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Arthropod Taxa (arthropod + taxa)
Selected AbstractsEffects of lambda-cyhalothrln in two ditch microcosm systems of different trophic statusENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2005Ivo Roessink Abstract The fate and effects of the pyrethroid insecticide lambda-cyhalothrin were compared in mesotrophic (macrophyte-dominated) and eutrophic (phytoplankton-dominated) ditch microcosms (,0.5 m3). Lambda-cyhalothrin was applied three times at one-week intervals at concentrations of 10, 25, 50, 100, and 250 ng/L. The rate of dissipation of lambda-cyhalothrin in the water column of the two types of test systems was similar. After 1 d, only 30% of the amount applied remained in the water phase. Initial, direct effects were observed primarily on arthropod taxa. The most sensitive species was the phantom midge (Chaoborus obscuripes). Threshold levels for slight and transient direct toxic effects were similar (10 ng/L) between types of test systems. At treatment levels of 25 ng/L and higher, apparent population and community responses occurred. At treatments of 100 and 250 ng/L, the rate of recovery of the macroinvertebrate community was lower in the macrophyte-dominated systems, primarily because of a prolonged decline of the amphipod Gammarus pulex. This species occurred at high densities only in the macrophyte-dominated enclosures. Indirect effects (e.g., increase of rotifers and microcrustaceans) were more pronounced in the plankton-dominated test systems, particularly at treatment levels of 25 ng/L and higher. [source] The bivalved arthropods Isoxys and Tuzoia with soft-part preservation from the Lower Cambrian Emu Bay Shale Lagerstätte (Kangaroo Island, Australia)PALAEONTOLOGY, Issue 6 2009DIEGO C. GARCÍA-BELLIDO Abstract:, Abundant material from a new quarry excavated in the lower Cambrian Emu Bay Shale (Kangaroo Island, South Australia) and, particularly, the preservation of soft-bodied features previously unknown from this Burgess Shale-type locality, permit the revision of two bivalved arthropod taxa described in the late 1970s, Isoxys communis and Tuzoia australis. The collections have also produced fossils belonging to two new species: Isoxys glaessneri and Tuzoia sp. Among the soft parts preserved in these taxa are stalked eyes, digestive structures and cephalic and trunk appendages, rivalling in quality and quantity those described from better-known Lagerstätten, notably the lower Cambrian Chengjiang fauna of China and the middle Cambrian Burgess Shale of Canada. [source] Arthropod responses to experimental fire regimes in an Australian tropical savannah: ordinal-level analysisAUSTRAL ECOLOGY, Issue 2 2000Alan N. Andersen Abstract Fire is widely used for conservation management in the savannah landscapes of northern Australia, yet there is considerable uncertainty over the ecological effects of different fire regimes. The responses of insects and other arthropods to fire are especially poorly known, despite their dominant roles in the functioning of savannah ecosystems. Fire often appears to have little long-term effect on ordinal-level abundance of arthropods in temperate woodlands and open forests of southern Australia, and this paper addresses the extent to which such ordinal-level resilience also occurs in Australia's tropical savannahs. The data are from a multidisciplinary, landscape-scale fire experiment at Kapalga in Kakadu National Park. Arthropods were sampled in the two major savannah habitats (woodland and open forest) using pitfall traps and sweep nets, in 15,20 km2 compartments subjected to one of three fire regimes, each with three replicates: ,early' (annual fires lit early in the dry season), ,late' (annual fires lit late in the dry season), and ,unburnt' (fires absent during the five-year experimental period 1990,94). Floristic cover, richness and composition were also measured in each sampling plot, using point quadrats. There were substantial habitat differences in floristic composition, but fire had no measured effect on plant richness, overall composition, or cover of three of the four dominant species. Of the 11 ordinal arthropod taxa considered from pitfall traps, only four were significantly affected by fire according to repeated-measures ANOVA. There was a marked reduction in ant abundance in the absence of fire, and declines in spiders, homopterans and silverfish under late fires. Similarly, the abundances of only four of the 10 ordinal taxa from sweep catches were affected by fire, with crickets and beetles declining in the absence of fire, and caterpillars declining under late fires. Therefore, most of the ordinal taxa from the ground and grass-layer were unaffected by the fire treatments, despite the treatments representing the most extreme fire regimes possible in the region. This indicates that the considerable ordinal-level resilience to fire of arthropod assemblages that has previously been demonstrated in temperate woodlands and open forests of southern Australia, also occurs in tropical savannah woodlands and open forests of northern Australia. [source] An evaluation of two biochemical methods of age determination in insects (pteridines and lipofuscins) using the ant Polyrhachis sexpinosa Latrielle (Hymenoptera: Formicidae)AUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 2 2009Simon K A Robson Abstract Accurate information on the age of wild-caught animals is valuable for a variety of areas, but can be particularly difficult to obtain for small holometabolous insects, whose body size is fixed at the time of pupal eclosion. A variety of chemical groups, such as lipofuscins and pteridines accumulate in body tissues through time and can be used to predict age in a variety of arthropod taxa. Here we use spectrofluorometry to confirm the presence of extractable levels of lipofuscins and pteridines in individual social insects (using the ant Polyrhachis sexpinosa Latrielle, average body size 25 mg, as an example) and evaluate their ability to predict age. Pteridine levels were independent of age but lipofuscin levels increased with age in a predictable manner (r2 = 72.8%). Lipofuscin levels therefore represent a new method of age determination for social insects that should be applicable to both individual laboratory and wild-caught animals. [source] Arthropod prey of shelterbelt-associated birds: linking faecal samples with biological control of agricultural pestsAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 4 2007Sagrario Gámez-Virués Abstract, The value of insectivorous birds as agents for biological control of arthropod pests has been little studied, especially in Australia. This paper reports on the extent to which arthropods from various pest and non-pest taxa feature in the diets of birds captured in farm shelterbelts in central western New South Wales. The parameters examined were the types of arthropod fragments in bird faeces and percentage volume and frequency of occurrence of each component. The faecal data were compared with samples of the arthropod fauna trapped in shelterbelts during the period the birds were captured. In 26 of 29 faecal samples, arthropod fragments were the predominant components, the most common being from Coleoptera, Hymenoptera (especially Formicidae), Orthoptera and Araneae. The recognisable pest taxa in faecal samples were Scarabaeidae and wingless grasshopper Phaulacridium vittatum (Sjöstedt) (Orthoptera: Acrididae). The results indicate that the native bird species common in farm shelterbelts preyed on a range of arthropod taxa including several that are pests of crops and pastures. Accordingly, conservation of birds in farmlands could contribute to suppression of arthropod pests. [source] Generalised regressions provide good estimates of insect and spider biomass in the monsoonal tropics of AustraliaAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 3 2006Christopher J Brady Abstract, The estimation of arthropod biomass is often important in studies of terrestrial ecosystem structure and function, including analyses of the relative importance of different arthropod taxa in the diet of insectivorous animals. In order to estimate arthropod biomass in eucalypt woodlands and rehabilitated mine-land in the monsoonal tropics of northern Australia, insect morpho-species (n = 693) and spider morpho-species (n = 100) were collected, sorted, then weighed and measured. Body length,weight regressions were determined for spiders, nine insect orders and all insects combined. There was a significant relationship between body length and weight for all taxonomic groups, with the power model being a better predictor than linear or exponential models for all groups except Diptera (which was best predicted by the linear model). Whilst Schoener (1980) found that the length,weight regression slopes of neotropical insects (all orders combined, as well as several individual orders) differed from those of their temperate North American counterparts, our comparisons between monsoon-tropical and temperate Australian arthropods suggested differences among Dipterans and spiders only. We conclude that generalised regressions provide adequate estimates of arthropod biomass across Australia, providing that the body proportions of the dominant taxa do not vary substantively. [source] | ||||||||||