Ana J. Marmolejo-Rodríguez

Lead in shrimp Litopenaeus vannamei Boone in sublethal concentrations.

Determination of the accumulation and elimination of sublethal lead (Pb) in different shrimp tissues may be useful as an indicator of uptake and elimination characteristics of this metal. Aquaculture ponds are particularly influenced by Pb contamination, where aquatic animals may acquire the metal through adsorption to exoskeletons or gills from the surrounding water. Cationic Pb is accumulated preferentially in the nonedible fraction of shrimp, followed by exoskeleton, and to a minor extent in muscle. Lead contents in different tissues were lower than metal levels in exoskeleton. However, the presence of Pb in sediment due to purging may exert adverse consequences on shrimp as bottom feeders.

Mercury concentrations in three ray species from the Pacific coast of Baja California Sur, Mexico: Variations by tissue type, sex and length

Total mercury concentrations ([THg]) were determined in muscle and liver of the bat ray (Myliobatis californica), shovelnose guitarfish (Pseudobatos productus) and banded guitarfish (Zapteryx exasperata). Generalized linear models (GLM) were used to determine the effects of size and sex in [THg] and showed that both are determinants of [THg] in these species. The [THg] in both tissues significantly increased with length especially in sexually mature organisms with a steeper slope for mature male than mature female. This may relate to elasmobranchs sexual dimorphism driven variation in growth rates. Median muscle [THg] was significantly greater than liver in each ray species but there were some individuals with higher liver [THg] than muscle. There were individuals with muscle [THg] higher than the advisory thresholds of 0.2 and 0.5mgkg-1ww (2.4 and 11% of the bat ray; 2.1 and 10% of the shovelnose guitarfish; 12.6 and 45% of the banded guitarfish, respectively).