No abstract

The communication and reproduction of insects are driven by chemical sensing. During this process, chemical compounds are transported across the sensillum lymph to the sensory neurons assisted by different types of soluble binding proteins: odorant-binding proteins (OBPs); chemosensory proteins (CSPs); some members of ML-family proteins (MD-2 (myeloid differentiation factor-2)-related Lipid-recognition), also known as NPC2-like proteins. Potential transcripts involved in chemosensing were identified by an in silico analysis of whole-body female and male transcriptomes of the parasitic wasp Diachasmimorpha longicaudata. This analysis facilitated the characterization of fourteen OBPs (all belonging to the Classic type), seven CSPs (and two possible isoforms), and four NPC2-like proteins. A differential expression analysis by qPCR showed that eleven of these proteins (CSPs 2 and 8, OBPs 2, 3, 4, 5, 6, 9, 10, and 11, and NPC2b) were over-expressed in female antenna and two (CSP 1 and OBP 12) in the body without antennae. Foraging behavior trials (linked to RNA interference) suggest that OBPs 9, 10, and 11 are potentially involved in the female orientation to chemical cues associated with the host. OBP 12 seems to be related to physiological processes of female longevity regulation. In addition, transcriptional silencing of CSP 3 showed that this protein is potentially associated with the regulation of foraging behavior. This study supports the hypothesis that soluble binding proteins are potentially linked to fundamental physiological processes and behaviors in D. longicaudata. The results obtained here contribute useful information to increase the parasitoid performance as a biological control agent of fruit fly pest species.

Varroa-Resistance in Argentinian Honey Bees selection. Percentage of damaged mites appears to be a reliable measure to enhance this behavior in honey bee colonies by selective breeding. Finally, the importance of improving and protecting locally adapted honey bee populations with natural Varroa resistance for regional apiculture is discussed.

Grooming behavior confers resistance to honey bees against Varroa destructor, being of interest to social immunity studies and breeding programs. The objective of this study was to characterize at the individual level the grooming behavior of mite-resistant (R) and susceptible (S) A. mellifera stocks from Argentina. Assays were performed in experimental arenas by applying two treatments to nurse bees: (1) placing a V. destructor mite on the bee's thorax and (2) touching the bee with a paintbrush. Grooming reactions were recorded on bees from both stocks at the ages of 6, 10, and 14 days after emergence. R bees exhibited lower time of first response against the mite, performed more cleaning attempts, and used all their legs with a higher probability compared to S bees. The same pattern was evident when younger and older bees from the R stock were compared. The results demonstrate that bee age and genetic origin are critical factors of grooming behavior in honey bees.

Varroa destructor, a parasitic mite of the Western honey bee Apis mellifera L., is a serious threat to colonies and beekeeping worldwide. Population genetics of the mite has provided information of two mitochondrial haplotypes infecting honey bee colonies, named K (Korea) and J (Japan). In the American continent, the K haplotype was most frequently found. The aim of this research was to study the genetic diversity of V. destructor populations from the major beekeeping region of Argentina, previously unexplored. Phoretic mites were collected from managed A. mellifera colonies in ten localities, and four mtDNA regions (cox1, nad4, nad4L, and nad5) were analyzed. Based on cox1 sequence, the exclusive presence of K haplotype was detected. Two sub-haplotypes (KArg-N1 and KArg-N2) were identified from a variation in nad4 sequence. The frequency of these sub-haplotypes significantly correlates with the geographic latitude. The occurrence of site heteroplasmy was also evidenced for this gene. The nad4 mtDNA marker appears to be a sensitive marker to detect genetic variability in mite populations. The site heteroplasmy emerges as a phenomenon that could be relatively frequent in V. destructor.

2012) Rearing of the fruit fly parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae) on X-ray irradiated larvae of Ceratitis capitata (Diptera: Tephritidae), We evaluated the effects of X-ray irradiation on larvae of Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), with the aim of finding a treatment that prevented adult fly emergence, yet did not adversely affect larval quality as rearing hosts for the parasitoid Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Ichneumonidae). Two experiments were carried out. In the first experiment, small numbers of larvae were held in Petri dishes with and without small amounts of rearing media and then irradiated with doses of X-rays ranging from 0 to 8333.6 R (equivalent to 80 Gy). In the second experiment, higher numbers of larvae were held in a manner resembling mass-rearing conditions, and were then irradiated with X-rays ranging from 0 to 10,417 R (equivalent to 100 Gy). In both experiments, the only factor that significantly affected fly emergence was irradiation of larvae. Fly emergence decreased markedly as the irradiation dose increased, and complete suppression of fly emergence was achieved at 6250.2 R (equivalent to 60 Gy) when larvae were irradiated in small batches with or without rearing media. Irradiation also affected the fertility of those flies that did emerge following treatment. In the second experiment, we found the parasitoids reared from irradiated larvae produced a higher parasitism rate and a higher number of female offspring than did parasitoids reared from control (nonirradiated) larvae. Mean fecundity of F1 parasitoids reared from irradiated larvae were affected positively by irradiation only at the 8333.6 R (80 Gy) dose. Our results show that X-ray irradiation can be used to inhibit fruit fly adult emergence and that irradiated larvae are at least as good a rearing substrate as nonirradiated larvae. Future studies should focus on the adjustment of our findings to a mass-rearing scale.

Varroa destructor Anderson & Trueman (Acari: Varroidae) is one of the major contributors to the significant losses of western honey bee, Apis mellifera L. (Hymenoptera: Apidae), colonies worldwide. Hygienic behavior, in which individual workers detect, uncap, and remove unhealthy brood, is a type of social immunity that reduces pathogen and parasite loads in the colony. Previous evidence suggests that hygienic worker bees identify diseased brood through olfactory cues. The aims of the present work were (1) to study the hygienic behavior of worker bees toward V. destructor-infested cells at different stages of brood development, (2) to explore changes in brood volatile profiles associated with the progression of mite infestation, and (3) to analyze the role of specific volatile compounds in triggering the hygienic behavior. Results showed that the removal rate of infested brood changed along its development and the progression of mite reproduction. Two compounds, ethyl hexanoate and a-pinene, were present in volatile collections from mite-infested pupae but absent from uninfested pupae. Field bioassays showed that these volatiles are relevant to elicit the hygienic behavior. A third compound, b-ocimene, was present in infested and uninfested brood but its abundance pattern varied according to the infestation status throughout brood development. Specifically, for uninfested brood, the abundance of b-ocimene showed a reduction in black-eyed pupae, whereas for infested brood, its abundance decreased drastically in light-pink-eyed pupae and remained constant in blackeyed pupae. Our results revealed that olfactory signals associated with V. destructor infestation change as the reproductive cycle of V. destructor progresses inside the cell. These changes can be mimicked to some extent by adding specific volatile compounds to the cell to induce hygienic removal. These findings shed light on the chemical basis of hygienic behavior against V. destructor and could facilitate the development of improved hygienic selection tools to breed mite-resistant honey bee colonies.

We studied the sex determination in Diachasmimorpha longicaudata, a parasitoid braconid wasp widely used as biological control agent of fruit pest tephritid flies. We tested the complementary sex determination hypothesis (CSD) known in at least 60 species of Hymenoptera. According to CSD, male or female development depends on the allelic composition of one sex locus (single-locus CSD) or multiple sex loci (multiple-locus CSD). Hemizygote individuals are normal haploid males, and heterozygotes for at least one sex locus are normal diploid females, but homozygotes for all the sex loci are diploid males. In order to force the occurrence of diploid males in D. longicaudata, we established highly inbred lines and examined their offspring using chromosome counting, flow cytometry, and sex ratio analysis. We found that when mother-son crosses were studied, this wasp produced about 20% of diploid males out of the total male progeny. Our results suggest that this parasitoid may represent the second genus with multiple-locus CSD in Hymenoptera. Knowledge about the sex determination system in D. longicaudata is relevant for the improvement of mass rearing protocols of this species. This information also provides the necessary background for further investigations on the underlying molecular mechanisms of sex determination in this species, and a better insight into the evolution of this pathway in Hymenoptera in particular and insects in general.