Green Treefrogs Hyla Cinerea Research Articles

Rapid effects of elevated stress hormones on male courtship signals suggest a major role for the acute stress response in intra‐ and intersexual selection

AbstractShort‐term elevations in circulating stress hormones (glucocorticoids) often mediate reduced investment in reproductive behaviour in favour of self‐maintenance and survival, but the significance of these effects in sexual selection and communication remain largely unexplored.Here we examine the acute stress response in the context of intra‐ and intersexual selection in the green treefrogHyla cinerea. Males of this species produce agonistic acoustic signals that stimulate elevations in the stress hormone corticosterone (CORT) in rival males, suggesting a central role forCORTin male–male competition. We hypothesized that elevatedCORTlevels in losers of vocal contests mediate an increase in the energy allocated towards self‐maintenance and survival that compromises investment in courtship signalling, resulting in reduced attractiveness to females.Consistent with this hypothesis, we show thatCORTadministration to calling males, simulatingCORTproduction in vocal contest losers, caused a rapid reduction in the duration of advertisement calls and vocal effort. ElevatedCORTalso increased the propensity to produce aggressive calls during simulated territorial intrusions that was followed by an increased probability of non‐calling “satellite” mating behaviour. This suite ofCORTeffects on vocal behaviour are known to decrease attractiveness to females and were not related to a decrease in androgen level or differences in body condition inCORT‐ vs. saline‐injected males.Our results suggest thatCORTproduction during intraspecific vocal contests compromises male attractiveness. Male vocalizations may therefore reliably indicate recent contest outcomes and/or the stress status of males, implicatingCORTas a mediator of honest signalling. We propose that the effects of agonistic acoustic signals onCORTproduction in this species are maintained byCORT‐mediated life‐history trade‐offs; decreased conspicuous signalling in high stress‐responsive males potentially increases survival by reducing the likelihood of escalated contests with dominant males and detection by predators. Adoption of alternative non‐calling satellite mating tactics may contribute to maintaining individual variation in stress responsiveness by increasing the chances that competitively inferior males acquire mates.Aplain language summaryis available for this article.

GABAergic projection neurons in the basal ganglia of the green tree frog ( Hyla cinerea)

The basal ganglia of tetrapods have been considered to be a conservative system sharing a common pattern with respect to connectivity and transmitters. One important transmitter found in mammalian basal ganglia is gamma-aminobutyric acid (GABA) which is used by nearly all striatal and pallidal projection neurons. In order to investigate whether GABAergic projection neurons exist in the basal ganglia of anurans as well, we combined tracer applications in the diencephalic portion of the lateral forebrain bundle with GABA immunohistochemistry in an isolated brain preparation of the green tree frog Hyla cinerea. Additionally, double-labeling studies using antibodies against GABA, GAD 65, and GAD 67 helped to clarify which neurons could be regarded as GABAergic. On average 7.29–7.40% of striatal and 3.29–3.98% of pallidal projection neurons were strongly GABA-immunoreactive; lightly labeled neurons were disregarded. We conclude that GABAergic projection neurons are present in the striatum and dorsal pallidum of H. cinerea, but their numbers are much lower compared to the same regions in mammals.

Biological Half-Life and Distribution of Radiocesium in a Contaminated Population of Green Treefrogs Hyla cinerea

Biological Half-Life and Distribution of Radiocesium in a Contaminated Population of Green Treefrogs Hyla cinerea