Toxins in Gills and Flesh of Synodontissorex and Bagrusfilamentosus

The concentrations of Cadmiun (Cd), Chromium (Cr), Lead (Pb), Manganese (Mn) and Alumin ium (Al) in water, sediments, gills and flesh of both SynodntisSorex and Bagrusfilamentosus from River Jega in Kebbi State, Nigeria,were determined by atomic absorption spectrophotometer. The pattern of d istribution of the heavy metals showed a preponderance of Cr and Mnover other metals in the organs of the two fish species as well as in the water and sediment samples. The highest concentration of Mn was in the sediment and lowest in water. The unexpectedly high concentration value obtained for Cr and Mncalls for medical alertness since it exceeded the WHO recommended acceptable limits for consumption. Al was not detected in the organs of fish species, water and sediment. Cd and Pb distribution in all the samples was lower than the WHO and USEPA recommended acceptable limits for consumption.


Introduction
Heavy metals pose a great concern to the Scientists as they cause environmental contamination by exh ibit ing behaviours consistent with those persistent toxic chemicals. The heavy metals cannot be degraded further, and their toxic effects can be long lasting, unlike the organic contaminants that decompose into other chemicals with t ime [1]. Heavy metals are known to have to xic effects even at low concentration, and their concentration in biota can be increased through bio-accumu lations [2].
Many water bodies in Nigeria as revealed by studies are found to contain various levels of heavy metals pollutants [3,4,5,6,7]. Weathering process or mass activities such as agricu ltural and industrial waste d isposal are the ro ute th ro u g h wh ich th es e meta ls g et in to th e aq u at ic environment [8,9]. Fish is often the last lin k in aquatic food chain therefore it is the need of time to determine its to xic metal concentration [10]. Accord ing toAbou-Arab [11] fish accumulate these heavy metals fro m the surrounding water and sediment. Many disease conditions in man are lin ked to the consumption of fishes contaminated with to xic metals [1]. Cad miu m (Cd) and Lead (Pb)in any concentration can cause kidney damage, their symptoms of chronic to xicity include impaired kidney in fect ion , poo r reproduct iv e cap acity, hypertens ion et c. Ch ro miu m as Cr (v i) pen et rat es cell memb ranes and can cause genotoxic effect and cancer [12,13]. The main aim of this study were to determine the levels of Cad miu m (Cd), Cro miu m (Cr), Lead (Pb),Magnesium (Mn) and Alu miniu m (Al)in d ifferent organs of fish species, water and sediment as well as their potential health effects on human.

Synodontissorex
Scientific Name: Synodontissorex; Ety mology:Synodontis: Fro m the Greek "syn"meaning together, and "odontos", mean ing tooth; in reference to the closely-spaced lower jaw teeth; Habitat: Africa: Chad, Niger, Nile, Vo lta basins and Bénoué River Identificat ion: All species in the genus Synodontishave a hardened head cap that has attached a process (humeral process) which is situated behind the gill opening and pointed towards the posterior. The dorsal fin and pectoral fins have a hardened first ray which is serrated. There is one pair of maxillary barbels, so metimes having membranes and occasionally branched. The two pairs of mandibular barbels are often branched and can have nodes attached. The cone-shaped teeth in the upper jaw are short. S-shaped and movable in the lower jaw. These fish produce audible sounds when disturbed rubbing the base of the pectoral spine against the pectoral girdle [14].

Bagrusfilamentosus
Scientific name:Bagrusfilamentosus Ety mology:The generic name comes fro m the Mozarabicbagre, taken fro m the Greek pagros, meaning a fish (Dentex sp.). Bagrus: Fro m 'bagre', a South American name for a catfish, but is only used for African and Asian species. Habitat; Africa: Niger River system.
Identificat ion: A nocturnal feeder on cichlids on rocky shores, and occurs from the lower reaches of rivers to the deepest habitable parts of the lake. It also feeds on molluscs, crabs and zooplankton. Identification: Head about twice as long as broad, with smooth texture. Dorsal fins widely separated, Body Bronze/silver. Fins have a ruby colouration when reaching adulthood [15]

Consumption of Fishesexposed to Heavy Metal
Heavy metals are classified as essential (if they play basic role as co mponents of vital b iochemical or enzy mat ic activities in hu man body e.g Fe, Mn, Mo, Cr, V, Zn ) and as non-essential (if the metals are classified as with no biological, chemical and physiological importance in man. Deficiency or high concentrations of these metals may have detrimental effect on health. Once liberated into environ ment, man-made chemicals and products of heavy metals are taken up into the body via inhalation, ingestion and skin absorption. Heavy metals on exposure may not necessarily produce a state of toxicity in the body as they accumulate in the tissues over time until they reach toxic concentration [16] Exposure to to xic metals is associated with many chronic diseases. As per availab le report, when metallic to xicant finds their way into the body, there are possible mechanisms through which they act. So me of which are: (a) Inhib ition of En zy matic Activ ities: This is so because some metals such as Pb, Hg and Cd have affinity for sulphur and therefore attack sulphur bonds in enzy me, thus immob ilizing them. Other site of attack include the free amino (-NH 2 ) and carbo xyl (-COOH) groups in protein (b) Attacks on Cell Membrane and Receptor: The heavy metals bind to cell membrane and receptor, thereby altering their structures. This affect transport and other inter or intra cellu lar processes in the body. Cd inhibits oxidative phosphorylation in the body (c) Interference with Metabolic Cat ions: Heavy metals interfere with the metabolism of essential cations such as absorption, transportation, decomposition and storage. Cd follows the pathway of Zn and Cu metabolisms. Pb rep laces Ca in bones (d) Action on the Artery:Heavy metals can increase the acidity of the blood. The body draws Ca fro m the bones to help restore blood pH. Further to xic metals set up conditions that lead to inflammat ion in arteries and tissues, causing more Ca to be d rawn to the area as a buffer. The Ca, coats the inflamed area in the blood vessel but creating another by the hardening of the artery walls and its progressive blockage of the arteries. This leads to osteoporosis[16]

Materials and Methods
Sampling of water, fishes and sediments were conducted at the River side. Water and sediment samp les were co llected and preserved using Atuma and Egbroge method [18].
The fish species were collected fro m the fisher men at Jegariverand were put in p lastic bags and refrigerated in the laboratory. Gills and muscular section were removed using a plastic knife and then dried in an oven of about 105±20 0 C for about 24 hours, after wh ich were weighed prior to digestion, the dried gills and flesh of fish species were pounded and milled with a mortar and pestle until a powder was obtained [19]. They were then put in plastic containers and stored in desiccators until digestion. 10cm 3 conc. H 2 SO 4 and 5cm 3 conc. HNO 3 was added. The sample was digested in a fume cupboard until the solution volume was reduced to 2cm 3 . The digestion continued until the solution was colourless. This ensured the removal of all HNO 3 . The sample was allo wed to cool, and 15cm 3 of distilled water was added with gentle swirling. 1M NaOH was added drop wise until a p ink-brown or colourlesssolution was produced. The solution was filtered using a What man filter paper No. 42, followed by dilution to the mark in a 25cm 3 volu metric flask. The water and sediment were digested according to the method prescribed by Sreedevi et al., [20]. Fo llowing the digestion, all samples were analy zed fo r Cd, Pb, Cr, Mn and Al.

Results and Discussion
The distribution of Cd and Pb in the g ills and flesh of Synodontissorex and Bagrus fish species was generally low when compared to WHO and USEPA [12,21] reco mmended levels Tables 1 and 2. Al is not detected in the organs of all the fish species. Which shows that the study area is unpolluted with these meta ls [7]? The concentration of Cr in all the fish species is higher in the gills than in the flesh, wh ile the concentration of Mn in synodyntis is higher in the flesh than the gills. The concentrations of Cr and Mn in all the fish species are higher than the permissible consumption limits [22]. Table 2 shows the concentration of of Cr and Mn in gills higher than in flesh of Bagrusflamentos fish species. The specificity of concentrations of heavy metals is irrespective of the locality of fish capture and uptake route of the metals [23].
The distribution of the concentration of metals in both water and sediment was observedin this order Cr>Mn>Pb >Cd table 3. The result of this study shows that the concentration of metals in the sediment is higher than in water. Heavy metals entering an estuary in the solid form adhere to sediments whereas, the soluble form is precip itated to increase the sediment metal load and decrease the open water colu mn concentration [24]. The concentration of Cr and Mn in sediment is higher thanWHO standard as reported byBhatia [25]. The presence of Cr in soaps and detergents used for washing and bathing in the River could be responsible for Cr h ighest level in sediment [26]. The Cr concentration level above WHO limit is a threat to hu man health as people were actually using the water fro m the River for drinking and do mestic purposes. The high concentration of Mn in both water and sediment could be attributed to its presence in many types of rock [26]. It is above the permissible limits for d rin king water.

Conclusions
This study revealed that Cr and Mn levels in all the test samples were not only high but above the permissible limits asrecommended by WHO. The bioaccu mulat ion of these metals may pose great hazardto health of humans and animals that relay on the fish and water from River Jega. The concentrations of Cd and Pb in all the samp les were however, low and below the standard limits. Al could not be detected in all the samp les.