Mean + S.E.M urinary corticosterone metabolite level in male cane toads during 14 days of acclimation at 25°C for 14 days.

<p>Sample size for each group was n = 8.</p

Mean + S.E.M urinary corticosterone (upper panel) and testosterone (lower panel) metabolite responses in male cane toads acclimated at 25°C for 14 days and then subjected to acute temperature treatments of either 30°C (^___▪^___), 35°C (^___▴^___) or 40°C (- - - ▾ - - -).

<p>Control group represents male toads that were sampled using the capture handling protocol at 25°C (- - - • - - -). Sample size for each group was n = 8.</p

Histogram showing mean durations of righting response (seconds) of male cane toads after exposure to 25°, 30°, 35° or 40°C.

<p>Sample sizes at each time point were n = 8.</p

Correlation between total integrated corticosterone and testosterone responses.

<p>Temperature treatments are denoted using numbers by the data points.</p

The Neuro-Hormonal Control of Rapid Dynamic Skin Colour Change in an Amphibian during Amplexus

<div><p>Sexual signalling using dynamic skin colouration is a key feature in some vertebrates; however, it is rarely studied in amphibians. Consequently, little is known about the hormonal basis of this interesting biological phenomenon for many species. Male stony creek frogs (<i>Litoria wilcoxii</i>) are known to change dorsal colouration from brown to lemon yellow within minutes. This striking change is faster then what has been seen most amphibians, and could therefore be under neuronal regulation, a factor that is rarely observed in amphibians. In this study, we observed colour changes in wild frogs during amplexus to determine the natural timing of colour change. We also investigated the hypothesis that colour change is mediated by either reproductive or neuro- hormones. This was achieved by injecting frogs with epinephrine, testosterone, saline solution (control 1) or sesame oil (control 2). A non-invasive approach was also used wherein hormones and controls were administered topically. Male frogs turned a vivid yellow within 5 minutes of initiation of amplexus and remained so for 3–5 hours before rapidly fading back to brown. Epinephrine-treated frogs showed a significant colour change from brown to yellow within 5 minutes, however, testosterone-treated frogs did not change colour. Our results provide evidence of the role neuronal regulation plays in colour change systems.</p></div

Colour change in <i>L</i>. <i>wilcoxii</i> in response to control and hormone treatments (n = 5 individual frogs per group).

<p>Each point indicates the dorsal colour of a frog at each time point (0–120 minutes).</p

Mean (+ S.E.) urinary corticosterone metabolite concentrations in male Fijian ground frogs during exposure to a cane toad, a ball, another male ground frog or control (no stimulus).

<p>Sample sizes at each time point were n = 7. Mean urinary corticosterone data for each four group (control and three treatments) were used to obtain the data for time = 0 h.</p

Male <i>L. wilcoxii</i> during amplexus at time 0 (top left), after 10 minutes (top right), baseline pre-amplectic male (bottom left), and post epinephrine injection (bottom right).

<p>Colour score for the brown male is −1.93 (RGB = 67, 58, 30) and the amplexing male is 3.01(RGB = 254, 249, 78).</p

<i>L. wilcoxii</i> male dorsal colour change during amplexus (n = 19).

<p>Points indicate colour of each individual male, colour changes over time (0–300 minutes). Colour score of a single female throughout amplexus is provided as a reference (lower line where now increase is observed). There was a significant difference in colour between baseline and all tested time points (p = 0.0001) until 240 minutes (p = 0.2920). From time 270 to 330, scores were significantly lower than baseline (p = 0.0001).</p

Mean (+ S.E.) locations of the Fijian ground frogs during exposure to a cane toad or another frog.

<p>Location 1 was closest to the test compartment and location 6 was furthest away from the test compartment. The location of the frog was recorded at 5, 15, 20, 40 and 60 min after the test began (Fig. 3A, frogs sampled up to 60 min) or 5, 20, 40, 60, 120, 180 (Fig. 3B, frogs sampled up to 180 min) or 5, 20, 40, 60, 120, 180, 240 and 360 min (Fig. 3C, frogs sampled up to 360 min). Sample sizes at each time point were n = 7.</p