Exposure and post-exposure effects of endosulfan on Bufo bufo tadpoles: Morpho-histological and ultrastructural study on epidermis and iNOS localization

• Published in: Aquatic toxicology 2013-10, Vol.142-143, p.164-175
• Main Authors: Bernabò, Ilaria, Guardia, Antonello, La Russa, Daniele, Madeo, Giuseppe, Tripepi, Sandro, Brunelli, Elvira
• Format: Article
• Language: English
• Subjects: abnormal development; amphibians; Animals; Behavior, Animal - drug effects; Bufo bufo; Bufo bufo - physiology; endosulfan; Endosulfan - toxicity; Epidermis - drug effects; Epidermis - enzymology; Epidermis - ultrastructure; intercellular spaces; laboratory animals; Larva - drug effects; mortality; nitric oxide synthase; Nitric Oxide Synthase Type II - metabolism; nontarget organisms; secretion; seizures; sublethal effects; Survival Analysis; tadpoles; Water Pollutants, Chemical - toxicity
• ISSN: 0166-445X; 1879-1514
• DOI: 10.1016/j.aquatox.2013.08.002

•We investigate direct and post-exposure effects of endosulfan on Bufo bufo tadpoles.•Sublethal effects include hyperactivity, convulsions, and axis malformation.•Endosulfan is able to induce severe lag effects.•Epidermis morphology and ultrastructure are affected by endosulfan exposure.•iNOS is differentially expressed in epidermis after exposure and post-exposure period. 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 (96h) at an environmentally-realistic concentration (200μg 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.