Sublethal Exposure Effects of the Neonicotinoid Clothianidin Strongly Modify the Brain Transcriptome and Proteome in the Male Moth Agrotis ipsilon

Insect pest management relies mainly on neurotoxic insecticides, including neonicotinoids such as clothianidin. The residual accumulation of low concentrations of these insecticides can have positive effects on target pest insects by enhancing various life traits. Because pest insects often rely on sex pheromones for reproduction and olfactory synaptic transmission is cholinergic, neonicotinoid residues could indeed modify chemical communication. We recently showed that treatments with low doses of clothianidin could induce hormetic effects on behavioral and neuronal sex pheromone responses in the male moth, Agrotis ipsilon. In this study, we used high-throughput RNAseq and proteomic analyses from brains of A. ipsilon males that were intoxicated with a low dose of clothianidin to investigate the molecular mechanisms leading to the observed hormetic effect. Our results showed that clothianidin induced significant changes in transcript levels and protein quantity in the brain of treated moths: 1229 genes and 49 proteins were differentially expressed upon clothianidin exposure. In particular, our analyses highlighted a regulation in numerous enzymes as a possible detoxification response to the insecticide and also numerous changes in neuronal processes, which could act as a form of acclimatization to the insecticide-contaminated environment, both leading to enhanced neuronal and behavioral responses to sex pheromone.

Gender associated morphological differences in Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae)

The sexual dimorphism in pupal and adult stages of rice moth, Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) was studied. Distinct slit on eighth abdominal segment is present in female pupa, while it absent in male pupa. Female moths have longer and snout- like palpi and male moth has shorter and blunt labial palpi.

Identification and field evaluation of female sex pheromone of leaf-eating caterpillar, Opisina arenosella (Lepidoptera: Oecophoridae)

The leaf-eating caterpillar,Opisina arenosellaWalker, is the most destructive pest of coconut palm in India and Southeast Asia. The management practices employed againstO. arenosellaso far have been unsuccessful in many instances in India, due to the pest behaviour and coconut palm phenology. The life cycle, incidence and behaviour ofO. arenosellaare rather interesting and useful for the intervention of pheromone trapping technique for its management. We conducted the present study with the intention of identifying the female sex pheromone ofO. arenosellaand testing its efficacy under field conditions. Gas chromatography coupled electroantennographic detection (GC–EAD) and gas chromatography–mass spectrometry (GC–MS) analysis of female pheromone glands extract of one-day-oldO. arenosellafemales confirmed the presence of (Z,Z,Z)-3,6,9-tricosatriene (Z3Z6Z9-23Hy) as the dominant sex pheromone component. The male antennal response to female pheromone gland extract and syntheticZ3Z6Z9-23Hy was recorded using GC–EAD, and the results revealed that antennal response was positive to both the treatments at 0.13 mV and 0.14 mV respectively, compared to control (air), which was 0.016 mV. It was also evident from wind-tunnel experiments that the male moth response was high (80%) with the female gland extract, compared to 60% with synthetic pheromone and 0% for control (air). Male moths caught in the traps with and without lure were assessed in two field sites and recorded 69.26% and 54.25% more moth catches in the traps with the lure. We also observed a similar result in the cage experiment in which male moths caught in the traps with and without lure were 64.50% and 12.40%, respectively. The study also confirmed that 93.20% moths caught in the pheromone-baited traps were male. From the study, it is evident that the presence of (Z,Z,Z)-3,6,9-tricosatriene, which is the sex pheromone compound from the female gland extract ofO. arenosella, is an effective attractant in pheromone traps for the male moth under field conditions.

Conservation of wild silkworm genetic resources through cryopreservation: Standardization of sperm processing

Conservation of the invaluable sericigenous genetic resources is of prime importance with respect to their utilization and improvement for wider exploitation. Conservation of wild silkworms and its applicability in hybridization have limitations due to incompatibility, less amenability, change of behaviour under ex situ conditions, non-synchronization of moth eclosion and difficulties in mating between variables. In view of this, the newer technologies such as cryopreservation and artificial insemination are offering better strategies for preservation of biologically active samples like semen at sub-zero temperature (-196º C) conditions for longer duration. In this context, under standardization of sperms preservation from wild silkworms, two methods of semen collection were scrutinized for obtaining active and viable sperm for cryopreservation and further artificial insemination. Semen collection from the seminal vesicle of freshly emerged male moth and the other from the bursa copulatrix (BC) and spermatheca of the female moth after mating. The sperms in the semen collected from seminal vesicle are in the form of bundles known as eupyrene sperm bundles and apyrene sperms. The morphology and behaviour of these sperm bundles were recorded through microscopic examination. To study the density and motility behaviour of the sperms, sperm bundles were treated with proteolytic enzyme (~2-3µg/ml) to digest the membrane and release the sperms. The density and motility behaviour of sperms in the semen recovered from the BC and spermatheca of female moth after mating were higher compared to those released after digestion of sperm bundles from seminal vesicle of the male moth.

Similar worldwide patterns in the sex pheromone signal and response in the oriental fruit moth, Grapholita molesta (Lepidoptera: Tortricidae)

The response of Grapholita molesta (Busck) males to three-component sex pheromone blends containing a 100% ratio of the major sex pheromone component, (Z)-8-dodecenyl acetate and a 10% ratio of (Z)-8-dodecenol, but with varying ratios of (E)-8-dodecenyl acetate (0.4, 5.4, 10.4, 30.4, and 100.1% E-blends) was tested with populations in eight stone and pome fruit orchards in Europe, Asia, and North and South America. Traps baited with the 5.4% E-blend caught significantly more males than traps with any other blend with all populations. Significantly more males were caught in traps baited with the 10.4% E-blend than in traps with the remaining blends, except with the 0.4% E-blend in Turkey. Significant differences in male moth catches occurred between the other blends with the 0.4>30.4% E-blend, and the 30.4>100.1% E-blend. Male moth catches with the 100.1% E-blend only differed from the hexane control in Chile. No apparent differences were noted to these blends in populations collected from pome or stone fruits. Flight tunnel assays to synthetic blends with a subset of populations were similar to the field results, but the breadth of the most attractive E-blends was wider. Flight tunnel assays also demonstrated a high level of male–female cross-attraction among field-collected populations. Female gland extracts from field-collected populations did not show any significant variation in their three-component blends. The only exceptions in these assays were that long-term laboratory populations were less responsive and attractive, and produced different blend ratios of the two minor components than recently collected field populations.

Ejaculate economics: an experimental test in a moth

Increasing evidence shows that spermatogenesis is costly. As a consequence, males should optimize the use of their sperm to maximize their reproductive outputs in their lifetime. However, experimental evidence on this prediction is largely lacking. Here, we examine how a male moth Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) responds to the presence of rivals or additional mates and how such response influences his lifetime reproductive fitness. We show that when rival males are present around a copulating pair, the male ejaculates more sperm to win a sperm competition battle but in such an environment he inseminates fewer females, sires fewer offspring and lives shorter. The opposite is the case when additional females are present during copulation. These findings reveal that elevated reproductive expenditure owing to sperm competition intensity is made at the expense of longevity and future reproduction.