Competitive PCR reveals the complexity of postcopulatory sexual selection in Teleogryllus commodus

The outcome of mate choice depends on complex interactions between males and females both before and after copulation. Although the competition between males for access to mates and premating choice by females are relatively well understood, the nature of interactions between cryptic female choice and male sperm competition within the female reproductive tract is less clear. Understanding the complexity of postcopulatory sexual selection requires an understanding of how anatomy, physiology and behaviour mediate sperm transfer and storage within multiply mated females. Here we use a newly developed molecular technique to directly quantify mixed sperm stores in multiple mating females of the black field cricket, Teleogryllus commodus. In this species, female postcopulatory choice is easily observed and manipulated as females delay the removal of the spermatophore in favour of preferred males. Using twice‐mated females, we find that the proportion of sperm in the spermatheca attributed to the second male to mate with a female (S₂) increases linearly with the time of spermatophore attachment. Moreover, we show that the insemination success of a male increases with its attractiveness and decreases with the size of the female. The effect of male attractiveness in this context suggests a previously unknown episode of mate choice in this species that reinforces the sexual selection imposed by premating choice and conflicts with the outcome of postmating male harassment. Our results provide some of the clearest evidence yet for how sperm transfer and displacement in multiply mated females can lead directly to cryptic female choice, and that three distinct periods of sexual selection operate in black field crickets.     

A fossil Cenozoic monoplacophoran

Taviani, M., Sabelli, B. & Candini, F. 1990 04 15: A fossil Cenozoic monoplacophoran. Lethaia , Vol. 23 , pp. 213–216. Oslo. ISSN 0024–1164.
A few shells of Micropilina (Mollusca, Monoplacophora) have been found in middle Pleistocene (Sicilian) epibathyal clays at Archi (Reggio Calabria, southern Italy). The species appears conchologically indistinguishable from the Recent Atlantic taxon Micropilina minuta Warén, 1989. This finding represents the first record of a Cenozoic fossil monoplacophoran.     

Food selection and nutritional ecology of woodlice in Central Chile

Abstract.  Phenotypic flexibility in food selection and digestive efficiency in response is examined in relation to variations in food quality in a detritivorous species of Mediterranean ecosystems, the woodlouse Porcellio laevis Latreille (Isopoda: Oniscidea). It is hypothesized that diet selection should show a positive correlation between diet quality and digestive efficiency. The studied plants are isocaloric but exhibit significant differences in terms of nitrogen, carbon and fibre content. The observations appear to support the hypothesis that these isopods show compensatory feeding behaviour when feeding on poor diets. Contrary to expectation, a dietary effect on relative growth rate is not observed. It is concluded that behavioural skills associated with diet selection and physiological flexibility may allow P. laevis to satisfy and maintain equivalent nutritional levels during exposure to different diet qualities. In general, it appears that physiological flexibility plays an important role in determining nutritional balance in P. laevis , which can be of great benefit in the highly seasonal environment that it inhabits.     

Direct and correlated responses to artificial selection on flight activity in the oriental fruit moth (Lepidoptera: Tortricidae)

The ability of a sufficient number of individuals to disperse is crucial for long‐term survival of populations. However, dispersal is often energetically costly, and thus is expected to trade‐off against other life‐history traits. In insect pest species, the occurrence of individuals with high flight activity challenges management practices. We performed artificial selection on flight activity and measured correlated responses to selection in the oriental fruit moth, Grapholita (= Cydia) molesta, a widely distributed and expanding lepidopteran pest of fruit crops. Both sexes rapidly responded to the imposed regime of divergent selection, indicating an adaptive potential of flight activity in this species. Upward‐selected moths died sooner than downward‐selected ones, providing evidence for a cost of flight activity to adult survival, reputedly associated with enhanced metabolic rates. Oppositely‐selected females had similar total reproductive output, disproving a trade‐off between dispersal and reproduction, although females with higher flight activity laid their eggs sooner. The ratio of body weight to forewing surface (forewing loading) did not significantly differ between selected lines. The present study contributes to the understanding of dispersal evolution, and also provides new insights into life‐history theory as well as important baseline data for the improvement of pest management practices. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 879–889.     

Heterocyst Structure Alteration and O2-Mediated Inhibition of Dinitrogen Fixation by Trichlorfon in Anabaena PCC 7119

The involvement of a primary inhibition of dinitrogen fixationin the toxic effect of trichlorfon in cyanobacteria has beeninvestigated. Significant inhibition of nitrogenase activitycan be detected 3 h after the addition of insecticide to batchcultures of Anabaena PCC 7119. Recovery of nitrogenase activitystarts between 6–12 h after removal of the insecticide,suggesting a requirement for the induction of new heterocysts.Under anaerobic conditions the inhibitory effect of the insecticideis largely prevented. Biochemical analysis indicates that envelopeglycolipids exist in trichlorfon-treated cultures. However,ultrastructural examination shows heterocyst deterioration andthe failure of the inner glycolipid layer of the heterocystenvelope. Our data are consistent with the view that destabilizationof the heterocyst envelope is the first target of insecticidalaction. Inhibition of dinitrogen fixation and growth have alsobeen shown in the cyanobacteria Gloeothece PCC 6501, NostocUAM 205, and Chlorogloeopsis PCC 6912.     

The Comparative Ultrastructure of Sperm Flagella Central Sheath in Clitellata Reveals a New Autapomorphy of the Group

A comparative ultrastructural analysis of sperm tails of the hirudinean Hirudo medicinalis the branchiobdellid Branchiobdella pentodonta , and various microdrile oligochaetes ( Pananais frici, Paranais lioralis, Monopylephorus rubroniveus, Enchytraeus sp. and Bythonomus lemani has revealed a common modification of the primitive axonemal structure. A prominent central sheath embeds the two central tubules of the flagellum for a tract of variable length in the different species. The structure of radial links and link heads appears also modified: link heads, which are three for each radial link, are disposed in rows. Adjacent link heads arc also transversely connected to each other. The absence of these peculiar modifications in megadriles is interpreted as a secondary phenomenon. Since no homologous modification of the sperm tails is present in other spermatozoa, the prominent central sheath and radial links here described in three of the four taxa belonging to the Clitellata is considered a new autapomorphy for the whole group.     

Males do not prolong copulation in response to competitor males in the polyandrous fly Drosophila bifasciata

Males in many taxa exhibit behavioural plasticity in response to the perceived threat of sperm competition. Drosophila males prolong mating in response to the presence of competitor males before copulation. The benefits of this behaviour to males are evident in Drosophila melanogaster. However, the adaptive nature of the trait is challenged by the observation that it is present in four other Drosophila species, two of which are largely monandrous, raising the possibility that this plasticity is not evolutionarily labile. In the present study, behavioural plasticity and the mating system in Drosophila bifasciata Pominini (Diptera, Drosophilidae) are analyzed. By contrast to other Drosophila species, male D. bifasciata do not exhibit plasticity in copulation duration when competitor males are present before mating. Thus, plasticity in mating duration is not fixed in the genus Drosophila. The mating system of D. bifasciata is also examined. The species is polyandrous but, uncommonly for the genus Drosophila, males transfer a mating plug composed of sperm to females, which forms very shortly after copulation and fills the female uterus. The absence of plasticity observed in D. bifasciata may arise from the sperm plug.