Sexual Mosaicism and Teratogenesis in Simulium guianense s.l. and S. incrustatum s.l. (Diptera: Simuliidae), Onchocerciasis vectors, from Environmentally Impacted Areas in the Yanomami Indigenous Land, Brazil.

Sexual mosaics in Simuliidae members have been detected at low frequencies in various locations worldwide. These phenotypic expressions are expected in very small amounts in any natural insect population and may result from inherent individual formation factors, such as hormonal or external elements, i.e., environmental pollution and parasitism, both of which can disrupt sexual differentiation development processes. This study assessed a Simuliidae collection sampled as a result of the Brazilian focus on endemic onchocerciasis in the Yanomami Indigenous Land in 2013, 2014, 2017, and 2021. Some specimens exhibited morphological alterations comprising sexual mosaic and teratogenicity phenotypes. In total, three Simulium guianense Wise, 1911 s.l. and three S. incrustatum Lutz, 1910 s.l. specimens presenting significant sexual anomalies were observed, two of which were teratogenic. No specimens were found parasitized by nematodes. A detailed morphological description of each specimen is provided. This study suggests the importance of assessing and monitoring the environmental toxicity of the sampling area and potential associations between anomalous specimens and environmental pollution by mercury, as all specimens were found in mining-impacted areas. This is the first record of sexual mosaic and teratogeny in Simuliidae specimens from Brazil.