Reproductive alterations in Scinax x-signatus (Anura: Hylidae) in agriculture ecosystems in northeastern Brazil

Roberta da Rocha Braga, Patrícia Menezes Gondim, Daniel de Araújo Viana, Eliana Reiko Matushima

Amphibians have been considered bioindicators of environmental changes. A cross-sectional study was carried out to compare morphopysiological alterations in gonads of the anuran Scinax X-signatus collected in controlled and cultivated areas in Vale do Jaguaribe, Ceará, northeastern Brazil. The specimens were collected manually and submitted to euthanasia by lidocaine 30mg/kg injection in foramen magnum. They were dissected, gonads were removed, fixed in formaldehyde 10%  and processed for routine histology. Ovaries and testicles were examined under light microscope and statistical analysis were performed using R. A total of 118 specimens were collected: 86 females, 28 males and 4 juveniles. In the cultivated area, it was found plastic bottles for dimethoate and oxime-carbamate. It was observed significant majority of immature individuals (X2 = 4.2, df = 1, p = 0.04). It was observed no difference between adults out of the two areas; however, immature individuals of cultivated areas were found significant smaller (W = 1024, p<0.001). The smaller mature male and female measured SVL=2.93cm and 2.34cm, respectively. Nevertheless, a male (SVL=3.12cm) and a female(SVL=3.13cm) were found larger than the smaller mature ones but presented inactive gonads, with reduced volume and absence of gametes. Among analyzed gonads, 14,28% (7/49) presented alterations, as 4/7 atrophic organ and 5/7 ovotestis, but with no significant difference between areas. Some pesticide can delay metamorphosis and reduce growth rate, with no effects in survival rates. Some others can cause feminization, due to aromatase expression. Although multiple factors can be involved, results of current work evoque possible significant negative effects of the agricultural practices in a local frog population. More studies are underway to substantiate these observations.

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