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

Abstract

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.

Effects of diapause duration on diapause termination and post‐diapause reproduction in Orius sauteri

“…For example, diapause eggs of the spider mite Eotetranychus smithi General equation: y = a + bx, where 'a' is the intercept, 'b' the coefficient, and 'r 2 ' the multiple R-squared. Pritchard & Baker require a certain duration of chilling for termination of diapause (Takano et al, 2017). However, for many insects, chilling is not a prerequisite for the completion of diapause (Hodek & Hodlov a, 1988;Hodek, 2002).…”

High-throughput profiling of diapause regulated genes from Trichogramma dendrolimi (Hymenoptera: Trichogrammatidae)

“…Many aspects of diapause have been comprehensively reviewed in insects, and these show that diapause is a complicated process [13][14][15]. Some studies have focused on optimized conditions for diapause induction or termination to improve biological control programs [16][17][18][19][20]. Several diapause-associated genes, such as dilp1, forkhead box protein O (foxo), and akt, have been identified in insect species [21][22][23][24][25][26].…”

High-throughput profiling of diapause regulated genes from Trichogramma dendrolimi, an important egg parasitoid

“…Previous studies have comprehensively reviewed diapause from many aspects, ranging from insects to mammals, and shown that diapause is a complicated process [13][14][15] . To date, many studies have focused on ecological characteristics to optimize conditions for diapause induction or termination to improve biological control programs [16][17][18][19][20] . Several diapause-associated genes, such as dilp1, forkhead box protein O (foxo), and akt, have been identi ed in other insect species [21][22][23][24][25][26] .…”