Effect of temperature on diapause termination and post-diapause development in Eotetranychus smithi (Acari: Tetranychidae)

• Published in: Experimental & applied acarology 2017-12, Vol.73 (3-4), p.353-363
• Main Authors: Takano, Y., Ullah, M. S., Gotoh, T.
• Format: Article
• Language: English
• Subjects: Animal Ecology; Animal Genetics and Genomics; Animal Systematics/Taxonomy/Biogeography; Biomedical and Life Sciences; Chilling; Cooling; Diapause; Diapause termination; Eggs; Embryogenesis; Embryonic growth stage; Entomology; Females; Hatchability; Hatching; High temperature; Life Sciences; Low temperature; Mites; Temperature; Temperature effects
• ISSN: 0168-8162; 1572-9702
• DOI: 10.1007/s10493-017-0199-6

Previous studies on the spider mite Eotetranychus smithi Pritchard & Baker have shown that diapause in eggs is induced by low temperature alone and that females developed at ≤ 17.5 °C laid diapause eggs, regardless of the photoperiod. In this study, diapause eggs were kept at 5 °C and a photoperiod of 16L:8D for 0–120 days and then maintained at 25 °C to know the effect of chilling on diapause termination. Diapause eggs mostly hatched when they were maintained at 25 °C after chilling for 30–90 days at 5 °C, which suggests that diapause termination is favored by low temperatures. To clarify the hatching conditions after diapause termination, diapause eggs kept at 5 °C for 45 days were subsequently maintained at various constant temperatures (from 15 to 25 °C) under a long-day photoperiod (16L:8D). The hatchability at all temperatures tested was high (> 90%) and did not significantly differ among the high temperatures. Duration of embryonic development was shorter with increasing warming temperature after chilling. The lower thermal threshold ( t ) and thermal constant ( k ) for post-diapause egg development were 10.5 °C and 76.9 degree-days, respectively. Females, which developed from diapause eggs that were chilled at 5 °C for 45 days and then maintained at 15 °C, laid only non-diapause eggs, which indicates that they were prevented from re-entering diapause even under diapause-inducing conditions (15 °C). Thus, temperature is the main factor to control diapause termination and post-diapause development, which has also been found for other spider mites that enter diapause at the egg stage.