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This study aims to investigate the developmental interactions of Asecodes hispinarum Boucek on Brontispa longissima Gestro and Octodonta nipae Maulik, as well as the cellular immune responses of B. longissima and O. nipae larvae in response to parasitism by A. hispinarum, with the hope of determining the reason for the difference in larval breeding of A. hispinarum in B. longissima and O. nipae. The effects of parasitism by A. hispinarum on the larval development, hemocyte count, and proportion of the hemocyte composition of the two hosts were carried out through selective assay and non-selective assay using statistical analysis and anatomical imaging. There was no significant difference in parasitic selection for A. hispinarum on the larvae of these two beetles; however, more eggs were laid to B. longissima larvae than to O. nipae larvae after parasitism by A. hispinarum. The eggs of A. hispinarum were able to grow and develop normally inside the larvae of B. longissima, and the parasitism caused the larvae of B. longissima become rigid within 7 d, with a high larval mortality rate of 98.88%. In contrast, the eggs of A. hispinarum were not able to develop normally inside the O. nipae larvae, with a high encapsulation rate of 99.05%. In addition, the parasitism by A. hispinarum caused a 15.31% mortality rate in O. nipae larvae and prolonged the larval stage by 5 d and the pupal stage by 1 d. The number of hemocytes during the 12, 24, 48, 72, and 96 h of the four instars from O. nipae larvae was 6.08 times higher than from B. longissima larvae of the same age. After 24 h of being parasitized by A. hispinarum, the total number of hemocytes and granulocyte proportion of B. longissima larvae increased significantly. However, the total number of hemocytes and plasmatocyte proportion of O. nipae increased significantly after 24, 72, and 96 h, and the proportion of granulocytes increased significantly after 12 h post-parasitism. The results in the present study indicated that A. hispinarum was unable to successfully reproduce offspring in O. nipae, but its spawning behavior had an adverse effect on the larval development of its host. In addition, the adequate number of hemocytes and more pronounced changes in the hemocyte count and hemocyte composition ratio in the larvae after parasitization may be important factors for the successful encapsulation in O. nipae larvae.

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To determine population genomic structure through high-throughput sequencing techniques has revolutionized research on non-model organisms. The coconut leaf beetle, Brontispa longissima (Gestro), is a widely distributed pest in Southern China. Here, we used restriction site-associated DNA (RAD) genotyping to assess the invasion pathway by detecting and estimating the degree of genetic differentiation among 51 B. longissima accessions collected from Southern China. A total of 10,127 SNPs were obtained, the screened single nucleotide polymorphism (SNP) information was used to construct the phylogenetic tree, FST analysis, principal component analysis, and population structure analysis. Genetic structure analysis was used to infer the population structure; the result showed that all accessions were divided into Hainan population and non-Hainan population. The Hainan population remained stable, only the Sansha population differentiated, and the non-Hainan populations have gradually differentiated into smaller sub-populations. We concluded that there are two sources of invasion of B. longissima into mainland China: Taiwan and Hainan. With the increase of the invasion time, the Hainan population was relatively stable, and the Taiwan population was differentiated into three sub-populations. Based on the unrooted phylogenetic tree, we infer that Taiwan and Hainan are the two invasive base points. The Taiwan population invaded Fujian, Guangdong, and Guangxi, while the Hainan population invaded Yunnan and Sansha. Our results provide strong evidence for the utility of RAD sequencing (RAD-seq) in population genetics studies, and our generated SNP resource could provide a valuable tool for population genomics studies of B. longissima in the future.

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BACKGROUND: Invasions of a number of tree-feeding beetles have increased globally and pose a mounting threat to the world's trees, production forests and natural habitats. An in-depth understanding of the determinants of invasion potential of a given species and invasibility of novel environments can help forecast future invasions and avert undesirable socio-economic impacts. Here, we quantitatively assess the (multivariate) drivers of historic invasions of the coconut hispid Brontispa longissima (Coleoptera: Chrysomelidae) across the Asia-Pacific region and critically assess its invasion potential for other key coconut-growing regions. RESULTS: Genetic variation of B. longissima in its invaded range indicated multiple incursions, likely associated with (short-range) natural dispersal and (long-range) trade in ornamental palms and coconut plantlets. Interception records at China's ports of entry accentuate the role of traded planting material. The high fecundity and prolonged, yet adaptable, oviposition period of B. longissima further enhance the invasiveness of this species and aid its successful establishment. Coconut-growing areas are identified with high climatic suitability for B. longissima, and where strengthened biosecurity protocols can prevent future invasions. CONCLUSION: A combined assessment of inter-country trade patterns, population genetics and species bio-ecology (e.g. climate-related development) illuminates the dispersal pathways of invasive species, assesses invasibility of particular geographies, guides quarantine interventions and thus can effectively avert future invasions. © 2019 Society of Chemical Industry.

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The venom apparatus is a conserved organ in parasitoids that shows adaptations correlated with life-style diversification. Combining transcriptomics and label-free quantitative proteomics, here we explored the venom apparatus components of the endoparasitoid Tetrastichus brontispae (Eulophidae), and provide a comparison of the venom apparatus proteomes between its two closely related strains, T. brontispae-Octodonta nipae (Tb-On) and T. brontispae-Brontispa longissima (Tb-Bl). Tb-Bl targets the B. longissima pupa as its habitual host. However, Tb-On is an experimental derivative of Tb-Bl, which has been exposed to the O. nipae pupa as host consecutively for over 40 generation. Results showed that approximately 1505 venom proteins were identified in the T. brontispae venom apparatus. The extracts contained novel venom proteins, such as 4-coumarate-CoA ligase 4. A comparative venom proteome analysis revealed that significant quantitative and qualitative differences in venom composition exist between the two strains; although the most abundant venom proteins were shared between them. The differentially produced proteins were mainly enriched in fatty acid biosynthesis and melanotic encapsulation response. Six of these enriched proteins presented increased levels in Tb-On, and this result was validated by parallel reaction monitoring (PRM) analysis. Overall, our data reveal that venom composition can evolve quickly and respond to host selection.

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The intracellular bacterium Wolbachia pipientis is widespread in arthropods. Recently, possibilities of novel Wolbachia-mediated hosts, their distribution, and natural rate have been anticipated, and the coconut leaf beetle Brontispa longissima (Gestro) (Coleoptera: Chrysomelidae), which has garnered attention as a serious pest of palms, was subjected to this interrogation. By adopting Wolbachia surface protein (wsp) and multilocus sequence type (MLST) genotypic systems, we determined the Wolbachia infection density within host developmental stages, body parts, and tissues, and the results revealed that all the tested samples of B. longissima were infected with the same Wolbachia strain (wLog), suggesting complete vertical transmission. The MLST profile elucidated two new alleles (ftsZ-234 and coxA-266) that define a new sequence type (ST-483), which indicates the particular genotypic association of B. longissima and Wolbachia. The quantitative real-time PCR analysis revealed a higher infection density in the eggs and adult stage, followed by the abdomen and reproductive tissues, respectively. However, no significant differences were observed in the infection density between sexes. Moreover, the wsp and concatenated MLST alignment analysis of this study with other known Wolbachia-mediated arthropods revealed similar clustering with distinct monophyletic supergroup B. This is the first comprehensive report on the prevalence, infection dynamics, and phylogeny of the Wolbachia endosymbiont in B. longissima, which demonstrated that Wolbachia is ubiquitous across all developmental stages and distributed in the entire body of B. longissima. Understanding the Wolbachia infection dynamics would provide useful insight to build a framework for future investigations, understand its impacts on host physiology, and exploit it as a potential biocontrol agent.

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The costs and benefits of polyandry are still not well understood. We studied the effects of multiple mating on the reproductive performance of female Brontispa longissima (Coleoptera: Chrysomelidae), one of the most serious pests of the coconut palm, by using three experimental treatments: (1) singly-mated females (single treatment); (2) females that mated 10 times with the same male (repetition treatment); and (3) females that mated once with each of 10 different males (polyandry treatment). Both multiple mating treatments resulted in significantly greater total egg production and the proportion of eggs that successfully hatched (hatching success) than with the single mating treatment. Furthermore, the polyandry treatment resulted in greater total egg production and hatching success than with the repetition treatment. Thus, mate diversity may affect the direct and indirect benefits of multiple mating. Female longevity, the length of the preoviposition period, the length of the period from emergence to termination of oviposition, and the length of the ovipositing period did not differ among treatments. The pronounced fecundity and fertility benefits that females gain from multiple mating, coupled with a lack of longevity costs, apparently explain the extreme polyandry in B. longissima.

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Octodonta nipae (Maulik) is morphologically and biologically similar to Brontispa longissima (Gestro), one of the most damaging pests of coconut. The two species share several palm hosts and produce similar symptoms. They are easily confused when they invade a new area, and without professional taxonomic expertise accurate identification is arduous and time-consuming. Thus, a method of rapidly distinguishing these two invasive insects rapidly is critical for quarantine. Based on the first internal transcribed spacer and the mitochondrial cytochrome oxidase I gene, two pairs of special primers and corresponding polymerase chain reaction processes have been developed to enhance a single objective band only from the O. nipae DNA template. This will quickly discriminate between these two species. The present results provide a rapid method of distinguishing O. nipae from B. longissima to help avoid misidentification, and furthermore, to facilitate rapid and appropriate quarantine decisions and effective treatments to the pest.

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