Edible Amphibian Species: Local Knowledge of their Consumption in Southwest Nigeria and their Nutritional Value A. B. Onadeko*, R. I. Egonmwan and J. K. Saliu Department of Zoology, University of Lagos, Akoka, Lagos, Nigeria *Corresponding author; E-mail: [email protected] Abstract The knowledge of the consumption of edible amphibian species in southwest Nigeria was investigated based on interviews. There were a total of 900 respondents of which 92.8% were aware of edible frogs being consumed by humans. Six hundred and sixty (73.3%) respondents had seen various individuals eating frogs. Examining the respondents themselves, 387 (43.0%) has eaten frogs. The occupation with the highest consumption of amphibian species was the farmers (64.1%) followed by the secondary school teachers (57.0%) and the least being the housewives (27.3%). Ptychadena pumilio has the highest protein content (19.79%) followed by Xenopus muelleri (19.53%). Hoplobatrachus occipitalis has a protein content of 19.46% and fats and oils of 1.06%. Xenopus muelleri has the highest fat and oil percentage while Ptychadena pumilio has the lowest (0.97%). Glutamic acid followed by aspartic acid was the highest concentration of amino acid in all the species. The Analysis of Variance (ANOVA) showed that there was no significant difference in the concentration of the amino acid among the three species of edible anurans at (P > 0.05). Frog meat serves as a good source of protein for the local inhabitants. But the unsustainable use of these edible frog species would have a detrimental effect on the ecosystem. Hence frog farming and conservation efforts must be encouraged. Introduction Recently, there has been an increasing trend Amphibians are one of the most threatened in the exportation of frogs from developing to groups of vertebrates, with at least one third the developed countries. Frog legs are a of over 6,000 known species being popular delicacy in Europe and eaten in threatened with extinction (Stuart et al., countries where it is against the law to hunt 2004, 2008). Many reasons are attributed to them (Ashton et al., 1988). A recent report by the decline of amphibian species such as Niasse et al. (2004) states that utilization is global warming, habitat destruction and the main threat for 281 amphibians species, modification, pollution, disease, etc. But 54% of these already listed as vulnerable, overexploitation, being one of the major endangered or critically endangered when causes (Gibbons et al., 2000; Halliday, IUCN Red List categories are applied. The 2008), is rarely mentioned while other frogs are also collected for leather production causes have gained much research interest. and souvenirs, for pet trade and cultural Stuart et al. (2004), however, have reasons, including traditional medicine (Oza, mentioned that overexploitation is one of the 1990; Veith et al., 2000; Young et al., 2004; reasons for the world wide amphibian Kusrini & Alford, 2006; Gonwouo & Rodel, decline. 2008). Many species of anuran (Class Amphibia) In many countries including Nigeria, frogs are eaten in many parts of the world. have been collected on a local scale as an 68 West African Journal of Applied Ecology, vol. 19, 2011 Onadeko et al.: Edible Amphibian Species: Local Knowledge of their Consumption 69 essential source of animal protein (Angulo, Jabore; in Oyo State were Eruwa, Ado- Ash content. The ash content was flask was cooled and anti-bumping granules 2008; Mohneke et al, 2009). But within the Awaye, Iseyin, Ogbomosho, Onidundun and determined by weighing about 5 g of (4 seeds) were added to the flask and past decade, frog has become an Oyo Town. Three hundred individuals (50 specimen sample into a dry, clean and connected to a distillation apparatus. 85 ml of international trading item, involving more from each town) were interviewed from each weighed porcelain dish. The dish and 50% NaOH was added to the mixture and the than 30 countries, and in 1998 was valued at state totaling 900. The respondents were of content were placed over a bunsen burner liberated ammonia gas was bubbled into a approximately USD 48.7 million (Teixeira various occupations comprising different flame in a fume cupboard and burned until 2% solution of boric acid. At the expiration et al., 2001). Such exploitation without ethnic groups. no more soot was given off. The dish and the of the bubbling process the resulting mixture sustainability of these amphibian species The questionnaires were written in content were then transferred into a muffle was back titrated with a standard sulphuric 0 would have direct and indirect impacts on English. To avoid communication problems, furnace and heated at 500–550 C until it was acid (H2SO4) solution (0.05 M). The protein the frog species and the ecosystem, all interviews were carried out with the help fully ashed after about 1 h. The ash content content was calculated using the expression: respectively. For it is a well known fact that of field assistants speaking the local corresponds to the weight difference amphibians are important components in languages. In general the questionnaires between the crucible containing the ash and % Protein = V × 0.0014 × F × 100 various terrestrial and aquatic ecosystems comprised questions eliciting information on the empty crucible, expressed as a W (Toledo et al., 2007; Mohneke & Rodel, the knowledge/experience the interviewees percentage of the mass of sample used. where V = volume of H2SO4 required to 2009). had concerning the different types of Fat and oil. Fat and oil was determined by reach dull state colour end point, W = mass of The present study attempts to investigate amphibian species, their habitat, colour and gravimetric extraction method. About 10 g sample used, and F = Protein factor; 6.25 the awareness of the populace in relation to especially their consumption. of sample was mashed and acidified at a pH Amino acid analysis. The amino acid their knowledge of edible amphibian of 2 with a 1:1 HCl solution, and was profile in the known sample was determined species in southwest Nigeria. The study also Proximate composition of edible anurans properly mixed in a beaker. The resulting using methods described by Spackman et al. investigates the nutritional content of three The parameters analyzed were the mixture was transferred into a separating (1958). The known sample was dried to edible species investigated previously proteins, ash content, moisture, fats and oil funnel. The mixture was shaken vigorously constant weight, defatted, hydrolyzed, (Mohneke et al., 2010), which serves as percentages. The protein content was further and extracted with 20 cm3 of chloroform. evaporated in a rotary evaporator and loaded source of protein in the diet of many who analyzed to determine its amino acid profile. The extraction with chloroform was into the Technicon sequential multi-sample consume it. Based on the interviews The detailed methods of food estimate repeated twice and all the extract collected in amino acid analyzer (TSM) for analysis. conducted in southwest Nigeria (Lagos, analysis employed are as described by a beaker containing about 2 g anhydrous Ogun and Oyo States), this study aims to get Krishna & Ranjhan (1980). sodium sulphate. After swirling the content Results an overview of the awareness of and the Moisture content. The moisture content it was filtered into a clean, dry and weighed Knowledge of anurans nutritional values of these edible amphibian was determined based on loss of water on beaker followed by evaporation over a water Out of the 900 respondents, only 1 had not species. drying of the specimen in the oven at bath. Increase in weight of the beaker seen a frog or toad before, constituting 0.1%. temperature of 105 oC. About 5 g of the expressed as percentage represents the fat Materials and methods 899 of the respondents had seen an anuran. Interview survey specimen sample was accurately weighed in and oil content. Majority (38.2%) had seen only two types of The study was conducted in southwest a dry and clean porcelain dish (crucible). The Protein. The protein content was anurans while 11.0% had seen five or more Nigeria in the states of Lagos, Ogun and porcelain dish and the content were determined by the Kjeldahl digestion types of anurans. 44.7% of the respondents o Oyo. Questionnaires were administered and transferred into an air-tight oven at 105 C method. About 5 g of sample was weighed observed anuran species mainly around interviews were conducted in six selected and were allowed to dry for about 3 h. It was into a Kjeldahl flask and 25 ml of ponds, streams and rivers. This was followed towns in each state. The places visited in transferred into a desiccator and allowed to concentrated sulphuric acid (H2SO4) was by the swamp habitat in which 28.6% of Lagos State were Epe, Abule Ogba, Festac cool and re-weighed. The difference between added to the flask. Two tablets of copper respondents observed anuran species. The Town, Badore/Ajah, Ijede and Badagry; in the initial and final weight, expressed in catalyst were added and the flask in an least habitat in which anuran species were Ogun State were Abeokuta, Ijebu-Oru, percentage, corresponds to the moisture inclined form was heated gently and later seen was in the town as observed by 7.3% of Pakoto/Ifo, Sagamu, Ishara and Odo- content. strongly until the liquid became clear. The the respondents. 68 West African Journal of Applied Ecology, vol. 19, 2011 Onadeko et al.: Edible Amphibian Species: Local Knowledge of their Consumption 69 essential source of animal protein (Angulo, Jabore; in Oyo State were Eruwa, Ado- Ash content. The ash content was flask was cooled and anti-bumping granules 2008; Mohneke et al, 2009). But within the Awaye, Iseyin, Ogbomosho, Onidundun and determined by weighing about 5 g of (4 seeds) were added to the flask and past decade, frog has become an Oyo Town.