Fasting in the ureotelic Lake Magadi tilapia, Alcolapia grahami , does not reduce its high metabolic demand, increasing its vulnerability to siltation events.

Autor: De Boeck G; SPHERE, Department of Biology, Groenenborgerlaan 171, University of Antwerp, Antwerp B-2020, Belgium.; Department of Veterinary Anatomy and Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, PO Box 30197-00100, Nairobi 30197, Kenya., Wood CM; Department of Biology, McMaster University, 1280 Main St W, Hamilton, ON L8S 4K1, Canada.; Department of Zoology, University of British Columbia, 6270 Univ Blvd, Vancouver, BC V6T 1Z4, Canada.; Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, USA.; Department of Veterinary Anatomy and Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, PO Box 30197-00100, Nairobi 30197, Kenya., Brix KV; Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, USA.; EcoTox, 3211 19th Terrace, Miami, FL 33145, USA.; Department of Veterinary Anatomy and Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, PO Box 30197-00100, Nairobi 30197, Kenya., Sinha AK; SPHERE, Department of Biology, Groenenborgerlaan 171, University of Antwerp, Antwerp B-2020, Belgium.; Department of Aquaculture and Fisheries, University of Arkansas, 1200 North Univ Dr, Pine Bluff, AR 71601, USA., Matey V; Department of Biology, San Diego State University, 5500 Campanile Dr., San Diego, CA 92182, USA., Johannsson OE; Department of Zoology, University of British Columbia, 6270 Univ Blvd, Vancouver, BC V6T 1Z4, Canada.; Department of Veterinary Anatomy and Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, PO Box 30197-00100, Nairobi 30197, Kenya., Bianchini A; Instituto de Ciências Biológicas, Universidade Federal do Rio Grande, Ave Italia Km 8, Rio Grande, RS 96203-900, Brazil.; Department of Veterinary Anatomy and Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, PO Box 30197-00100, Nairobi 30197, Kenya., Bianchini LF; Instituto de Ciências Biológicas, Universidade Federal do Rio Grande, Ave Italia Km 8, Rio Grande, RS 96203-900, Brazil.; Department of Veterinary Anatomy and Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, PO Box 30197-00100, Nairobi 30197, Kenya., Maina JN; Department of Zoology, University of Johannesburg, PO Box 524 Auckland Park, Johannesburg 2006, South Africa.; Department of Veterinary Anatomy and Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, PO Box 30197-00100, Nairobi 30197, Kenya., Kavembe GD; School of Dryland Agriculture Science and Technology, South Eastern Kenya University, PO Box 170, Kitui 90200, Kenya.; Department of Veterinary Anatomy and Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, PO Box 30197-00100, Nairobi 30197, Kenya., Papah MB; Department of Animal and Food Sciences, University of Delaware, 531 S. College Ave., Newark, DE 19716, USA.; Department of Veterinary Anatomy and Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, PO Box 30197-00100, Nairobi 30197, Kenya., Kisipan ML; Department of Veterinary Anatomy and Physiology, Egerton University, Njoro Campus PO Box 536, Egerton 20115, Kenya.; Department of Veterinary Anatomy and Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, PO Box 30197-00100, Nairobi 30197, Kenya., Ojoo RO; Department of Veterinary Anatomy and Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, PO Box 30197-00100, Nairobi 30197, Kenya.
Jazyk: angličtina
Zdroj: Conservation physiology [Conserv Physiol] 2019 Oct 31; Vol. 7 (1), pp. coz060. Date of Electronic Publication: 2019 Oct 31 (Print Publication: 2019).
DOI: 10.1093/conphys/coz060
Abstrakt: Lake Magadi, Kenya, is one of the most extreme aquatic environments on Earth (pH~10, anoxic to hyperoxic, high temperatures). Recently, increased water demand and siltation have threatened the viable hot springs near the margins of the lake where Alcolapia grahami , the only fish surviving in the lake, live. These Lake Magadi tilapia largely depend on nitrogen-rich cyanobacteria for food and are 100% ureotelic. Their exceptionally high aerobic metabolic rate, together with their emaciated appearance, suggests that they are energy-limited. Therefore, we hypothesized that during food deprivation, Magadi tilapia would economize their energy expenditure and reduce metabolic rate, aerobic performance and urea-N excretion. Surprisingly, during a 5-day fasting period, routine metabolic rates increased and swimming performance (critical swimming speed) was not affected. Urea-N excretion remained stable despite the lack of their N-rich food source. Their nitrogen use switched to endogenous sources as liver and muscle protein levels decreased after a 5-day fast, indicating proteolysis. Additionally, fish relied on carbohydrates with lowered muscle glycogen levels, but there were no signs indicating use of lipid stores. Gene expression of gill and gut urea transporters were transiently reduced as were gill rhesus glycoprotein Rhbg and Rhcg-2. The reduction in gill glutamine synthetase expression concomitant with the reduction in Rh glycoprotein gene expression indicates reduced nitrogen/ammonia metabolism, most likely decreased protein synthesis. Additionally, fish showed reduced plasma total CO 2 , osmolality and Na + (but not Cl - ) levels, possibly related to reduced drinking rates and metabolic acidosis. Our work shows that Lake Magadi tilapia have the capacity to survive short periods of starvation which could occur when siltation linked to flash floods covers their main food source, but their seemingly hardwired high metabolic rates would compromise long-term survival.
(© The Author(s) 2019. Published by Oxford University Press and the Society for Experimental Biology.)
Databáze: MEDLINE
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