Abstract
The present study was undertaken to assess the ability of gulf toadfish (Opsanus beta) from an intertidal population in northern Florida to make and excrete urea as a nitrogenous waste product. Using an electronic tide gauge and data logger, we were able to demonstrate that toadfish in the intertidal mudflats at Panacea. Florida were air-exposed approximately 9.3% of the over 2000 h monitored, and that these periods could last as long as 9 h. Toadfish were collected from this site during several seasons in 1993-1994, and were subjected to experiments which measured their nitrogenous waste production (as ammonia and urea). Samples were also analyzed for several biochemical proxies of urea excretion (including liver ornithine-urea cycle (O-UC) enzyme activities, and activities of nitrogen feeder enzymes, including the key enzyme glutamine synthetase. G Sase), as well as plasma cortisol, urea and other variables. Although freshly collected toadfish from Panacea exhibited relatively high activities of the O-UC enzymes, they showed rather low activities of GSase, indicating a low potential for immediate urea production. Furthermore, urea excretion rates were extremely low during the first 24-36 h in captivity, even when toadfish were subjected to an experimental emersion period of 8 h intended to simulate air-exposure in nature. When compared to responses and values of subtidal toadfish from Biscayne Bay. Florida published in a prior report, and from a single sample of subtidal toadfish at Panacea, it is apparent that urea synthesis and excretion in the gult toadfish are likely not a direct consequence of air-exposure during the tidal cycle. Our data are discussed in the context of an ammonia-exposure hypothesis explaining urea synthesis and excretion in this species.
Original language | English (US) |
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Pages (from-to) | 21-34 |
Number of pages | 14 |
Journal | Marine and Freshwater Behaviour and Physiology |
Volume | 33 |
Issue number | 1 |
DOIs | |
State | Published - 1999 |
Externally published | Yes |
Keywords
- Ammonia
- Gulf toadfish
- Intertidal
- Opsamus beta
- Urea
- Ureogenesis
ASJC Scopus subject areas
- Aquatic Science
- Oceanography