Mating Delay Reduces Reproductive Performance but not Longevity in a Monandrous Moth

Regulation of opsin and circadian clock genes on mate-finding behavior of the day-flying red moth, Phauda flammans (Walker)

First, significantly higher mate-finding success was found under light condition than under constant darkness condition in Phauda flammans, a typical diurnal moth. We speculate that mate-finding behavior in P. flammans may be influenced by the light-sensitive opsin genes Long wavelength opsin (PfLW), Ultraviolet opsin (PfUV) and Blue opsin (PfBL), which are potentially regulated by both light-cues and endogenous circadian rhythms. Second, the circadian clock genes Period (PfPer), Timeless (PfTim), Cryptochrome1 (PfCry1), Cryptochrome2 (PfCRY2), Cryptochrome3 (PfCry-like), Clock (PfClk), Cycle (PfCyc), Vrille (PfVri), and Slimb (PfSli) were identified in P. flammans. Third, circadian rhythms in the relative expression levels of opsin and circadian clock genes were demonstrated via quantitative real-time PCR analysis, with peak expression coinciding with the mate-finding peak. Notably, the relative expression of PfLW in males P. flammans was significantly higher than that in females P. flammans at the mate-finding peaks Zeitgeber time (ZT) 8 and ZT 10 under light, while the expression of the opsin gene PfBL showed a similar pattern at ZT 10 under light. Additionally, the expression of the clock gene PfCry-like was significantly higher in males than in females at ZT 8 and ZT 10 under light, while PfPer, PfTim, PfClk and PfCyc exhibited similar male-biased expression patterns at ZT 10 under light. Conversely, PfCry1 and PfVri expression was significantly higher in females than in male at ZT 8 under light. In conclusion, sex differences were detected in the expression of opsin and circadian clock genes, which indicated that light-mediated regulation of these genes may contribute to the daytime mate-finding behavior of P. flammans.

Sast1-mediated manifold effects inhibit Plutella xylostella fertility

BACKGROUND

Plutella xylostella (Linnaeus) is a destructive pest of cruciferous crops due to its strong reproductive capacity and extensive resistance to pesticides. Seminal fluid proteins (SFPs) are the main effective factors that determine the reproductive physiology and behaviour of both sexes. Although an increasing number of SFPs have been identified, the effects of astacins in SFPs on agricultural pests have not yet been reported. Here, we elucidated the mechanisms by which Sast1 (seminal astacin 1) regulates the fertility of Plutella xylostella (L.).

RESULTS

PxSast1 was specifically expressed in the testis and accesssory gland. CRISPR/Cas9-induced PxSast1 knockout successfully constructed two homozygous mutant strains. Sast1 impaired the fertility of P. xylostella by separately regulating the reproductive capacity of males and females. Loss of PxSast1, on the one hand, significantly decreased the ability of males to mate and fertilize, mainly manifested as shortened mating duration, reduced mating competitiveness and decreased eupyrene sperm production; on the other hand, it significantly inhibited the expression of chorion genes in females, resulting in oogenesis deficits. Simultaneously, for mated females, the differentially expressed genes in signalling pathways related to oogenesis and chorion formation were significantly enriched after PxSast1 knockout.

CONCLUSION

These analyses of the functions of PxSast1 as the regulator of spermatogenesis and oogenesis establish its importance in the fertility process of P. xylostella, as well as its potential as a promising target for genetic regulation-based pest control. © 2024 Society of Chemical Industry.

Molecular Characterization and Expression Patterns of Two Pheromone-Binding Proteins from the Diurnal Moth Phauda flammans (Walker) (Lepidoptera: Zygaenoidea: Phaudidae)

Sex pheromone-binding proteins (PBPs) play an important role in sex pheromone recognition in Lepidoptera. However, the mechanisms of chemical communication mediating the response to sex pheromones remain unclear in the diurnal moths of the superfamily Zygaenoidea. In this study, Phauda flammans (Walker) (Lepidoptera: Zygaenoidea: Phaudidae) was used as a model insect to explore the molecular mechanism of sex pheromone perception in the superfamily Zygaenoidea. Two novel pheromone-binding proteins (PflaPBP1 and PflaPBP2) from P. flammans were identified. The two pheromone-binding proteins were predominantly expressed in the antennae of P. flammans male and female moths, in which PflaPBP1 had stronger binding affinity to the female sex pheromones Z-9-hexadecenal and (Z, Z, Z)-9, 12, 15-octadecatrienal, PflaPBP2 had stronger binding affinity only for (Z, Z, Z)-9, 12, 15-octadecatrienal, and no apparent binding affinity to Z-9-hexadecenal. The molecular docking results indicated that Ile 170 and Leu 169 are predicted to be important in the binding of the sex pheromone to PflaPBP1 and PflaPBP2. We concluded that PflaPBP1 and PflaPBP2 may be responsible for the recognition of two sex pheromone components and may function differently in female and male P. flammans. These results provide a foundation for the development of pest control by exploring sex pheromone blocking agents and the application of sex pheromones and their analogs for insect pests in the superfamily Zygaenoidea.

Reproductive Behaviour of 150-Gy-Treated Female Lobesia botrana (Lepidoptera: Tortricidae)

Simple Summary

Environment-friendly and sustainable insect pest control approaches such as the sterile insect technique/inherited sterility (SIT/IS) have been proposed against the European grapevine moth Lobesia botrana. Reproductive behaviour, such as oviposition, mating ability, and multiple mating of 150 Gy-treated females, was studied. Moreover, the last-male sperm precedence (P2 value) and male’s flight response to treated females were also investigated. The present study aims to provide basic information which is essential to ensure successful implementation of SIT/IS as part of an integrated approach for the management of L. botrana.

Abstract

The sterile insect technique/inherited sterility (SIT/IS) has been suggested as an eco-friendly control tactic for area-wide integrated pest management approaches in order to control the European grapevine moth, Lobesia botrana. This study assessed the effects of an irradiation dose of 150 Gy administered to newly emerged female moths on their egg laying behaviour and mating ability at different ages at mating. Moreover, the effects of multiple mating on the mating ability of treated females, pattern of sperm precedence in twice-mated females and the flight response of treated and untreated males to treated and untreated calling females were also investigated. Females treated with 150 Gy initiated calling in a way similar to untreated females. When treated females were paired with untreated males, the mean number of eggs oviposited per female during 6 days was reduced (59.6 and 82.8 eggs/female, respectively), as was their mating ability and multiple mating compared with untreated females. The proportion of offspring fertilized by the second of the two males to mate with the female or last-male sperm precedence (P2 value) constituted 97% of the eggs, suggesting that the second male mate fathered the most offspring. The outcome of this work could be viewed as an integrated approach for improving effectiveness and enabling successful implementation of a SIT/IS program against L. botrana.

Effects of Delayed Mating on the Reproductive Performance and Longevity of the Fall Armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae)

The fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), a severe pest on agricultural crops occurring throughout the tropical Americas, has been reported to occur in China since 2019. To develop novel pest management practices, we studied the effect of delayed mating on the reproductive performance and longevity of S. frugiperda. Delayed mating, progressing from 0 to 7 days, was respectively imposed on both sexes simultaneously, female only, and male only. We demonstrated that delayed mating reduced mating success, number of eggs laid, egg hatch rate, and female oviposition period, while increased copulation duration and longevity. The correlations between the number of delayed days and mating success, number of eggs laid, hatch rate, and oviposition period were all significantly negative irrespective of the sex that was delayed. Meanwhile, there was a positive correlation between delayed days and copulation duration when both sexes were delayed simultaneously or males delayed only. Overall our results indicated that delayed mating in both males and females drastically reduced female reproductive output.

Sex pheromone signal and stability covary with fitness

If sexual signals are costly, covariance between signal expression and fitness is expected. Signal-fitness covariance is important, because it can contribute to the maintenance of genetic variation in signals that are under natural or sexual selection. Chemical signals, such as female sex pheromones in moths, have traditionally been assumed to be species-recognition signals, but their relationship with fitness is unclear. Here, we test whether chemical, conspecific mate finding signals covary with fitness in the moth Heliothis subflexa. Additionally, as moth signals are synthesized de novo every night, the maintenance of the signal can be costly. Therefore, we also hypothesized that fitness covaries with signal stability (i.e. lack of temporal intra-individual variation). We measured among- and within-individual variation in pheromone characteristics as well as fecundity, fertility and lifespan in two independent groups that differed in the time in between two pheromone samples. In both groups, we found fitness to be correlated with pheromone amount, composition and stability, supporting both our hypotheses. This study is, to our knowledge, the first to report a correlation between fitness and sex pheromone composition in moths, supporting evidence of condition-dependence and highlighting how signal-fitness covariance may contribute to heritable variation in chemical signals both among and within individuals.

Effects of Delayed Mating on Mating Performance and Reproductive Fitness of the Willow Leaf Beetle (Coleoptera: Chrysomelidae) under Laboratory Conditions

Simple Summary

Mating disruption is one of the most effective methods for pest management. The willow leaf beetle Plagiodera versicolora Laicharting is a serious pest of poplar and willow. We studied the effects of delayed mating on the mating performance and reproductive fitness of P. versicolora, as part of an effort to control P. versicolora using mating disruption. Delayed mating of females and males impacts their mating performance, but has only a limited impact on the females’ reproductive fitness. These results indicate that delayed mating is unlikely to contribute to the success of mating disruption, when applied to control P. versicolora.

Abstract

Age at mating is one of the most important factors that affect mating selection, sexual performance, and fecundity. We studied the effects of mating age on the mating performance and reproductive fitness of Plagiodera versicolora Laicharting, a serious pest of poplar and willow, by measuring the time from pairing to successful mating, mating duration, fecundity, hatching probability, and female lifespan. Delayed mating of females and males significantly prolonged the time from pairing to successful mating and the mating duration, but had no effect on the duration of the egg-laying period. Delayed mating of females did not significantly affect fecundity or egg hatching, but significantly prolonged the female lifespan. Although delayed mating of males had a significant negative impact on egg hatching, it had no effect on the lifespan or fecundity of females. These results indicate that delayed mating affects the mating performance of P. versicolora, although it has a limited effect on reproductive fitness. This suggests that delayed mating is unlikely to contribute to the success of mating disruption, when applied to control P. versicolora.

Socially cued anticipatory adjustment of female signalling effort in a moth

Juvenile population density has profound effects on subsequent adult development, morphology and reproductive investment. Yet, little is known about how the juvenile social environment affects adult investment into chemical sexual signalling. Male gumleaf skeletonizer moths, Uraba lugens, facultatively increase investment into antennae (pheromone receiving structures) when reared at low juvenile population densities, but whether there is comparable adjustment by females into pheromone investment is not known. We investigate how juvenile population density influences the 'calling' (pheromone-releasing) behaviour of females and the attractiveness of their pheromones. Female U. lugens adjust their calling behaviour in response to socio-sexual cues: adult females reared in high juvenile population densities called earlier and for longer than those from low juvenile densities. Juvenile density also affected female pheromonal attractiveness: Y-maze olfactometer assays revealed that males prefer pheromones produced by females reared at high juvenile densities. This strategic investment in calling behaviour by females, based on juvenile cues that anticipate the future socio-sexual environment, likely reflects a response to avoid mating failure through competition with neighbouring signallers.