Cross-generational effects of temperature on flight performance, and associated life-history traits in an insect.

Nongenetic parental effects may affect offspring phenotype, and in species with multiple generations per year, these effects may cause life-history traits to vary over the season. We investigated the effects of parental, offspring developmental and offspring adult temperatures on a suite of life-history traits in the globally invasive agricultural pest Grapholita molesta. A low parental temperature resulted in female offspring that developed faster at low developmental temperature compared with females whose parents were reared at high temperature. Furthermore, females whose parents were reared at low temperature were heavier and more fecund and had better flight abilities than females whose parents were reared at high temperature. In addition to these cross-generational effects, females developed at low temperature had similar flight abilities at low and high ambient temperatures, whereas females developed at high temperature had poorer flight abilities at low than at high ambient temperature. Our findings demonstrate a pronounced benefit of low parental temperature on offspring performance, as well as between- and within-generation effects of acclimation to low temperature. In cooler environments, the offspring generation is expected to develop more rapidly than the parental generation and to comprise more fecund and more dispersive females. By producing phenotypes that are adaptive to the conditions inducing them as well as heritable, cross-generational plasticity can influence the evolutionary trajectory of populations. The potential for short-term acclimation to low temperature may allow expanding insect populations to better cope with novel environments and may help to explain the spread and establishment of invasive species.

A myosin-Va tail fragment sequesters dynein light chains leading to apoptosis in melanoma cells.

Previous studies proposed that myosin-Va regulates apoptosis by sequestering pro-apoptotic Bmf to the actin cytoskeleton through dynein light chain-2 (DLC2). Adhesion loss or other cytoskeletal perturbations would unleash Bmf, allowing it to bind and inhibit pro-survival Bcl2 proteins. Here, we demonstrated that overexpression of a myosin-Va medial tail fragment (MVaf) harboring the binding site for DLC2 dramatically decreased melanoma cell viability. Morphological and molecular changes, including surface blebbing, mitochondrial outer membrane permeabilization, cytochrome-c and Smac release, as well as caspase-9/-3 activation and DNA fragmentation indicated that melanoma cells died of apoptosis. Immobilized MVaf interacted directly with DLCs, but complexed MVaf/DLCs did not interact with Bmf. Overexpression of DLC2 attenuated MVaf-induced apoptosis. Thus, we suggest that, MVaf induces apoptosis by sequestering DLC2 and DLC1, thereby unleashing the pair of sensitizer and activator BH3-only proteins Bmf and Bim. Murine embryonic fibroblasts (MEFs) lacking Bim and Bmf or Bax and Bak were less sensitive to apoptosis caused by MVaf expression than wild-type MEFs, strengthening the putative role of the intrinsic apoptotic pathway in this response. Finally, MVaf expression attenuated B16-F10 solid tumor growth in mice, suggesting that this peptide may be useful as an apoptosis-inducing tool for basic and translational studies.

Two distinct genomic regions, harbouring the period and fruitless genes, affect male courtship song in Drosophila montana.

Acoustic signals often have a significant role in pair formation and in species recognition. Determining the genetic basis of signal divergence will help to understand signal evolution by sexual selection and its role in the speciation process. An earlier study investigated quantitative trait locus for male courtship song carrier frequency (FRE) in Drosophila montana using microsatellite markers. We refined this study by adding to the linkage map markers for 10 candidate genes known to affect song production in Drosophila melanogaster. We also extended the analyses to additional song characters (pulse train length (PTL), pulse number (PN), interpulse interval, pulse length (PL) and cycle number (CN)). Our results indicate that loci in two different regions of the genome control distinct features of the courtship song. Pulse train traits (PTL and PN) mapped to the X chromosome, showing significant linkage with the period gene. In contrast, characters related to song pulse properties (PL, CN and carrier FRE) mapped to the region of chromosome 2 near the candidate gene fruitless, identifying these genes as suitable loci for further investigations. In previous studies, the pulse train traits have been found to vary substantially between Drosophila species, and so are potential species recognition signals, while the pulse traits may be more important in intra-specific mate choice.

Inbreeding in a natural population of the gregarious parasitoid wasp Cotesia glomerata.

Inbreeding occurs in numerous animal and plant species. In haplodiploid hymenopterans with the widespread single locus complementary sex determination, the frequency of diploid males, which are produced at the expense of females, is increased under inbreeding. Diploid males in species of bees, ants and wasps are typically either unviable or effectively sterile and thus impose a severe genetic load on populations. However, a recent study indicated that diploid males can be reproductive in the gregarious parasitoid wasp Cotesia glomerata, effectively reducing the diploid male load. To understand the role of inbreeding as a potential selective pressure towards the evolution of diploid male fertility, we genotyped specimens collected in the field at four locations using microsatellite markers to estimate the ratio of sibling matings under natural conditions. Results show that more than half of all matings involved siblings. We argue that the frequent occurrence of inbreeding has driven the evolution of diploid male fertility.

A microsatellite linkage map for Drosophila montana shows large variation in recombination rates, and a courtship song trait maps to an area of low recombination.

Current advances in genetic analysis are opening up our knowledge of the genetics of species differences, but challenges remain, particularly for out-bred natural populations. We constructed a microsatellite-based linkage map for two out-bred lines of Drosophila montana derived from divergent populations by taking advantage of the Drosophila virilis genome and available cytological maps of both species. Although the placement of markers was quite consistent with cytological predictions, the map indicated large heterogeneity in recombination rates along chromosomes. We also performed a quantitative trait locus (QTL) analysis on a courtship song character (carrier frequency), which differs between populations and is subject to strong sexual selection. Linkage mapping yielded two significant QTLs, which explained 3% and 14% of the variation in carrier frequency, respectively. Interestingly, as in other recent studies of traits which can influence speciation, the strongest QTL mapped to a genomic region partly covered by an inversion polymorphism.

The extent of variation in male song, wing and genital characters among allopatric Drosophila montana populations.

Drosophila montana, a species of the Drosophila virilis group, has distributed around the northern hemisphere. Phylogeographic analyses of two North American and one Eurasian population of this species offer a good background for the studies on the extent of variation in phenotypic traits between populations as well as for tracing the selection pressures likely to play a role in character divergence. In the present paper, we studied variation in the male courtship song, wing and genital characters among flies from Colorado (USA), Vancouver (Canada) and Oulanka (Finland) populations. The phenotypic divergence among populations did not coincide with the extent of their genetic divergence, suggesting that the characters are not evolving neutrally. Divergence in phenotypic traits was especially high between the Colorado and Vancouver populations, which are closer to each other in terms of their mtDNA genotypes than they are to the Oulanka population. The males of the Colorado population showed high divergence especially in song traits and the males of the Vancouver population in wing characters. Among the male song traits, two characters known to be under sexual selection and a trait important in species recognition differed clearly between populations, implying a history of directional and/or diversifying rather than balancing selection. The population divergence in wing characters is likely to have been enhanced by natural selection associated with environmental factors, whereas the male genitalia traits may have been influenced by sexual selection and/or sexual conflict.

Parasites make male pipefish careless.

Parasite-mediated sexual selection is expected to favour the avoidance of matings with infected individuals. However, the extent to which the costs and benefits of discriminating against parasitized mates trade off may depend upon numerous factors. I investigated the effects of sex and infection status on choosiness in sex-role reversed deep-snouted pipefish (Syngnathus typhle L.) that were either artificially infected with the trematode parasite Cryptocotyle sp. or sham-infected. Sham-infected males were significantly more likely to associate with a sham-infected female rather than with a Cryptocotyle-infected female. Infected males failed to discriminate against infected potential partners. Males were choosier the larger they were relative to the females available for choice. Females were not discriminatory, regardless of their infection status. Given an inverse relation between female fecundity and parasite load, choosy unparasitized males may gain enhanced reproductive success from their choice decisions. In contrast, more heavily infected wild-caught males gave birth to slightly fewer, but not smaller offspring than did uninfected or lightly infected males, suggesting only a low direct premium on choosy females. The detrimental effects of parasitism on male choosiness, and the lack of female discrimination against infected males likely have profound repercussions on the strength of sexual selection acting on the two sexes and on the dynamics of host-parasite interactions in this system.

A predator's dilemma: prey choice and parasite susceptibility in three-spined sticklebacks.

The acanthocephalan parasite Pomphorhynchus laevis is transmitted by a suitable intermediate host such as the amphipod Gammarus pulex to its definitive fish host. Parasite-induced alterations in both appearance and behaviour concur to render infected gammarids more vulnerable to predation, thus promoting parasite transmission. Experimental infection of laboratory bred full- and half-sib groups of three-spined sticklebacks (Gasterosteus aculeatus) provided evidence that the parasite imposes a survival cost proportional to the severity of infection on its final host. Variation among sibships in the susceptibility to infection was consistent. When given a choice, fish consumed significantly more infected than uninfected prey. Overall, more resistant fish did not prey upon infected gammarids more often than did relatively susceptible fish. Only fish with a relatively high physical condition properly adjusted prey selection to the extent of their parasite susceptibility, thus exploiting the enhanced profitability of infected prey.

Inbreeding and developmental stability in three-spined sticklebacks (Gasterosteus aculeatus L.).

Fluctuating asymmetry, small non-directional departures from perfect symmetry in bilateral traits, results from the inability of individuals to buffer development against genetic and environmental perturbations. Fluctuating asymmetry is a widely used measure of developmental stability, and developmental stability has been hypothesised to be inversely related to heterozygosity. We compared male three-spined sticklebacks (Gasterosteus aculeatus L.) that had been inbred for one generation to outbred control males with respect to the asymmetry of a set of bilateral morphometric traits. Inbred fish developed significantly more asymmetric pectoral fins than their outbred counterparts, whereas neither the magnitude of asymmetry for pelvic spines nor for gill covers significantly responded to the treatment. Our results conform to a pattern of heterogeneity amongst traits in their tendency to develop asymmetrically in response to stress.

MDMA (Ecstasy) precipitation of panic disorder.

The authors describe three patients whose panic disorder began during recreational use of MDMA (Ecstasy) and was subsequently complicated by agoraphobic avoidance that continued autonomously after cessation of the drug. Their panic disorder responded well to serotoninergic antidepressant drugs. Theoretical and practical implications are discussed.