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Haematology has the potential to be a valuable tool in determining the health status of wild fish populations and wider ecosystem health. However, limited haematological data are available for wild Australian fish species, and the interpretation and nomenclature of leukocytes is variable and inconsistent in fish. The morphology and cytochemical reactions of erythrocytes, thrombocytes and leukocytes of 189 wild eel-tailed catfish (Tandanus tandanus), Wet Tropics tandan (Tandanus tropicanus), Hyrtyl’s tandan (Neosilurus hyrtlii), black catfish (Neosilurus ater), lesser salmon catfish (Neoarius graeffei), and silver cobbler (Neoarius midgleyi) are described. Erythrocytes, thrombocytes, lymphocytes, monocytes and heterophils in all six species are morphologically similar to those reported in other Siluriformes. Basophils and eosinophils are rarely reported in fish; however basophils were observed in peripheral blood smears of T. tropicanus and N. ater, and eosinophils were observed in N. graeffei. Periodic acid Schiff positive granular leukocytes were observed in N. graeffei, N. midgleyi, N. ater and T. tandanus. This is the first report on the leukocyte morphology and cytochemistry of any native Australian catfish species, and provides useful baseline data for future assessments of fish health and ecosystem integrity in Australia.
The natural history and intraspecific interactions of Servaea incana, a common jumping spider of temperate Australia, are described. S. incana inhabits the trunks of eucalypt trees, where it builds silken retreats and nests under loose bark. Like other jumping spiders, S. incana males use elaborate visual displays (Type I courtship) when they encounter females in the open. Male jumping spiders usually rely on silk-borne vibrations to communicate with females residing within retreats and nests (Type II courtship). S. incana often uses visual displays in this context, because the thin silken walls allow conspecifics to see each other. Adult males that encounter subadult females at retreats sometimes build their own retreat nearby and cohabit until the subadult female moults to maturity, copulating shortly afterwards. Adult females and immature stages of both sexes possess similar display repertoires that contain fewer display elements than the repertoire of males. We found no evidence that visual displays of S. incana contain seismic elements, in contrast to some of its closest relatives. S. incana preys upon a variety of small arthropods and, unusually amongst salticids, ants make up a large portion of the diet. Identified enemies of S. incana include spiders, a pompilid wasp and a mantispid.
Lateralisation in forelimb use at the population and/or individual level has been found in a wide variety of vertebrate species. However, some large taxa have not yet been investigated and that limits a proper evolutionary interpretation of forelimb preferences. Among mammals lateralised use of the forelimbs has been shown for both placentals and marsupials, but nothing is known about behavioural lateralisation in monotremes. Here we examined lateral preferences in forelimb use in four long-beaked echidnas (male and female Zaglossus bruijni, and male and female Z. bartoni) in captivity. Three individuals showed significant forelimb preferences in unimanual behaviours associated with feeding. When stepping on an eminence with one forelimb first, the lateralisation at the individual level was found only in males of both species. During male–female interactions, the male Z. bartoni significantly preferred to put one of the forelimbs on the female’s back. In both males, the direction of preferences was consistent across different types of behaviour. Our results confirm that manual lateralisation, at least at the individual level, is widespread among mammals. Further research is needed to investigate whether the monotremes display population-level lateralisation in forelimb use.
Access to nest sites is critical to species survival and habitat suitability for most faunal species worldwide. We report on nest-site selection and use by the long-nosed bandicoot (Perameles nasuta) following a wildfire in late 2003. Thirty-eight bandicoots were tracked to 213 nests. The number of nests, frequency of nest use, nest range, nest size and nest site microhabitat in burnt and unburnt habitat were analysed. The mean number of nests used in burnt areas was 5.9, not significantly different from the number used in non-burnt areas (5.3). However, there were significant fire effects on nest location and frequency of use. Six months after the wildfire, 60% of nests in burnt forest and woodland habitat were in patches of unburnt microhabitat. These nests were significantly larger and were used more frequently than nests located in burnt microhabitat. After fire, P. nasuta typically uses nests under dense grasses and midstorey in unburnt microhabitat in burnt areas. However, the species will also nest in open areas and respond to fire-affected areas by constructing smaller nests. When conducting prescribed fires, the practice of ‘burning out’ should be minimised and patchiness at a microhabitat level be a desired outcome for bandicoot management.
In animals with a complex life cycle, changes in biotic and abiotic conditions during development can alter growth and maturation rates, causing carry-over effects in postmetamorphic phenotypes. In anurans, this developmental plasticity can result in a trade-off between length of larval period and body size at metamorphosis in stressful environments. Secondary salinisation has been identified as a substantial stressor to amphibians; however, little is known about how salinity-induced developmental plasticity differs between anuran populations. We examined differences in survival, time to metamorphosis, size at metamorphosis (mass and snout–vent length) and body condition at metamorphosis in response to elevated salinity in three populations of the brown tree frog (Litoria ewingii). Significant differences in size at metamorphosis between salinity treatments were observed in tadpoles sourced from freshwater wetlands and ephemeral wetlands, with tadpoles showing a reduced mass and snout–vent length at metamorphosis in the higher-salinity treatment. There were no significant differences in metamorphic traits between salinity treatments in tadpoles sourced from a consistently brackish wetland, suggesting either an erosion of developmental plasticity in response to elevated salinity, or the magnitude of salinity required to alter developmental traits is higher in this population. Our results indicate that environmental conditions of source populations need to be considered when studying life-history adaptations in response to environmental change.
This paper describes a 10-year study of the community of two species of small rodents (Mastacomys fuscus, Rattus fuscipes) and one species of dasyurid marsupial (Antechinus swainsonii) in the subalpine zone of the Australian Alps. Each species exhibited differing life-histories with respect to population numbers, intra- and interannual fluctuations in numbers, reproduction, proportion of young in the population, winter survival, immigration and longevity. Of the two species of rodents, M. fuscus had the lowest population numbers, was the least fecund, had the highest rate of survival, and the smallest fluctuations in numbers. A. swainsonii was the least numerous species, and the winter die-off of males and the high fecundity of females resulted in much greater fluctuations in numbers than for either rodent. For all species, there were interannual variations in most demographic parameters, suggesting considerable flexibility in response to annual variations in the environment. None of the three species is known to hibernate, nor is there any evidence of cyclicity, as shown by some species of subarctic and arctic small mammals. Comparisons are made with subalpine small mammals in other parts of the world and the influence of the subalpine environment in determining population numbers is considered.
The critically endangered Capricorn yellow chat (CYC) is endemic to coastal central Queensland on marine plains where it occurs in three areas, numbering <300 birds. Recent industrial expansion in the region has increased the threat to the CYC. To assist management of the subspecies, a phylogeographical evaluation of the CYC using mitochondrial DNA was undertaken. We found no genetic diversity within, nor genetic divergence between, the two areas at the northern and southern extremes of their current distribution, and only slight morphological differences. These findings suggest that the two groups of CYC represent daughter populations of an ancestral population that was affected by a genetic bottleneck in the recent past. Implications for conservation of the subspecies could be increased vulnerability to environmental change. A preliminary evaluation of the divergence between the CYC and its nearest subspecies, the widespread inland yellow chat, indicate a time to the most recent common ancestor of 215 000 years or less. This timespan overlaps two periods of glacial aridity during which xeric habitats used by yellow chats for breeding, such as semiarid and arid swamps, may have expanded, allowing colonisation of the coastal marine plains. CYCs may represent a relictual population from a previously more xeric era that has subsequently become isolated as the region became wetter following glacial maxima.
Variation in abundance and diversity of organisms along habitat edges has long been a key research focus in both terrestrial and marine ecosystems. Previous investigations into edge effects in seagrass ecosystems have predominantly focussed on the seagrass–sandy substrate boundary. However, little is known about what role other habitats (e.g. rocky algal reefs) may play in faunal assemblage patterns. This study investigated the strength to which habitat type influenced gastropod assemblages within seagrass (Posidonia australis) beds, bordered by both sandy substrate and rocky algal reef. We found that benthic invertebrate community composition significantly changed with distance from rocky algal reef, but not with distance from sandy substrate. Proximity to rocky reef had a stronger effect on community composition than other local drivers examined (seagrass biomass and sand particle size). We hypothesise that gastropod affinity for rocky algal reef may be a result of both species-specific habitat preference, and lower predation pressure along adjacent rocky algal reef habitats. This study provides evidence that heterogeneous habitats within close proximity to seagrass beds may exert previously overlooked effects on the distribution of gastropod assemblages, highlighting the need for the inclusion of adjacent habitat type in experimental design for gastropod assemblage distribution studies.