T7 AM Metals in the Environment: Dietary Concerns in Aquatic Systems
Tuesday, 15 November 2005: 8:00 AM - 11:40 AM in 327-329

(ZHA-1117-421171) Digestive physiology and metal subcellular partitioning in affecting the metal assimilation in a marine fish.

ZHANG, L¹, WANG, WX¹, ¹ Department of Biology, Hong Kong University of Science and Technology, Hong Kong, China

ABSTRACT- Metal dietary assimilation is important in their trophic transfer and bioaccumulation in aquatic animals. Assimilation efficiency (AE) is a key parameter in kinetically modeling the transfer of metals along diverse food chains. This study investigated the internal metal speciation in the prey and the digestive physiology in affecting the metal dietary assimilation in a marine fish, the grunt Terapon jarbua. The AEs in the grunt varied among the different preys including the brine shrimps, copepods, barnacles, clams, mussels, and fish viscera, and were 3.4% - 12.3% for Cd, 12.7% - 39.0% for Se, and 1.5% - 52.3% for Zn. The AEs of Se and Zn were significantly correlated with the subcellular Se and Zn distributions in the preys, suggesting that Se and Zn internal speciation in the diet affected their dietary assimilation. Further experiments determined the AEs using pure subcellular fractions of the brine shrimps, mussels, and barnacles as the diet for fish. The AEs were higher in the grunts fed with the heat stable protein fraction than those with the heat sensitive protein fractions or insoluble fractions, consistent with the desorption of these three subcellular fractions in the water. The AEs were comparable in the fish fed with heat stable protein fraction purified from different animals, further indicating the importance of the internal metal speciation in metal assimilation. We found that the AEs of Se and Zn but not Cd were significantly dependent on the ingestion rate of fish and the gut passage time of metals, suggesting that the fish had different digestive strategies to handle the essential and non-essential elements. Overall, the assimilation of metals by the marine fish is determined both by the internal metal speciation in the preys and the digestive physiology of the fish.

Key words: Assimilation, Subcellular partitioning, Ingestion rate, Gut passage time