title: Effects of diapause and cold acclimation on egg ultrastructure: new insights into the cold hardiness mechanisms of the Asian tiger mosquito Aedes (Stegomyia) albopictus.
abstract: The Asian tiger mosquito, Aedes albopictus (Diptera: Culicidae, SKUSE), is an important threat to public health due to its rapid spread and its potential as a vector. The eggs of Ae. albopictus are the most cold resistant life stage and thus, the cold hardiness of eggs is used to predict the future occurrence of the species in distribution models. However, the mechanism of cold hardiness has yet to be revealed. To address this question, we analyzed the layers of diapausing and cold acclimatized eggs of a temperate population of Ae. albopictus in a full factorial test design using transmission electron microscopy. We reviewed the hypotheses that a thickened wax layer or chorion is the cause of cold hardiness but found no evidence. As a result of the induced diapause, the thickness of the dark endochorion as a layer of high electron density and thus an assumed location for waxes was decreasing. We therefore hypothesized a qualitative alteration of the wax layer due to compaction. Cold acclimation was causing an increase in the thickness of the middle serosa cuticle indicating a detachment of serosa membrane from the endochorion as a potential adaptation strategy to isolate inoculating ice formations in the inter-membranous space.
authors.affiliation: Senckenberg Biodiversity and Climate Research Centre (BiKF), Department Climate and Adaptation, Senckenberganlage 25, 60325 Frankfurt am Main, Germany. kress@bio.uni-frankfurt.de.|Goethe University Frankfurt am Main, Department Aquatic Ecotoxicology, Max-von-Laue-Str. 13, 60438 Frankfurt am Main, Germany. kress@bio.uni-frankfurt.de.
authors.forename: Aljoscha
authors.initials: A
authors.lastname: Kreß
authors.affiliation: Goethe University Frankfurt am Main, Institute of Occupational Medicine, Social Medicine and Environmental Medicine, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Kuch
authors.affiliation: Senckenberg Biodiversity and Climate Research Centre (BiKF), Department Climate and Adaptation, Senckenberganlage 25, 60325 Frankfurt am Main, Germany.|Goethe University Frankfurt am Main, Department Aquatic Ecotoxicology, Max-von-Laue-Str. 13, 60438 Frankfurt am Main, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Oehlmann
authors.affiliation: Goethe University Frankfurt am Main, Institute of Occupational Medicine, Social Medicine and Environmental Medicine, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany.
authors.forename: Ruth
authors.initials: R
authors.lastname: Müller
mesh_terms: D000064:Acclimatization; D000330:Aedes / Q000502:physiology*; D000818:Animals; D003080:Cold Temperature; D058865:Introduced Species; D000072138:Mosquito Vectors / Q000502:physiology; D010063:Ovum / Q000648:ultrastructure*
keywords: Chorion; cold tolerance; compaction; freeze avoidance; wax layer; winter survival