Teratological changes in postembryos of Eratigena atrica obtained by the application of alternating temperatures on spider embryos

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.

Appendage abnormalities in spiders induced by an alternating temperature protocol in the context of recent advances in molecular spider embryology

In the literature there are numerous reports of developmental deformities in arthropods collected in their natural habitat. Since such teratogenically affected individuals are found purely by chance, the causes of their defects are unknown. Numerous potential physical, mechanical, chemical, and biological teratogens have been considered and tested in the laboratory. Thermal shocks, frequently used in teratological research on the spider Eratigena atrica, have led to deformities on both the prosoma and the opisthosoma. In the 2020/2021 breeding season, by applying alternating temperatures (14 °C and 32 °C, changed every 12 h) for the first 10 days of embryonic development, we obtained 212 postembryos (out of 3,007) with the following anomalies: oligomely, heterosymely, bicephaly, schistomely, symely, polymely, complex anomalies, and others. From these we selected six spiders with defects on the prosoma and two with short appendages on the pedicel for further consideration. The latter cases seem particularly interesting because appendages do not normally develop on this body part, viewed as the first segment of the opisthosoma, and appear to represent examples of atavism. In view of the ongoing development of molecular techniques and recent research on developmental mechanisms in spiders, we believe the observed phenotypes may result, at least in part, from the erroneous suppression or expression of segmentation or appendage patterning genes. We consider "knockdown" experiments described in the literature as a means for generating hypotheses about the sources of temperature-induced body abnormalities in E. atrica.