title: A waterborne chemical cue from Gulf toadfish, Opsanus beta, prompts pulsatile urea excretion in conspecifics.
abstract: The Gulf toadfish (Opsanus beta) has a fully functional ornithine urea cycle (O-UC) that allows it to excrete nitrogenous waste in the form of urea. Interestingly, urea is excreted in a pulse across the gill that lasts 1-3h and occurs once or twice a day. Both the stress hormone, cortisol, and the neurotransmitter, serotonin (5-HT) are involved in the control of pulsatile urea excretion. This and other evidence suggests that urea pulsing may be linked to toadfish social behavior. The hypothesis of the present study was that toadfish urea pulses can be triggered by waterborne chemical cues from conspecifics. Our findings indicate that exposure to seawater that held a donor conspecific for up to 48h (pre-conditioned seawater; PC-SW) induced a urea pulse within 7h in naïve conspecifics compared to a pulse latency of 20h when exposed to seawater alone. Factors such as PC-SW intensity and donor body mass influenced the pulse latency response of naïve conspecifics. Fractionation and heat treatment of PC-SW to narrow possible signal candidates revealed that the active chemical was both water-soluble and heat-stable. Fish exposed to urea, cortisol or 5-HT in seawater did not have a pulse latency that was significantly different than seawater alone; however, ammonia, perhaps in the form of NH4Cl, was found to be a factor in the pulse latency response of toadfish to PC-SW and could be one component of a multi-component cue used for chemical communication in toadfish. Further studies are needed to fully identify the chemical cue as well as determine its adaptive significance in this marine teleost fish.
authors.affiliation: Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Fulton
authors.affiliation: Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada; Department of Biology, Brandon University, Brandon, MB R7A 6A9, Canada.
authors.forename: Christophe M R
authors.initials: CMR
authors.lastname: LeMoine
authors.affiliation: Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada; Department of Biology, York University, Toronto, ON M3J 1P3, Canada.
authors.forename: Carol
authors.initials: C
authors.lastname: Bucking
authors.affiliation: Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149, USA.
authors.forename: Kevin V
authors.initials: KV
authors.lastname: Brix
authors.affiliation: Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada; Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149, USA.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Walsh
authors.affiliation: Department of Marine Biology and Ecology, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL 33149, USA. Electronic address: dmcdonald@rsmas.miami.edu.
authors.forename: M Danielle
authors.initials: MD
authors.lastname: McDonald
mesh_terms: D000641:Ammonia / Q000032:analysis; D000819:Animal Communication; D000818:Animals; D024541:Batrachoidiformes / Q000502:physiology*; D003463:Cues; D005880:Gills / Q000502:physiology; D006854:Hydrocortisone / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D012623:Seawater / Q000737:chemistry; D012701:Serotonin / Q000378:metabolism; D014508:Urea / Q000378:metabolism*
chemical_list: D012701:Serotonin; D000641:Ammonia; D014508:Urea; D009584:Nitrogen; D006854:Hydrocortisone
keywords: Ammonia; Chemical communication; Cortisol; Nitrogen excretion; Serotonin; Social/territorial signaling; Urea; Ureotely