INTEGRATION AND SYMMETRY IN BEROE

Despite the fact that certain prominent structures such as theeight comb-rows at first suggest an octomerous radial symmetryin ctenophores, close examination of their anatomy reveals ratherthe existence of two main planes, the sagittal and the transverse.Further, in certain forms in which one plane or the other hasbecome predominant, an apparent bilateral symmetry emerges. Relationships between anatomical and physiological symmetrywere looked for by studying the behavior of Beroe ovata andBeroe forskalii, both with regard to coordinated ciliary movementsbetween the comb-rows, and to the postures assumed during locomotion,balance, and rest in intact animals, and in animals from whichthe aboral organ had been removed. Swimming behavior is found to exhibit an octomerous functionalsymmetry. Bendings and vertical balance, however, show a tetramerousorganization. In the last case the unique properties of thestatocyst, with a structure characteristic of a regulator ofcybernetic patterns, the machines of which are the comb-rows,permit the most efficient integration of all the phenomena involvedin maintaining the vertical position. Finally the resting horizontalposition reflects a physiological bilateral symmetry basic tothe sagittal plane.     

The influence of climate on patterns of termite eating in Australian mammals and lizards

Abstract The present paper examines patterns of termite eating in Australian mammals and lizards (total numbers of species, volume percentage of diet) relative to climate (arid, semi-arid, temperate-mesic). Most termite eaters in arid and semi-arid Australia are lizards. Termite consumptio as a proportion of total lizard diet decreases from arid to mesic climates. More mammal species are relatively termite specialized (>50%) in arid than in semi-arid and mesic regions. Termite consumption in echidnas resembles that of the lizards: relatively high in the arid and relatively low in the mesic zone. For the Dasyuridae, termites comprise only a minor fraction (< 10%) in their diet, irrespective of climate. It is argued that the climatic peculiarities of inland Australia (scant and variable rainfall) cause marked seasonality in termite availability, supporting specialized termite eaters in only the most energy-frugal forms (lizards, echidnas). Areas of future research are identified.     

Species abundance and habitat differences in biomass of subterranean termites (Isoptera) in the wheatbelt of Western Australia

The distribution and abundance, and habitat differences in biomass of subterranean termites, were assessed through soil trenching for woodland, mallee and heath habitats in the central wheatbelt of Western Australia. Over an 11 month sampling period, there were no significant habitat differences in biomass. Mean dry biomass in the surficial layer of soil (per 5000 cm³) averaged 46 mg in woodland, 28 mg in mallee, and 23 mg in heath. Termite biomass peaked in September, with 141 mg for woodland, 83 mg for mallee and 47 mg for heath (per 5000 cm³). Soil moisture and termite activity near the surface were positively correlated. A total of 36 species of termites, comprising 11 genera, were identified, and species abundance within and across habitats differed significantly.     

Sodium‐specific foraging by leafcutter ant workers (Atta cephalotes,Hymenoptera: Formicidae)

1. Sodium is often a limiting nutrient for terrestrial animals, and may be especially sought by herbivores. Leafcutter ants are dominant herbivores in the Neotropics, and leafcutter foraging may be affected by nutritional demands of the colony and/or the demands of their symbiotic fungal mutualists. We hypothesized that leafcutter colonies are sodium limited, and that leafcutter ants will therefore forage specifically for sodium. 2. Previous studies demonstrated that leafcutter Atta cephalotes Linnaeus workers preferentially cut and remove paper baits treated with NaCl relative to water control baits. Atta cephalotes colonies in this study were presented with baits offering NaCl, Na₂SO₄, and KCl to test whether leafcutters forage specifically for sodium. Sucrose and water were used as positive and negative controls, respectively. 3. Atta foragers removed significantly more of the baits treated with NaCl and Na₂SO₄ than the KCl treatment, which did not differ from water. The NaCl and Na₂SO₄ treatments were collected at similar rates. We conclude A. cephalotes forage specifically for sodium rather than for anions (chloride) or solutes in general. This study supports the hypothesis that leafcutter ants are limited by, and preferentially forage for, sodium.     

Growth Control and Cyclic Alterations of Cyclic AMP in the Cell Cycle

Growth stimulated by protease treatment of untransformed cells is correlated with a decrease in cell cAMP levels and can be prevented by dibutyryl cAMP. The changed growth characteristics of transformed cells are discussed with regard to cAMP levels.     

An assessment of a natural wetland receiving sewage effluent

An assessment of the performance of a wetland dominated by opportunistic weeds in removing nutrients from a secondary sewage effluent was carried out at Thredbo in Kosciusko National Park. Water quality sampling of the inflow and outflow showed a reduction in turbidity, pH and conductivity with passage through the wetland. Dissolved oxygen levels also decreased. In summer 1982, the phosphorus toad of 1.8 kg P day^-1 was reduced by 44% as wastewater moved through the wetland, and the nitrogen load of 6.4 kg N day^-1 by 65%. Winter retentions were 10% and 14% of inflowing loads, respectively. In 1983 there was a net release of phosphorus and reduced retention of nitrogen. This was regarded as being a result of physical disturbance of the wetland. Vegetation downstream of the effluent inflow was dominated by the opportunistic weeds Epilobium sarmantaceum and Rumex crispus. Upstream, Carex gaudichaudiana and Baeckea gunniana dominated. Marked seasonal changes in vigour and biomass were recorded. Plants, but not sediments, downstream of the inflow contained more nutrients than those upstream. Seed bank analysis showed more seeds downstream than upstream. A moist treatment promoted more seed germination than a flooded treatment. E. sarmantaceum and to a lesser extent R. crispus dominated in each treatment. In an effort to promote greater water retention and replacement of the weed species, channels in the wetland have been blocked with gravel and planted with Phragmites australis and Schoenoplectus validus.     

Coordination in Sponges. The Foundations of Integration

Coordination mechanisms in sponges involve not only epitheliabut also the mesenchyne, which is the basic internal milieufor aii primitive Metazoa. There are three main types of coordination pathways: (i) Fluidextracellular coordination pathways are used for the spreadingof materials through the mesenchymal connective matrix. Examplesare provided by the processes of wound healing, regeneration,gametogenesis, and gemmulation. (ii) Mobile cellular coordinationpathways follow the transitory contacts and consecutive exchangesperformed by amoeboid cells which wander in the mesenchymalmatrix. Examples are provided by the processes of cell reaggregationand morphogenesis, (iii) Fixed tissue coordination pathwaysare achieved by permanent connections between cells belongingto the same unit structure, which can be an epithelium or whichcan be composed of mesenchymal cell networks and bundles. Examplesare provided by contractile activities of oscular membranes,internal canals, or of the whole sponge. The first and the secondpathways do not undergo significant modifications in the variousspecies of sponges. The third pathway, and especially the mesenchymalcontractile tissue, appears to be significantly well developedonly in thick-walled sponges. The discussion compares the three coordination systems of spongeswith integrative systems in higher Metazoa. The conclusion isthat if the coordination mechanisms in Porifera do not quiteresemble those found in higher animals, nevertheless they wouldhave been suitable for a further advent of true hormonal, immune,muscle, and nervous systems such as we know in other Metazoa.