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Wolbachiaare the most widespread endosymbiotic bacteria in animals. In many arthropod host species, they manipulate reproduction via several mechanisms that favor their maternal transmission to offspring. Among them, cytoplasmic incompatibility (CI) promotes the spread of the symbiont by specifically decreasing the fertility of crosses involving infected males and uninfected females, via embryo mortality. These differences in reproductive efficiency may select for the avoidance of incompatible mating, a process called reinforcement, and thus contribute to population divergence. In the terrestrial isopod Porcellio dilatatus, the Wolbachia wPet strain infecting the subspecies P. d. petitiinduces unidirectional CI with uninfected individuals of the subspecies P. d. dilatatus. To study the consequences of CI on P. d. dilatatusand P. d. petitihybridization, mitochondrial haplotypes and Wolbachiainfection dynamics, we used population cages seeded with different proportions of the 2 subspecies in which we monitored these genetic parameters 5 and 7 years after the initial setup. Analysis of microsatellite markers allowed evaluating the degree of hybridization between individuals of the 2 subspecies. These markers revealed an increase in P. d. dilatatusnuclear genetic signature in all mixed cages, reflecting an asymmetry in hybridization. Hybridization led to the introgressive acquisition of Wolbachiaand mitochondrial haplotype from P. d. petitiinto nuclear genomes dominated by alleles of P. d. dilatatus. We discuss these results with regards to Wolbachiaeffects on their host (CI and putative fitness cost), and to a possible reinforcement that may have led to assortative mating, as possible factors contributing to the observed results.

In the terrestrial crustacean Armadillidium vulgare, the prolonged presence of males along with females is known to boost female reproductive physiology, and the so-called 'male-effect' was best characterized by a significant shortening of the pre-parturial intermoult (PPI) during which oocyte maturation spontaneously takes place. Continuous presence of a male over that period can speed up vitellogenesis and the moulting cycle, so to reduce female PPI by 15-20 days (shortening of 30-40%, in comparison to females reared with other females or in isolation, respectively). In the last investigation on the subject, we revealed that sexual interactions may start much sooner than previously thought in this species, and suggested that the observed 'male-effect' may likely result from early mating stimulations. Here we tested the specific effect of controlled mating interactions (one or two mating events at different times) on female PPI. We revealed that male presence for the time (about 2 h) that allowed a single mating to occur was enough to reduce the female intermoult by about 10 days (shortening of 19%, in comparison to females reared in similar conditions but in the absence of a mating interaction). Moreover, results indicate that the earlier and longer the copulations, the stronger the 'male-effect'. Altogether, the data support the conclusion that A. vulgare females are adjust their reproductive physiology according to the presence/absence and the intensity of male mating stimuli. We place the findings in a broader ecological context, revise the so far prevailing view on the 'male-effect', and stress its possible significance in relation to the occurrence of feminising bacteria in this and other terrestrial isopod species.

Wolbachia is a genus of maternally inherited, intracellular, alpha-Proteobacteria which are widespread among arthropods and cause various reproductive alterations such as cytoplasmic incompatibility and feminization. Wolbachia strains in arthropods have been phylogenetically divided into two supergroups, A and B. Here, we determined the phylogenetic relationships among Wolbachia strains harbored by insects and isopod crustaceans by using groE operon sequences, which encode highly conserved bacterial heat shock proteins. This study includes the first survey for Wolbachia in isopods from a Southeast Asian country, i.e., Thailand. Two isopod species from different parts of Thailand were found to be infected by Wolbachia. Their groE sequences were also included in the phylogenetic analysis. Our results showed clearly that 19 strains from tropical insects, 11 strains from French isopods, and two strains from Thai isopods were in the B supergroup, and 15 strains from tropical insects were in the A supergroup. This is the first report of phylogenetic analysis of a large data set comprising Wolbachia groE sequences from both insects and isopod crustaceans. [ABSTRACT FROM AUTHOR]

In the terrestrial Crustacean Armadillidium vulgare, the onset of female reproduction can be sped up by a male-induced stimulation. This male-effect is mainly characterized by a shortening of the vitellogenesis period, which occurs during the preparturial intermoult. The determinism of this phenomenon, for the first time reported by Jassem in 1982, was investigated here by both experimental and ethological approaches. It was shown that a male deprived of its copulatory organs is significantly less stimulating than an integrated one. On the other hand, a paired female with obturated genital apertures is significantly less stimulated. According to the literature, mating takes place only when vitellogenesis is nearly over and therefore cannot be related to the male-effect. Nevertheless, the ethological approach has revealed that females are early attractive for males, and that mating postures can be observed during the whole preparturial intermoult. In fact, insemination can happen as early as the initiation of the secondary vitellogenesis. Before this stage, short mating postures are still observed but no sperm was found in the female genital ducts (pseudocopulation). However, spermatozoa and other seminal substances are not implicated in this phenomenon since a male unable to ejaculate is as efficient as a normal one. Therefore, it is strongly assumed that the male-effect results from mating postures during which male copulatory organs act on mechanoreceptors located in the female genital apparatus.

AbstractThis review illustrates the role of preimaginal experiences in four main aspects of insect life: feeding, habitat choice, host selection, and social relationships. After an illustration of the two former aspects with examples taken from various species, special attention is paid to the two latter aspects. First, an experiment is described, which demonstrates the existence of preimaginal induction involved in host selection by the solitary parasitoid wasp Dinarmus basalis(Hymenoptera: Pteromalidae). Then, a review of preimaginal induction in ants' behaviour is presented; orientation of social behaviour, particularly altruism, is mainly determined by preimaginal imprinting. All the examples developed in this review clearly show that insects can no longer be considered as strictly, rigidly “pre-programmed” beings. Their complex behavioural development and plasticity is clearly documented.