title: Exposure and post-exposure effects of endosulfan on Bufo bufo tadpoles: morpho-histological and ultrastructural study on epidermis and iNOS localization.
abstract: Endosulfan is a persistent organic pollutant (POP) that has lethal and sublethal effects on non-target organisms, including amphibians. In a laboratory study, we investigated direct and post-exposure effects of endosulfan on Bufo bufo tadpoles. For this purpose we exposed the tadpoles to a single short-term contamination event (96 h) at an environmentally-realistic concentration (200 μg endosulfan/L). This was followed by a recovery period of 10 days when the experimental animals were kept in pesticide-free water. The endpoints were assessed in terms of mortality, incidence of deformity, effects on behavior, and the morpho-functional features of the epidermis. We found that a short-term exposure to the tested concentration of endosulfan did not cause mortality but induced severe sublethal effects, such as hyperactivity, convulsions, and axis malformations. Following relocation to a pesticide-free environment, we noted two types of response within the experimental sample, in terms of morphological and behavioral traits. Moreover, by using both ultrastructural and a morpho-functional approach, we found that a short-term exposure to endosulfan negatively affected the amphibian epidermis. We also observed several histo-pathological alterations: increased mucous secretion, an increase in intercellular spaces and extensive cell degeneration, together with the induction of an inducible isoform of nitric oxide synthase (iNOS). Following the post-exposure period, we found large areas of epidermis in which degeneration phenomena were moderate or absent, as well as a further increase in iNOS immunoreactivity. Thus, after 10 days in a free-pesticide environment, the larval epidermis was able to partially replace elements that had been compromised due to a physiological and/or a pathological response to the pesticide. These results highlight the need for both exposure and post-exposure experiments, when attempting to assess pollutant effects.
authors.affiliation: Department of Biology, Ecology and Earth Sciences (DiBEST), University of Calabria, Via P. Bucci 4B 87036 Rende (CS), Italy.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Bernabò
authors.forename: Antonello
authors.initials: A
authors.lastname: Guardia
authors.forename: Daniele
authors.initials: D
authors.lastname: La Russa
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Madeo
authors.forename: Sandro
authors.initials: S
authors.lastname: Tripepi
authors.forename: Elvira
authors.initials: E
authors.lastname: Brunelli
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D002023:Bufo bufo / Q000502:physiology*; D004726:Endosulfan / Q000633:toxicity*; D004817:Epidermis / Q000187:drug effects* / Q000201:enzymology / Q000648:ultrastructure; D007814:Larva / Q000187:drug effects; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*; D016019:Survival Analysis; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D014874:Water Pollutants, Chemical; D052247:Nitric Oxide Synthase Type II; D004726:Endosulfan