5-Hydroxytryptamine initiates pulsatile urea excretion from perfused gills of the gulf toadfish (Opsanus beta)

A waterborne chemical cue from Gulf toadfish, Opsanus beta, prompts pulsatile urea excretion in conspecifics

“…Heat treatment of PC-SWin the present study allowed for various compounds to be removed by volatilization or denaturation such as large proteins and steroids, aromatics, as well as low molecular weight organics such as ketones.The data of the present study clearly show that the signaling mechanism used by toadfish is not heat-labile as naïve toadfish still responded to heat-treated,PC-SW with alow pulse latency. In addition to exhibiting heatstability, the active cue compounds(s) were found to be located within the polar, aqueous fraction and not the non-polar fraction, further eliminating steroids, hydrophobic amino acids and most organic compounds as possible candidates.The elimination of steroid compounds by heat and solid-phase extraction is consistent with the additional finding that waterborne exposure to the steroid hormone, cortisol, does not result in a decrease in pulse latency, despite its involvement in the control of toadfish pulsatile urea excretion and social behavior (reviewed by Wood et al, 2003;McDonald et al, 2012;Sørensen et al, 2014).…”

“…Since cortisol and 5-HT are highly involved in controlling the pulsatile urea excretion mechanism of toadfishand PC-SW contains urea and a certain amount of ammonia (McDonald et al, 2012;reviewed by Wood et al, 2003), the ability of these compounds to elicit a urea pulse on their own when placed in seawater was tested. The cortisol concentration (10 mg•L -1 ) used in this experiment was predicted to be the amount of cortisol one toadfish may excrete into its environment based on average plasma cortisol levels (Hopkins et al, 1995;Rodela et al, 2009;Wood et al, 1997, Wood et al, 2001).…”