Water Flow Through the Gills of Port Jackson Sharks

Evidence is presented for the existence of a countercurrent flow between water and blood at the respiratory surfaces of the Port Jackson shark gill

Metabolic Rate, Ql0 and Respiratory Quotient (RQ) in Crocodylus Porosus, and Some Generalizations About Low RQ In Reptiles

In juvenile Crocodylus porosus, the dependence of oxygen consumption on temperature can be described by the relationship log10QO2 = 0.7221 + 0.0428T C. The Q10 was found to be 2.68 over the temperature range 20-33 C. No trend was observed between body weight and weight-specific oxygen consumption. At Ta (27-33 C) respiratory quotient (RQ (measured gasometrically) was invariably low (0.32 - 0.74, mean 0.49, 0.13 SD) in animals from freshwater. The low values of gasometric RQ are attributed to incorporation of carbon dioxide in the urine, forming ammonium bicarbonate. Support for this hypothesis is afforded by the similarity of measured values (0.49) to values predicted by the hypothesis (0.51)

The Lungfish: Creature from the Past

The survivor from prehistoric times, the salmon-fleshed Queensland lungfish, may fall victim to agricultural destruction of its habitat

Conservation Benefit from Harvesting Kangaroos: Status Report at the Start of a New Millennium - A Paper to Stimulate Discussion and Research

Over the last twenty years, kangaroo harvesting has gained much greater public acceptance and risen in monetary value. However, most landholders still regard kangaroos mainly as pests, and are a long way from making enough money from kangaroos to encourage any shift away from their focus on sheep. Yet kangaroo meat is now sold legally for human consumption in all Australian States and is common on restaurant menus, while its export is rising steadily. Extensive aerial surveys have established the abundance of the three large kangaroo species and their resilience to harvesting. A small number of landholders are benefiting from kangaroos, either by selling access to shooters/processors or through direct involvement as licensed operators. The International Union for the Conservation of Nature has supported the concept of achieving conservation benefits from the sustainable use of wildlife, and this has been incorporated into kangaroo management programs (for leather and meat) by most Australian governments. Despite all these positives, the low price of kangaroo meat, which has still not found the place it deserves on the international game meat market, is a major impediment to implementing "sheep replacement therapy for rangelands", and only when prices rise significantly will landholders choose to reduce sheep numbers and invest their hopes in kangaroos. Meanwhile, land degradation continues unabated and low prices for coarse fibre wool, while encouraging woolgrowers in the sheep rangelands to overstock, also provide a stimulus to landholders to diversify. Alarmingly, many landholders are choosing to diversify into goats which, though profitable in the short term, will extend the damage done by sheep. Low prices for wool from the sheep rangelands also amplify the clamour for kangaroo control, and governments are responding by researching or implementing programs designed to significantly reduce kangaroo numbers. South Australia now has a program which, if implemented fully, would reduce kangaroos by 60%. In Queensland and NSW, research projects are examining more effective ways to reduce kangaroo numbers. These goals reflect an acceptance of the folklore that competition from kangaroos compromises wool production and markedly reduces sheep carrying capacity, even though scientific evidence for this is lacking. But reducing kangaroos will not bring the anticipated benefits to woolgrowers, because kangaroos at typical densities are a much smaller component of the total grazing pressure (TGP) than is generally assumed. This is because the factor of 0.7 DSE (dry sheep equivalent), by which kangaroo numbers are translated into forage lost to sheep, is an overestimate. Taking body weights into account the factor should be about 0.4 and, taking measurements of field metabolic rate into account, may be as low as 0.15-0.2. Hence, even if the desired reductions in kangaroos could be achieved, there would be little or no difference to the economic viability of woolgrowers in the sheep rangelands. Furthermore, if governments decide to institute significant reductions in kangaroos without data to confirm the conservation and economic benefits of doing so, there will probably be strong criticism from conservation and animal rights organisations as well as from Australians at large, and this approach may have to be abandoned. For these reasons, the focus of kangaroo management as pest control aimed at improving wool productivity is doomed to failure. I still support the alternative view that the best way to reduce grazing pressure on the rangelands is by reducing sheep, and that the best way to achieve this is to develop a market for a high-value kangaroo industry and to sell its monopoly product on the world market for game meat. A significant increase in the value of kangaroo meat could make the harvest of free-range kangaroos for skins and meat a profitable and ecologically desirable enterprise for landholders. This would harness economic incentives in the service of ecological sustainability and rangeland rehabilitation and thus provide another example of achieving conservation goals through the sustainable use of wildlife. Furthermore, the development of a high value, sustainable kangaroo industry stands in sharp contrast to the fatalism of some ecological commentators who can only prescribe mass closure of Australian rural communities and essentially evacuating marginal country. What is needed to achieve these desirable social, economic and conservation goals is a strong marketing effort and I provide some suggestions about the attributes of kangaroo meat and the benefits of kangaroo harvesting which could feature in a marketing campaign

Water Relations of Crocodilian Eggs: Management Considerations

This paper reviews knowledge about water relations of the eggs of Crocodylus porosus and makes it clear that, It is clear that, for a crocodile farmer, more information is needed to establish the relationship between the visible signs that occur at different incubation humidities and the fitness of resultant hatchlings. It may turn out that water availability, like temperature, has subtle but important effects which should not be overlooked

Lack of Metabolic Acclimation to Different Thermal Histories by Tadpoles of Limnodynastes Peroni (Anura: Leptodactylidae) 1

Tadpoles of Limnodynastes peroni show no evidence of any ability to undergo thermal metabolic acclimation when kept at 15 degrees C and 25 degrees C for periods up to 75 days. When kept for 90-120 days, small differences were seen between rate-temperature curves of 15 degrees C and 25 degrees C history tadpoles. The reality of these differences as evidence for thermal metabolic acclimation is difficult to assess. An overall equation to describe the effect of temperature (T, C) and weight (W, grams) on oxygen consumption (QO2, ml g-1 h-1) is log10 QO2 = -2.13 + 0.05T - 0.48 log10 W, for which r2 = 0.86 (no. = 360). Q10 is 3.16 and in the relationship M +/- Wb (where M = oxygen consumption, ml h-1), the exponent b = 0.52. The results suggest that in tadpoles of L. peroni any adaptations to fluctuating temperatures may be behavioral rather than physiological or biochemical

Control of Thermal Conductance is Insignificant to Thermoregulation in Small Reptiles

Five small species of Australian scincid lizard

Thermal Ecology of the Australian Agamid Pogona barbata

This study compares the thermal ecology of male bearded dragon lizards (Pogona barbata) from south-east Queensland across two seasons: summer (1994-1995) and autumn (1995). Seasonal patterns of body temperature (Tb) were explored in terms of changes in the physical properties of the thermal environment and thermoregulatory effort. To quantify thermoregulatory effort, we compared behavioral and physiological variables recorded for observed lizards with those estimated for a thermoconforming lizard. The study lizards' field Tbs varied seasonally (summer: grand daily mean (GDM) 34.6 +/- 0.6 degrees C, autumn: GDM 27.5 +/- 0.3 degrees C) as did maximum and minimum available operative temperatures (summer: GDM Tmax 42.1 +/- 1.7 degrees C, Tmin 32.2 +/- 1.0 degrees C, autumn: GDM Tmax 31.7 +/- 1.2 degrees C, Tmin 26.4 +/- 0.5 degrees C). Interestingly, the range of temperatures that lizards selected in a gradient (selected range) did not change seasonally. However, P. barbata thermoregulated more extensively and more accurately in summer than in autumn; lizards generally displayed behaviors affecting heat load nonrandomly in summer and randomly in autumn, leading to the GDM of the mean deviations of lizards' field Tbs from their selected ranges being only 2.1 +/- 0.5 degrees C in summer, compared to 4.4 +/- 0.5 degrees C in autumn. This seasonal difference was not a consequence of different heat availability in the two seasons, because the seasonally available ranges of operative temperatures rarely precluded lizards from attaining field Tbs within their selected range, should that have been the goal. Rather, thermal microhabitat distribution and social behavior appear to have had an important influence on seasonal levels of thermoregulatory effort

Studies on the Queensland Lungfish, Neoceratodus Forsteri (Krefft): II. Thermal Acclimation

Six juvenile Neoceratodus of convenient size for respirometry (27-51 g) were available for study. Fish of this size are very rarely taken and the opportunity was used to examine the ability to examine the ability of Neoceratodus to undergo metabolic acclimation. Metabolic rate-temperature curves were constructed for fish with cold (18 degrees C) and warm (25 degrees C) thermal histories, using oxygen consumption as a measure of the rate of metabolism. The Q10 of fish with warm history (Q10 = 2.42) was higher than that for fish with cold history (Q10 = 1.55) and it was seen that there was partial thermal acclimation over the range investigated