expressed genes involved in purine synthesis and iridophore development (e.g., arfgapl, arfgap2, airc, and gairt). Our results provide evidence that several gene networks known to affect color and pattern in vertebrates play a role in color and pattern variation in this species of poison frog.

Desarrollo neural, somitogénesis y morfología interna de los embriones de Hyloxalus vertebralis y Dendrobates auratus (Anura: Dendrobatidae)

Se analizaron y compararon las características de la neurulación, morfología interna de los embriones desde la néurula hasta la eclosión del renacuajo y el modo de miogénesis de dos especies de ranas de la familia Dendrobatidae (Hyloxalus vertebralis y Dendrobates auratus) con otras especies de la misma familia y Xenopus laevis. Se realizó este análisis debido a que los huevos de H. vertebralis y D. auratus tienen el tamaño más grande detectado hasta ahora en la familia Dendrobatidae (2.6 y 3.5 mm de diámetro, respectivamente). La morfología interna de los embriones y la neurulación de H. vertebralis y D. auratus fueron similares a lo observado en X. laevis y otros Dendrobatidae. Se observó retraso en la diferenciación del cerebro en estas especies en comparación con X. laevis. La miogénesis de H. vertebralis y D. auratus ocurre por interdigitación celular como en Bombina variegata (Bombinatoridae), cuatro especies adicionales de Dendrobatidae, dos especies de Leiuperidae y una especie de Hemiphractidae. El estudio comparativo permite documentar la diversidad de programas del desarrollo entre los anuros y contribuir al conocimiento de la fauna ecuatoriana.

Bufadienolide and alkaloid-based chemical defences in two different species of neotropical anurans are equally effective against the same arthropod predators

Defensive chemicals in anuran skin secretions function in protection against potential predators. Although studies have demonstrated that particular chemicals are effective against certain predators, very little is known about how different chemicals from different species function against the same predators. Understanding how different chemicals function as a defence against similar predators is fundamental to the ecology and evolution of chemical defences in frogs. In the present study, the defensive function of bufadienolide-based defences in adult Rhaebo haematiticus (Bufonidae) were compared with alkaloid-based defences in adult and juvenile Dendrobates auratus (Dendrobatidae) against the same predators. Most bufonids contain synthesized bufadienolides, whereas dendrobatids contain dietary-derived alkaloids. Predation trials were performed with two potential invertebrate predators, Paraponera clavata (bullet ant) and Cupiennius coccineus (ctenid spider), to determine how these predators respond to two different types of frog chemical defence. The non-chemically defended frog Craugastor fitzingeri served as a control in all predation trials. Our results suggest that bufadienolide defences of R. haematiticus and alkaloid defences of D. auratus are equally effective towards bullet ant and ctenid spider predators. The similar avoidance and cleaning behaviours exhibited by these ants and spiders after contact with bufadienolides and alkaloids suggest that both types of defence are unpalatable to these arthropod predators.

Sexual conflict and deception in poison frogs

I review evidence that females deceive males in the context of sexual selection and sexual conflict in the green poison frog, Dendrobates auratus. In this species, males mate polygynously when they have the opportunity, but polygyny imposes a cost on female reproductive success. Some females attempt to guard their mates when those males are approached by other females. This behavior involves both aggression toward other females and active “pseudo-courtship” of the male. This courtship is hypothesized to be a deceptive signal that functions to prevent the male from mating with other females. Observational and comparative evidence is presented in support of the predictions of this hypothesis. This form of deception is compared to similar behaviors that occur in other species, and the possibility that other forms of deception occur in poison frogs is discussed.