Australian Journal of Zoology 

About: Australian Journal of Zoology is an academic journal published by CSIRO Publishing. The journal publishes majorly in the area(s): Population & Genus. It has an ISSN identifier of 0004-959X. Over the lifetime, 2972 publications have been published receiving 69893 citations. The journal is also known as: Aust. J. Zool..

An outline of the dynamics of animal populations.

Abstract: This article is itself a summarized statement concerning the various influences which affect population densities and the population systems these lead to. Known facts concerning animal populations have been analysed. systematized. and critically examined. using the experimental and mathematical approaches in the simpler situations. The more outstanding conclusions are listed below. Populations are self-governing systems. They regulate their densities in relation to their own properties and those of their environments. This they do by depleting and impairing essential things to the threshold of favourability, or by maintaining reactive inimical factors, such as the attack of natural enemies, at the limit of tolerance. The mechanism of density governance is almost always intraspecific competition, either amongst the animals for a critically important requisite, or amongst natural enemies for which the animals concerned are requisites. Governing reaction induced by density change holds populations in a state of balance in their environments. The characteristic of balance is sustained and effective compensatory reaction which maintains populations in being in spite of even violent changes in the environment, and which adjusts their densities in general conformity with prevailing conditions. Far from being a stationary state, balance is commonly a state of oscillation about the level of the equilibrium density which is for ever changing with environmental conditions. Destructive factors do not add to mortality when they continue to operate over long periods, but merely cause a redistribution of mortality, for the intensity of competition automatically relaxes sufficiently to make room for the destruction they cause. Such compensatory reaction causes the effect of destructive factors upon density to be much less when balance is reattained than that which they produce when they first operate.

The statistical analysis of the Canadian Lynx cycle.

Abstract: It is shown that trapping figures for the lynx are definitely related to weather conditions. The significance of this for the various theories of the origin and synchronization of the cycle is discussed.

Histone H3 and U2 snRNA DNA sequences and arthropod molecular evolution

Abstract: The range of DNA sequences used to study the interrelationships of the major arthropod groups (chelicerates, myriapods, hexapods and crustaceans) is limited. Here we investigate the value of two genes not previously employed in arthropod phylogenetics. Histone H3 data were collected for 31 species and small nuclear ribonucleic acid U2 data for 29 species. The sequences provided a total of 460 sites and 192 parsimony-informative characters. H3 analyses showed substantial codon usage bias, but had a low consistency index (0.26). Consistency indices were higher for the U2 data (0.49), suggesting that the class of snRNAs may provide several phylogenetically useful genes. The present data are not by themselves sufficient to clarify major arthropod group relationships. Partitioned data for H3 and U2 are incongruent according to Incongruence Length Difference tests. Although the most parsimonious trees, based on combined analyses of all taxa, differ substantially from morphology-based trees, anomalous groupings are weakly supported with only one exception. The trees uphold monophyly of Onychophora, Branchiopoda, and Malacostraca (rather than the rival Phyllopoda). Cladistic analyses constraining the monophyly of morphologically defined classes do not significantly distinguish between the main rival hypotheses of major clade relationships. Combined (‘spliced’) analysis of both genes improves topological congruence with morphological groupings relative to that of either partition. Character congruence between H3, U2, and morphology is increased by downweighting (but not excluding) transitions and third codons. Analyses of four-taxon statements using PHYLTEST found significant support for the basal position of the Crustacea among the euarthropods. This support may be due to the similarity of chelicerates, myriapods and hexapods in percentage GC content.

The Biology and Ecology of Heliothis-Armigera (hubner) and Heliothis-Punctigera Wallengren (lepidoptera, Noctuidae) in Australia - What Do We Know

Abstract: The taxonomy and identification of Heliothis armigera and H. punctigera, their distribution and host plants in Australia, the effect of host plant on reproduction and on the development and survival of immature stages, their movements, population biology and dynamics, and their control, are reviewed. Areas where further study is desirable include: the nature of host plant selection and host species preference; adaptability to new cultivars; effects of host plant on development; detailed life-table studies on different host plants; the contribution of predation, parasitism and disease to mortality; factors responsible for fluctuations in populations between years, including the origins of outbreak populations; and control strategies other than insecticide treatment.

The structure and fuction of the Epididymis. 1. The histology of the Rat Epididymis.

Abstract: Epididymides from six white rats have been examined by standard histological techniques. The epididymis, consisting of rete, efferent ducts, and epididymal duct possesses an epithelium containing six cell types-principal, basal, ciliated, apical, halo, and clear cells-each of which is described. Cytoplasmic differences in the principal cells permit two zones to be recognized in the efferent ducts. The principal cells along the length of the epididymal duct vary in a number of features such as: height, depth and distribution of staining, the incidence, size, and intracellular distribution of vacuoles, the shape of the nuclei, and the distribution of chromatin within them. Such differences permit definition of six major zones, some of which may be further subdivided. Variations in the histological characteristics of the various zones in different individuals have been described. These zones have been related to the usual anatomical divisions of head, isthmus, and tail. The lumen of the epididymis contains spermatids and their breakdown products in addition to spermatozoa. The latter vary in density (number per unit volume), and in their arrangement with respect to one another, in the various zones of the efferent epididymal ducts. The implications of these histological findings in the physiology of the epididymis are discussed.