The short-term and long-term effects of parental age in the bean weevil (Acanthoscelides obtectus)

We examined the influence of parental age on life history traits of their offspring in the lines of bean weevil that have evolved different rates of senescence. Measurements included preadult traits (egg size, embryonic developmental time, total preadult developmental time, preadult viability) and adult traits (body weight, total realized fecundity of females, first day of egg laying, early fecundity, late fecundity and longevity). The negative parental age effects were observed for all traits except for the early and total realized fecundity. We did not detect statistically significant line×parental age interactions for either preadult- or adult-survival, so offspring survival did not change with parental age after selection for early vs. late reproduction. It seems that selection acting on the quality of offspring produced by parents of different ages has not been responsible for the evolution of senescence in bean weevil. This revised version was published online in August 2006 with corrections to the Cover Date.     

Seasonal dynamics of foliar antioxidative enzymes and total anthocyanins in natural populations of Iris pumila L.

Aims Plants in their natural habitats frequently cope with a multitude of abiotic stresses, such as high light intensity, extreme temperatures and water deficit, which often co-occur during periods of drought, especially in semi-arid and arid regions. Exposure of plants to stressful environmental conditions usually induce overproduction of reactive oxygen species (ROS) that, as highly toxic derivatives of O 2, can assault all cell macromolecules, leading to the disruption of cellular homeostasis and, consequently, the uncoupling of major metabolic processes, the photosynthesis and photorespiration. In order to minimize ROS-mediated cellular damage, plants have evolved highly efficient antioxidative defense systems that include both enzymatic and non-enzymatic components. Since abiotic stress can also operate as a strong evolutionary force that shapes adaptations in natural plant populations, the aim of this study was to examine the seasonal variation patterns of two distinct antioxidative systems, ROS-scavenging enzymes and anthocyanin pigments, in the leaf tissue of a steppe plant, Iris pumila, as expressed under contrasting light conditions that the species regularly experiences in the wild.Methods We selected two natural populations of I.pumila inhabiting the alternative radiation environments in the Deliblato Sands, a sun-exposed dune site and a woodland understory. The specific activity of three antioxidative enzymes, superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) and the content of total anthocyanins were examined in leaves of I.pumila plants collected from each of the 31 Iris clones (17 in the exposed population and 14 in the shaded population) once during each of the three seasons, spring, summer and autumn in 2004. Specifically, a fully expanded leaf was cut from each clonal plant between 15:00 and 16:00 h, immediately frozen in liquid nitrogen and stored at ?70°C until preparation.Important findings Generally, all three antioxidative enzymes were up-regulated in summer-harvested leaves compared to their spring or autumn counterparts, as was observed for the concentration of foliar anthocyanins, indicating that strengthening of antioxidant systems was the key mechanism for long-term acclimatization of I.pumila plants to stressful environmental conditions within their natural ecological niches. When plants from contrasting radiation environments were compared, SOD and CAT activities appeared to be greater in shade-exposed than in sun-exposed leaves. Conversely, POD activity and the content of foliar anthocyanins were notably higher in foliage experiencing full sunlight relative to those developed under vegetation canopy, suggesting the synergistic function of these two molecules in protecting leaf cells against photoinhibitory and photooxidative effects of strong light.     

The effects of selection for early and late reproduction on metabolite pools in Acanthoscelides obtectus Say

Abstract The present study was aimed at revealing the responses of metabolite pools to selection for alternative reproductive schedules in the seed beetle, Acanthoscelides obtectus Say (Coleoptera: Chrysomelidae: Bruchinae). The levels of metabolites (free sugars, glycogen, lipids, soluble and hydrophobic proteins) that were determined in virgin females and males at three ages from adult eclosion onwards were compared among the base population (B) and two derived lines that were selected for either early (Y) or late (O) reproduction. The results showed differences in the accumulation of metabolites during pre‐adult development, as well as in the pattern of their changes during adult ageing. Generally, in comparison to the B population, the short‐lived beetles from the Y line showed increased protein content and reduced carbohydrate and lipid content, whereas the opposite was true for the long‐lived beetles from the O line. Females from the O line exhibited slower utilization of energy reserves and a slower increase in protein contents than females from the Y line. Females contained higher levels of free sugars, glycogen and hydrophobic proteins and lower levels of lipids and soluble proteins than males, although the sexual dimorphism was not evenly expressed among lines. Age‐specific changes in metabolite contents were slower in females than males. Our findings suggest that trade‐offs among capital resources are a physiological basis of early/late fitness trade‐offs and point to a conservation of resources that can be used for somatic maintenance.     

Quicolor: A novel system for rapid antibacterial susceptibility testing

Early determination of antibacterial susceptibility increases the success of therapy, decreases unnecessary use of antibacterials and side effects and lowers the overall healthcare costs. We have evaluated a rapid antibacterial susceptibility test, Quicolor (Salubris Inc., Massachusetts, USA), which is based on a rapid culture medium that indicates growth early by changing its colour. Quicolor proved to be a reliable rapid test for determining antibacterial susceptibility, having an overall agreement of 97.6% with the conventional CLSI sisk diffusion susceptibility test results. Between two methods overall agreement was 96.7% for Enterobacteriaceae, 96.8% for staphylococci and 94.2% for non-fermentative bacteria. There was only 0.6% major discrepancy in Enterobacteriaceae, 1.7% in staphylococci and 0.9% in non-fermentative bacteria. Since the test provides results in 3.5–6 h, it can provide the means to choose the right treatment regimen the same day the infectious agent is isolated.     

The cagA status of Helicobacter pylori isolates from dyspeptic children in Turkey

There are inconsistent reports regarding cytotoxin-associated gene A (cagA) status of Helicobacter pylori isolates and the severity of the mucosal lesions in children. The aim of this study was to determine the prevalence of cagA(+) strains and to evaluate its correlation with clinic and endoscopic findings. We examined 45 H. pylori strains that were grown on brain-heart infusion agar supplemented with 7% horse blood. Following 72 h of incubation colonies were harvested and bacterial DNA was extracted. Polymerase chain reaction primers F1 and B1 were used to amplify a 348-bp internal fragment of cagA. The prevalence of cagA in Turkish pediatric patients was 55.6%. No association was found between cagA status and the severity of gastro-duodenal lesions.     

Role of apoptosis and mitosis during human eye development

The spatial and temporal distribution as well as ultrastructural and biochemical characteristics of apoptotic and mitotic cells during human eye development were investigated in 14 human conceptuses of 4-9 postovulatory weeks, using electron and light microscopy. In the 5th developmental week, apoptotic and mitotic cells were found in the neuroepithelium of the optic cup and stalk, being the most numerous at the borderline between the two layers of the optic cup, and at the place of transition of the optic cup into stalk. They were also found at the region of detachment of the lens pit from the surface ectoderm. In the later developmental stages (the 6th-the 9th week), apoptotic and mitotic cells were observed in the neural retina and the anterior lens epithelium. Throughout all stages examined, mitotic cells were found exclusively adjacent to the lumen either of the intraretinal space or the optic stalk ventricle, or were restricted to the superficial epithelial layer of the lens primordium. Unlike mitotic cells, apoptotic cells occurred throughout the whole width both of the neuroepithelium and the surface epithelium. Ultrastructurally, apoptotic cells were characterised by round- or crescent-shaped condensations of chromatin near the nuclear membrane, while in the more advanced stages of apoptosis by apoptotic bodies. The distribution of caspase-3-positive cells coincided with the location of apoptotic cells described by morphological techniques indicating that the caspase-3-dependent apoptotic pathway operates during the all stages of human eye development. The location of cells positive for anti-apoptotic bcl-2 protein was in accordance with the regions of eye with high mitotic activity, confirming the role of bcl-2 in protecting cells from apoptosis. In the earliest stage of eye development, apoptosis and mitosis might be associated with the sculpturing of the walls of optic cup and stalk, while high mitotic activity along the intraretinal space and optic stalk ventricle indicates its role in the gradual luminal closure. These processes also participate in the detachment of the lens pit epithelium from the surface ectoderm as well as in further closure of the lens vesicle. Later on, both processes seem to be involved in the neural retina differentiation, lens morphogenesis and secondary lens fibre differentiation.     

Selection for developmental time in bean weevil (Acanthoscelides obtectus): correlated responses for other life history traits and genetic architecture of line differentiation

In this article we investigate the direct and correlated responses to selection for developmental time in order to discern differences between lines in several preadult and adult life history traits of Acanthoscelides obtectus (Coleoptera, Bruchidae). Selection for fast development was about five times as effective as selection for slow development, as judged by realized heritabilities. The correlated responses on the following life‐history traits were studied: egg size, hatching success, embryonic developmental time, egg‐to‐adult viability, body weight, first day of egg laying, total fecundity, and longevity. Analyses of the terminal generation of selection showed that all life history traits examined, except for hatching success, were affected by selection. The findings suggest that body weight, total fecundity, and longevity traded off to preadult developmental time. Unlike the adult traits, none of the preadult traits showed negative correlations with developmental time. We also present data concerning the underlying genetic basis that produces changes in preadult developmental time, body weight, and egg‐to‐adult viability in the lines selected for fast and slow preadult developmental time. Additive‐dominance genetic architecture for both preadult developmental time and body weight was found. In addition, it appears that the responses to selection for preadult developmental time involved between 10 and 28 loci, which were correlated with at least one to four genes for body weight. Epistasis makes a significant contribution to genetic divergence between fast and slow selected lines only with respect to preadult viability. The observed levels of dominance and epistasis underscore the important role of nonadditive genetic effects to the adaptive diversifications of bean weevil populations.     

Experimentally induced host‐shift changes life‐history strategy in a seed beetle

Expansion of the host range in phytophagous insects depends on their ability to form an association with a novel plant through changes in host‐related traits. Phenotypic plasticity has important effects on initial survival of individuals faced with a new plant, as well as on the courses of evolutionary change during long‐term adaptation to novel conditions. Using experimental populations of the seed beetle that evolved on ancestral (common bean) or novel (chickpea) host and applying reciprocal transplant at both larval and adult stage on the alternative host plant, we studied the relationship between the initial (plastic) phases of host‐shift and the subsequent stages of evolutionary divergence in life‐history strategies between populations exposed to the host‐shift process. After 48 generations, populations became well adapted to chickpea by evolving the life‐history strategy with prolonged larval development, increased body mass, earlier reproduction, shorter lifespan and decreased plasticity of all traits compared with ancestral conditions. In chickpea‐adapted beetles, negative fitness consequences of low plasticity of pre‐adult development (revealed as severe decrease in egg‐to‐adult viability on beans) exhibited mismatch with positive effects of low plasticity (i.e. low host sensitivity) in oviposition and fecundity. In contrast, beetles adapted to the ancestral host showed high plasticity of developmental process, which enabled high larval survival on chickpea, whereas elevated plasticity in adult behaviour (i.e. high host sensitivity) resulted in delayed reproduction and decreased fecundity on chickpea. The analysis of population growth parameters revealed significant fluctuation during successive phases of the host‐shift process in A. obtectus.     

LABORATORY EVOLUTION OF LIFE-HISTORY TRAITS IN THE BEAN WEEVIL (ACANTHOSCELIDES OBTECTUS): THE EFFECTS OF DENSITY-DEPENDENT AND AGE-SPECIFIC SELECTION

Four types of laboratory populations of the bean weevil (Acanthoscelides obtectus) have been developed to study the effects of density-dependent and age-specific selection. These populations have been selected at high (K) and low larval densities (r) as well as for reproduction early (Y) and late (O) in life. The results presented here suggest that the r- and K-populations (density-dependent selection regimes) have differentiated from each other with respect to the following life-history traits: egg-to-adult viability at high larval density (K > r), preadult developmental time (r > K), body weight (r > K), late fecundity (K > r), total realized fecundity (r > K), and longevity of males (r > K). It was also found that the following traits responded in statistically significant manner in populations subjected to different age-specific selection regimes: egg-to-adult viability (O > Y), body weight (O > Y), early fecundity (Y > O), late fecundity (O > Y), and longevity of females and males (O > Y). Although several life-history traits (viability, body weight, late fecundity) responded in similar manner to both density-dependent and age-specific selection regimes, it appears that underlying genetic and physiological mechanisms responsible for differentiation of the r/K and Y/O populations are different. We have also tested quantitative genetic basis of the bean weevil life-history traits in the populations experiencing density-dependent and age-specific selection. Among the traits traded-off within age-specific selection regimes, only early fecundity showed directional dominance, whereas late fecundity and longevity data indicated additive inheritance. In contrast to age-specific selecton regimes, three life-history traits (developmental time, body size, total fecundity) in the density-sependent regimes exhibited significant dominance effects. Lastly, we have tested the congruence between short-term and long-term effects of larval densities. The comparisons of the outcomes of the r/K selection regimes and those obtained from the low- and high-larval densities revealed that there is no congruence between the selection results and phenotypic plasticity for the analyzed life-history traits in the bean weevil.     

Sexual Activity and Reproductive Isolation Between Age‐specific Selected Populations of Seed Beetle

We evaluated the degree of reproductive isolation between laboratory populations of the seed beetle (Acanthoscelides obtectus) selected to reproduce early (E) or late (L) in life, where different levels of sexual activity and sexual discrimination have been detected. We found a significant level of behavioral isolation among populations within the E selection regime in which beetles showed enhanced early‐life fitness traits and low sexual activity. In contrast, substantially higher levels of sexual activity and an indiscriminate mating system inhibited rather than promoted pre‐zygotic isolation between the L populations. Our results indicate that the study of sexual activity levels may be crucial for understanding the first steps in the pre‐zygotic isolation among allopatric populations subjected to uniform selection.