In Mexico, Ae. aegypti and Cx. quinquefasciatus are competent vectors of dengue virus and West Nile virus, respectively (Elizondo-Quiroga et al. 2005; Baak-Baak et al. 2019). In nature, there are few reported cases of morphologic anomalies in Ae. aegypti. A slight anomaly consisting of a reduction in the length of the lateral saddle seta was previously reported (Verna and Munstermann 2011). In contrast, the findings of the present work are impressive because the fourth-instar larvae of Ae. aegypti presented severely abnormal development. However, they were mobile like any normal larva. Insecticide selection pressure has been applied to both mosquito species during vector control programs, and genes associated with pyrethroid resistance have been found (Chi-Chim et al. 2018; Garcia-Rejon et al. 2018). Aedes aegypti with knockdown resistance homozygous mutations (Val1, 016) were discovered to have delayed larval development, higher mortality in late stages, decreased blood intake, and larger body sizes (Garcia-Rejon et al. 2018). In an experimental investigation, it was discovered that Ae. aegypti larvae reared under copper (Cu2+) stress underwent phenotypic and physiological alterations. The tissue of the mosquito larvae and adults was less robust, pale, and translucent in appearance. In addition, adults had reduced body mass, fewer reserves of neutral lipids at emergence, and a reduced tolerance to starvation (Perez and Noriega 2014). Chemical compounds and metals as copper are used in the manufacture of insecticides and artificial containers, which could induce abnormal development of immature stages of aquatic arthropods. However, in the present work, the phenotypic abnormality of Ae. aegypti was severe, and we cannot be sure if it was induced by any compound or was a coding error in the mosquito genome.
The first cases of gynandromorphism in Cx. quinquefasciatus were reported by Roth (1947) in the United States. A mosquito presented oblique gynandromorphism with the right antenna, right palp, right fore, and left midtarsi as in males, but in the distal part of the abdomen, it was observed to have female genitalia with spermathecae. Another Cx. quinquefasciatus presented polar gynandromorphism, with antennae and palps characteristic of males and genitalia characteristic of females. In Pakistan, Cx. quinquefasciatus with polar gynandromorphism was also identified. The head and thorax had female characteristics, while the abdomen had well-developed male genitalia (Ali and Rasheed 2008). The specimen we identified coincides with the one reported in Pakistan. The doublesex (Agdsx) and Nix genes can control sex determination in Anopheles gambiae and Ae. aegypti, respectively. Disruption of the genes can promote the development of male genitalia in female mosquitoes (or vice versa) and generate a gynandromorph (Hall et al. 2015; Kyrou et al. 2018). Gynandromorphism impacts the reproductive success of the species. Polar mosquitoes with female anterior portions respond to mating stimuli, but the presence of male genitalia reduces the probability of copulation. Likewise, if the females take blood from the hosts, they will not be able to oviposit the eggs.