Did detoxification processes cause complex life to emerge?

Excess oxygen is toxic for many cells and cell function can be disrupted by calcium, even if present in small amounts. Cells avoid the toxic effects of these substances by excreting oxygen-rich or Ca-containing molecules. The origin of macroscopic multi-celled animals (metazoans) can be attributed to the excretion of oxygen-rich collagen molecules (or their precursors) at a time when the seas were for the first time both oxygenated and sufficiently loaded with phosphorus for the energy (ATP) requirements of sizable metazoans. With subsequent increase of Ca in the marine environment, hard parts of CaCO₃ were produced. Excretion of oxygen in combination with abundant phosphorus permitted phosphate biomineralization. In this view, the most informative biological development during the late Neoproterozoic was not the emergence of metazoans but the initial construction of viable tissues. When tissue integrity is lost, whether due to low oxygen, collagen failure, injury, chemical insult or other reasons, individual cells are released from tissue-constraints. To survive, they may then revert to unicellular life-styles that emphasize cellular proliferation and variation. When this occurs in metazoans, the result may be cancer.     

Origin of the phyla and cancer

Multicelled animals with specialized cells (metazoans) emerged shortly after rising oxygen levels in the seas permitted formation of collagen-family molecules. Certain unicells then formed 3-D clusters, some with disc- or ball-like shapes that happened to resemble blastulas. These became unstable beyond a certain size due to contrasting metabolic styles among their component cells. For whereas cells near their exteriors could employ oxygen respiration, cells closer to the oxygen-deprived interiors were obliged to rely on anaerobic metabolism (fermentation), a process that produces waste molecules that, if retained within cells, cause disproportionate cell growth. Unstable blastula-like forms would either disintegrate or reorganize along surfaces of relative weakness in a process that may be likened to gastrulation. Initial cell-differentiation depended on the quantity and diversity of retained fermentation products and on the pumping of molecules from cell to cell by the consequent electro-chemical gradients. In subsequent contexts, oxygen deprivation, fermentation, excess cell growth, and disintegration or reorganization of tissues produce cancer.     

Calcification of Spirostomum ambiguum

SYNOPSIS. A method is described for cultivation of large numbers of Spirostomum ambiguum , calcified intracellularly with hydroxyapatite (bone salt deposits). The structure and activity of living animals at various stages of calcification is described and also illustrated with unstained and silver impregnated ciliates. A suitable modification of von Kossa's method for localization of insoluble phosphate deposits is given.     

Movement and phenology of bees in a subtropical Australian agricultural landscape

Bees are mobile organisms that seek food and nesting opportunities from a range of habitats. It is important to understand the way they move in agricultural landscapes if we are to conserve them and benefit from their activity as pollinators. We surveyed bees using directional flight interception (Malaise) traps over a 1‐year period in two agricultural landscapes in south‐east Queensland, Australia. We placed traps at the ecotone between crops and remnant vegetation to establish the pattern of movement between these habitats. Species richness in these landscapes (70) was high relative to that in comparable studies. Some bees were active year round, but most were caught in the period September to March. Across the whole assemblage there was a significant pattern where more species were detected leaving rather than entering remnant vegetation. The same bias was true for the number of individuals of the two most abundant species (Homalictus urbanus and Apis mellifera). Species exclusively found in crops were smaller on average (and therefore have smaller foraging range) than their non‐crop counterparts. Together, these patterns indicate that while bees are abundant in crop habitat, the remnant vegetation is important as the point of origin for bee movements, and the riparian remnant in particular is richer than the dry native remnant. Compositional similarity among samples was significantly explained by landscape but also movement direction (i.e. to or from the riparian remnant) because different species showed different patterns of response. The landscape with greater native vegetation cover supported more species in and around crops than the landscape with less native vegetation.     

Differential and delayed response of two ant species to habitat fragmentation via the introduction of a pine matrix

1. Ants are a ubiquitous and crucial component of Australian Eucalyptus forests, but responses to long‐term habitat fragmentation remain poorly understood. Two ant species were followed across a 21‐year history of pine plantation establishment and maturation in a southeast Australian Eucalyptus forest. 2. At Wog Wog in southeastern Australia, a Native Eucalyptus forest was clear‐cut to make way for plantation establishment and 12 remnant patches of forest were left intact and subsequently surrounded by a pine matrix. Pitfall traps were placed in the continuous native forest, remnant Eucalyptus patches, and the pine matrix between fragments, and were stratified based on proximity to remnant patch edges and habitat type. Two ant species are focused on that represent the only remaining data for the early years of the experiment. 3. While Leptomyrmex erythrocephalus (Fabricius), the rarer of the two species, was not affected by fragmentation in the short term, 21 years after fragmentation, it was less likely to occur in both the mature pine matrix and fragments than in continuous forest controls. Aphaenogaster longiceps (Smith F.) was equally likely to occur in the fragments, continuous forest, and pine matrix early in the experiment but by year 21 post‐fragmentation was less likely to occur in the pine matrix than fragments or controls. 4. Importantly, we only detected negative impacts of fragmentation on ant occurrence as the pine plantation matrix matured and isolated ant populations on fragments. 5. It is concluded that changes in matrix suitability and specific habitat characteristics influence ant persistence in Eucalyptus fragments.     

Leaf Water Potential Response to Transpiration by Citrus

This paper reports on further studies of a model for interpreting leaf water potential data for Citrus. Experimental data confirmed the assumption that the ratio of vapor pressure deficit to leaf diffusion resistance adequately estimates transpiration when leaf-to-air temperature differences are small. Data collected diurnally indicated that the relationship between leaf water potential and transpiration followed a sequence of steady states without hysteresis. No difference in water transport characteristics was found for Valencia orange on three rootstocks in well-watered soil, but the two rootstocks Cleopatra mandarin and Rangpur gave slightly greater leaf water stress in Valencia orange leaves than‘Troyer’ citrange rootstock at high transpiration rates under mild soil water deficits. In laboratory studies, previously unstressed seedlings had higher leaf water potentials than field trees at equivalent transpiration rates. After several drying cycles, however, leaf water potentials were similar to those observed in the field.