Uptake and Effects on Detoxication Enzymes of Cypermethrin in Embryos and Tadpoles of Amphibians

Abstract

A number of factors have been suggested for recently observed amphibian decreases, and one potential factor is pesticide exposure. We studied the uptake and effects of environmentally relevant concentrations of the pyrethroid insecticide cypermethrin on two different amphibian species, Bombina variegata and Rana arvalis. The uptake from water of 14C-labeled cypermethrin (0.4 microg/L) by eggs and tadpoles of B. variegata was investigated. After 24 hours of exposure, 153.9 ng cypermethrin/g fresh weight were found in embryos, thus indicating that the jelly mass of the eggs does not act as a sufficient physical barrier to protect embryos from exposure to this compound. Uptake of cypermethrin into tadpoles of both species and in all exposed individuals caused dose-dependent deformities; behavioral abnormalities such as twisting, writhing, and coordinated swimming; and mortality. In tadpoles of B. variegata and R. arvalis, the activity of microsomal and cytosolic glutathione S-transferase (mGST and sGST, respectively) were measured after treatment with cypermethrin. Activities of both GST systems increased significantly with increasing duration and concentration of cypermethrin exposure, with the reaction seeming stronger in B. variegata than in R. arvalis tadpoles. Alpha-cypermethrin--a racemic mixture of two cis isomers of cypermethrin--induced a stronger enzymatic response in the cytosolic fraction of R. arvalis tadpoles than cypermethrin at the same concentration. The observed physical and behavioral abnormities caused by environmentally relevant concentrations of cypermethrin indicate that despite detoxication of the chemical via GST-system contamination of ponds by cypermethrin could result in adverse effects on the development of amphibian embryos and tadpoles.

Bioconcentration and metabolism of pesticides and industrial chemicals in the frog

“…A similar increase of GST activity in the same species was induced by cypermethrin. 23) About a 4-fold increase of GST activity was clearly observed in the liver of adult B. regularis by 28-day exposure to endosulfan, and such an effect was also caused in the brain by exposure to diazinon, which may originate from the detoxification processes of these pesticides. 89) Azinphos-methyl and carbaryl increased the GST activity in tadpole R. arenarum by 30 to 40%, but GSH reductase and peroxidase were not affected.…”

“…22,23) When the spawn of R. temporaria within 3 days before hatching was exposed to DDT (log K ow =6.9) at 0.5 ppm for a day, no pesticide residue was detected in tadpoles hatching 21 days later, while the exposure of spawn 5 days before hatching resulted in significant residues (19.4 ppm) in the tadpoles with toxic signs and poor development. 24) This may imply the ability of a well-developed jelly coat to act as a barrier to pesticide exposure, but the possibility of less metabolic detoxification at an early developmental stage cannot be ruled out.…”

“…In contrast to bioconcentration, bioaccumulation through the dietary route has been experimentally examined in the few stud- 2, lindane (6 hr); 45) 3, parathion (4 days); 46) 4, fenthion (4 days); 46) 5, triclosan (4 days); 43) 6, fluoranthene (2 days); 17) 7, dieldrin (1 to 28 days); 24,35) 8, DDT (1 day); 24,41) 9, cypermethrin (1 day); 23) 10, deltamethrin (13 hr); 45) 11, fipronil (6 days); 14) 12, methoxychlor (1 day); 47) 13, benzo[a]pyrene (6 days).…”

Glycopattern analysis and structure of the egg extra-cellular matrix in the Apennine yellow-bellied toad, <i>Bombina pachypus (Anura: Bombinatoridae)</i>

“…The number of layers itself can be linked to an increased protection against pathogens, since species with thicker jelly-coated eggs are less exposed to water mold infection than species with thinner coats [22]. Nonetheless, the jelly coat is not a sufficient barrier against penetration by herbicides like isoproturon [24], or insecticides like a-cypermethrin and endosulfan [25,66], although it seems to reduce penetration by polycyclic aromatic hydrocarbons [21] and 2,4-D butoxyethyl ester [23], even though it is supposed that eggs of species with different jelly-coat thickness should differ in resistance to chemical penetration [21].…”

“…Amphibians with a more complex jelly coat covering show a higher resistance to water molds [22]. The penetration of contaminants is significantly reduced and/or slowed by jelly coat layers [21,23], even if this is not always observed [24,25]. The resistance of egg ECM to environmental stresses can even vary geographically within a single species [26].…”