Comparative phenology of four satyrine butterflies inhabiting dry grasslands in Sweden

The phenology of the satyrine butterflies Coenonympha pamphilus L., Lasiommata megera L., Hipparchia semele L. and Maniola jurtina L. was compared under seminatural conditions with Festuca ovina as the food-plant. Coenonympha pamphilus shows striking phenotypic plasticity as revealed by initiating cohorts at successive dates during the whole flight period. Growth rate is finely tuned depending on season, and larvae can hibernate in any of the three first instars, but also aestivate when 'surplus'time is available. Hipparchia semele and M. jurtina have reduced growth rates as last instar larvae at the beginning of summer. Lasiommata megera , which has an obligate bivoltine life cycle, shows the highest overall growth rate of all four species. Results suggest that egg size variation has consequences for the life cycles of these species.     

A comparison of stress tolerance in YPD and industrial lignocellulose-based medium among industrial and laboratory yeast strains

In general, it is believed that fermentation by yeast under harsh industrial conditions, especially if substrates such as wood hydrolysate or lignocellulosic substrates are used, requires the use of so-called industrial strains. In order to check whether this is always true, a comparison of performance was made using two industrial strains and four commonly used laboratory strains, the haploid and diploid versions of CEN-PK and X2180, under industrially relevant stress conditions. The industrial strains were a Swedish commercial baker’s yeast strain and a strain previously isolated from an industrial bioethanol production plant using lignocellulosic substrate. Stress conditions included, apart from growth in the lignocellulosic substrate itself, elevated concentrations of glucose, NaCl, ethanol, and lactate as well as low pH. Results showed that, indeed, the strain adapted to lignocellulosic substrate also possessed the highest growth rate as well as shortest duration of the lag phase in this type of medium. However, the higher the additional stress level, the lower the difference compared to other strains, and X2180 in particular displayed a high resistance to these additional stress conditions. Furthermore, no difference in performance could be detected between the haploid or diploid versions of the laboratory strains. It might be that, at least under some circumstances, a laboratory strain such as X2180 could be an industrially attractive production organism with the advantage of facilitating the possibilities for making controlled genetic manipulations.     

Seasonal polyphenism and leaf mimicry in the comma butterfly

The comma butterfly, Polygonia c-album, exhibits seasonal polyphenism with a darkish winter morph and a lighter summer one. Phylogenetic analysis suggests that the winter morph represents the ancestral condition. We suggest two hypotheses for the evolution of the summer morph and the maintenance of seasonal polyphenism in the comma: (1) that the summer morph is better protected against predation on summer roost sites, whereas the winter morph is better protected on hibernation sites, and (2) that the summer morph is energetically less expensive and results from deallocation of resources from soma (e.g. dark wing pigmentation) to reproduction. We tested the antipredation hypothesis in experiments using great tits, Parus major, as predators on winter and summer morph commas presented simultaneously on tree trunks or on nettles. However, this hypothesis was not supported as the winter morph was better protected than the summer morph on both backgrounds. Predation when both morphs were present was lower on nettles, and summer morphs placed in exposed positions on tree trunks outdoors disappeared sooner than winter morphs placed on the same background. In addition, in a final experiment, 18 summer morphs released in their natural habitat in the evening exclusively chose leaves for roost sites, whereas 12 of 19 winter morphs chose a tree trunk, branch or twig. We conclude that evolution of the summer morph is consistent with the life history hypothesis and that its choice of summer roost sites is associated with a low predation pressure.     

Generation-dependent female choice: behavioral polyphenism in a bivoltine butterfly

Climatic and biotic circumstances vary as seasons shift, anddifferent cohorts of multivoltine species are likely subjectedto different selection regimes. The bivoltine butterfly Leptideareali (Réal's wood white; Lepidoptera: Pieridae) appearsduring May and June in central Sweden and has a partial secondgeneration in late July. We manipulated both generations toappear simultaneously and performed laboratory mating experimentsthat showed the presence of a behavioral polyphenism in matingpropensity, which is induced during the developmental stages.Females of the summer generation expressed higher mating propensitiesthan spring generation females. Spring females showed an increasein mating propensity with increasing age, whereas summer femalesaccepted most matings already when they were only 1 or 2 daysold. It is likely that larval time constraints, a lower abundanceof males and a lower risk of accepting a male of their univoltinesister species Leptidea sinapis (wood white), have relaxed selectionon mate discrimination among summer generation females. A majorchallenge for future research is to further investigate thedevelopmental pathways causing the polyphenism and the adaptiveimplications of cohort-dependent behaviors.     

Abundance and trophic structure of pine forest nematodes in relation to soil layers and ground cover

In a 15-20 yr old forest of Scots pine, the total number of nematodes under the dominating cover grass Deschampsia flexuosa , reached 4.0–4.7 × 10⁶ ind. m⁻² stone free soil, corresponding to densities of 8770–9090 and 3500–3790 ind. 100 ml⁻¹ in FH and mineral soil, respectively. Root/fungal feeding nematodes formed 53–59% of the total nematode fauna. The majority in this group was potential mycophages. Obligate root feeders formed only 11–17% of the total number of nematodes. Soil layers and ground cover affected the abundance of trophic groups. Bacterial feeders, potential mycophages and miscellaneous feeders reached their maximal abundance in the FH-layer. Obligate root feeders tended to reach higher densities in the mineral soil. Higher abundance values of most trophic groups were found under forest grass. The species Calamagrostis arundinacea had a striking positive effect on the relative and absolute abundance of obligate root feeders. This group may be most numerous in early stages of forest development.     

A long-wavelength absorbing form of protochlorophyll and crystalloids in the inner seed coat of Luffa cylindrica

The inner seed coat of seeds of Luffa cylindrica (L.) Roem. (cv. Luffa sponge vine) was used to study the development of the protochlorophyll-containing plastids during different stages of maturity of the fruits. The inner seed coats had an absorption spectrum with a main peak in the red region at 675 nm and a shoulder at 630 nm. The fourth derivative spectrum gave a clear peak at 630 nm and also a small additional peak at 650 nm. An acetone extract showed a peak at 626 nm and a Soret band at 440 nm indicating that the main pigment in the seed coat was protochlorophyll. The ultrastructure of the protochlorophyll-containing plastids changed during maturation of the seed. In the young stage an elaborate membrane system was present. In a more mature stage the membrane system degenerated and crystalloids were formed. Some of these crystalloids seemed to develop into plastoglobuli in the most mature stage.     

The influence of predator regime on reproductive traits in <Emphasis Type="Italic">Gammarus</Emphasis> <Emphasis Type="Italic">pulex</Emphasis> populations

Selection on traits conferring reduced predation may be opposed by selection on other traits associated with reproduction. Here, we examined the hypothesis that traits associated with reproduction in Gammarus pulex are driven by predation. We studied G. pulex originating from ponds with two different kinds of predator regimes: (1) ponds with fish—often large, non-gap-limited predators and (2) ponds without fish where invertebrates are the dominant predators—often small, gap-limited predators with a much more restricted prey size range. We examined the body size of males and females in G. pulex amplexus pairs originating from fish and fishless ponds. We also examined, in the laboratory, their mating success, the number of offspring per female and offspring mortality under different rearing conditions, with or without fish cue. Mating success, defined as the percentage of amplexus pairs that produced live offspring, was higher for G. pulex from fishless ponds independent of rearing condition. Individuals from fish ponds were larger and they produced a higher number of offspring which tended to be related to female body size. Offspring mortality was higher in populations from fish ponds compared to populations from fishless ponds. Despite the higher offspring mortality, females from fish ponds had a higher number of offspring alive after 13 weeks, which is the approximate time it takes for G. pulex to reach maturity. Our data imply that no trade-off between reducing body size to reduce mortality caused by fish and maximising reproductive success exist in G. pulex from fish ponds. The strategy with many offspring may be the correct strategy in fishponds where predation pressure generally is higher than in fishless ponds.     

Sex pheromone biosynthesis in the Asian corn borer Ostrinia furnacalis (II): Biosynthesis of (E)- and (Z)-12-tetradecenyl acetate involves Δ14 desaturation

Sex pheromone biosynthesis in the Asian corn borer Ostrinia furnacalis was studied by topical application of deuterium labelled fatty acids to the pheromone gland. The incorporation of the labelled acids into pheromone components and precursors was determined by gas chromatography with flame ionization detection and mass spectrometry in the selected ion monitoring mode. The labelling experiments suggest that the pheromone components (E)- and (Z)-12-tetradecenyl acetates are biosynthesized from palmitic acid by δ14 desaturation, followed by chain shortening (β-oxidation), reduction, and acetylation. This is the first confirmation of a Δ14 desaturase in an eukaryotic system.     

A taxonomic and faunistic survey of the marine Tubificidae and Enchytraeidae (Oligochaeta) of Italy. Introduction and preliminary results

On the basis of material collected along the Ligurian, Tyrrhenian, Ionic and Adriatic coasts of Italy, a tentative list of 26 species (18 tubificids, 8 enchytraeids) of marine Oligochaeta is presented. Most of the species are new to science, and it can therefore be concluded that there is a very high diversity of oligochaetes in the Mediterranean Sea.