Behavioral and Physiological Resistance to Desiccation in Spotted Wing Drosophila (Diptera: Drosophilidae)

Abstract

With a high surface to volume ratio, small organisms must carefully regulate their internal water status. Spotted-wing drosophila, Drosophila suzukii (Matsumura), is an invasive frugivorous insect distributed across a wide range of geographical regions that can have periods of dry and hot weather, suggesting that this species has strategies to avoid stressful environments and reduce water loss. It also survives winter as an adult fly, indicating that it has adaptations to the low air humidity of this season. To determine the importance of water stress to D. suzukii, we studied their survival in environments of low humidity, which was manipulated using Drierite, and their survival and water loss in response to desiccation. Survival of both sexes was lower in drier conditions, and while female winter morph D. suzukii had higher mortality early on, remaining flies were able to survive longer in the drier conditions than the summer morphs. A bioassay method was adapted from Enjin et al. (2016) using 48-well plates to videotape the location of flies and quantify their behavioral responses to humidity. Male and female D. suzukii avoided dry conditions within the bioassay system, but only when there was at least 25% differential between humidity extremes. This response was observed for both summer and winter morphs of D. suzukii and our results provide guidance for attempts to manipulate crop environments to reduce the economic impact of this pest.

Transcriptional Control of Quality Differences in the Lipid-Based Cuticle Barrier in Drosophila suzukii and Drosophila melanogaster

“…D. suzukii appears in two morphs, i.e., the summer and the winter morph with distinct ecological traits. The winter morph, for instance, is more robust at low humidity conditions than the summer morph (Toxopeus et al, 2016;Fanning et al, 2019). D. melanogaster as a cosmopolitan species also shows geographical variation (Rajpurohit et al, 2017;Dong et al, 2019).…”

Endosymbiosis allows Sitophilus oryzae to persist in dry conditions

“…Nevertheless, we would still expect that a large portion of water is lost via the cuticle during desiccation stress in live insects. Studies have shown that cuticular transpiration is largely passive ( Hadley et al, 1986 ) and accounts for >80% of the water loss during desiccation events ( Gibbs et al, 1998 , 2004 ; Fanning et al, 2019 ).…”

“…Despite this, insects show a remarkable ability to maintain water balance using an arsenal of behavioral, morphological and physiological adaptations ( Chown et al, 2011 ). These adaptations involve mechanisms to acquire water, and to reduce or tolerate water loss, thereby enabling insects to subsist in dry and hot environments ( Sheikh et al, 2017 ; Fanning et al, 2019 ).…”

Eco‐genetics of desiccation resistance in Drosophila

“…In the Sonoran Desert (Arizona, USA), for example, adult flies choose cooler and moist microhabitats such as necrotic cacti (Gibbs, 2002 b ). In the laboratory, D. suzukii flies preferred a moist environment when the air humidity difference between the conditions offered was at least 25% (Fanning et al ., 2019). D. melanogaster adults also rapidly move to moist locations in both natural environments and under laboratory conditions (Sun et al ., 2018).…”