Wolbachia infections in world populations of bean beetles (Coleoptera: Chrysomelidae: Bruchinae) infesting cultivated and wild legumes.

Wolbachia endosymbionts are widespread among insects and other arthropods, often causing cytoplasmic incompatibility and other reproductive phenotypes in their hosts. Recently, possibilities of Wolbachia-mediated pest control and management have been proposed, and the bean beetles of the subfamily Bruchinae are known as serious pests of harvested and stored beans worldwide. Here we investigated Wolbachia infections in bean beetles from the world, representing seven genera, 20 species and 87 populations. Of 20 species examined, Wolbachia infections were detected in four species, Megabruchidius sophorae, Callosobruchus analis, C. latealbus and C. chinensis. Infection frequencies were partial in M. sophorae but perfect in the other species. In addition to C. chinensis described in the previous studies, C. latealbus was infected with two distinct Wolbachia strains. These Wolbachia strains from the bean beetles were phylogenetically not closely related to each other. Among world populations of C. chinensis, some Taiwanese populations on a wild leguminous plant, Rhynchosia minima, exhibited a peculiar Wolbachia infection pattern, suggesting the possibility that these populations comprise a distinct host race or a cryptic species.

Modeling population dynamics of two cockroach species: effects of the circadian clock, interspecific competition and pest control.

The German cockroach Blattella germanica is obviously one of the most spread household pests in the world, and is now virtually impossible to sustain outside human constructions. The double-striped cockroach B. bisignata, on the other hand, is limited to Southeast Asia and mostly living in the open space, yet is able to establish in cockroach-free households, too. In this article, we develop a stage-structured population model of these two species to explore (i) whether their circadian clocks impact their long-term population dynamics, (ii) which of these species is a superior competitor, and (iii) how stringent potential pest control strategies have to be to significantly impact established populations of the German cockroach. The results of the model are as follows. Firstly, phase shifts in the light-to-dark cycle did not affect cockroach population dynamics unless males and females were out of phase and their mate finding abilities rather limited. In addition, for the hypothesized circadian clock genotypes, the shorter is the inactivity period relative to the activity one or the less arrhythmic is the population, the more viable the population is and the quicker it grows to large numbers. Secondly, the German cockroach was the superior competitor: it was able to invade and drive out established populations of the double-striped cockroach and prevent any invasion of the latter. Finally, only a significant and simultaneous reduction in a number of most sensitive German cockroach parameters resulted in species extirpation. Only carefully designed and data-based models of German (and double-striped) cockroach population dynamics can be helpful in our quest to win the fight over this unwelcome but very sturdy species.

Apvasa marks germ-cell migration in the parthenogenetic pea aphid Acyrthosiphon pisum (Hemiptera: Aphidoidea).

In the parthenogenetic and viviparous pea aphid Acyrthosiphon pisum, germline specification depends on the germ plasm localized to the posterior region of the egg chamber before the formation of the blastoderm. During blastulation, germline segregation occurs at the egg posterior, and in early gastrulation germ cells are pushed inward by the invaginating germ band. Previous studies suggest that germ cells remain dorsal in the embryo in subsequent developmental stages. In fact, though, it is not known whether germ cells remain in place or migrate dynamically during katatrepsis and germ-band retraction. We cloned Apvasa, a pea aphid homologue of Drosophila vasa, and used it as a germline marker to monitor the migration of germ cells. Apvasa messenger RNA (mRNA) was first restricted to morphologically identifiable germ cells after blastoderm formation but that expression soon faded. Apvasa transcripts were again identified in germ cells from the stage when the endosymbiotic bacteria invaded the embryo, and after that, Apvasa mRNA was present in germ cells throughout all developmental stages. At the beginning of katatrepsis, germ cells were detected at the anteriormost region of the egg chamber as they were migrating into the body cavity. During the early period of germ-band retraction, germ cells were separated into several groups surrounded by a layer of somatic cells devoid of Apvasa staining, suggesting that the coalescence between migrating germ cells and the somatic gonadal mesoderm occurs between late katatrepsis and early germ-band retraction.

Testing and mapping non-stationarity in animal behavioral processes: a case study on an individual female bean weevil.

Statistical analysis based on two characteristics of a small-world network, and on Lempel-Ziv's measure of Kolmogorov-Chaitin's algorithmic complexity are first proposed to scan through an individual behavioral sequence for possible existence of non-stationarity. Due to fixed window width, these tests have drawbacks in mapping out regions of non-stationarity. A non-parametric approach based on sparse coding schemes is employed to segment the whole behavioral sequence into unequal length segments, thus resultant avoiding further efforts for grouping. Then attempts are made to entangle the resultant segmentation with other non-local behavioral patterns onto such sequence to ascertain that the non-stationarity corresponds to a sequence of different categories of underlying driving force. It is of potential importance that this segmentation, represented by a hierarchy of code sequences, provides a natural platform for detecting intrinsically coherent behavioral patterns based on continuously recorded data. Illustrations throughout the developments are made exclusively on data encoded from a nearly 4-h video-recording of a female bean weevil's behavior.

Characterization of resistance to Callosobruchus maculatus (Coleoptera: Bruchidae) in mungbean variety VC6089A and its resistance-associated protein VrD1.

Characteristics of resistance of VC6089A, a mungbean, Vigna radiata (L.) Wilczek, bred by using a wild Vigna species, V. sublobata (Roxburgh) Verdcourt (accession no. TC1966), and containing a novel protein, VrD1, were investigated against the cowpea weevil, Callosobruchus maculatus (F.). The seeds of VC6089A showed high level of resistance; > 96% of the bruchid eggs failed to develop into adults, whereas 85% of eggs laid on susceptible cultivar VC1973A became adults. Mortality of surviving bruchids raised for five generations on VC6089A remained higher than 96%; however, female adults maintained high fecundity and thus showed a positive population growth through these generations. We therefore cannot exclude the possibility that the beetles could develop resistance to the resistant mungbean VC6089A. The protein VrD1 purified from seeds of VC6089A showed marked toxicity to C. maculatus when beetles were reared on artificial seeds containing varying levels of VrD1. Thorough inhibition of development was observed when artificial seeds containing 0.2% (wt:wt) VrD1 was provided for insect feeding. Our findings demonstrated the insecticidal activity of VC6089A mungbean seeds and VrD1 protein against C. maculatus. These results may facilitate safer control against bruchid infestation.