Toxicity induced by dieldrin and chlorpyrifos in the freshwater crayfish Cambarellus montezumae (Cambaridae).

The toxicity induced by insecticides in aquatic organisms is of utmost relevance because it may give a clue about the degree of health or damage of the involved ecosystem. In the present report, we determined the effect of dieldrin (DD) and chlorpyrifos (CP) on the freshwater crayfish, Cambarellus montezumae. The organisms (4-6 cm in diameter) were collected in the Ignacio Ramirez Reservoir, situated at 50 km Northeast of Mexico City, in the Rio Lerma Basin.

Effects of heavy metals on the oyster (Crassostrea virginica) at Mandinga Lagoon, Veracruz, Mexico.

The Mandinga Lagoon in the Mexican State of Veracruz is an important ecological zone that produces 32% of the oyster output in the state of Veracruz, the main oyster producer in Mexico. Samples of water, sediment, and oysters were collected in 2003 and 2004 to study heavy metal pollution. Metal concentrations were determined in water, soil, and oyster tissues from fresh and detoxified Crassostrea virginica, and histology samples were analyzed.

[Effect of zinc-enriched sediments, in open and isolated systems, on three species of benthonic invertebrates].

Availability of toxics in aquatic bodies is limited by the physicochemical characteristics of sediments and water, as well as by the interactions between the different xenobiotics and inhabits species. The aim of this work was to relate the effect produced by zinc (Zn) spiked in sediments of the Ignacio Ramirez dam (PIR), in isolated and microcosms models, on ATP concentration of three benthic organisms with the metal biodisponibility. The selected species were a crustacean, an annelid and a mollusk: Hyalella azteca (Amphipoda: Hyalellidae), Limnodrilus hoffmeisteri (Oligochaeta: Tubificidae) and Stagnicola attenuata (Basommatophora: Lymnaeidae), species that are found at high proportions in the reservoir and use different spaces in the benthos.

Toxic effects of waterborne polychlorinated biphenyls and sex differences in an endangered goodeid fish (Girardinichthys viviparus).

Polychlorinated biphenyls (PCBs) elicit toxic effects in different species. PCBs undergo biotransformation by enzymes associated with the mixed functional oxidase system, such as cytochrome P450 (cyt P450), this biotransformation being sex-dependent. No other metabolic pathways are known, however, in connection with this process.

Vitellogenin induction in the endangered goodeid fish Girardinichthys viviparus: vitellogenin characterization and estrogenic effects of polychlorinated biphenyls.

Vitellogenin (VTG) is a widely used biomarker in studies of endocrine disruption induced by xenobiotics such as polychlorinated biphenyls (PCBs). This study evaluates the estrogenic effects of these compounds on the black-fin goodeid Girardinichthys viviparus, an endangered fish species in Mexico with a reduced range of distribution due to pollution of its natural environment. Adult fish born in the laboratory were exposed to half the LC(0) of Inerteen commercial PCB mixture.