Thermoregulation in a large bird,the emu (Dromaius novaehollandiae)

The emu is a large, flightless bird native to Australia. Its habitats range from the high snow country to the arid interior of the continent. Our experiments show that the emu maintains a constant body temperature within the ambient temperature range-5 to 45°C. The males regulate their body temperature about 0.5°C lower than the females. With falling ambient temperature the emu regulates its body temperature initially by reducing conductance and then by increasing heat production. At-5°C the cost of maintaining thermal balance is 2.6 times basal metabolic rate. By sitting down and reducing heat loss from the legs the cost of homeothermy at-5°C is reduced to 1.5 times basal metabolic rate. At high ambient temperatures the emu utilises cutaneous evaporative water loss in addition to panting. At 45°C evaporation is equal to 160% of heat production. Panting accounts for 70% of total evaporation at 45°C. The cost of utilising cutaneous evaporation for the other 30% appears to be an increase in dry conductance.Abbreviations A _r Effective radiating surface area - BMR basal metabolic rate - C _dry dry conductance - CEWL cutaneous evaporative water loss - EHL evaporative heat loss - EWL evaporative water loss - FECO₂ fractional concentration of CO₂ in excurrent air - FF_H2O water content of chamber excurrent air - FEO₂ fractional concentration of O₂ in chamber excurrent air - FICO₂ fractional concentration of CO₂ in incurrent air - FIO₂ fractional concentration of O₂ in chamber incurrent air - MHP metabolic heat production - MR metabolic rate - REWL respiratory evaporative water loss - RH relative humidity - RQ respiratory quotient ; - SA surface area - SEM standard error of the mean - SNK Student-Newman-Keuls multiple range test - STPD standard temperature and pressure dry - T _a ambient temperature(s) - T _b body temperature(s) - T _e surface temperature(s) - flow rate of air into the chamber - carbon dioxide production - oxygen consumption - vapour pressure of water     

Structural peculiarities associated with multiflagellate sperm in the emu, Dromaius novaehollandiae

Multiflagellate sperm represent a rare defect in mammals and also in the emu where an incidence of only 1% multiflagellate sperm was recorded in semen samples from 15 birds. Biflagellate sperm were the most frequent form of the defect observed, but 3- to 5-tailed sperm were also noted. An association was apparent between multiple tails and macrocephalic sperm, which accounted for 0.6% of multiflagellate sperm. Structural features of the defect were generally similar to those seen in mammals. The duplicated tails shared a single midpiece, which housed supernumerary centriolar complexes, each surrounded by a mitochondrial sheath. A single row of mitochondria separated adjacent centriolar complexes. Elements of the connecting piece (segmented columns, capitellum) appeared normal. The nuclear base appeared flat, staggered, or scalloped depending on the number and depth of additional implantation fossae. Multiflagellate emu sperm of normal head dimensions displayed a widened nuclear base (in the form of an attenuated peripheral nuclear extension) to accommodate the attachment of the additional centriolar complexes. Defective mammalian sperm do not show this modification of the nuclear base as the inherently wider sperm head is able to accommodate the supernumerary centrioles. Although often spiraled around each other, the duplicated principal pieces of the tail were generally separated and free. However, in some cells the proximal parts were collectively bound within the plasmalemma. Multiflagellate sperm appear to have a dual origin with some defective cells originating from incomplete cytokinesis and others as a result of abnormal centriolar duplication.     

Sperm viability, motility and morphology in emus (Dromaius novaehollandiae) are independent of the ambient collection temperature but are influenced by storage temperature

A protocol for storage of emu semen >6 h has not yet been optimized. The objective was to determine: a) whether sperm quality was adversely affected by sudden exposure to low temperatures (5, 10 and 20 °C) during collection; and b) the effects of three storage temperatures (5, 10 and 20 °C) on survival of emu sperm. In two experiments, each repeated three times on alternate days, ejaculates were diluted 1:1 with precooled (5, 10, or 20°C) UWA-E3 diluent and stored for up to 48 h. Collection temperature, or interaction with either the storage time or storage temperature, had no significant effect on sperm viability, motility, or morphology. Mass Motility Score (2.91-3.27 ± 0.26, mean ± SEM), and percentages of live (72.4-76.2 ± 2.4) and morphologically normal sperm (63.3-64.5 ± 2.3) were comparable among collection temperatures. Conversely, storage temperature and storage time affected (P < 0.05) sperm viability, motility, and morphology. After storage for 48 h, percentages of viable, normal, and motile sperm were higher (P < 0.001) at 5 °C (58.7% ± 1.1, 44.7% ± 1.3, and 50.7% ± 4.9, respectively) and 10 °C (62.6% ± 1.1, 54.1% ± 1.3, and 60.4% ± 4.9) than at 20 °C (27.6% ± 1.1, 20.1% ± 1.3, and 25.9% ± 4.9). Beyond 6 h of storage, the percentage of abnormal sperm was higher (P < 0.001) for storage at 5 °C compared to 10 and 20 °C. After 48 h, bacterial counts were considerably higher at 20 °C compared to 5 and 10 °C (P < 0.001). The pH of stored sperm suspension remained unaffected at 5 and 10 °C, but at 20 °C declined to 6.5 ± 0.03 after 24 h (P < 0.05) and to 6.0 ± 0.03 after 48 h (P < 0.001). We concluded that emu semen could be collected at low ambient temperatures (5-20 °C) without compromising its in vitro storage duration and that semen quality during storage for 48 h was better if it was stored at 10 °C than at 5 or 20 °C.     

Histochemical Characterization and Distribution of Fiber Types in the Pectoralis Muscle of the Ostrich (Struthio camelus) and Emu (Dromaius novaehollandiae)

The muscle fibers of the pectoralis (M. pectoralis pars thoracicus) of a male and a female ostrich (Struthio camelus) and a male and a female emu (Dromaius novaehollandiae) were studied histochemically for succinate dehydrogenase and myofibrillar adenosine triphosphatase. Slow-tonic (ST), fast-twitch oxidative-glycolytic (FOG) and fast-twitch glycolytic (FG) fibers were approximately equal in number and distribution in the emu pectoralis examined. In the ostriches, both predominantly FG and approximately equal areas, were present. ST fibers were significantly (P ≤ 0.05) larger than the similarly (P ≥ 0.05) sized FG and FOG fibers in the female ostrich and emus. In the male ostrich ST fibers were smaller (P ≤ 0.05) than FG fibers, neither of which were significantly (P ≥ 0.05) different from FOG fibers. The ratites have the greatest percentage and widest distribution of ST fibers found in any avian pectoralis studied to date. This could represent the ancestoral avian pectoralis, neoteny or an effect of flightlessness. ST fibers are used in the maintenance of posture, which is probably the main role of the pectoralis in the emu. The predominantly FG areas of the ostrich are indicative of an additional function, namely, behavioural display. Sexual dimorphism in the ostrich pectoralis is strongly suggested.     

Distribution and characterization of microsatellites in the emu (Dromaius novaehollandiae) genome

This study generates data concerning the genome of a flightless species of bird, the emu. We examined and ultimately rejected the following hypotheses: (1) Microsatellites are randomly distributed throughout the emu genome. (2) The relative order of abundance of dinucleotides will be constant across genomes. (3) Interspersion distances for a given dinucleotide will be equal across vertebrate genomes. (4) In all genomes, a dinucleotide will be more frequent than any trinucleotide. (5) The percentage of single-copy DNA will remain the same in emus as in other volant birds. A cosmid library representing 4.48% of the emu genome was probed with 23 microsatellites. Hybridizations were scored on a scale of 0-3. The average insert size, approximately 40 kb, was used to determine frequency and interspersion. The cosmid library was probed with genomic DNA to determine the percent single copy. Co-occurrence frequencies and confidence intervals were compared to expected using chi-squared. The genome is estimated to contain a microsatellite repeat every 48 kb. Of 1632 clones probed for single-copy DNA, 643 displayed maximal hybridization, 220 displayed moderate hybridization, and 202 had minimal hybridization. After 3 days, 567 showed no hybridization.     

Osteology and myology of the wing of the Emu (Dromaius novaehollandiae), and its bearing on the evolution of vestigial structures

Emus have reduced their wing skeleton to only a single functional digit, but the myological changes associated with this reduction have never been properly described. Moreover, the intraspecific variability associated with these changes has not previously been examined, dissections having been restricted in the past to only one or two individuals. In this paper, the myology and osteology of the Emu wing is described for a sample of five female birds. The Emu showed a marked reduction in the number of muscles in the wing, even compared with other ratites. Many wing muscles showed diversity in structure, origin and insertion sites, number of heads, as well as presence-absence variation. This variability dramatically exceeds that found in flying birds. Evolutionary theory predicts that relaxed selection on vestigial organs should allow more variation to persist in the population, and corresponds to what is observed here. A large amount of fluctuating asymmetry was also detected, indicating reduced canalization of the wing during development.     

Microsatellite analysis of genetic diversity in wild and farmed Emus (Dromaius novaehollandiae)

The emu (Dromaius novaehollandiae) occupies most regions of the Australian continent and in recent times has been farmed for meat, oil, and leather. Very little is known about the genetic structure of natural or farmed populations of these birds. We report a preliminary study of genetic variation in emus undertaken by typing birds from five farms and two natural populations at five polymorphic microsatellite loci. Genetic diversity was high for all populations and there was little evidence of inbreeding, with most populations conforming to Hardy-Weinberg equilibrium for most loci. Significant heterozygote deficiencies at one locus in a number of populations were detected and may indicate the presence of null alleles. Comparisons of allele frequencies showed little evidence of genetic differentiation either among farmed populations or between farmed and natural populations.     

Ventilatory accommodation of oxygen demand and respiratory water loss in a large bird,the emu (Dromaius novaehollandiae), and a re-examination of ventilatory allometry for birds

Ventilation was studied in the emu, a large flightless bird of mass 40kg, within the range of ambient temperatures from-5 to 45°C. Data for the emu and 21 other species were used to calculate allometric relationships for resting ventilatory parameters in birds (breath frequency=13.5 mass^-0.314; tidal volume=20.7 mass^1.0). At low ambient temperatures the ventilatory system must accommodate the increased metabolic demand for oxygen. In the emu this was achieved by a combination of increased tidal volume and increased oxygen extraction. Data from emus sitting and standing at-5°C, when metabolism is 1.5x and 2.6x basal metabolic rate, respectively, indicate that at least in the emu an increase in oxygen extraction can be stimulated by low temperature independent of oxygen demand. At higher ambient temperatures ventilation was increased to facilitate respiratory water loss. The emu achieved this by increased respiratory frequency. At moderate heat loads (30–35°C) tidal volume fell. This is usually interpreted as a mechanism whereby respiratory water loss can be increased without increasing parabronchial ventilation. At 45°C tidal volume increased; however, past studies have shown that CO₂ washout is minimal under these conditions. The mechanism whereby this is possible is discussed.Abbreviations BMR basal metabolic rate - BTPS body temperature, ambient pressure, saturated - EO ₂ oxygen extraction - EWL evaporative water loss - f _R ventilation frequency - RH relative humidity - RHL respiratory heat loss - SEM standard error of the mean - SNK student-Newman-Keuls multiple range test - STPD standard temperature and pressure, dry - T _a ambient temperatures(s) - T _b body temperature(s) - T _ex expired air temperature(s) - T _rh chamber excurrent air temperature - V _J ventilation - VO₂ oxygen consumption - V _T tidal volume - V/Q air ventilation to blood perfusion ratio     

Hip joint contact force in the emu (Dromaius novaehollandiae) during normal level walking

The emu is a large, (bipedal) flightless bird that potentially can be used to study various orthopaedic disorders in which load protection of the experimental limb is a limitation of quadrupedal models. An anatomy-based analysis of normal emu walking gait was undertaken to determine hip contact forces for comparison with human data. Kinematic and kinetic data captured for two laboratory-habituated emus were used to drive the model. Muscle attachment data were obtained by dissection, and bony geometries were obtained by CT scan. Inverse dynamics calculations at all major lower-limb joints were used in conjunction with optimization of muscle forces to determine hip contact forces. Like human walking gait, emu ground reaction forces showed a bimodal distribution over the course of the stance phase. Two-bird averaged maximum hip contact force was approximately 5.5 times body weight, directed nominally axially along the femur. This value is only modestly larger than optimization-based hip contact forces reported in literature for humans. The interspecies similarity in hip contact forces makes the emu a biomechanically attractive animal in which to model loading-dependent human orthopaedic hip disorders.     

Characterization of new microsatellite markers derived from sequence databases for the emu (Dromaius novaehollandiae)

The emu (Dromaius novaehollandiae), a member of ratite family, is native to Australia and has been introduced to other countries worldwide. In this work, 10 polymorphic microsatellite loci were isolated and characterized for emu from public sequences. Polymorphism was surveyed in 22 individuals from two different populations kept in captivity. Between two and 11 alleles were found per locus, and the observed heterozygosity ranged from 0.05 to 0.85, in accordance with expectations. These markers will be useful as tools for detecting levels of genetic variation, reconstructing pedigrees (for quantitative genetic analysis) and identifying markers associated to fitness traits in emu populations.     

Lipids in digestive gland of Littorina saxatilis rudis (Maton) and in daughter sporocysts of Microphallus similis (Jäg. 1900)

Parasitism by sporocysts was associated with a slight decrease in triglycerides and fatty acids in host digestive gland cells suggesting that the parasite digests, absorbs, and metabolises fats of host origin. An increase in phospholipids and a marked increase in the incorporation of acetate-1-¹⁴C in parasitised digestive glands may be the result of attempted cell regeneration. The parasite had less monoglycerides, triglycerides, and fatty acids but took up more palmitate-1-¹⁴C than the host. Sterols and sterol esters are more concentrated and more readily synthesised in the parasite than in the host. The relatively high level of phospholipids in the former may be related to number of cercariae within the sporocysts.     

Development of a CAPS (cleaved amplified polymorphics sequence) assay for sex identification of the emu (Dromaius novaehollandiae)

Polymerase chain reaction (PCR) based procedures that have been used to identify the sex of most birds cannot be used in ratites. This paper describes the identification of a female (W‐chromosome) specific randomly amplified polymorphic (RAPD) 1.3 kb DNA fragment (ESEXW) in the emu (Dromaius novaehollandiae). Southern blot experiments and sequence analysis revealed that a related (96% similarity) sequence exists on the emu Z‐chromosome (ESEXZ). The sequences of ESEXW and ESEXZ have been used for the development of a two‐primer CAPS (cleaved amplified polymorphic sequence) assay for reliable sex identification of the emu.     

Distribution and structure of glandular tissue in the oropharynx and proximal esophagus of the emu (Dromaius novaehollandiae)

Crole, M.R., Soley, J.T. 2011. Distribution and structure of glandular tissue in the oropharynx and proximal esophagus of the emu (Dromaius novaehollandiae). —Acta Zoologica (Stockholm) 92 : 206–215. The glandular regions of the upper digestive tract in the emu were non‐pigmented (except for the tongue in most specimens) and invested by a non‐keratinised stratified squamous epithelium. The glands found in these regions were exclusively simple in nature and composed of tubular secretory units lined by Periodic Acid Schiff Stain‐positive mucus‐secreting cells. The naming of the various glandular fields was based on previously identified anatomical features and on nomenclature modified from previous studies on birds. The glands were classified into two main types, namely, simple tubular and simple branched tubular mucus‐secreting glands. Simple branched tubular glands were a feature of the regions exposed to the greatest amount of friction during feeding, whereas simple tubular glands were a feature of regions exposed to less friction. The saliva produced by the salivary glands in birds functions to moisturize and lubricate food boli. Mucins in saliva also protect mucosal surfaces from desiccation and mechanical damage, assist in maintaining cellular water balance, provide lubrication and have an antimicrobial action. This study suggests that, in addition to the role of specific gross anatomical features, the type and distribution of glandular tissue in the emu upper digestive tract supports the cranio‐inertial feeding method employed by this species.     

Pelvic limb musculature in the emu Dromaius novaehollandiae (Aves: Struthioniformes: Dromaiidae): Adaptations to high-speed running

Emus provide an excellent opportunity for studying sustained high-speed running by a bird. Their pelvic limb musculature is described in detail and morphological features characteristic of a cursorial lifestyle are identified. Several anatomical features of the pelvic limb reflect the emus' ability for sustained running at high speeds: (1) emus have a reduced number of toes and associated muscles, (2) emus are unique among birds in having a M. gastrocnemius, the most powerful muscle in the shank, that has four muscle bellies, not the usual three, and (3) contribution to total body mass of the pelvic limb muscles of emus is similar to that of the flight muscles of flying birds, whereas the pelvic limb muscles of flying birds constitute a much smaller proportion of total body mass. Generally, the pelvic limb musculature of emus resembles that of other ratites with the notable exception of M. gastrocnemius. The presence and arrangement of four muscle bellies may increase the effectiveness of M. gastrocnemius and other muscles during cursorial locomotion by moving the limb in a cranio-caudal rather than a latero-medial plane. J. Morphol. 238:23–37, 1998. © 1998 Wiley-Liss, Inc.     

Membrane Lipids, Selectively Diminished in Alzheimer Brains, Suggest Synapse Loss as a Primary Event in Early-Onset Form (Type I) and Demyelination in Late-Onset Form (Type II)

Abstract: Major membrane lipids were quantified in frontal (Brodmann area 9) and temporal (Brodmann areas 21 and 22) cortices, caudate nucleus, hippocampus, and frontal white matter of 12 cases with Alzheimer's disease (AD) type I (early onset), 21 cases with AD type II (late onset), and 20 age-matched controls. The concentration of gangliosides—a marker for axodendritic arborization—was reduced to 58–70% of the control concentration in all four gray areas (p < 0.0001) and to 81 % in frontal white matter (p < 0.01) of AD type I cases, whereas it was only significantly reduced in temporal cortex (p < 0.01), hippocampus (p < 0.05), and frontal white matter (p < 0.05) in AD type II cases. The concentration of phospholipids was also significantly reduced (p < 0.01–0.0001) in all four gray areas of AD type I cases but in no area of AD type II cases. The loss of cholesterol was only 50% of the corresponding phospholipid diminution in AD type I. These results suggested a pronounced loss of nerve endings in AD type 1. The characteristic membrane lipid disturbance in AD type II was a loss of myelin lipids. This is the first time a fundamental biochemical difference has been shown between the two major forms of AD.