Response of biomarkers in amphibian larvae to in situ exposures in a fruit‐producing region in North Patagonia, Argentina

Abstract

The authors evaluated biomarker responses in caged larvae of the amphibian Rhinella arenarum in water channels during fruit production season and compared them with those elicited by a transient exposure to azinphos methyl (AzM) (0.02-2 mg/L; 4 h), the main pesticide applied in the Alto Valle region, Patagonia, Argentina, taking into account the maximum environmental concentration detected in superficial water (22.5 µg/L). The traditional biomarkers of organophosphate exposure, acetylcholinesterase (AChE) and carboxylesterase, were inhibited in tadpoles after one week of exposure in channels potentially receiving pesticide drift, whereas the antioxidant glutathione (GSH) and the detoxifying activity of GSH S-transferase (GST) were induced. In a two-week monitoring study, AChE activity was induced in larvae exposed at the agricultural site, and carboxylesterase showed an inhibition followed by return to control values, suggesting an exposure-recovery episode. Antioxidant glutathione levels were first depleted and then surpassed control levels, whereas GST activity was continuously induced. These responses were mimicked in the laboratory by 2 mg/L AzM-pulse exposure, which notably exceeds the expected environmental concentrations. The results draw attention to the complexity of responses after pesticide exposure, strongly depending on exposure time-concentration and recovery periods, among other possible factors, and support the necessity of the integrated use of biomarkers to assess exposure episodes in agricultural areas.

Developmental and polyamine metabolism alterations in Rhinella arenarum embryos exposed to the organophosphate chlorpyrifos

“…The reported maximum environmental concentrations of OP in water currently range in the micrograms per liter order, as it has been recently published for chlorpyrifos (1.16 mg/L) and azinphos methyl (22.5 mg/L) for superficial and ground water in the Alto Valle de Río Negro y Neuquén [4]. This is also suggested by biomarker responses in environmental studies on R. arenarum larvae exposed in irrigation channels [6]. The ponds and channels located in productive orchards are heavily impacted by the 500 tons of formulated pesticides that are applied annually in the region [5].…”

“…Organophosphorus pesticides have been detected in superficial and groundwater in the valley of Río Negro and Neuquén, Patagonia, Argentina [4], an area where more than 35,000 hectares are subjected to intensive agriculture. The exceedence of environmental concentrations of OPs in superficial water in this region might range from one to two orders of magnitude, as suggested by biomarker studies performed with amphibian larvae exposed in situ in irrigation channels of the region [6]; although the maximum concentration of the OP azinphos methyl detected in water was 22.5 mg/L, larvae showed altered biomarker responses compatible with 2 mg/L, as suggested by laboratory studies. Moreover, higher concentrations of these pesticides may be transiently present in ponds and irrigation channels of orchards because of aerial drift and runoff, considering that insecticide applications can reach a biweekly frequency in concentrations of approximately 100 g/L per hectare [5].…”

“…The ponds and channels located in productive orchards are heavily impacted by the 500 tons of formulated pesticides that are applied annually in the region [5]. This is also suggested by biomarker responses in environmental studies on R. arenarum larvae exposed in irrigation channels [6]. Then, polyamine metabolism and in particular ODC activity becomes an attractive biomarker for OP exposure, not related to the common cholinergic pathway but giving complementary information to be used in environmental evaluations of pesticide impact.…”

“…Moreover, higher concentrations of these pesticides may be transiently present in ponds and irrigation channels of orchards because of aerial drift and runoff, considering that insecticide applications can reach a biweekly frequency in concentrations of approximately 100 g/L per hectare [5]. The exceedence of environmental concentrations of OPs in superficial water in this region might range from one to two orders of magnitude, as suggested by biomarker studies performed with amphibian larvae exposed in situ in irrigation channels of the region [6]; although the maximum concentration of the OP azinphos methyl detected in water was 22.5 mg/L, larvae showed altered biomarker responses compatible with 2 mg/L, as suggested by laboratory studies.…”

Chronic toxicity of arsenic during Rhinella arenarum embryonic and larval development: Potential biomarkers of oxidative stress and antioxidant response

“…This allows overcoming a high variability in the responses depending on seasonal aspects, duration and frequency of contamination episodes, and many other factors including the organisms themselves. Even those biomarkers considered specific for a group of toxicants may show diverging responses, as reported for the biomarker of neurotoxic effects acetylcholinesterase, which was induced in R. arenarum larvae exposed in situ for 2 wk in an orchard receiving organophosphate pesticide applications [28].…”