Morphological anomalies in the fourth instar larvae of Aedes aegypti and a case of gynandromorphism in Culex quinquefasciatus in Yucatán, México

Abstract Two cases of mosquitoes with morphological anomalies were documented. Both cases occurred in mosquitoes collected in the field. Twenty-five larvae of the fourth instar of Aedes aegypti with severe anomalies were observed. The distal part of the siphon displays a chitinized bulb. The siphon displays two pecten; one in the middle and one at the base of the chitinized bulb. The seta 1-S triple developed twice in the siphon; in the middle and distally at the base of the chitinized bulb. Larvae display two combs in two separate curve rows; one in the eighth abdominal segment and one in the base of the siphon. The anal segment had double development; the first did not present a saddle and the ventral brushes. The other was less developed; it displays a saddle, dorsal brushes, and ventral brushes. A Culex quinquefasciatus adult displayed a gynandromorph of the polar type, with the head of a female (filiform antennae, palps shorter than the proboscis), and an abdomen with male genitalia. Mosquito phenotypic anomalies occur in nature and have a negative impact on reproductive success and vector competence.