title: Serosal cuticle formation and distinct degrees of desiccation resistance in embryos of the mosquito vectors Aedes aegypti, Anopheles aquasalis and Culex quinquefasciatus.
abstract: Given their medical importance, mosquitoes have been studied as vectors of parasites since the late 1800's. However, there are still many gaps concerning some aspects of their biology, such as embryogenesis. The embryonic desiccation resistance (EDR), already described in Aedes and Anopheles gambiae mosquitoes, is a peculiar trait. Freshly laid eggs are susceptible to water loss, a condition that can impair their viability. EDR is acquired during embryogenesis through the formation of the serosal cuticle (SC), protecting eggs from desiccation. Nevertheless, conservation of both traits (SC presence and EDR acquisition) throughout mosquito evolution is unknown. Comparative physiological studies with mosquito embryos from different genera, exhibiting distinct evolutionary histories and habits is a feasible approach. In this sense, the process of EDR acquisition of Aedes aegypti, Anopheles aquasalis and Culex quinquefasciatus at 25°C was evaluated. Completion of embryogenesis occurs in Ae. aegypti, An. aquasalis and Cx. quinquefasciatus at, respectively 77.4, 51.3 and 34.3hours after egg laying, Cx. quinquefasciatus embryonic development taking less than half the time of Ae. aegypti. In all cases, EDR is acquired in correlation with SC formation. For both Ae. aegypti and An. aquasalis, EDR and SC appear at 21% of total embryonic development, corresponding to the morphological stage of complete germ band elongation/beginning of germ band retraction. Although phylogenetically closer to Ae. aegypti than to An. aquasalis, Cx. quinquefasciatus acquires both EDR and serosal cuticle later, with 35% of total development, when the embryo already progresses to the middle of germ band retraction. EDR confers distinct egg viability in these species. While Ae. aegypti eggs demonstrated high viability when left up to 72hours in a dry environment, those of An. aquasalis and Cx. quinquefasciatus supported these conditions for only 24 and 5hours, respectively. Our data suggest that serosa development is at least partially uncoupled from embryo development and that, depending upon the mosquito species, EDR bestows distinct levels of egg viability.
authors.affiliation: Laboratório de Fisiologia e Controle de Artrópodes Vetores, IOC, Fiocruz, Rio de Janeiro, RJ 21045-900, Brazil; Laboratório de Entomologia, Instituto de Biologia do Exército, Rio de Janeiro, RJ 20911-270, Brazil. Electronic address: helenacvargas@gmail.com.
authors.forename: Helena Carolina Martins
authors.initials: HC
authors.lastname: Vargas
authors.affiliation: Laboratório de Fisiologia e Controle de Artrópodes Vetores, IOC, Fiocruz, Rio de Janeiro, RJ 21045-900, Brazil; Laboratório de Entomologia, Instituto de Biologia do Exército, Rio de Janeiro, RJ 20911-270, Brazil. Electronic address: lfarnesi@ioc.fiocruz.br.
authors.forename: Luana Cristina
authors.initials: LC
authors.lastname: Farnesi
authors.affiliation: Laboratório de Fisiologia e Controle de Artrópodes Vetores, IOC, Fiocruz, Rio de Janeiro, RJ 21045-900, Brazil; Laboratório de Entomologia, Instituto de Biologia do Exército, Rio de Janeiro, RJ 20911-270, Brazil; Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Rio de Janeiro, RJ 21941-902, Brazil. Electronic address: ademirjr@ioc.fiocruz.br.
authors.forename: Ademir Jesus
authors.initials: AJ
authors.lastname: Martins
authors.affiliation: Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Rio de Janeiro, RJ 21941-902, Brazil; Laboratório de Biologia Molecular de Flavivírus, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, RJ 21045-900, Brazil.. Electronic address: dvalle@ioc.fiocruz.br.
authors.forename: Denise
authors.initials: D
authors.lastname: Valle
authors.affiliation: Laboratório de Química e Função de Proteínas e Peptídeos, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, Campos dos Goytacazes, RJ 28013-602, Brazil; Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Rio de Janeiro, RJ 21941-902, Brazil. Electronic address: grezende@uenf.br.
authors.forename: Gustavo Lazzaro
authors.initials: GL
authors.lastname: Rezende
mesh_terms: D000330:Aedes / Q000737:chemistry / Q000196:embryology / Q000502:physiology*; D000818:Animals; D000852:Anopheles / Q000737:chemistry / Q000196:embryology / Q000502:physiology*; D005075:Biological Evolution; D003465:Culex / Q000737:chemistry / Q000196:embryology / Q000502:physiology*; D003890:Desiccation; D007303:Insect Vectors / Q000737:chemistry / Q000196:embryology / Q000502:physiology*; D010058:Oviposition; D010063:Ovum / Q000737:chemistry* / Q000254:growth & development / Q000502:physiology; D012621:Seasons
keywords: Desiccation resistance; Embryogenesis; Impermeability; Mosquito vectors; Serosal cuticle; Viability under dry conditions