Heat tolerance of developmental and seasonal stages of Chilo suppressalis

Abstract

Global warming means that the ability to withstand heat stress is of crucial importance to insects' survival and reproduction. Insects have various ways of achieving thermal tolerance, which can be affected by thermal history, physiological state, and seasonal cycles. In this study, we compared the thermal tolerance of life stages and seasons of a wild population of the striped stem borer, Chilo suppressalis (Walker) (Lepidoptera: Pyralidae), an economically significant pest of rice crops in Asia. Our results demonstrate that the eggs, larvae, and adults of C. suppressalis collected in rice fields in Yangzhou, China, are able to tolerate extremely high temperatures, in excess of those this species encounters in nature. We found that egg masses had a survival rate of 75% after being kept at 42 °C for 8 h. Egg masses exposed to 39 °C for 8 h had the longest hatching time (3.3 days). LTemp50 and LTemp90 (i.e., the temperatures at which 50 or 90% of individuals died within 2 h) of larvae collected in late summer were 45.4 and 47.3 °C, respectively. LTime50 and LTime90 (i.e., the time required to kill 50 or 90% of individuals) at 44 °C were 6.2 and 9.6 h, respectively. The corresponding values for 46 °C were 1.5 and 2.6 h. We also found that the heat tolerance of adults collected in late summer was lower than that of larvae. For example, LTemp50 of male and female adults was 43.8 and 43.6 °C, respectively. Other measures of the heat tolerance of adults, such as LTime50 at 42 °C, also differed between the sexes, being 5.9 h for males and 7.2 h for females. Although adult survival was robust to heat stress, adult fertility was more sensitive. Our results also indicate that although the second generation of adults (i.e., the summer generation) typically encountered higher temperatures than the overwintering generation, survival of the second generation adults was lower.

Functional analysis of small heat shock proteins providing evidence of temperature tolerance in Hyphantria cunea

“…However, in the natural condition, a 37°C temperature usually lasts for less than 5 hr per day, suggesting that much more larvae may survive in the field during the warmest days of the year in South China. Our study also shows that fall webworms can also endure extremely high temperatures, such as 40 and 43°C, for relatively longer periods (Chidawanyika & Terblanche, 2011; Lu, Cao et al., 2014; Nguyen et al., 2014). These results showed that H. cunea exhibited strong resistance to high temperature, which indicated a high risk of this pest to spread to low‐latitude areas.…”

“…SHSPs usually show tissue specificity in many insects, whereas HC sHSPs were found to be widely distributed in the Malpighian tubules, fat body, gut and cuticle and were all upregulated after temperature treatments (Saravanakumar et al., 2008; Shen et al., 2011). Previous studies have shown that the sHSPs that are specifically expressed in cuticle may be evolutionarily conserved in Lepidoptera and may play undetermined special roles (Lu, Cao, et al., 2014; Lu, Hua, et al., 2014; Quan et al, 2018). It is supported by the results from our study, that is, the highest abundance of HC sHSP20.0 was observed in the cuticle after heat shock.…”

Chilo suppressalis heat shock proteins are regulated by heat shock factor 1 during heat stress

“…In the city of Yangzhou (32.39°N, 119.42°E), C. suppressalis larvae survived in the range of temperatures from −21 to 46°C (Lu et al, 2012). We have shown that the egg masses, larvae, and male and female adults collected from rice fields could withstand the maximum temperatures of 42, 45.4, 43.8, and 43.6°C, respectively (Lu et al, 2014). Further studies demonstrated that the HSPs were involved in both development and temperature tolerance in C. suppressalis (Dong et al, 2021; Gao et al, 2019; Lu et al, 2013; Lu et al, 2014; Qiang et al, 2010; Song et al, 2020).…”