The Hypopharynx of Male and Female Mosquitoes

Abstract

Abstract:In blood-feeder female mosquitoes, the hypopharynx stylet is one part of the fascicle, the structure that pierces into the host skin during blood feeding. As other parts, the hypopharynx is a free stylet. However, since male mosquitoes do not feed blood, their mouthparts are less developed. The hypopharynx fuses with the inner wall of the labium, while maxillae and mandibles are much shorter than the labium. Only the labrum and the labium are well developed and function as food canal and its sheath, respectively. Light microscopy (LM) and scanning electron microscopy (SEM) were done to compare the hypopharynx of males of several mosquito genera and, in addition, females of autogenous mosquitoes.The hypopharynxs of males of both autogenous and anautogenous mosquitoes fuse with the labium inner wall as long as the labium length, but are distinctly different structures from the labium. Dissociation occurs on the hypopharynx of female autogenous mosquitoes: Toxorhynchites spp. have a free hypopharynx as in anautogeny mosquitoes, whereas it fuses with the labium wall in Malaya genurostris Leicester, as in male mosquitoes.

Conserved molecular pathways underlying biting in two divergent mosquito genera

“…The evolutionary transition from a biting to nonbiting life history has occurred multiple times in mosquitoes, including three entire genera of mosquitoes that never bite ( Malaya , Topomyia , Toxorhynchites ), and several nonbiting species that occur in genera comprised mostly of species that do bite (Downes, 1958; Foster, 1995; Miyagi et al, 2012; Rattanarithikul et al, 2007; Rioux et al, 1975; Spielman, 1971; Wahid et al, 2007; Zhou et al, 2014). Additionally, several mosquito species make a transition from a biting to a nonbiting life history when they enter adult, reproductive diapause in response to short days (reviewed in Denlinger & Armbruster, 2014, 2016).…”

“…The evolutionary transition from a biting to a nonbiting life history has occurred multiple times in mosquitoes. In fact, three complete genera of mosquitoes never bite ( Malaya , Topomyia , Toxorhynchites ), and several nonbiting species occur in genera comprised mostly of species that do bite (Downes, 1958; Foster, 1995; Miyagi et al, 2012; Rattanarithikul et al, 2007; Wahid et al, 2007; Zhou et al, 2014). Furthermore, many species are able to produce a single clutch of eggs without biting, but then require a blood meal for all subsequent egg clutches (O'Meara, 1985; Rioux et al, 1975; Spielman, 1971).…”

Evolutionary transition from blood feeding to obligate nonbiting in a mosquito

“…In actuality, blood feeding is not universal among mosquitoes. Three genera ( Toxorhynchites , Malaya , and Topomyia ) and several species in otherwise biting genera never bite ( 2 – 7 ). Individuals of many species may or may not take a blood meal (bite) for the first ovarian cycle, but all these species require a blood meal for their second and subsequent ovarian cycles ( 8 – 10 ).…”