Photo-orientation regulates seasonal habitat selection in the two-spotted spider miteTetranychus urticae

Abstract

SUMMARYNon-diapausing spider mites (Tetranychus urticae) live on the undersurface of host leaves during summer, but diapausing mites overwinter in dark hibernacula. The light environments of these habitats differ: visible radiation (VIS) but not ultraviolet radiation (UV) reaches the undersurface of leaves, but neither enters dark hibernacula. Thus, mites of either seasonal form could locate their preferred habitat by photo-orientation responses to UV and VIS. To investigate this possibility, we analysed the mitesʼ locomotion behaviour on a virtual field with a programmed chequered pattern of light and dark patches in a micro-locomotion compensator. Both non-diapausing and diapausing mites moved away from UV-illuminated patches into dark patches. Nondiapausing mites moved towards VIS-illuminated patches, whereas diapausing mites did not show a preference. Our results show that non-diapausing mites avoid UV and are attracted to VIS, suggesting that this can guide them beneath a leaf. Diapausing mites simply avoid UV. The lack of a preference for VIS during diapause could be due to changes in carotenoid metabolism, which also involve orange pigmentation of diapausing mites. We consider that a diapause-mediated switch of the response to VIS, together with regular avoidance of UV, plays a key role in the seasonal change of habitat selection in this species. This seasonal polyphenism involves alterations in not only reproductive state and pigmentation, but also in photospectral responses.

Transcriptome and proteome analyses reveal complex mechanisms of reproductive diapause in the two‐spotted spider mite, Tetranychus urticae

“…In the green form, diapausing females cease ovarian development immediately after adult emergence and gradually change colour to orange (Kawakami et al ., ). Once the colour has changed, diapausing females begin to migrate from the plants to dark hibernacula (such as clods of soil, cracks in trees and under bark; Veerman, ), and a diapause‐mediated switch of photo‐spectral responses regulates this habitat selection process (Suzuki et al ., ). At the biochemical level, many metabolites were found to be profoundly influenced by the state of diapause, including amino acids, tricarboxylic acid cycle intermediates and polyols (Khodayari et al ., ).…”

Genome wide gene-expression analysis of facultative reproductive diapause in the two-spotted spider mite Tetranychus urticae

“…At the time of color change to the typical orange forms, the hindgut is emptied and mites become positively geotactic [28] and negatively phototactic to find shelter [29, 30]. …”

When do predatory mites (Phytoseiidae) attack? Understanding their diel and seasonal predation patterns

“…In predator-prey systems, light or dark preferences could influence feeding or reproduction, as these are frequently associated with the spatial distribution of food sources (e.g., adaxial or abaxial side of the leaf) (Villanueva & Childers, 2005;Sudo & Osakabe, 2011). Tetranychus urticae and P. citri distributions, mostly on lower and upper leaf surfaces, respectively (Tachi & Osakabe, 2012), have been associated with their different sensitivity to UV radiation (Ohtsuka & Osakabe, 2009;Fukaya et al, 2013;Suzuki et al, 2013;Ghazy et al, 2016). Therefore, differences in the time of day at which predation occurred could be related to the position of the preferred prey and/or their different UV sensitivity, such as P. persimilis being less UV sensitive than N. californicus (Tachi & Osakabe, 2012Ghazy et al, 2016).…”