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

Abstract

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.

Sex-specific divergence for adaptations to dehydration stress in Drosophila kikkawai

“…In the case of the Asian tiger mosquito, Aedes albopictus, diapause involves quantitative but not compositional changes in surface lipids (Urbanski et al, 2010). This study showed an ~33% increase in surface hydrocarbons in diapause eggs of a temperate population of A. albopictus exposed to short day photoperiodic conditions.…”

“…Several studies have shown quantitative changes in surface lipids associated with desiccation resistance in a wide variety of insects (Armold and Regnier, 1975;Yoder et al, 1995;Kaneko and Katagiri, 2004;Urbanski et al, 2010). In the case of the Asian tiger mosquito, Aedes albopictus, diapause involves quantitative but not compositional changes in surface lipids (Urbanski et al, 2010).…”

“…This study showed an ~33% increase in surface hydrocarbons in diapause eggs of a temperate population of A. albopictus exposed to short day photoperiodic conditions. It was suggested that in temperate regions, changes in surface lipid amount of the eggs are associated with increased desiccation resistance of A. albopictus, which is likely to contribute to the rapid global spread of this invasive mosquito (Urbanski et al, 2010 …”

Photoperiodic Diapause and the Establishment ofAedes albopictus(Diptera: Culicidae) in North America

“…Another metabolism-related change is the increased expression of pepck, a gene which encodes a protein controlling the rate-limiting step of gluconeogenesis that has been implicated in the diapause response of other insects (Poelchau et al 2013a). Finally, the increased desiccation resistance of diapause eggs relative to nondiapause eggs is associated with increased abundance of a fatty acyl coA elongase (face) transcript under diapause conditions, both in mature oocytes before oviposition (Urbanski et al 2010) and during embryological development (Reynolds et al 2012). This increased abundance of the face transcript corresponds with an increase in quantities of egg surface hydrocarbons that presumably function to minimize water loss of eggs (Urbanski et al 2010).…”

“…Finally, the increased desiccation resistance of diapause eggs relative to nondiapause eggs is associated with increased abundance of a fatty acyl coA elongase (face) transcript under diapause conditions, both in mature oocytes before oviposition (Urbanski et al 2010) and during embryological development (Reynolds et al 2012). This increased abundance of the face transcript corresponds with an increase in quantities of egg surface hydrocarbons that presumably function to minimize water loss of eggs (Urbanski et al 2010). These results thus provide a likely mechanistic explanation for the observation that diapause eggs have higher survivorship than nondiapause eggs under warm, dry conditions (Sota andMogi 1992, Lounibos et al 2011).…”