Abstract
African lungfish, Protopterus annectens (P. annectens; mean weight, 338.8g and mean length, 39.5cm) procured from Imo River at Umuna in Imo State, Nigeria, were, after acclimation in dechlorinated water, transferred into each of the following concentrations of seawater:-0%0, 1.9%0, 3.7%0, 5.6%0 , 7.4%0 , 9.3%0 , and 11.1%0 , and placed there for four weeks after which the levels of their blood nitrogenous wastes (urea, uric acid and creatinine) were determined . There was a significant positive linear correlation between salinity and mean blood urea, uric acid and creatinine concentrations respectively. The study strongly suggests some metabolic adjustments that occur whilst maintaining or culturing P. annectens in brackish or estuarine water regimes.
Highlights
The African lungfish, P.annectens lives in shallow and swampy parts of some Rivers and Lakes of some West African countries such as Cameroun, Nigeria, Togo Republic, Ghana, Senegal etc (Laberge and Walsh, 2011; Loong et al, 2012 a,b; Lopez et al, 2012; Nakamuta et al, 2012) Recent studies have shown that it can tolerate seawater up to a maximum of 10.5%o (Okafor, 2004, 2008) the fish has got the potential of being cultured in brackish water
In order to fill the lacunae in knowledge, the study aims to determine precisely the changes in serum nitrogenous wastes when P. annectens is transferred from freshwater into different concentrations of dilute seawater and
Ammonia production rate decreased as standard length of fish increased. (Table 2)
Summary
The African lungfish, P.annectens lives in shallow and swampy parts of some Rivers and Lakes of some West African countries such as Cameroun, Nigeria, Togo Republic, Ghana, Senegal etc (Laberge and Walsh, 2011; Loong et al, 2012 a,b; Lopez et al, 2012; Nakamuta et al, 2012) Recent studies have shown that it can tolerate seawater up to a maximum of 10.5%o (Okafor, 2004, 2008) the fish has got the potential of being cultured in brackish water. There is very little or no existing information on the nitrogenous excretion of lungfish in brackish or estuarine waters. In order to fill the lacunae in knowledge, the study aims to determine precisely the changes in serum nitrogenous wastes when P. annectens is transferred from freshwater into different concentrations of dilute seawater and. All fishes were fed and all tanks were neither covered nor aerated with air pumps throughout the four week period of immersion in dilute seawater. 2.5 Determination of Rate of Ammonia Production and the Concentration of Serum Nitrogenous Wastes. After 28 days of immersion in various concentrations of dilute seawater (1.9-11.1%0 ) ammonia production rate over a 12 hr period of every P. annectens specimen was investigated, following the method of Okafor (2008). The serum urea, uric acid and creatinine concentrations of each sample were determined by the use of Diacetylmonoxine, Folin/Trimble and Jaffer’s standard methods respectively. (Dyer, 1965., Wharton and McCarty, 1972; Brewer et al, 1974; Cheesbrough,2007)
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