Embryonic desiccation resistance in Aedes aegypti: presumptive role of the chitinized Serosal Cuticle

Rezende, Gustavo Lazzaro; Martins, Ademir Jesús; Gentile, Carla; Farnesi, Luana Cristina; Pelajo-Machado, Marcelo; Peixoto, Alexandre A.; Valle, Denise

doi:10.1186/1471-213x-8-82

Cited by 163 publications

(191 citation statements)

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“…Increased production of epicuticular lipids thus appears to be a common component of both diapause and aestivation (dry season diapause) in insects (Tauber et al 1986). Previous studies on A. gambiae (Goltsev et al 2009) and several Aedes (Telford 1957;Beckel 1958;Rezende et al 2008) have implicated the serosal cuticle to be important in determining desiccation resistance of eggs. While we cannot rule out the possibility that the hexane extraction procedure we used may have removed some lipids from the serosal cuticle inside the chorion, our results emphasize that surface lipids on the outside of the chorion can play an important role in determining the egg desiccation resistance.…”

Section: Discussionmentioning

confidence: 99%

The molecular physiology of increased egg desiccation resistance during diapause in the invasive mosquito,Aedes albopictus

et al. 2010

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Photoperiodic diapause is a crucial adaptation to seasonal environmental variation in a wide range of arthropods, but relatively little is known regarding the molecular basis of this important trait. In temperate populations of the mosquito Aedes albopictus, exposure to short-day (SD) lengths causes the female to produce diapause eggs. Tropical populations do not undergo a photoperiodic diapause. We identified a fatty acyl coA elongase transcript that is more abundant under SD versus long-day (LD) photoperiods in mature oocyte tissue of replicate temperate, but not tropical, A. albopictus populations. Fatty acyl CoA elongases are involved in the synthesis of long chain fatty acids (hydrocarbon precursors). Diapause eggs from a temperate population had one-third more surface hydrocarbons and one-half the water loss rates of non-diapause eggs. Eggs from a tropical population reared under SD and LD photoperiods did not differ in surface hydrocarbon abundance or water loss rates. In both a temperate and tropical population, composition of hydrocarbon chain lengths did not differ between eggs from SD versus LD conditions. These results implicate the expression of fatty acyl coA elongase and changes in quantity, but not composition, of egg surface hydrocarbons as important components of increased desiccation resistance during diapause in A. albopictus.

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Section: Discussionmentioning

confidence: 99%

The molecular physiology of increased egg desiccation resistance during diapause in the invasive mosquito,Aedes albopictus

et al. 2010

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“…Preliminary experiments have been performed in order to time this event, by adding YES at distinct hours after egg laying. Synchronous egg laying was performed during 20 min, as recently described (Rezende et al 2008). After this period, eggs were kept at the distinct temperatures employed in the experiments.…”

Section: Despite Its Vector Importance Little Attention Is Given Tomentioning

confidence: 99%

“…Moreover, knowledge of the effect of temperature on the embryonic development of culicids may serve as a basis for other studies such as the possibility of systematic evaluation of gene expression and physiological changes during embryogenesis (Rezende et al 2008). The precise identification of embryonic kinetics can also assist the development of new alternatives to the control of disease vectors, based on information obtained from embryological studies.…”

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confidence: 99%

“…aegypti embryogenesis takes 96 h at this temperature. With Trpiš clarification solution (Trpiš 1970, Rezende et al 2008 we analyzed whether there were apparent morphological differences between embryos 77.5 h and 96 h old. In both cases embryos displayed the same external morphological characters, i.e., separated head, three fused thoracic segments, eight abdominal segments and respiratory siphon with associated structures (Christophers 1960) (Fig.…”

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Embryonic development of Aedes aegypti (Diptera: Culicidae): influence of different constant temperatures

Farnesi

Martins

Valle

et al. 2009

Mem. Inst. Oswaldo Cruz

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105

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Despite its vector importance little attention is given toDengue and yellow fever are considered two of the most important viral diseases transmitted by arthropods (Gould & Solomon 2008). The mosquito Aedes aegypti, vector of urban yellow fever and also the main dengue vector, is widely distributed worldwide, being usually found between latitudes 35° N and 35° S (OPAS, 1995). Ae. aegypti embryos tend to enter dormancy at the end of embryogenesis, being able to keep its viability inside the egg for six months or more, according to the environmental relative humidity (Christophers 1960, Kliewer 1961, Clements 1992. When the surroundings become favorable to larval development, e.g. flooding of larvae habitat, dormancy is interrupted and the larva hatches (Christophers 1960, Clements 1992. Little attention has been given to the influence of temperature on Ae. aegypti embryonic development, when compared to other mosquito species (Rosay 1959, Christophers 1960, Trpiš et al. 1973, Clements 1992, Gillooly & Dodson 2000. The precise time Ae. aegypti takes to complete its embryogenesis at distinct temperatures is not known (Christophers 1960, Consoli & Lourenço-de-Oliveira 1994. In the present work the influence of distinct constant temperatures on Ae. aegypti embryogenesis, egg viability and the time course of larval hatching were analyzed.To induce Ae. aegypti larval eclosion from eggs previously stored in our laboratory for one month, preliminary tests were performed utilizing conditions described as effective stimuli in the literature (Gander 1951, Barbosa & Peters 1969, Novak & Shoroyer 1978. In all cases mosquitoes from the Rockefeller strain were used. The conditions used were: (i) dechlorinated water; (ii) deaerated dechlorinated water; (iii) 0.3 mM ascorbic acid in Ae. aegypti larval hatching, in our laboratory conditions, is the 0.3% (w/v) YES, the rate of egg hatching being 80% on average (data not shown).We observed that the embryonic dormancy state of Ae. aegypti is facultative, as expected for a multivoltine species (Forattini 2002), and could be bypassed by adding YES at the end of embryogenesis. Preliminary experiments have been performed in order to time this event, by adding YES at distinct hours after egg laying. Synchronous egg laying was performed during 20 min, as recently described (Rezende et al. 2008). After this period, eggs were kept at the distinct temperatures employed in the experiments. The precise moment of hatching of the first larvae was then observed for each temperature (see Table for the values). For all further experiments, YES was added 2 h before this moment. In this way, it was possible to monitor Ae. aegypti eclosion immediately after completion of embryonic development. For each experiment at a constant temperature, triplicates from the same egg laying were utilized. These eggs were kept on moist Whatman # 1 paper until YES was added. From this moment on, larvae hatching was observed every 30 min, until no more hatching occurred. Three experiments were performed for each tested ...

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“…Interestingly, the serosa secretes a chitinized cuticle underneath the maternal eggshell [34]. Since eggs of the mosquitoes Aedes aegypti and Anopheles gambiae gain desiccation resistance at the time of serosal cuticle secretion, the serosal cuticle has been suggested to protect the developing embryo against desiccation [35,36]. However, no experimental evidence exists because it is impossible to physically remove the zygotic serosa or serosal cuticle in insects without affecting the overlying maternal eggshell, which consists of an exochorion, endochorion and vitelline membrane [37].…”

Section: Introductionmentioning

confidence: 99%

The extraembryonic serosa protects the insect egg against desiccation

et al. 2013

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Insects have been extraordinarily successful in occupying terrestrial habitats, in contrast to their mostly aquatic sister group, the crustaceans. This success is typically attributed to adult traits such as flight, whereas little attention has been paid to adaptation of the egg. An evolutionary novelty of insect eggs is the serosa, an extraembryonic membrane that enfolds the embryo and secretes a cuticle. To experimentally test the protective function of the serosa, we exploit an exceptional possibility to eliminate this membrane by zerknü llt1 RNAi in the beetle Tribolium castaneum. We analyse hatching rates of eggs under a range of humidities and find dramatically decreasing hatching rates with decreasing humidities for serosa-less eggs, but not for control eggs. Furthermore, we show serosal expression of Tc-chitin-synthase1 and demonstrate that its knockdown leads to absence of the serosal cuticle and a reduction in hatching rates at low humidities. These developmental genetic techniques in combination with ecological testing provide experimental evidence for a crucial role of the serosa in desiccation resistance. We propose that the origin of this extraembryonic membrane facilitated the spectacular radiation of insects on land, as did the origin of the amniote egg in the terrestrial invasion of vertebrates.

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Embryonic desiccation resistance in Aedes aegypti: presumptive role of the chitinized Serosal Cuticle

Cited by 163 publications

References 70 publications

The molecular physiology of increased egg desiccation resistance during diapause in the invasive mosquito,Aedes albopictus

The molecular physiology of increased egg desiccation resistance during diapause in the invasive mosquito,Aedes albopictus

Embryonic development of Aedes aegypti (Diptera: Culicidae): influence of different constant temperatures

The extraembryonic serosa protects the insect egg against desiccation

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