Heavy Metal Distribution in Tissues and Eggs of Chinese Alligator (Alligator sinensis)

Abstract

Chinese alligator (Alligator sinensis) is a critically endangered species endemic to China. Concentrations of heavy metals (As, Fe, Mn, Cu, Pb, Cd, Cr, Zn, and Hg) were examined in the tissues of Chinese alligators to elucidate the background distribution of these metals in the alligator body. Generally, within the body compartments, metal concentrations were high in liver, kidney, and heart, and low in pancreas and gonad. Study of heavy metal levels in the feces and eggs of Chinese alligator suggested that Chinese alligators could reduce body burden of toxic substances by excreting them to feces and/or sequestrating them into eggs to a lesser extent. In addition, to test whether eggshell or egg membrane could be used as surrogates to measure heavy metal load in egg contents, the correlation of metal concentrations between three egg compartments was determined. Of the nine elements analyzed, concentrations of iron, copper, and zinc in the shell membrane were highly correlated with the levels in egg contents, whereas no metal was significantly correlated between eggshell and egg contents. This suggested that the shell membrane could be a useful bioindicator for Fe, Cu, and Zn contaminations in the eggs of Chinese alligator. In a comparison of metal contents in the eggs of individuals from the Anhui captive population, the wild population in Anhui Province, and those of the Changxing captive population, higher Cu, Zn, and Cd levels and a lower Pb level were found in the Changxing individuals, indicative of specific pollutants in different areas. In addition, the majority of metal elements in the muscles of Chinese alligators and American alligators are in the same ranges. As a result of the data found in the eggs of the two alligator species, the Chinese alligators may be exposed to a higher level of metal pollutants. The study provided measurement of the heavy metal distribution in the endangered Chinese alligator for the first time and could serve as the background for the monitoring of possible heavy metal contaminations in the alligator habitats.

Blood lead concentrations in free-ranging Nile crocodiles (Crocodylus niloticus) from South Africa

“…The function of crocodile gastroliths (stomach stones) is not fully known but they likely help serve as ballast and/or grind down food items (Wallace and Leslie 2008). The small crocodilian pylorus prevents gastroliths from passing into the duodenum and being excreted as waste (Chiasson 1962), but small metal fragments that are ingested but not absorbed may be eliminated through the feces (Xu et al 2006). The rate of retention and erosion of Pb solids in the crocodilian gastrointestinal tract is not well understood.…”

Non-lethal sampling for mercury evaluation in crocodilians

“…The specific characteristics of the group allow an accurate diagnosis of the conditions imposed by these pollutants in the study areas. Several different xenobiotics -primarily metals and organochlorine pesticides -have been detected in Alligatoridae at countless locations worldwide (Ding et al, 2001;Rumbold et al, 2002;Campbell, 2003;Roe et al, 2004;Almli et al, 2005;Jeffree et al, 2005;Presley et al, 2006;Wu et al, 2006;Xu et al, 2006;Yoshikane et al, 2006). This study has two main objectives: (1) to evaluate concentrations of THg in C. yacare at flood-prone areas of the northern Pantanal, and relate the variation in Hg of the specimens to areas with and without a history of gold mining and to hydrological cycles (flood and drought) and (2) to assess the relationships between Hg concentrations in caudal scute and claw to test which of these non-lethal sampled tissues is the best predictor of Hg concentration in crocodilians.…”

Addressing current knowledge gaps on radionuclide transfer to reptiles

“…In oviparous species, egg laying is a recognised route through which contaminants may be excreted by females [23][24][25]. Therefore, some studies have considered the extent to which egg contaminant burdens may be used to predict tissue and whole-body contaminant burdens in the female which laid the egg (e.g.…”