Respiration and energetics of embryonic development in a large altricial bird, the Australian pelican (Pelecanus conspicillatus)

We examined whether the previously reported low cost of embryonic development in pelicans could be attributed to a more efficient conversion of egg energy to hatchling tissues as a result of high initial egg water content, low embryonic metabolic rate and growth later in incubation than in more precocious species. We therefore determined egg and hatchling composition and the development of embryonic respiration in the Australian pelican Pelecanus conspicillatus, which lays one of the largest eggs (140-210 g) with an altricial developmental mode. The small yolk fraction (21%) is typical of all pelecaniforms; however, we found that intraspecific variability in fresh egg mass was related to water content (principally in the albumen), but independent of yolk mass (mean 13 g dry mass). P. conspicillatus eggs have, on average, 635 kJ of energy, irrespective of egg mass across the whole range of egg mass. The embryonic developmental pattern of O2 consumption and CO2 production showed clear plateaus lasting 2-3 days immediately prior to internal pipping, resembling the typical precocial pattern. However, the rate of pre-internal pipping O2 consumption was low in comparison with that of precocial species of similar egg mass. There is no evidence to support the hypothesis that the observed plateau in rates of O2 uptake is due to a diffusion limitation of the eggshell gas conductance in this species. Embryonic metabolic rate nearly doubled during the pipping period, but the mass-independent metabolic rate of the hatchling was low in comparison with that of the resting adult. The total O2 consumed (11 063 ml) is equivalent to 217.3 kJ (or 34% of egg energy) based on indirect calorimetry and the observed respiratory exchange ratio of 0.71. Thus, the cost of development (direct calorimetry) was 0.29 kJ J-1 in the egg (mean egg mass 168 g), which is one of lowest reported values. As a result, the production efficiency of pelican embryonic development was 61.6%, higher than the average for birds in general (56.9%) and, in particular, of seabirds that have prolonged incubation periods on the basis of egg mass. High efficiency in embryonic development in this species was attained as a result of rapid embryonic growth later in incubation, low hatchling energy density (23.6 kJ g-1 dry matter) and dry matter content, low embryonic metabolic rate throughout incubation and a shorter than expected incubation period of 33 days (predicted 36 days).James T. Pearson, Roger S. Seymour, Russell V. Baudinette and Susan Runcima

Developmental allometry of pulmonary structure and function in the altricial Australian pelican Pelecanus conspicillatus.

Quantitative methods have been used to correlate maximal oxygen uptake with lung development in Australian pelicans. These birds produce the largest altricial neonates and become some of the largest birds capable of flight. During post-hatching growth to adults, body mass increases by two orders of magnitude (from 88·g to 8.8·kg). Oxygen consumption rates were measured at rest and during exposure to cold and during exercise. Then the lungs were quantitatively assessed using morphometric techniques. Allometric relationships between body mass (M) and gas exchange parameters (Y) were determined and evaluated by examining the exponents of the equation Y=aMb. This intraspecific study was compared to interspecific studies of adult birds reported in the literature. Total lung volume scales similarly in juvenile pelicans (b=1.05) as in adult birds (b=1.02). However, surface area of the blood–gas barrier greatly increases (b=1.25), and its harmonic mean thickness does not significantly change (b=0.02), in comparison to exponents from adult birds (b=0.86 and 0.07, respectively). As a result, the diffusing capacity of the blood–gas tissue barrier increases much more during development (b=1.23) than it does in adult birds of different sizes (b=0.79). It increases in parallel to maximal oxygen consumption rate (b=1.28), suggesting that the gas exchange system is either limited by lung development or possibly symmorphic. The capacity of the oxygen delivery system is theoretically sufficient for powered flight well in advance of the bird’s need to use it.Roger S. Seymour, Sue Runciman, Russell V. Baudinette and James T. Pearso

Food cost and availability in a rural setting in Australia

Introduction: The burden of chronic diseases is rapidly increasing worldwide. In&nbsp; Australia rural populations have a greater burden of disease. Chronic diseases are largely preventable with diet as a key risk factor. With respect to diet-related chronic disease, dietary risk may be due to poor food access, namely, poor availability and/or the high cost of healthy food. It is likely that poor food access is an issue in rural areas. Objective: To assess food access in rural south-west (SW) Victoria, Australia.Methods: A total of 53 supermarkets and grocery stores in 42 towns participated in a survey of food cost and availability in the rural area of SW Victoria. The survey assessed availability and cost of a Healthy Food Access Basket (HFAB) which was designed to meet the nutritional needs of a family of 6 for 2 weeks.Results: Seventy-two percent of the eligible shops in SW Victoria were surveyed. The study found that the complete HFAB was significantly more likely to be available in a town with a chain-owned store (p&lt;0.00). The complete HFAB was less likely to be available from an independently owned store in a town with only one grocery shop (p&lt;0.004). The average cost of the HFAB across SW Victoria was AU380.30 ± 25.10 (mean &plusmn; SD). There was a mean range in difference of cost of the HFAB of $36.92. In particular, high variability was found in the cost of fruits and vegetables.Conclusions: Cost and availability of healthy food may be compromised in rural areas. Implications: Improvements in food access in rural areas could reduce the high burden of disease suffered by rural communities.<br /

Development of maximum metabolic rate and pulmonary diffusing capacity in the superprecocial Australian Brush Turkey Alectura lathami: An allometric and morphometric study

Copyright © 2006 Elsevier Inc. All rights reserved.The Australian Brush Turkey Alectura lathami is a member of the Megapodiidae, the mound-building birds that produce totally independent, "superprecocial" hatchlings. This study examined the post-hatching development of resting and maximal metabolic rates, and the morphometrically determined changes in pulmonary gas exchange anatomy, in chicks during 3.7 months of growth from hatchlings (122 g) to subadults (1.1 kg). Allometric equations of the form y=aM(b) related gas exchange variables (y) to body mass (M, g). Metabolic rates were measured with open-flow respirometry (mL O2 min(-1)) of chicks resting in the dark and running above the aerobic limit on a treadmill. Resting metabolic rate (RMR=0.02 M(0.99)) and maximal metabolic rate (MMR=0.05 M(1.07)) scaled with exponents significantly above those of interspecific allometries of adult birds. However MMR was below that expected for other species of adult birds in flapping flight, consistent with the Brush Turkey's ground-dwelling habits. Total lung volumes (mL) increased faster than isometrically (V(L)=0.0075 M(1.19)), as did the surface area (cm(2)) of the blood-gas barrier (S(t)=7.80 M(1.23)), but the data overlapped those of adult species. Harmonic mean thickness of the blood-gas barrier was independent of body size (mean tau(ht),=0.39 microm) and was about twice that expected for flying birds. Diffusing capacity (mL O2 min(-1) kPa(-1)) of the blood-gas tissue barrier increased faster than isometrically (Dto2=0.049 M(1.23)); in hatchling Brush Turkeys, it was about 30% expected for adult birds, but this difference disappeared when they became subadults. When compared to altricial Australian pelicans that hatch at similar body masses, superprecocial Brush Turkeys had higher MMR and higher Dto2 at the same body size. A parallel allometry between MMR and Dto2 in Brush Turkeys and pelicans is consistent with the concept of symmorphosis during development.Roger S. Seymour, Sue Runciman and Russell V. Baudinettehttp://www.elsevier.com/wps/find/journaldescription.cws_home/525464/description#descriptio

Morphometric estimate of gas-exchange tissue in the new-born tammar wallaby, Macropus eugenii

The lung of the new-born marsupial is at the terminal air sac stage of development. The maturational status of the lung of new-born tammar wallaby was assessed using established morphometric techniques and the results were compared with data from a morphometric study of the lung of the rat. Volume densities of the parenchyma and non-parenchyma, conducting airways and blood vessels, the relative volumes of airspace and tissue, the thickness and the composition of the septa differed between the two species. In addition the volume of capillaries and the surface area of the effective gas-exchange tissue was greater in the new-born rat than in the new-born tammar pouch young. The lung of the new-born tammar appears to be at an earlier phase of the terminal air sac stage than that of the new-born rat. Lung development up to birth appears to be commensurate to the metabolic needs of the organism at birth.S.I.C. Runciman, R.V. Baudinette, B.J. Gannon and J. Lipset

Morphometric analysis of postnatal lung development in the tammar wallaby: Light microscopy

Postnatal growth of the lung in the tammar wallaby, Macropus eugenii, was investigated using morphometric techniques with light microscopy. Lung volume, parenchymal and non-parenchymal volume densities were measured. Volume densities of parenchymal airspace and tissue and non-parenchymal conducting airways and large blood vessels were determined. Lung volume and all the other parameters that were measured showed a biphasic increase in relation to increase in body mass. All parameters, with the exception of airway volume, increased relatively slowly in relation to increase in mass in the first 70 days after birth, when the pouch young are ectothermic. Between 70 and 180 days, during the period of transition from ectothermy to endothermy, the parameters increased more rapidly, suggesting accelerated lung growth in preparation for the extra metabolic demands associated with the establishment of thermoregulatory control in the pouch young. Specific lung volume in the adult tammar is lower than that of eutherians of equivalent mass, however, the parenchymal volume is relatively high.S.I.C Runciman, R.V Baudinette, B.J Gannon and J Lipset

Morphometric analysis of postnatal lung development in a marsupial: transmission electron microscopy

Postnatal lung development in the tammar wallaby was investigated using transmission electron microscopy and stereological morphometry. Volume densities of interstitial, epithelial and endothelial tissue and capillaries in the parenchymal septa were measured as were surface densities of the airspaces and gas exchange capillaries. Absolute changes in these parameters were related to body mass. Three phases of development were identified. During the ectothermic period, in the first 70 days after birth when the lung was in the terminal air sac phase, the most marked change was an increase in volume density of septal interstitium. The transitional period between ectothermy and endothermy, between 70 and 180 days after birth, corresponded to the alveolar phase and was characterised by accelerated increase in air space surface area. Maturation of the parenchymal septa and establishment of the mature capillary system occurred largely after 180 days when endothermy was established. The anatomical diffusion factor in the tammar wallaby adult is similar to that for eutherians.Runciman, S.I.C ; Baudinette, R.V ; Gannon, B.J ; Lipsett,

Fur does not fly, it floats: buoyancy of pelage in semi-aquatic mammals

The transition from a terrestrial to an aquatic lifestyle in mammals required the evolution of specific adaptations for locomotion and stability in water. We postulated that the non-wettable fur of semi-aquatic mammals is an important adjunct to buoyancy control. Fur buoyancy characteristics and hair morphology were examined for two terrestrial mammals (opossum, Didelphis virginiana and Norway rat, Rattus norvegicus), and seven semi-aquatic mammals, (beaver, Castor canadensis; sea otter, Enhydra lutris; Australian water rat, Hydromys chrysogaster; river otter, Lutra canadensis; American mink, Mustela vison; muskrat, Ondatra zibethicus; and platypus, Ornithorhynchus anatinus). We determined buoyancy hydrostatically, measured hair density on histological skin samples, and hair length and diameter. Buoyancy was positively correlated with hair density, but was not with hair length or thickness. As expected, buoyancy was considerably greater in aquatic mammals than in terrestrial mammals. Enhydra displayed the greatest hair density (1188.8 hairs/mm2) with a buoyant force of 0.94 N, whereas Rattus had the lowest hair density (95.2 hairs/mm2) and Didelphis had the lowest fur buoyancy of 0.12 N. High hair density of non-wettable fur traps large amounts of air and thus provides semi-aquatic mammals with positive buoyancy and decreases the effort needed to float.Frank E. Fish, Jennifer Smelstoys, Russell V. Baudinette, and Penny S. Reynold