Large‐sized insects show stronger seasonality than small‐sized ones: a case study of fruit‐feeding butterflies

Animal species have a restricted period during the year when conditions for development are optimal, and this is known as the temporal window. Duration of the temporal window can vary among species, although the causes of variation are still poorly understood. In the present study, examining butterflies, we assume that the temporal window duration is correlated with the seasonal period of flight (termed seasonality). To understand how species characteristics are correlated with this, we examine whether there is a relationship between body size and length of flight period of fruit‐feeding butterflies in forest fragments, and whether these two parameters have a phylogenetic signal. Using wing size as a measure of body size and the period of adult flight as a measure of seasonality, we found significant positive correlations between body size and seasonality among subfamilies but not within subfamilies. We also found a clear phylogenetic signal in size but not in seasonality. The results obtained suggest the existence of a trade‐off between insect size and seasonality, with size limiting flight period length. The relationship between body size and seasonality and the synchrony with their resources may be one factor explaining the vulnerability of large insects to forest fragmentation. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 820–827.     

Switch of voltage-gated K+ channel expression in the plasma membrane of chondrogenic cells affects cytosolic Ca2+-oscillations and cartilage formation

Background

Understanding the key elements of signaling of chondroprogenitor cells at the earliest steps of differentiation may substantially improve our opportunities for the application of mesenchymal stem cells in cartilage tissue engineering, which is a promising approach of regenerative therapy of joint diseases. Ion channels, membrane potential and Ca²⁺-signaling are important regulators of cell proliferation and differentiation. Our aim was to identify such plasma membrane ion channels involved in signaling during chondrogenesis, which may serve as specific molecular targets for influencing chondrogenic differentiation and ultimately cartilage formation.

Methodology/Principal Findings

Using patch-clamp, RT-PCR and Western-blot experiments, we found that chondrogenic cells in primary micromass cell cultures obtained from embryonic chicken limb buds expressed voltage-gated Na_V1.4, K_V1.1, K_V1.3 and K_V4.1 channels, although K_V1.3 was not detectable in the plasma membrane. Tetrodotoxin (TTX), the inhibitor of Na_V1.4 channels, had no effect on cartilage formation. In contrast, presence of 20 mM of the K⁺ channel blocker tetraethyl-ammonium (TEA) during the time-window of the final commitment of chondrogenic cells reduced K_V currents (to 27±3% of control), cell proliferation (thymidine incorporation: to 39±4.4% of control), expression of cartilage-specific genes and consequently, cartilage formation (metachromasia: to 18.0±6.4% of control) and also depolarized the membrane potential (by 9.3±2.1 mV). High-frequency Ca²⁺-oscillations were also suppressed by 10 mM TEA (confocal microscopy: frequency to 8.5±2.6% of the control). Peak expression of TEA-sensitive K_V1.1 in the plasma membrane overlapped with this period. Application of TEA to differentiated chondrocytes, mainly expressing the TEA-insensitive K_V4.1 did not affect cartilage formation.

Conclusions/Significance

These data demonstrate that the differentiation and proliferation of chondrogenic cells depend on rapid Ca²⁺-oscillations, which are modulated by K_V-driven membrane potential changes. K_V1.1 function seems especially critical during the final commitment period. We show the critical role of voltage-gated cation channels in the differentiation of non-excitable cells with potential therapeutic use.     

<Emphasis Type="Italic">tdd8</Emphasis>: a TerD domain-encoding gene involved in <Emphasis Type="Italic">Streptomyces coelicolor</Emphasis> differentiation

The Streptomyces coelicolor genome contains 17 TerD domain-encoding genes (tdd genes) of unknown function. The proteins encoded by these genes have been presumed to be involved in tellurite resistance on the basis of their homology with the protein TerD of Serratia marcescens. To elucidate the role of a Tdd protein (Tdd8), both a deletion mutant for the corresponding gene tdd8 (SCO2368) and a recombinant strain over-expressing tdd8 were produced in S. coelicolor M145. The deletion mutant (Δtdd8), like the wild strain, was not resistant to potassium tellurite. The deletion was not lethal but had a marked effect on differentiation. The deletion strain showed more rapid growth in liquid medium and produced long chains of short spores with a dense and non-spherical spore wall on agar plates. The strain over-expressing tdd8 had a growth delay in liquid medium and produced very few spores of irregular shapes and sizes on solid medium. The results of this study demonstrated that Tdd proteins might have a function other than tellurite resistance and this function seems to be of crucial importance for the proper development of the actinomycete S. coelicolor.     

Calcium-dioxolene complexes: rate constants of pyrocatechol oxidation in the presence of Ca2+

The effect of calcium ions on the rate of pyrocatechol autoxidation at pH 9.0 has been studied by mathematical modeling. The effect of Ca2+ on the oxygen absorption rate has been studied, and a kinetic model has been suggested, which takes different stages of interaction of pyrocatechol and its radical form with oxygen into account. It has been shown that the prooxidant action of Ca2+ is related to an abrupt increase (approximately by three orders of magnitude) in the rate constant of comproportionation (reaction of chain branching and formation of o-semiquinonates) and a marked decrease (by two orders of magnitude, from 1.4 10(7) to 0.6 10(5) M(-1)s(-1)) in the rate constant of disproportionation of o-semiquinones. The system can be used as a model for studying the prooxidant action of calcium ions.     

Evaluation of mosquito (Diptera: Culicidae) species richness using two sampling methods in the hydroelectric reservoir of Simplício, Minas Gerais, Brazil

We compared two types of light traps used for monitoring mosquito abundance in the hydroelectric reservoir of Simplício, Além Paraíba - Minas Gerais. Mosquitoes were captured bimonthly using automatic CDC and Shannon traps before the filling of the hydroelectric plant reservoir from December 2008 to December 2009. In total, 1474 specimens from 13 genera were captured. Among the captured specimens, several species known to be vectors of disease-causing agents for humans and/or animals were identified, including Anopheles aquasalis, Aedes albopictus, Coquillettidia venezuelensis, Haemagogus leucocelaenus, and Aedes scapularis. Sampling efficacy between the four capture sites was not found to be significantly different, irrespective of species captured or type of trap used. Poor correlation (r (x, y) = -0.0444) between the number of mosquito species and capture site was observed when not influenced by the type of trap used. Among the installation sites of the CDC and Shannon traps in the areas investigated, CDC traps fixed in livestock shelters obtained an overall higher abundance of species captured.     

Population differences in density and resource allocation of ornamental tail feathers in the barn swallow

Many organisms show well‐defined latitudinal clines in morphology, which appear to be caused by spatially varying natural selection, resulting in different optimal phenotypes in each location. Such spatial variability raises an interesting question, with different prospects for the action of sexual selection on characters that have a dual purpose, such as locomotion and sexual attraction. The outermost tail feathers of barn swallows (Hirundo rustica) represent one such character, and their evolution has been a classic model subject to intense debate. In the present study, we examined individuals from four European populations to analyze geographical variation in the length and mass of tail feathers in relation to body size and wing size. Tail feather length differed between sexes and populations, and such variation was a result of the effects of natural selection, acting through differences in body size and wing size, as well as the effects of sexual selection that favours longer tails. The extra enlargement of the tail promoted by sexual selection (i.e. beyond the natural selection optimum) could be achieved by increasing investment in ornaments, and by modifying feather structure to produce longer feathers of lower density. These two separate processes accounting for the production of longer and more costly tail feathers and less dense feathers, respectively, are consistent with the hypothesis that both Zahavian and Fisherian mechanisms may be involved in the evolution of the long tails of male barn swallows. We hypothesize that the strength of sexual selection increases with latitude because of the need for rapid mating as a result of the short duration of the breeding season at high latitudes. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 925–936.     

The origin of two cryptic species of African desert jerboas (Dipodidae: Jaculus)

The desert biota is exposed to extreme and variable conditions that shape its evolution and diversification processes. In this respect, the Jaculus jerboas have gained the attention of researchers as a result of their broad Saharan–Arabian distribution and their high and unexplained, morphological, anatomical, and molecular variation. In the present study, mitochondrial and nuclear genealogies where used to confirm monophyly of two cryptic species: Jaculus jaculus and Jaculus deserti. The reconstructed demography showed that the evolutionary histories of the species are markedly different and that the expansion into North‐West Africa by J. deserti was more recent than that of J. jaculus. The weak ecological separation between species and the signs of recent population growth and expansion of J. deserti suggest that its sympatric occurrence with J. jaculus is recent and that these species evolved in isolated populations, after diverging around the Pliocene–Pleistocene boundary. The importance of climate changes on the Sahara Desert biota is discussed in the context of genetic diversification. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 435–445.     

The response of life‐history traits to a new species in the community: a story of Drosophila parasitoids from the Rhône and Saône valleys

In the present study, we investigated the evolution of life‐history traits in the main species of a community, after the arrival of a new competitor. Two parasitoid species, Leptopilina heterotoma and Asobara tabida, are present throughout the Rhône and Saône valleys, whereas a third species, Leptopilina boulardi, is slowly extending its distribution northwards. In the presence of L. boulardi, competing parasitoids experience a higher mortality and lower host availability. Resources should thus be re‐allocated between traits according to these new factors. We compared life‐history traits of populations of L. heterotoma and A. tabida in areas with and without L. boulardi. As predicted by both Price's balanced mortality hypothesis and the theory of life‐history traits, we found that investment in reproduction is higher in southern populations for both native species, coupled with higher travelling abilities. However, only A. tabida paid their higher fecundity by a lower longevity. The absence of a clear trade‐off between these traits in L. heterotoma may be explained by a lower metabolic rate in southern populations. These results highlight the importance of the community change over climate in the evolution of life‐history traits in this parasitoid community. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, ?? , ??–??.