title: The Nile monitor (Varanus niloticus; Squamata: Varanidae) as a sentinel species for lead and cadmium contamination in sub-Saharan wetlands.
abstract: Wetland pollution is a matter of concern in sub-Saharan Africa. Though regularly exploited, the Nile monitor (Varanus niloticus), a large amphibious lizard, is not threatened. This work aims at assessing the value of this varanid as a sentinel species in surveys of environmental contamination by metals. Lead and cadmium quantifications were performed by graphite furnace-atomic absorption spectrophotometry in bone, intestine, kidney, liver and muscle in 71 monitors from three unevenly polluted sites in Mali and Niger, plus a reference site. The effects of sex, size and fat reserves as well as factors related to the sampling strategy (tissue sampled, sampling site) were studied with a mixed linear model. Metal contamination is moderate at the four sites but clear differences nevertheless occur. Lead levels are generally maximal in bone, with a gender-independent median value 320ng.g(-1). Median cadmium concentrations never exceed 70.2ng.g(-1) in females (kidney) and 57.5ng.g(-1) in males (intestine). Such levels should have no detrimental effects on the monitors. Lead and cadmium levels in muscles are generally below 200 and 20ng.g(-1), respectively, and should provoke no health hazard to occasional consumers of monitor meat. Metal organotropisms are consistent with those observed in other studies about Squamates: for lead: bone>[kidney, intestine, liver]>muscle in males and [bone, kidney]>[intestine, liver]>muscle in females; for cadmium: [liver, intestine, kidney]>[bone, muscle] for both genders. Females are more contaminated, especially in their kidneys. In this tissue, median values in ng.g(-1) are 129.7 and 344.0 for lead and 43.0 and 70.2 for cadmium, for males and females, respectively. Nile monitors can reveal subtle differences in local pollution by metals; moreover, the spatial resolution of the pollution indication that they give seems to be very sharp. The practical relevance of this new tool is thus validated.
authors: Université de Lyon, F-69000, Lyon, France.
authors: Alexandre
authors: A
authors: Ciliberti
authors: Philippe
authors: P
authors: Berny
authors: Marie-Laure
authors: ML
authors: Delignette-Muller
authors: Vivian
authors: V
authors: de Buffrénil
mesh_terms: D017954:Africa South of the Sahara; D000818:Animals; D001842:Bone and Bones / Q000737:chemistry; D002104:Cadmium / Q000032:analysis*; D004784:Environmental Monitoring / Q000379:methods / Q000706:statistics & numerical data*; D004787:Environmental Pollution / Q000032:analysis*; D005260:Female; D007854:Lead / Q000032:analysis*; D008116:Lizards / Q000378:metabolism*; D008297:Male; D018482:Muscle, Skeletal / Q000737:chemistry; D018571:Sentinel Surveillance / Q000662:veterinary*; D012737:Sex Factors; D013054:Spectrophotometry, Atomic; D014781:Viscera / Q000737:chemistry; D053833:Wetlands
chemical_list: D002104:Cadmium; D007854:Lead