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Johannsson, et al. "Air breathing in Magadi tilapia Alcolapia grahami, under normoxic and hyperoxic conditions, and the association with sunlight and reactive oxygen species." Journal Fish Biology. 2014;84(3):844-863.

Observations of the Magadi tilapia Alcolapia grahami in hot, highly alkaline Lake Magadi revealed that they air breathe not only during hypoxia, as described previously, but also during normoxia and hyperoxia. Air breathing under these latter conditions occurred within distinct groupings of fish (pods) and involved only a small proportion of the population. Air breathing properties (duration and frequency) were quantified from video footage. Air breathing within the population followed a diel pattern with the maximum extent of pod formation occurring in early afternoon. High levels of reactive oxygen species (ROS) in the water may be an irritant that encourages the air-breathing behaviour. The diel pattern of air breathing in the field and in experiments followed the diel pattern of ROS concentrations in the water which are amongst the highest reported in the literature (maximum daytime values of 2·53–8·10 μM H2O2). Interlamellar cell masses (ILCM) occurred between the gill lamellae of fish from the lagoon with highest ROS and highest oxygen levels, while fish from a normoxic lagoon with one third the ROS had little or no ILCM. This is the first record of air breathing in a facultative air-breathing fish in hyperoxic conditions and the first record of an ILCM in a cichlid species.
Key words: diel patterns; gill remodelling; interlamellar cell mass.
© 2014 The Fisheries Society of the British Isles

Papah, et al. "Lake Magadi Ecosystem: Current Research Trends and Future Perspectives.". In: 1st International One Health Conference. Hilton Hotel, Addis Ababa Ethiopia; 2013.
Papah MB, et al. "Morphological evaluation of spermatogenesis in Lake Magadi tilapia (Alcolapia grahami): A fish living on the edge." Tissue and cell. 2013;45:371-382. AbstractSciencedirect

Spermatogenesis in Lake Magadi tilapia (Alcolapia grahami), a cichlid fish endemic to the highly alkaline and saline Lake Magadi in Kenya, was evaluated using light and transmission electron microscopy. Spermatogenesis, typified by its three major phases (spermatocytogenesis, meiosis and spermiogenesis), was demonstrated by the presence of maturational spermatogenic cells namely spermatogonia, spermatocytes, spermatids and spermatozoa. Primary spermatogonia, the largest of all the germ cells, underwent a series of mitotic divisions producing primary spermatocytes, which then entered two consecutive meiotic divisions to produce secondary spermatocytes and spermatids. Spermatids, in turn, passed through three structurally distinct developmental stages typical of type-I spermiogenesis to yield typical primitive anacrosomal spermatozoa of the externally fertilizing type (aquasperm). The spermatozoon of this fish exhibited a spheroidal head with the nucleus containing highly electron-dense chromatin globules, a midpiece containing ten ovoid mitochondria arranged in two rows and a flagellum formed by the typical 9+2 microtubule axoneme. In addition, the midpiece, with no cytoplasmic sheath, appeared to end blindly distally in a lobe-like pattern around the flagellum; a feature that was unique and considered adaptive for the spermatozoon of this species to the harsh external environment. These observations show that the testis of A. grahami often undergoes active spermatogenesis despite the harsh environmental conditions to which it is exposed on a daily basis within the lake. Further, the spermiogenic features and spermatozoal ultrastructure appear to be characteristic of Cichlidae and, therefore, may be of phylogenetic significance.

wood, et al. "Rh Proteins and NH4+ –activated Na+-ATPase in the Magadi Tilapia (Alcolapia grahami), a 100% Ureotelic Teleost Fish." Journal of Experimental Biology. 2013;216:2998-3007 . Abstract

The small cichlid fish Alcolapia grahami lives in Lake Magadi, Kenya, one of the most extreme aquatic environments on Earth (pH ~10, carbonate alkalinity ~300 mequiv l−1). The Magadi tilapia is the only 100% ureotelic teleost; it normally excretes no ammonia. This is interpreted as an evolutionary adaptation to overcome the near impossibility of sustaining an NH3 diffusion gradient across the gills against the high external pH. In standard ammoniotelic teleosts, branchial ammonia excretion is facilitated by Rh glycoproteins, and cortisol plays a role in upregulating these carriers, together with other components of a transport metabolon, so as to actively excrete ammonia during high environmental ammonia (HEA) exposure. In Magadi tilapia, we show that at least three Rh proteins (Rhag, Rhbg and Rhcg2) are expressed at the mRNA level in various tissues, and are recognized in the gills by specific antibodies. During HEA exposure, plasma ammonia levels and urea excretion rates increase markedly, and mRNA expression for the branchial urea transporter mtUT is elevated. Plasma cortisol increases and branchial mRNAs for Rhbg, Rhcg2 and Na+,K+-ATPase are all upregulated. Enzymatic activity of the latter is activated preferentially by NH4+ (versus K+), suggesting it can function as an NH4+-transporter. Model calculations suggest that active ammonia excretion against the gradient may become possible through a combination of Rh protein and NH4+-activated Na+-ATPase function.

Johannsson, et al. "Characteristics of Air Breathing in Lake Magadi Tilapia: is there a relationship with Diel Patterns in Reactive Oxygen Species (ROS) in the Lake?". In: The Canadian Society of Zoologists meeting. Mount Allison University, Sackville, NB Canada.; 2012.
Wilson, et al. "Immunohistochemical approach to understanding branchial ion regulation in the tilapia of Lake Magadi (pH10).". In: The society for experimental biology. Salzburg, Austria; 2012.
Papah, et al. "Spermiogenesis and sperm ultrastructure in Lake Magadi tilapia Alcolapia grahami (Teleostei, Perciformes, Cichlidae).". In: Joint Faculty of Veterinary Medicine 8th Biennial Scientific Conference and 46th Kenya Veterinary Association annual Scientific conference. Safari Park Hotel Nairobi.; 2012.
Papah, et al. "The structure of the male reproductive organs in lake magadi tilapia (Alcolapia grahami); a fish living on the edge.". In: TWAS-BiovisionAlexandria NXT Conference. Alexandria Egypt; 2012.
wood, et al. "The Magadi Tilapia- Coping with Extremity. .". In: Tropical fish symposium of the fish biology congress (American fisheries society). Madison Winconsin USA; 2012.
wood, et al. "Responses to Ammonia Loading in the Magadi Tilapia, a Completely Ureotelic Teleost Fish.". In: Canadian Society of Zoologists meeting. Mount Allison University, Sackville, NB Canada; 2012.
wood, et al. "Transepithelial potential in the Magadi tilapia, a fish living in extreme alkalinity." Journal of Comparative Physiology B. . 2012;182 (2):247-258. AbstractSpringer Link

We investigated the transepithelial potential (TEP) and its responses to changes in the external medium in Alcolapia grahami, a small cichlid fish living in Lake Magadi, Kenya. Magadi water is extremely alkaline (pH = 9.92) and otherwise unusual: titratable alkalinity (290 mequiv L−1, i.e. HCO3 − and CO3 2−) rather than Cl− (112 mmol L−1) represents the major anion matching Na+ = 356 mmol L−1, with very low concentrations of Ca2+ and Mg2+ (<1 mmol L−1). Immediately after fish capture, TEP was +4 mV (inside positive), but stabilized at +7 mV at 10–30 h post-capture when experiments were performed in Magadi water. Transfer to 250% Magadi water increased the TEP to +9.5 mV, and transfer to fresh water and deionized water decreased the TEP to −13 and −28 mV, respectively, effects which were not due to changes in pH or osmolality. The very negative TEP in deionized water was attenuated in a linear fashion by log elevations in [Ca2+]. Extreme cold (1 vs. 28°C) reduced the positive TEP in Magadi water by 60%, suggesting blockade of an electrogenic component, but did not alter the negative TEP in dilute solution. When fish were transferred to 350 mmol L−1 solutions of NaHCO3, NaCl, NaNO3, or choline Cl, only the 350 mmol L−1 NaHCO3 solution sustained the TEP unchanged at +7 mV; in all others, the TEP fell. Furthermore, after transfer to 50, 10, and 2% dilutions of 350 mmol L−1 NaHCO3, the TEPs remained identical to those in comparable dilutions of Magadi water, whereas this did not occur with comparable dilutions of 350 mmol L−1 NaCl—i.e. the fish behaves electrically as if living in an NaHCO3 solution equimolar to Magadi water. We conclude that the TEP is largely a Na+ diffusion potential attenuated by some permeability to anions. In Magadi water, the net electrochemical forces driving Na+ inwards (+9.9 mV) and Cl− outwards (+3.4 mV) are small relative to the strong gradient driving HCO3 − inwards (−82.7 mV). Estimated permeability ratios are P Cl/P Na = 0.51–0.68 and PHCO3/PNa = 0.10–0.33. The low permeability to HCO3 − is unusual, and reflects a unique adaptation to life in extreme alkalinity. Cl− is distributed close to Nernst equilibrium in Magadi water, so there is no need for lower P Cl. The higher P Na likely facilitates Na+ efflux through the paracellular pathway. The positive electrogenic component is probably due to active HCO3 − excretion.

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