Do Golden Egg Bugs (Phyllomorpha laciniata: Heteroptera, Coreidae) Require Conspecifics for Oviposition?

Golden egg bug (Phyllomorpha laciniata) females lay eggs on the bodies of conspecifics of both sexes. We investigated to what extent reproduction depended on the availability of conspecifics as oviposition substrate and the acceptability of the host plant as an alternative oviposition substrate in the absence of conspecifics. Mated females were placed in experimental enclosures each containing a sprig of fresh host plant. Each experimental female was subjected to one of three treatments: isolated from conspecifics (solitary), paired with another female, or paired with a male. Solitary females laid a few eggs on the host plant but then stopped laying eggs, and solitary females laid significantly fewer eggs than those enclosed with another female or a male. Females enclosed with a male laid no more eggs than those enclosed with a female. When two previously isolated females were later enclosed together, they soon renewed oviposition. Females in nature contained significantly more oviducal eggs than did females that were enclosed with other females for a short period. Thus the availability of suitable conspecifics as oviposition substrate stimulates the deposition of mature eggs, and reproduction depends on the presence of conspecifics of either sex as oviposition substrate.     

Is male back space limiting? An investigation into the reproductive demography of the giant water bug,Abedus indentatus (Heteroptera: Belostomatidae)

Because male giant water bugs in the subfamily Belostomatinae provide parental care by brooding eggs on their back, an accurate assessment can be made of both the actual and potential reproductive capacity of males. Two operational sex-ratio (OSR) indices were developed and empirically measured for a population of giant water bug, Abedus indentatus,in California. One index was based on reproductive rates measured in the laboratory; the other index was based on reproductive resources observed in the field. Both OSR indices suggest that the operational sex ratio fluctuates between maleskewed ratios in the summer and femaleskewed ratios in the winter. This pattern appears to be the consequence of two factors. First, the adult sex ratio is significantly female biased. Second, although males can outreproduce females at high ambient temperatures, the reverse is true at low temperatures. Possible reasons for the female-skewed adult sex ratio are examined, including differential recruitment, differential mortality, and sampling bias.     

Breeding strategy of the male brooding water bug,Diplonychus major esaki (Heteroptera: Belostomatidae): Is male back space limiting?

Breeding ecology of brooding males of the water bugDiplonychus major was investigated in the field and laboratory. During one breeding season an individual male may consecutively brood 3 or 4 egg-masses on his back until hatching. The 1st and the 2nd egg-masses brooded took about 1 month to hatch. Eggs generally hatched. Most of them hatched in synchronously, and males received a new brood of eggs within a few days. Therefore, total male back spaces in the pond, here regarded as the reproductive resource for females, showed considerable fluctuation. When the resource was in low availability, male back space was estimated to be strongly limiting, and in order to ensure successful oviposition in a competitive environment, females are expected to lay eggs aggressively. In laboratory studies, intensive competition to lay eggs was observed, and polygamy also occurred. Males always attempted to copulate before receiving eggs. However, some females sometimes thrust themselves into mating pairs and laid eggs without copulation before the copulating female laid her eggs. Repeated copulation was likely unnecessary for females. Furthermore, since individual male back space is always limiting for each individual male it is evolutionarily advantageous for a male to receive only eggs fertilized by himself. Oviposition occurring without additional copulations, as observed in this study, is new evidence supporting the paternity assurance hypothesis.     

Is Mate Choice in Humans MHC-Dependent?

In several species, including rodents and fish, it has been shown that the Major Histocompatibility Complex (MHC) influences mating preferences and, in some cases, that this may be mediated by preferences based on body odour. In humans, the picture has been less clear. Several studies have reported a tendency for humans to prefer MHC-dissimilar mates, a sexual selection that would favour the production of MHC-heterozygous offspring, who would be more resistant to pathogens, but these results are unsupported by other studies. Here, we report analyses of genome-wide genotype data (from the HapMap II dataset) and HLA types in African and European American couples to test whether humans tend to choose MHC-dissimilar mates. In order to distinguish MHC-specific effects from genome-wide effects, the pattern of similarity in the MHC region is compared to the pattern in the rest of the genome. African spouses show no significant pattern of similarity/dissimilarity across the MHC region (relatedness coefficient, R = 0.015, p = 0.23), whereas across the genome, they are more similar than random pairs of individuals (genome-wide R = 0.00185, p<10(-3)). We discuss several explanations for these observations, including demographic effects. On the other hand, the sampled European American couples are significantly more MHC-dissimilar than random pairs of individuals (R = -0.043, p = 0.015), and this pattern of dissimilarity is extreme when compared to the rest of the genome, both globally (genome-wide R = -0.00016, p = 0.739) and when broken into windows having the same length and recombination rate as the MHC (only nine genomic regions exhibit a higher level of genetic dissimilarity between spouses than does the MHC). This study thus supports the hypothesis that the MHC influences mate choice in some human populations.     

Meiotic studies in Acanonicus hahni (Stål) (Coreidae,Heteroptera) I. Behaviour of univalents in desynaptic individuals

Male meiosis was studied in a population of Acanonicus hahni (Stål), and nine of the sixteen individuals analyzed showed desynapsis. The frequency of univalents varied from one to seven percent in eight of them, while in the ninth the percentage of cells with univalents was higher (12%). The univalents auto-orientate at metaphase I in the center of the ring formed by autosomal bivalents and divide equationally at anaphase I; at metaphase II they show touch-and-go pairing, and lie in the center of the ring of autosomes.A desynaptic origin of the univalents is proposed, and the arrangement of the chromosomes in the first and second metaphase plate in the normal and desynaptic individuals is compared and discussed. The meiotic characteristics of these desynaptic individuals are also compared with those described in other insects with holocentric and monocentric chromosomes. It is suggested that any achiasmatic chromosome, whether a univalent, m or sex chromosome, will induce the formation of a ring and with some or all of them lying in its centre.     

Meiotic studies in Acanonicus hahni (Stål) (Coreidae,Heteroptera) II. Male chromosome behaviour in a spontaneous inversion mutant

The meiotic behaviour of a spontaneous chromosome rearrangement in a natural population of Acanonicus hahni (Stål)(Coreidae, Heteroptera) is described, which is concluded to be a heterozygous inversion. In this holokinetic system the principal consequences of a single cross-over located within the inversion loop are: (a) the appearance of a double bridge at anaphase I, instead of the single dicentric bridge and acentric fragment of monocentric systems; (b) the persistence of the double bridge at telophase I which inhibits cytokinesis; (c) the occurrence of double cells at metaphase II with the restored bivalent between the two nuclei; (d) the presence of single bridges at anaphase II; and (e) the production of a high percentage of abnormal spermatids. A possible explanation of all these phenomena is given and discussed.Fellow of the Argent. Res. Couneil, CONICET     

Is period gene causally involved in the photoperiodic regulation of reproductive diapause in the linden bug, Pyrrhocoris apterus?

Earlier experiments demonstrated a strong up-regulation of per mRNA in wild-type (Wt) females of Pyrrhocoris apterus reared under diapause-inducing short days, while per mRNA levels were low in females of two non-diapause mutant strains (Nd), irrespective of photoperiod. In the present study, different sequences of per DNA in two strains of geographically different origin enabled us to analyse genetic linkage between the per gene and the Nd phenotype. Crosses between Wt females originating from C. Budejovice (Czech Republic) and Nd males originating from Lyon (France) resulted in F(2) progeny where 411 females entered diapause under short days and 120 females were reproducing. Thus, the segregation was very close to the 3:1 ratio in favour of diapause females, suggesting that the Nd trait behaves as a single autosomal recessive. Analysis of DNA in 20 females of the F(2) progeny revealed that their phenotype was not linked to the per genotype. We conclude that the per gene is not primarily responsible for the block to diapause photoresponsiveness in Nd mutants and its role, if any, is downstream from other gene(s) controlling diapause. This is the first attempt at genetic linkage analysis between a bona fide circadian clock gene and photoperiodism in a "non-drosophilid" species.     

Good bug, bad bug: in the case of enteric inflammatory disease does the epithelium decide?

Many studies demonstrate that intestinal inflammation is either initiated or exaggerated by a component of the normal microbiota, most likely commensal bacteria or products derived from these organisms. We review the nature of human inflammatory bowel disease, the evidence for the involvement of the normal bacterial flora in these disorders and the relevance of maintaining the integrity of the epithelial barrier. Moreover, we, and others, have shown abnormal mitochondria structure in tissue resections from patients with inflammatory bowel disease and tissues from rodents that demonstrated psychological stress-induced increases in epithelial permeability. Thus, we also consider the possibility that a defect in epithelial mitochondrial function would predispose an individual to respond to their commensal bacteria flora--no longer considering them as a beneficial passive inhabitant, but rather perceiving them as a threatening and pro-inflammatory stimulus. In support of this postulate, we discuss our recent findings from an in vitro model showing that the human colon-derived T84 cell line exposed to the metabolic stressor, dinitrophenol, and the non-pathogenic, non-invasive, Escherichia coli (strain HB101) display a loss of barrier function, increased signal transduction and increased production of the chemokine, interleukin 8.     

Sex chromosome pre-reduction in male meiosis of Lethocerus patruelis (St?l, 1854) (Heteroptera,Belostomatidae) with some notes on the distribution?of?the species

The karyotype and meiosis in males of giant water bug Lethocerus patruelis (Heteroptera: Belostomatidae: Lethocerinae) were studied using standard and fluorochrome (CMA₃ and DAPI) staining of chromosomes. The species was shown to have 2n = 22A + 2m + XY where 2m are a pair of microchromosomes. NORs are located in X and Y chromosomes. Within Belostomatidae, Lethocerus patruelis is unique in showing sex chromosome pre-reduction in male meiosis, with the sex chromosomes undergoing reductional division at anaphase I and equational division at anaphase II. Cytogenetic data on the family Belostomatidae are summarized and compared. In addition, the structure of the male internal reproductive organs of Lethocerus patruelis is presented, the contemporary distribution of Lethocerus patruelis in Bulgaria and in the northern Aegean Islands is discussed, and the first information about the breeding and nymphal development of this species in Bulgaria is provided.     

The Nabidae (Insecta,Hemiptera, Heteroptera) of?Argentina

In Argentina, five genera and 14 species are recorded in the subfamilies Prostemmatinae and Nabinae: Hoplistoscelis sordidus Reuter, Lasiomerus constrictus Champion, Metatropiphorus alvarengai Reuter, Nabis argentinus Meyer-Dür, Nabis (Tropiconabis) capsiformis Germar, Nabis faminei Stål, Nabis paranensis Harris, Nabis punctipennis Blanchard, Nabis roripes Stål, Nabis setricus Harris, Nabis tandilensis Berg, Pagasa (Pagasa) costalis Reuter, Pagasa (Lampropagasa) fuscipennis Reuter and Pagasa (Pagasa) signatipennis Reuter.     

Mammalian development: Axes in the egg?

An enduring but erroneous belief is that the post-fertilisation period is irrelevant for axis development in mammals. Two recent studies further undermine this belief. Is information for axial developmental encoded in the egg cortex?     

Opposites attract? Mate choice for parasite evasion and the evolutionary stability of sex

If sex is naturally selected as a way to combat parasites, then sexual selection for disease resistance might increase the overall strength of selection for outcrossing. In the present study, we compared how two forms of mate choice affect the evolutionary stability of outcrossing in simultaneous hermaphrodites. In the first form, individuals preferred to mate with uninfected individuals (condition-dependent choice). In the second form, individuals preferred to mate with individuals that shared the least number of alleles in common at disease-resistance loci. The comparisons were made using individual-based computer simulations in which we varied parasite virulence, parasite transmission rate, and the rate of deleterious mutation at 500 viability loci. We found that alleles controlling both forms of mate choice spread when rare, but their effects on the evolutionary stability of sex were markedly different. Surprisingly, condition-dependent choice for uninfected mates had little effect on the evolutionary stability of sexual reproduction. In contrast, active choice for mates having different alleles at disease-resistance loci had a pronounced positive effect, especially under low rates of deleterious mutation. Based on these results, we suggest that mate choice that increases the genetic diversity of offspring can spread when rare in a randomly mating population, and, as an indirect consequence, increase the range of conditions under which sexual reproduction is evolutionarily stable.     

Is juvenile hormone involved in the maternal regulation of egg size and progeny characteristics in the desert locust?

The role of juvenile hormone (JH) in the maternal regulation of progeny characteristics was examined in the desert locust, Schistocerca gregaria. Female adults of this species are known to produce smaller but more eggs when reared in isolation than do those reared in a group. Eggs laid by isolated females develop green hatchlings typical of solitarious forms, whereas those laid by the latter produce black hatchlings typical of gregarious forms. Topical application of a juvenile hormone analog (JHA), fenoxycarb, or implantation of corpora allata (CA) taken from the migratory locust, Locusta migratoria, caused crowded S. gregaria females to deposit smaller eggs, but did not have a significant effect on the number of eggs per egg pod except at high doses of JHA. The production of smaller eggs by treated and untreated crowded females was closely associated with earlier deposition of the egg pods and shorter oviposition intervals. However, neither JHA application nor CA implantation influenced the progeny characteristics in actively reproducing aged females under crowded conditions, while untreated control females started producing smaller and more eggs upon transfer to isolated conditions. These results may suggest that JH is not directly involved in the maternal regulation of phase-dependent progeny characteristics.     

Mate choice in field crickets: can females acoustically detect male body size?

Females can potentially choose high-quality males by evaluating male secondary sexual traits such as acoustic signals. In field crickets (Orthoptera: Gryllidae), body size is thought to indicate male quality. Song carrier frequency (FQ) has been suggested to indicate male body size because the areas of the wing that control FQ (harp) scale with body size. However, no direct evidence showing that males can advertise their size via FQ exists for grylline crickets. Firstly, we show the lack of evidence indicating a clear relationship between FQ and body size for grylline crickets by conducting a literature review. We then calculate the three-way relationship between body size, harp size and FQ and show no relationship between FQ and body size for Gryllus bimaculatus. Eight other commonly measured song parameters also failed to indicate body size. Individual female preference functions for FQ are calculated and we demonstrate that females cannot select large males on the basis of FQ. Furthermore, we demonstrate that variation in male FQ falls within the range of female preference at the population level. Females probably cannot evaluate male body size based on the temporal and spectral properties of male calling song and alternative avenues of study are suggested.