Effect of thermoperiod on diapause intensity in Pyrrhocoris apterus (Heteroptera Pyrrhocoridae)

The intensity of adult diapause in Pyrrhocoris apterus was measured in two series of experiments as the duration of pre-oviposition period at a constant temperature of 25 degrees C after transfer from short (12L:12D) to long day conditions (18L:6D). Higher diapause intensity was induced with a thermoperiod than at constant temperatures. After the induction throughout larval instars 3-5 and during 4 weeks of adult life at short days and a thermoperiod of 25/15 degrees C the pre-oviposition period was 30+/-4 and 26+/-3 days. After induction at constant 25 degrees C the pre-oviposition period was 22+/-3 and 23+/-4 days, while after induction at constant 20 degrees C it was 17+/-4 and 19+/-4 days. Induction at a lower constant temperature of 20 degrees C was thus followed by a less intense diapause than the induction at a higher constant temperature of 25 degrees C. These counterintuitive results are discussed. The oxygen consumption rate measured at experimental temperatures prior to transfer from short to long days was higher at thermoperiodic conditions than at constant temperatures and it was similar at constant 20 and 25 degrees C. Thus, the oxygen consumption rate measured prior to the transfer was highest (indication of the least intense diapause) in the insects that showed later, after the transfer to long days, the longest pre-oviposition period (indication of the most intense diapause). Within the first two days after transfer to constant 25 degrees C, oxygen consumption rate measured at 25 degrees C decreased in the thermoperiodic insects, while it transiently increased in insects from constant 20 degrees C. Two days and later after the transfer, oxygen consumption rate was similar in all groups. Cold hardiness was not correlated with diapause intensity. The low lethal temperature in diapausing insects was correlated with the night temperature during diapause induction.     

C-value estimates for 31 species of ladybird beetles (Coleoptera: Coccinellidae)

This study provides C-value (haploid nuclear DNA content) estimates for 31 species of ladybird beetles (representing 6 subfamilies and 8 tribes), the first such data for the family Coccinellidae. Despite their unparalleled diversity, the Coleoptera have been very poorly studied in terms of genome size variation, such that even this relatively modest sample of species makes the Coccinellidae the third best studied family of beetles, behind the Tenebrionidae and Chrysomelidae. The present study provides a comparison of patterns of genome size variation with these two relatively well-studied families. No correlation was found between genome size and body size in the ladybirds, in contrast to some other invertebrate groups but in keeping with findings for other beetle families. However, there is some indication that developmental time and/or feeding ecology is related to genome size in this group. Some phylogenetic patterns and possible associations with subgenomic features are also discussed.     

Harmonia axyridis in Europe: spread and distribution of a non-native coccinellid

Native to Asia, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) is considered an invasive alien ladybird in Europe and North America, where it was widely introduced as a biological control agent of aphids and coccids. In Europe, H. axyridis was sold by various biological control companies from 1995 in France, Belgium and the Netherlands, and was also intentionally released in at least nine other countries. It has spread very rapidly, particularly since 2002, and is now regarded as established in thirteen European countries. The established range extends from Denmark in the north to southern France in the south, and from Czech Republic in the east to Great Britain in the west. In this paper we map the spread and distribution of H. axyridis in Europe, and examine the situation on a country-by-country basis. We report first records of the species in five countries; Spain, Sweden, Denmark, Czech Republic and Italy; and first evidence of H. axyridis establishment in the latter three countries. Despite releases of H. axyridis in Portugal, Spain and Greece, there is little evidence of establishment in southern Europe. It is predicted that the spread and increase within Europe will continue and that H. axyridis will become one of the most widely distributed coccinellids in the continent.     

Complementarity of statistical treatments to reconstruct worldwide routes of invasion: the case of the Asian ladybird Harmonia axyridis

Inferences about introduction histories of invasive species remain challenging because of the stochastic demographic processes involved. Approximate Bayesian computation (ABC) can help to overcome these problems, but such method requires a prior understanding of population structure over the study area, necessitating the use of alternative methods and an intense sampling design. In this study, we made inferences about the worldwide invasion history of the ladybird Harmonia axyridis by various population genetics statistical methods, using a large set of sampling sites distributed over most of the species’ native and invaded areas. We evaluated the complementarity of the statistical methods and the consequences of using different sets of site samples for ABC inferences. We found that the H. axyridis invasion has involved two bridgehead invasive populations in North America, which have served as the source populations for at least six independent introductions into other continents. We also identified several situations of genetic admixture between differentiated sources. Our results highlight the importance of coupling ABC methods with more traditional statistical approaches. We found that the choice of site samples could affect the conclusions of ABC analyses comparing possible scenarios. Approaches involving independent ABC analyses on several sample sets constitute a sensible solution, complementary to standard quality controls based on the analysis of pseudo‐observed data sets, to minimize erroneous conclusions. This study provides biologists without expertise in this area with detailed methodological and conceptual guidelines for making inferences about invasion routes when dealing with a large number of sampling sites and complex population genetic structures.     

Role of 5-aminolevulinic acid in the formation of winter rape resistance to sulfonylurea herbicides

Growing of winter rape (Brassica napus L.) plants for 7–8 days in the presence of a sulfonylurea herbicide Magnum (methsulfuron methyl; 200 and 500 mg/L) exerted an organ-specific influence on the seedlings: suppressed hypocotyl and root growth and increased the accumulation of fresh weight of cotyledonary leaves. Exogenous 5-aminolevulinic acid (ALA; 0.1, 1.0, and 10 mg/L) partially negated the adverse effect of Magnum on the length and fresh weight of roots and hypocotyls and stimulated the development of cotyledons. The herbicide suppressed the activity of ascorbate peroxidase (APX). The addition of ALA to the 200 mg/L herbicide solution caused a steady activation of APX as compared with the effect of herbicide alone. In plants grown on Magnum solutions, the activity of glutathione reductase (GR) rose. Positive effect of exogenous ALA was only observed when 500 mg/L herbicide was used (Magnum-500 type of treatment). In plants grown on the Magnum solution, the content of reduced and oxidized forms of glutathione rose. In contrasty, exogenous ALA reduced the total content of glutathione but in this case the ratio between its reduced and oxidized forms rose. In the presence of the herbicide, the content of anthocyans considerably decreased and upon the addition of exogenous ALA their levels rose. In rape plants treated with Magnum, the ability to generate superoxide anion radical was essentially the same as in control plants; however, the content of hydrogen peroxide (H₂O₂) therein rose. The addition of ALA to the herbicide reduced the ability to generate superoxide anion radical and the level of H₂O₂. The activity of acetolactate synthase remained on the control level when 200 mg/L Magnum was used, decreased in the plants of Magnum-500 treatment, and rose upon the addition of exogenous ALA to this type of treatment. It was concluded that ALA had a positive effect on the development of winter rape resistance to Magnum via stimulation of growth processes, activation of APX and GR, predominant elevation of the content of reduced glutathione and anthocyans, and partial recovery of acetolactate synthase activity, which on the whole caused a decrease in the H₂O₂ level and in the ability of plants to generate superoxide anion radical.     

Phylogeny of the New World Dysdercus (Insecta: Hemiptera: Pyrrhocoridae) and Evolution of their Colour Patterns

Evolution of colour patterns is reconstructed in the case of the New World species of Dysdercus (Hemiptera: Pyrrhocoridae). The phylogenetic species concept was applied to this group, elevating five subspecific taxa to specific rank (D. capitatus, D. discolor, D. fervidus, D. luteus, and D. neglectus), and the resulting 41 phylogenetic species were analysed cladistically. Using optimization methods, evolution of colour patterns of the group is hypothesized, and possible developmental mechanisms of colour-pattern evolutionary changes are inferred.     

Antifouling character of 'active' hybrid xerogel coatings with sequestered catalysts for the activation of hydrogen peroxide

Halide-permeable xerogel films prepared from sols containing 50 mol% aminopropyltriethoxysilane (APTES)/50 mol% tetraethoxysilane (TEOS) or 10 mol% APTES/90 mol% TEOS and 0.015 M selenoxide or telluride catalyst in the sol gave reduced settlement of cypris larvae of the barnacle Balanus amphitrite and larvae of the tubeworm Hydroides elegans in the presence of artificial seawater (ASW) and hydrogen peroxide (5-100 microM) relative to glass controls. Settlement of Ulva zoospores was lower on both the 50 mol% APTES/50 mol% TEOS and 10 mol% APTES/90 mol% TEOS xerogel formulations in comparison with glass controls with or without the added catalyst. The 50 mol% APTES/50 mol%TEOS xerogel containing telluride catalyst gave reduced settlement of Ulva zoospores in the presence of 100 microM H(2)O(2) in ASW compared with the same coating without added peroxide. Scanning electron microscopy and XPS data suggest that exposure to H(2)O(2) does not lead to chemical or morphological changes on the xerogel surface.     

Microbial biofilms facilitate adhesion in biofouling invertebrates

Much interest has focused on the role of microbial layers--biofilms--in stimulating attachment of invertebrates and algae to submerged marine surfaces. We investigated the influence of biofilms on the adhesion strength of settling invertebrates. Larvae of four species of biofouling invertebrate were allowed to attach to test surfaces that were either clean or coated with a natural biofilm. Measuring larval removal under precisely controlled flow forces, we found that biofilms significantly increased adhesion strength in the ascidian Phallusia nigra, the polychaete tubeworm Hydroides elegans, and the barnacle Balanus amphitrite at one or more developmental stages. Attachment strength in a fourth species, the bryozoan Bugula neritina, was neither facilitated nor inhibited by the presence of a biofilm. These results suggest that adhesive strength and perhaps composition may vary across different invertebrate taxa at various recruitment stages, and mark a new path of inquiry for biofouling research.