Heat Stress Impedes Development and Lowers Fecundity of the Brown Planthopper Nilaparvata lugens (Stål)

Abstract

This study investigated the effects of sub-lethal high temperatures on the development and reproduction of the brown plant hopper Nilaparvata lugens (Stål). When first instar nymphs were exposed at their ULT50 (41.8°C) mean development time to adult was increased in both males and females, from 15.2±0.3 and 18.2±0.3 days respectively in the control to 18.7±0.2 and 19±0.2 days in the treated insects. These differences in development arising from heat stress experienced in the first instar nymph did not persist into the adult stage (adult longevity of 23.5±1.1 and 24.4±1.1 days for treated males and females compared with 25.7±1.0 and 20.6±1.1 days in the control groups), although untreated males lived longer than untreated females. Total mean longevity was increased from 38.8±0.1 to 43.4±1.0 days in treated females, but male longevity was not affected (40.9±0.9 and 42.2±1.1 days respectively). When male and female first instar nymphs were exposed at their ULT50 of 41.8°C and allowed to mate on reaching adult, mean fecundity was reduced from 403.8±13.7 to 128.0±16.6 eggs per female in the treated insects. Following exposure of adult insects at their equivalent ULT50 (42.5°C), the three mating combinations of treated male x treated female, treated male x untreated female, and untreated male x treated female produced 169.3±14.7, 249.6±21.3 and 233.4±17.2 eggs per female respectively, all significantly lower than the control. Exposure of nymphs and adults at their respective ULT50 temperatures also significantly extended the time required for their progeny to complete egg development for all mating combinations compared with control. Overall, sub-lethal heat stress inhibited nymphal development, lowered fecundity and extended egg development time.

A Single Hot Event That Does Not Affect Survival but Decreases Reproduction in the Diamondback Moth, Plutella xylostella

“…In contrast to patterns for stressed H. armigera [12], D. melanogaster [11], [15], and Bicyclus anynana [43], we found effects on fertility immediately after heat exposure rather than after a few days. Heat exposure in females and males has previously been shown to strongly affect the reproductive fitness of various insect species [15], [44]–[49]. Some studies have found that heat stress leads to sterilized eggs through effects on male spermatogenesis [46], which may be more thermosensitive than oogenesis [50].…”

Effects of acclimation on the thermal tolerance of the brown planthopper Nilaparvata lugens (Stål)

“…We also observed that, at 15 • C, there was no nymph emergence after 25 days and few nymphs had emerged after 35 days. First, natural winter exposure will be for longer periods of time than in laboratory experiments used to determine lethal limits and, second, the relatively high threshold temperature at which eggs hatch (15 • C) would limit the development of such populations (Piyaphongkul et al, 2012b). However, many studies have reported a progressive warming trend for most regions in Asia, which is most pronounced over northern and north-eastern areas (e.g.…”

“…Recent studies on N. lugens showed that the upper lethal temperatures of nymphs and adults overlapped with summer high temperatures across parts of its Asian distribution and that insects could be immobilized by heat stress at lower temperatures than would be commonly experienced in some countries every year (Piyaphongkul et al, 2012a). A subsequent study (Piyaphongkul et al, 2012b) found that, after exposure of nymphs and adults of N. lugens at their respective upper lethal temperatures (i.e. As such, the status of N. lugens as the most serious pest of rice throughout India and south-east Asia would not necessarily change, although its relative importance might vary over time across its distribution.…”

Impact of hot events at different developmental stages of a moth: the closer to adult stage, the less reproductive output

“…Despite recent progress in understanding the sensitivity of different developmental stages to heat stress measured by immediate survival in insects and other small invertebrates9, there is limited information on the longer-term consequences of hot events. Some studies have considered effects of heat stress in early stages on subsequent adult reproduction1011121314. However, heat exposure on only one stage was usually considered, such as the egg stage1011, 1 st -instar larva12, or a more extended period of development131415.…”

“…Some studies have considered effects of heat stress in early stages on subsequent adult reproduction1011121314. However, heat exposure on only one stage was usually considered, such as the egg stage1011, 1 st -instar larva12, or a more extended period of development131415. The impacts of heat stress at different stages have only been compared in a few insects1617.…”