Effects of <i>Balanites aegyptiaca</i> on tadpoles and <i>Oreochromis niloticus</i>

Abstract

Objective: Fingerlings of Oreochromis niloticus and tadpoles were exposed to the acute concentrations of aqueous extract of the bark of Balanites aegyptiaca (date palm desert) to determine the 96h-LC50 (lethal concentration 50, concentration that will kill half of the test animals exposed). Methodology and results: The O. niloticus (Nile tilapia) was further subjected to sub-lethal concentrations of the plant extract to determine the effect on growth and haematological indices. The time for toxicity disappearance (TTD) was also estimated. The experiments were conducted using the static renewal bioassay technique at UNAAB Fish Laboratory. The 96h-LC50 for O. niloticus was estimated to be 26.22 mg l-1 while that of Tadpole (Rana species) was13.77 mg l-1. The TTD of B. aegyptiaca was estimated to be 48 hours. During sub-lethal exposure, there was a slight decrease in the mean body weight and all the haematological parameters as the concentration of the toxicant increased except MCV, MCH, MHC that were more or less equal. However, statistical analysis on these values of haematological indices did not show any significant difference at 5%. The use of Balanites aegyptiaca is recommended in control of predators e.g. tadpoles in pond fish culture system because the product is non-toxic to fish at lower concentration, biodegradable and very cheap. The uncontrolled use in open water body for fishing should be prohibited, as the resultant deleterious effects will subsequently lead to death of not only target fish but also other aquatic organism. Hence, contribute to reduction in the biodiversity. Conclusion and application of results: The results of this study show the toxic effect of B. aegyptiaca on O. niloticus and Tadpoles. The lethal doses (96h-LC50) obtained are 26.22 mg l-1 and 13.80 mg l-1 respectively. Therefore, B. aegyptiaca powder can be use in selective eradication of aquatic organism to control unwanted predatory species i.e. tadpoles. B. aegyptiaca bark powder can be recommended because it is biodegradable and leave no adverse effect on environment.

Acute toxicity evaluation of water extract stem barks of Balanites aegyptiaca on adults of three different fish species

“…All fishes subjected for higher concentration levels appeared in a more distressed condition at first, jumping over the surface and gasping air then they became inactive followed by loss of balance and finally sank to the bottom. The behavioral responses against acute concentration of B. aegyptiaca observed in the current studies are in tandem with earlier findings of Ufodike and Omoregie (1994), Absalom et al (2013), Abalaka et al (2014) and Alhou et al (2016). However, at lower concentrations (that is 15.0 and 17.5 mgL -1 ), such physical distress was recorded only for B. nurse within a short time of exposure and the other test fishes showed such behavioral actions after long exposure.…”

“…In addition to respiratory distress, the test fishes exhibited increasing states of motionlessness, adoption of different postures, sudden darts, slow sluggish movements and ataxia. These might be due to the acetyl cholinesterase inhibition property of the piscicide plant as similar hyperactivity, uncoordinated movements and acetyl cholinesterase inhibition was reported in Oreochromis niloticus exposed to B. aegyptiaca stem bark extract (Alhou et al, 2016).…”

“…For example, in the present study, the LC 50 was relatively smaller in L. bynni (18.99 mgL -1 ), showed that the extract was toxic to this fish as higher LC 50 values signify less toxicity (Eisler and Gardener, 1993). O. niloticus exposed for an aqueous extract of B. aegyptiaca showed signs of toxicosis and the LC 50 of the extract for this fish was 26.22 mgL -1 (Alhou et al, 2016). In another experiment done on juvenile Clarias gariepinus exposed for aqueous B. aegyptiaca fruit extract confirmed the 96 h LC 50 value of 12.59 gL -1 (Absalom et al, 2013).…”

“…This is in agreement with the study of Neuwinger (2004) and Abalaka et al (2014) in which B. aegyptiaca was in the first listing order among the piscicide plants widely used in Africa. Therefore, the efficacy of this commonly used plant piscicide was evaluated and found to be more toxic than other plant piscicides evaluated on different fish species (Neuwinger, 2004;Absalom et al, 2013;Alhou et al, 2016). In an experiment done for comparing the lethal toxicity effect of B. aegyptiaca and Kigelia africana on O. niloticus, the former was found more toxic and opercular ventilation and tail fin beat increased with concentration and then declined as the fish became fatigued (Ufodike and Omoregie, 1994).…”

“…Studies have been conducted about responses of different fish to some piscicide plant (Ameha, 2004;Singh and Yadav, 2010;Agbor and Okoi, 2014;Ekpendu et al, 2014), but the piscicidal effect of B. aegyptiaca is limited (Absalom et al, 2013;Alhou et al, 2016). The acute toxicity levels of B. aegyptiaca on fish has not been investigated in Ethiopia but extensively used by fishermen of the ALNP.…”