The influence of habitat use and foraging on the replacement of one introduced wasp species by another in New Zealand

Abstract.

• 1 New Zealand was colonized by the German wasp, Vespula germanica (F.), in the 1940s and it subsequently became established throughout the country. The common wasp, V.vulgaris (L), colonized in the late 1970s and is still spreading.
• 2 The common wasp has replaced the German wasp in some habitats in New Zealand. Samples from a nationwide postal survey indicate that the common wasp is now the more abundant species in honeydew beech forests (Nothofagus spp.), and to a lesser extent in other native forests. The German wasp is still the more abundant wasp in rural areas (excluding forest). The two species are at present co-dominant in urban areas, although this may be a transient phase.
• 3 In honeydew beech forest the two species show different foraging patterns that provide the potential for local coexistence. Although both species are generalist feeders, the German wasp is more commonly found foraging for protein amongst the forest litter, whereas the common wasp forages more on shrubs and tree saplings. Despite this difference, the common wasp can still replace the German wasp in honeydew beech forest within a few years of invasion.
• 4 In honeydew beech forests in which the German wasp is the more abundant species it dominates honeydew trunks (sugar resource), whereas the common wasp dominates honeydew trunks in areas where it is the more abundant species. The change from German to common wasp domination of honeydew trunks is more rapid than the change in dominance in other microhabitats. Aggressive interactions may be taking place on this high quality, potentially defensible sugar resource.

     

A scanning electron microscope technique for restoring deformed fossils

Deformed fossils which originally had a regular geometric outline, such as crinoid columnals, can be restored using a scanning electron microscope technique called tilt correction. This magnifies the specimen in one direction only. It is unsuitable for specimens where deformation has occurred unevenly and can also distort small structures while restoring the whole specimen. D Crinoid columnals, scanning electron microscope, tilt correction.     

Unsaturated Fatty Acid Synthesis During the Development of Isolated Sunflower (Helianthus annuus L.) Seeds

The effect of temperature on unsaturated fatty acid synthesisin developing sunflower seed embryos (Helianthus annuus L.)has been studied using isolated seeds grown in culture. Variabilitybetween individual embryos in the response to temperature wasalso investigated. Oil and dry matter accumulation in cultured embryos were similarto those of embryos allowed to develop in intact plants, andthe effect of increasing temperature in lowering the amountof linoleic acid in seed oil was reproduced in cultured embryos.The isolated seed culture system, therefore, constitutes a suitablemodel system for studies of oil synthesis in developing sunflowerembryos. The decrease in linoleic acid synthesis in response to highertemperature was detectable after only 18 day-degrees incubation,and the incorporation of labelled substrates suggests that alterationsin the fatty acid composition of seed oil in response to temperatureare produced by an effect on the desaturation of newly synthesizedoleate rather than through turnover of existing lipid. Variation in fatty acid composition between individual embryosgrown at constant temperature was considerable. The detectionof embryos with high linoleic acid levels following growth athigh temperature indicates that potential may exist for theselection of cultivars for temperature-stable fatty acid compositionin sunflower oil. Key words: Fatty acid synthesis, Helianthus annuus, Sunflower seeds     

The life habits of the Ordovician illaenine trilobite Bumastoides

The Ordovician illaenine Bumastoides exhibits a distinctive effaced and strongly convex morphology. Orientation of the visual field, the extreme convexity of the cephalon and the nature of the thoracic articulation support an interpretation of Bumastoides as an infaunal trilobite that was poorly suited to epifaunal crawling. The genus may have been sedentary; spending most of its post-larval life cycle within a burrow. Suspension feeding would be a viable existence for a sedentary trilobite such as Bumastoides. Maintenance of a burrow is essential for respiration and would require a firm, cohesive substrate. The infaunal niche had become occupied by trilobites by at least the Late Cambrian and continued to be exploited through the Ordovician, Silurian and. possibly, into the Devonian. Convergence has led to the appearance of the effaced, strongly convex morphotype in a number of unrelated families, including the Illaenidae, Asaphidac, Aulacopleuridae, Plethopeltidae and Scutelluidae. A high numerical abundance of illaenid trilobites, such as Illaenus and Bumastoides , is characteristic of the illaenid–chcirurid association, which persisted from the early Ordovician until at least the Late Silurian. This association has been recorded from shelf-edge and on-shelf carbonate buildups and shallow subtidal level bottom environments. It appears to be confined to firm substrates.     

Coexistence of Intraspecies and Interspecies Specific Antigenic Determinants on the Major Structural Polypeptide of Mammalian C-type Viruses

THE report of a shared viral antigen (termed gs-3) among mammalian C-type viruses from four species¹, extending an earlier report of cross reactivity between mouse and cat viral antigens², has far reaching implications in the search for human cancer viruses or their gene products. The report is confirmed both by the data presented here and also by the data obtained by another laboratory³. Our gel diffusion assays using various selected sera against mouse, hamster and cat crude and purified C-type viral antigens indicate that the cross reactive antigenic determinants are specifically present on the major structural polypeptide of C-type viruses. The polypeptide also carries species specific determinants. These conclusions are drawn from complement fixation and gel diffusion tests using six types of antisera (either individual sera or pools) prepared as described in Table 1.     

Synthesis by Ribosomes of Viral Coat Protein containing Ester Linkages

Peptidyl transferase, the ribosomal enzyme which synthesizes peptide bonds, can catalyse the formation of ester linkages between α-hydroxyacyl-tRNA and aminoacyl-tRNA when ribosomes carry out a specific translation of phage R17 RNA in vitro.