Osmoregulatory and Respiratory Adaptations of Lake Magadi Fish (Alcolapia grahami)

2016 ◽  
pp. 219-226 ◽  
Author(s):  
Daniel W. Onyango ◽  
Seth M. Kisia
Keyword(s):  
Lake Magadi ◽  
Alcolapia Grahami

scholarly journals Gyrodactylus magadiensis n. sp. (Monogenea, Gyrodactylidae) parasitising the gills of Alcolapia grahami (Perciformes, Cichlidae), a fish inhabiting the extreme environment of Lake Magadi, Kenya

Parasite ◽  
2019 ◽  
Vol 26 ◽  
pp. 76
Author(s):  
Quinton Marco Dos Santos ◽  
John Ndegwa Maina ◽  
Annemariè Avenant-Oldewage
Keyword(s):  
New Species ◽  
Cichlid Fish ◽  
Soda Lake ◽  
Its Region ◽  
Extreme Environment ◽  
Molecular Techniques ◽  
Diurnal Fluctuation ◽  
Lake Magadi ◽  
A New Species ◽  
Alcolapia Grahami

A new species of Gyrodactylus von Nordmann, 1832 is described from the gills of Alcolapia grahami, a tilapian fish endemic to Lake Magadi. This alkaline soda lake in the Rift Valley in Kenya is an extreme environment with pH as high as 11, temperatures up to 42 °C, and diurnal fluctuation between hyperoxia and virtual anoxia. Nevertheless, gyrodactylid monogeneans able to survive these hostile conditions were detected from the gills the Magadi tilapia. The worms were studied using light microscopy, isolated sclerites observed using scanning electron microscopy, and molecular techniques used to genetically characterize the specimens. The gyrodactylid was described as Gyrodactylus magadiensis n. sp. and could be distinguished from other Gyrodactylus species infecting African cichlid fish based on the comparatively long and narrow hamuli, a ventral bar with small rounded anterolateral processes and a tongue-shaped posterior membrane, and marginal hooks with slender sickles which are angled forward, a trapezoid to square toe, rounded heel, a long bridge prior to reaching marginal sickle shaft, and a long lateral edge of the toe. The species is also distinct from all other Gyrodactylus taxa based on the ITS region of rDNA (ITS1–5.8s–ITS2), strongly supporting the designation of a new species. These findings represent the second record of Gyrodactylus from Kenya, with the description of G. magadiensis bringing the total number of Gyrodactylus species described from African cichlids to 18.

Physiological and molecular characterization of urea transport by the gills of the Lake Magadi tilapia (Alcolapia grahami)

2001 ◽  
Vol 204 (3) ◽  
pp. 509-520 ◽  
Author(s):  
P.J. Walsh ◽  
M. Grosell ◽  
G.G. Goss ◽  
H.L. Bergman ◽  
A.N. Bergman ◽  
...  
Keyword(s):  
Short Interval ◽  
Northern Analysis ◽  
Xenopus Laevis Oocytes ◽  
Urea Transport ◽  
Urea Transporter ◽  
Pavement Cells ◽  
Urea Excretion ◽  
Lake Magadi ◽  
Alcolapia Grahami

The Lake Magadi tilapia (Alcolapia grahami) is an unusual fish, excreting all its nitrogenous waste as urea because of its highly alkaline and buffered aquatic habitat. Here, using both physiological and molecular studies, we describe the mechanism of branchial urea excretion in this species. In vivo, repeated short-interval sampling revealed that urea excretion is continuous. The computed urea permeability of A. grahami gill is 4.74×10(−)(5)+/−0.38×10(−)(5)cm s(−)(1) (mean +/− s.e.m., N=11), some 10 times higher than passive permeability through a lipid bilayer and some five times higher than that of even the most urea-permeable teleosts studied to date (e.g. the gulf toadfish). Transport of urea was bidirectional, as demonstrated by experiments in which external [urea] was elevated. Furthermore, urea transport was inhibited by classic inhibitors of mammalian and piscine urea transporters in the order thiourea>N-methylurea>acetamide. A 1700 base pair cDNA for a putative Magadi tilapia urea transporter (mtUT) was cloned, sequenced and found to display high homology with urea transporters from mammals, amphibians and other fishes. When cRNA transcribed from mtUT cDNA was injected into Xenopus laevis oocytes, phloretin-inhibitable urea uptake was enhanced 3.4-fold relative to water-injected controls. Northern analysis of gill, red blood cells, liver, muscle and brain using a portion of mtUT as a probe revealed that gill is the only tissue in which mtUT RNA is expressed. Magadi tilapia gill pavement cells exhibited a trafficking of dense-cored vesicles between the well-developed Golgi cisternae and the apical membrane. The absence of this trafficking and the poor development of the Golgi system in a non-ureotelic relative (Oreochromis niloticus) suggest that vesicle trafficking could be related to urea excretion in Alcolapia grahami. Taken together, the above findings suggest that the gills of this alkaline-lake-adapted species excrete urea constitutively via the specific facilitated urea transporter mtUT.

Physiological adaptations of the gut in the Lake Magadi tilapia, Alcolapia grahami, an alkaline- and saline-adapted teleost fish

2003 ◽  
Vol 136 (3) ◽  
pp. 701-715 ◽  
Author(s):  
Annie Narahara Bergman ◽  
Pierre Laurent ◽  
George Otiang'a-Owiti ◽  
Harold L. Bergman ◽  
Patrick J. Walsh ◽  
...  
Keyword(s):  
Teleost Fish ◽  
Lake Magadi ◽  
Physiological Adaptations ◽  
Alcolapia Grahami

Ionoregulatory strategies and the role of urea in the Magadi tilapia (Alcolapia grahami)

2002 ◽  
Vol 80 (3) ◽  
pp. 503-515 ◽  
Author(s):  
Chris M Wood ◽  
Paul Wilson ◽  
Harold L Bergman ◽  
Annie N Bergman ◽  
Pierre Laurent ◽  
...  
Keyword(s):  
Lake Water ◽  
Plasma Cortisol ◽  
Sea Water ◽  
Whole Body ◽  
Chloride Cells ◽  
Water Type ◽  
Plasma Ions ◽  
Lake Magadi ◽  
Simultaneous Control ◽  
Alcolapia Grahami

The unique ureotelic tilapia Alcolapia grahami lives in the highly alkaline and saline waters of Lake Magadi, Kenya (pH ~10.0, alkalinity ~380 mmol·L–1, Na+ ~350 mmol·L–1, Cl– ~110 mmol·L–1, osmolality ~580 mosmol·kg–1). In 100% lake water, the Magadi tilapia maintained plasma Na+, Cl–, and osmolality at levels typical of marine teleosts and drank the medium at 8.01 ± 1.29 mL·kg–1·h–1. Gill chloride cells were predominantly of the sea water type (recessed, with apical pits) but a few freshwater-type chloride cells (surficial, with flat apical exposure) were also present. Whole-body Na+ and Cl– concentrations were relatively high and exhibited larger relative changes in response to salinity transfers than did plasma ions. All fish succumbed upon acute transfer to 1% lake water, but tolerated acute transfer to 10% lake water well, and gradual long-term acclimation to both 10 and 1% lake water without change in plasma cortisol. Plasma osmolytes were here maintained at levels typical of freshwater teleosts. Curiously, drinking continued at the same rate in fish adapted to 1% lake water, but chloride cells were now exclusively of the freshwater type. Significant mortality and elevated cortisol occurred after acute transfer to 200% lake water. However, the fish survived well during gradual adaptation to 200% lake water, although plasma cortisol remained chronically elevated. Urea levels accounted for only 2–3% of internal osmolality in 100% lake water but responded to a greater extent than plasma ions during exposure to 10 and 200% lake water, decreasing by 28–42% in the former and increasing by over 500% in the latter relative to simultaneous-control values. Urea thereby played a small but significant role (up to 8% of internal osmolality) in osmoregulation.

Morphological evaluation of spermatogenesis in Lake Magadi tilapia (Alcolapia grahami): A fish living on the edge

2013 ◽  
Vol 45 (6) ◽  
pp. 371-382 ◽  
Author(s):  
M.B. Papah ◽  
S.M. Kisia ◽  
R.O. Ojoo ◽  
A.N. Makanya ◽  
C.M. Wood ◽  
...  
Keyword(s):  
Lake Magadi ◽  
Morphological Evaluation ◽  
Alcolapia Grahami

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

2019 ◽  
Vol 7 (1) ◽  
Author(s):  
Gudrun De Boeck ◽  
Chris M Wood ◽  
Kevin V Brix ◽  
Amit K Sinha ◽  
Victoria Matey ◽  
...  
Keyword(s):  
Gene Expression ◽  
Metabolic Rate ◽  
Food Source ◽  
Swimming Performance ◽  
Aerobic Performance ◽  
Metabolic Rates ◽  
Term Survival ◽  
Ammonia Metabolism ◽  
Lake Magadi ◽  
Alcolapia Grahami

Abstract 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 CO2, 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 SEDIMENTARY RECORD OF THE LAKE MAGADI BASIN: CORE ANALYSIS FROM HSPDP-MAG14 CORES 1A, 1C, AND 2A

2016 ◽  
Author(s):  
Emma P. McNulty ◽  
◽  
Tim K. Lowenstein ◽  
R. Bernhart Owen ◽  
Robin W. Renaut ◽  
...  
Keyword(s):  
Core Analysis ◽  
Sedimentary Record ◽  
Lake Magadi

LAKE MAGADI, KENYA: MODERN-PLEISTOCENE ANALOG FOR ALKALINE SALINE LAKE DEPOSITS

2016 ◽  
Author(s):  
Tim K. Lowenstein ◽  
◽  
R. Bernhart Owen ◽  
Robin W. Renaut ◽  
Daniel M. Deocampo ◽  
...  
Keyword(s):  
Saline Lake ◽  
Lake Magadi ◽  
Lake Deposits
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