Yolk corticosterone and progesterone levels in Greater Rhea (Rhea americana) eggs vary in a changing social environment.

Maternal hormones in avian egg yolks may signal and prepare offspring for the prevailing conditions. However, this adjustment requires some degree of flexibility in regulating yolk hormone deposition. The Greater Rhea (Rhea americana) has a particular mating system that combines mixed polygyny and polyandry, communal nesting, and exclusive paternal care of chicks. In this species, we previously found that yolk hormone deposition varies among eggs of different captive populations and could influence chicks' physiology and behavior. However, it is still unknown whether females can modify yolk hormone deposition in a changing social environment. Using a captive population of Greater Rheas, in this study, we quantified yolk hormone levels before and after a reduction in the number of females present in the population. We found that females deposited on average higher yolk corticosterone and lower yolk progesterone after the change in their social environment. Since corticosterone deposited into the yolk comes exclusively from the female's plasma, our results suggest that females had, on average, higher plasma corticosterone levels. The change in the number of females may increase the events of male-male competitions, courtships, and matings, leading to an increase of corticosterone in the females' plasma and then into their eggs. Since we previously found that higher yolk corticosterone and lower yolk progesterone were associated with the production of chicks that have an attenuated stress response, the present study results suggest that yolk hormone deposition is mediated by flexible mechanisms that could adjust development to the prevailing conditions.

Effect of maternal environment on yolk immunoreactive corticosterone and its influence on adrenocortical and behavioral activity in chicks of Greater Rhea (Rhea americana).

Maternal corticosterone in avian eggs may modify offspring phenotype in order to increase survival in poor environments. In the Greater Rhea (Rhea americana), we previously found that yolk immunoreactive corticosterone is influenced by the quality of the maternal environment: eggs laid by females of the intensive rearing system (IRS), living in poor captive conditions, had higher yolk immunoreactive corticosterone than those produced by females of the semi-extensive rearing system (SRS), living in better conditions. Here, we evaluate if these different hormone levels are associated with the production of different phenotypes. We collected eggs from the IRS and SRS for hormonal quantification and artificial incubation. Then, half of the chicks selected from each environment were exposed to a capture and restraint protocol, and the rest remained undisturbed and were used as controls. In the IRS, we found that higher yolk immunoreactive corticosterone was associated with the production of chicks that had reduced hatchability, lower hatchling mass and higher baseline fecal glucocorticoid metabolites (FGM) than those produced by SRS females. Moreover, after capture and restraint, IRS chicks did not modify their FGM nor their behaviors compared to their controls, while SRS chicks increased their FGM and spent more time ambulating and less time pecking, compared to their controls. These results indicate that yolk immunoreactive corticosterone could modify offspring phenotype. Although future studies are needed to elucidate their implications for fitness, our results suggest that yolk corticosterone could be mediating an adaptive maternal effect that allows individuals to better cope with poor conditions.

State of the art knowledge in adrenocortical and behavioral responses to environmental challenges in a threatened South American ratite: Implications to in situ and ex-situ conservation.

The Greater Rhea (Rhea americana) is an endemic ratite to South America, whose wild populations have undergone a remarkable decrease due to habitat degradation and fragmentation by the expansion of the agricultural frontier, poaching and predation by dogs. Anthropogenic perturbations in wild environments, as well as the management in captivity, can generate different stress responses in this species, thus, the monitoring of adrenocortical and behavioral activities are considered primary assessment tools with both conservation and welfare implications. In this review we analyze and integrate the different measurements of glucocorticoids (in plasma, feces, and yolk) carried out in different captive and wild populations, taking into account the diverse predictable and unpredictable conditions to which the Greater Rhea responds in each of those environments. In addition, the translocation of this bird is presented as an application of stress physiology in field ecology for conservation purposes, in which we evaluated how this species responds when it is released into a novel environment. Our results indicate that this ratite has a striking high sensitivity of the hypothalamic-pituitary-adrenal (HPA) axis compared to that of other bird species and shows a wide variety of adrenocortical responses depending on the environment in which it lives. This suggests that its HPA axis has a phenotypic plasticity that enables the rhea to cope with the environmental challenges. In this sense, we propose that one of the routes of this plasticity could be mediated by the maternal transfer of steroid hormones to the egg. Finally, we discuss the importance of integrating the monitoring of the adrenocortical response along with the environmental variables that define the life history of the species, in management and conservation programs ex-situ and in situ.

Meat quality traits in the Greater rhea (Rhea americana) as influenced by muscle, sex and age.

Meat from the Greater rhea (Rhea americana) could compete with traditional red meats, diversifying the market of protein products of animal origin. The meat from 32 rheas was used to study quality aspects and this included ultimate pH (pHu), color, water-holding capacity (WHC%), cooking loss (CL%) and tenderness. The muscles sampled were the Gastrocnemius pars externa, Iliofibularis and Obturatorius medialis from both sexes at multiple ages (10, 12, 14, 16 months). Age at slaughter affected WHC%, CL%, and color in raw meat and tenderness in cooked meat. Muscles under study showed differences in terms of pHu, raw meat color, and tenderness of cooked meat. Sex did not have a significant effect on any of the variables studied. According to our results, rhea meat from younger animals, between 10 to 14 months old, was tender and moderately juicy and the visual color was appreciated by the consumers.

Comparative analysis of structure and strength of vitelline membrane and physical parameters of yolk of ostrich, emu, and greater rhea eggs.

In this study, we analyzed selected morphological traits of eggs, as well as structure, strength, and protein composition of the vitelline membrane (VM) of ostrich, emu, and greater rhea eggs. Ninety eggs (30 for species) were analyzed for the following parameters: egg weight, yolk weight, yolk ratio, and yolk index. In addition, pH value, water activity, consistency index, and flow behavior index were determined. The strength of VM was measured using the TA.HDPlus Texture Analyzer. Micrograph images were taken via a scanning electron microscope. Polyacrylamide gel electrophoresis was conducted under denaturing conditions. Ostrich eggs were characterized by the highest egg and yolk weight compared with those of emu and greater rhea eggs, whereas emu eggs had the highest yolk ratio compared with those of ostrich and greater rhea eggs (P > 0.05). Yolk content differed among the species in terms of water activity; it was found to be higher in emu eggs than in ostrich and greater rhea eggs (P > 0.05). Based on flow curves, yolks of the ratites were classified as pseudoplastic non-Newtonian fluids. The consistency index was significantly higher in yolks of ostrich and emu than that of greater rhea eggs, whereas the VM of yolks of greater rhea eggs was the most resistant (had the highest breaking force = 26.4 g). All species differed significantly regarding the structure of VM, the outer layer (OL) in particular, which was found to constitute fibers of various thicknesses that were differently arranged. Fibers of the OL of the VM of emu, whose fibers were the least differentiated but formed the most compact network, were the most diverse in characterization. An electropherogram of the VM of ostrich revealed 11 primary protein bands: 6 for the OL and 5 for the inner layer (IL), that of emu revealed 9 bands: 5 for the OL and 4 for the IL, and that of greater rhea revealed 10 bands: 6 for the OL and 4 for the IL.

Influence of the rearing system on yolk corticosterone concentration in captive Greater Rheas (Rhea americana).

Many environmental conditions elevate plasma corticosterone in laying birds, leading to elevated hormone accumulation in the egg. We investigated whether maternal yolk corticosterone levels in Greater Rheas differ between fresh eggs collected from an intensive (IRS) and a semi-extensive (SRS) rearing system. After HPLC validation, yolk corticosterone was measured using a corticosterone (125) I radio-immunoassay kit. Results (mean ± SE) showed that eggs collected from the IRS exhibited a significantly higher corticosterone concentration than eggs from SRS (89.88 ± 8.93 vs. 45.41 ± 5.48 ng/g yolk, respectively). Our findings suggest that rearing conditions under an intensive scheme (e.g., small pens with bare ground, no direct foraging and handling) might be perceived as more stressful for Greater Rhea females than semi-extensive rearing conditions (e.g., low animal density distributed in extensive areas and direct foraging), which would result in the transfer of higher yolk corticosterone levels. A better understanding of environmental conditions and female traits that affect yolk corticosterone deposition provides a background for future studies concerning the roles of maternal corticosterone on offspring development. Zoo Biol. 35:246-250, 2016. © 2016 Wiley Periodicals, Inc.

Aspects of the Macroscopic Testicular and Epididymal Morphology in the Greater Rhea, Rhea Americana (Linneaus - 1758) Birds.

The purpose of this research was to study the macroscopic testicular and epididymal morphology of the greater rhea. The testicles of 54 greater rhea bred in captivity were utilized. The samples were collected November 2005 (n = 14), December 2006 (n = 20) and May 2007 (n = 20). During commercial slaughter, the testicles and epididymides were collected and their following morphometric parameters were immediately measured: length, width, thickness, circumference, volume, weight of the parenchyma and the tunica albuginea, also aspects such as shape, cavity implantation, relationship with other organs and vascularization. The testicles presented cylindrical shape, with a thin, dense and transparent tunica albuginea, and the vascularization was accomplished by the testicular artery that ramifies from the cranial rectal artery. In the samples from December 2006 and May 2007, the media from the macroscopic measures of the right testicles were volume 58.7 and 14.7 ml, length 9.87 and 3.5 cm, width 2.4 and 0.6 cm, thickness 2.4 and 0.5 cm, circumference 8.0 and 2.3 cm, parenchyma weight 27.6 and 6.1 g and tunica albuginea weight 1.0 and 0.3 g, P < 0.05, respectively. The epididymides, the media from macroscopic measures December 2006 and May 2007 were volume 7.7 and 3.0 ml, length 5.8 and 1.3 cm, width 0.7 and 0.3 cm, thickness 0.6 and 0.3 cm, circumference 2.5 and 1.2 cm, tissue weight 6.4 and 2.8 g and capsule weight 0.4 and 0.1 g, P < 0.05, respectively. Some measures from the right testicle and epididymis were superior to measures taken from the left ones (P < 0.05), but these were not characterizing asymmetry. The morphometric parameters observed during November 2005 remained on an intermediate situation (P < 0.05); however, they were quantitatively closer to the means of December 2006, which may characterize it as a potential transition period between repose and sexual activity. Morphologically, the testicles and epididymides of greater rhea have common points with other researched birds; however, differences were observed. The testicles and epididymides of the Rhea americana are influenced by the environment, presenting reproductive activity season (November-December) during late spring, early summer and sexual repose season (May) during autumn-winter. The morphometric testicular and epididymal measurements were introduced. The morphometric parameters of testicles and epididymides exhibited differences between winter and spring-summer that could be established like sexual activity season.

Seasonal changes in plasma levels of sex hormones in the greater Rhea (Rhea americana), a South American Ratite with a complex mating system.

Seasonal rhythm in sex hormones has been extensively studied in birds, as well as its relationship with the type of mating system. The Greater Rhea (Rhea americana), a South American ratite species, reproduces seasonally and has a complex mating system: female-defense polygyny and sequential polyandry. The present study aimed at analyzing the endocrine basis of reproduction in this species and its relationship with its mating system. We used HPLC and electrochemiluminescence techniques to identify and measure plasma testosterone and estradiol levels. Annual oscillations in sex hormones, testosterone and estradiol, in adult males and females were observed. Lower levels of these hormones were exhibited during the non reproductive season (February to July), whereas their maximum values were reached in September for males and November-December for females. These fluctuations reflect the seasonal changes in gonadal function. By contrast, no significant sex hormones oscillations were observed in juvenile males and females (negative control of seasonal changes). Greater rheas maintain high testosterone and estradiol levels throughout the reproductive period. The high testosterone levels during incubation and chick rearing did not inhibit parental behavior in males, which appears not to conform to the "Challenge Hypothesis". In females, the high estradiol levels throughout the reproductive season would be needed to sustain their long egg-laying period.

Uso do propofol na indução anestésica de emas (Rhea americana americana) / Propofol use during anesthetic induction of Rheas (Rhea americana americana)

O propofol é um anestésico injetável que promove indução e recuperação rápida, e toxicidade limitada. Apesar de suas vantagens, poucas pesquisas determinam a dose e os efeitos do propofol em emas. Objetivou-se com este estudo avaliar o uso do propofol na indução da anestesia de emas, bem como determinar a dose de indução anestésica do fármaco para a espécie. Foram utilizados 20 emas, machos jovens, os quais foram anestesiados com propofol, administrado por via intravenosa. A frequência cardíaca (FC) e respiratória (f), temperatura cloacal (TC) foram aferidas antes da administração do propofol e logo após a obtenção da anestesia. Nestes momentos, sangue venoso foi colhido para análise hemogasométrica. Para avaliação da anestesia, realizou-se pinçamento interdigital, sendo determinados, com base na resposta ao estímulo, o período de latência, período hábil e de recuperação anestésica. A dose capaz de promover anestesia nas emas foi de 5 mg.kg-1. As médias da FC, ƒ, TC basais foram 138 bpm, 35 rpm e 39,1ºC, respectivamente e, após a indução as médias foram 180 bpm, 25 rpm e 40,6ºC. A administração do propofol não resultou em alterações significativas nos valores de pressão parcial de oxigênio, excesso de base, bicarbonato, saturação de oxigênio, pH, pressão parcial de dióxido de carbono. As médias do tempo de indução, período hábil de anestesia e tempo de recuperação, em minutos, foram respectivamente 2,48; 2,98 e 7,85. A dose do propofol encontrada para emas foi compatível com as utilizadas para a indução em outras espécies de aves. O propofol, na dose de 5 mg.kg-1, mostrou-se um fármaco seguro para indução anestésica em emas, possibilitando recuperação rápida da anestesia além de promover poucas alterações cardiorrespiratórias e hemogasométricas na espécie.

Propofol is an intravenous anesthetic agent, which promotes rapid inductions and recovery as well, as limited toxicity. Despite its advantages, the dose and effects of such a drug on rheas has not been determined yet. This study aimed to evaluate the use of propofol in anesthesia induction of rheas, and to determine its dosage for the species. Twenty young male rheas were used, which were anesthetized with propofol administered intravenously. Heart rate (HR), respiratory rate (f), and cloacal temperature (TC) were measured before administration of propofol and soon after obtaining anesthesia. In those moments, venous blood was collected for hemogasimetric analysis. Interdigital pinch was held for evaluation of anesthesia, being determined, based on the response to the stimulus, the latency period as well as active period and anesthetic recovery. The dose able to induce anesthesia in rheas was 5mg.kg-1.The average HR, ƒ, TC levels were 138 bpm, 35rpm and 39.1ºC, respectively; and after inducing the averages were 180 bpm, 25rpm and 40.6ºC. Administration of propofol resulted in no significant changes in the values of oxygen partial pressure, base excess, bicarbonate, oxygen saturation, pH, and carbon dioxide partial pressure. The average induction time, active period of anesthesia and recovery time, in minutes, were respectively 2.48, 2.98 and 7.85. The dose of propofol found to rheas was compatible with those used for induction in other avian species. Propofol at a dose of 5 mg.kg-1 proved to be a safe drug for total intravenous anesthesia in rheas, enabling rapid induction and recovery from anesthesia in addition to promoting few changes in cardiorespiratory and blood gas in the species.

The influence of diet composition on egg and chick traits in captive Greater Rhea females.

1. This study was conducted to evaluate the influence of diet composition on egg number, physical and chemical characteristics of eggs and weight and survival of chicks throughout a breeding season in a captive-bred population of greater rheas (Rhea americana). 2. From August to December, individuals were offered two diets: processed feed for rheas and processed feed for chicken (which is the feed most commonly offered to farmed rheas in Argentina). Reproductive performance of 15 females was monitored and female body weight was recorded before egg-laying onset. Within each experimental group, the following variables were determined: egg morphometric variables and percentage of components, fatty acid composition, hatching success and initial weight of chicks and mortality during the first week of life. 3. Females that were fed on processed feed for rheas delayed onset of laying and reduced laying period and number of eggs produced. However, females of this group laid larger eggs, with higher percentages of yolk and yolk lipids, and exhibited higher hatching success and chick weight compared with those that received chicken diet. Survivorship of chicks in their first week of life was not affected by composition of the diet offered to parental female. 4. Some reproductive parameters of captive greater rhea females fed on processed feed for rheas were higher than those of individuals receiving processed feed for chicken.

Behavioral responses to short-term transport in male and female Greater Rheas (Rhea americana) reared in captivity.

Animal transport is an indispensable practice in species that need to be moved for management or commercial purposes. However, transport may have negative effects on individuals' welfare. The aims of the present work were to determine if the behavioral responses of adult Greater Rheas (Rhea americana) bred in captivity are sensitive to short-term transport and if males and females differ in their posttransport behavioral activity and recovery. Eight males and 8 females were placed in individual pens and allowed 6 d to habituate (d 1 to 6) before transport procedure. On the transport day (d 7), half of the birds (4 males and 4 females) were randomly assigned to a transport group that was captured and handled to be placed into the crates, exposed to a 30-min transport stressor, and immediately returned to their pens. Four transports with 1 different male and female each time were performed. The other half remained undisturbed and were used as controls. Behavior of all individuals was video-recorded during habituation days, after transport on d 7, and on the 2 following days (d 8 and 9) to evaluate pre- and posttransport behavioral activity for 2 h per day. No significant behavioral changes were observed during the last 2 d of the habituation period (d 5 and 6), suggesting that Greater Rheas were adapted to the housing conditions before transport. After transportation, several behaviors were affected: transported males and females showed null resting, transported females also showed reduced preening and increased vigilance (P < 0.05), whereas transported males showed increased drinking (P < 0.05) compared with their respective control groups. The results suggest that behavioral responses of captive-bred Greater Rheas are sensitive to short-term transport (which includes handling) and that males and females differ in their posttransport behavioral activity, recovering their overall basal levels on the third day posttransportation.

Corticosterone stress response of Greater Rhea (Rhea americana) during short-term road transport.

The effect of transport stress on blood corticosterone levels in captive Greater Rheas was investigated. Twelve adult individuals (7 males; 5 females) were loaded in pairs inside wooden crates and transported along a paved road for 30 min. Blood samples were taken before the individuals were introduced into the crate (baseline value) and immediately after they were unloaded (30 min after capture). To assess whether corticosterone levels were affected by the blood sampling procedure per se, another 6 (nontransport) control birds (3 males; 3 females) were also captured and sampled at the same times as their transported counterparts. Plasma corticosterone concentrations were measured using a commercially available corticosterone (125)I radio-immunoassay kit. Baseline corticosterone levels were similar in the control and transported birds (9.0 ± 1.6 and 10.4 ± 0.8 ng/mL, respectively). Transportation induced a highly significant (P < 0.001), more than 40-fold increase in the corticosterone levels (433.6 ± 35.4 ng/mL) that was about 5 times higher (P < 0.001) than in their nontransported counterparts (88.4 ± 14.8 ng/mL). The present findings suggest that Greater Rhea is a species highly sensitive to stressful manipulations. Both blood sampling and transportation induced highly significant adrenocortical responses. Considering that transportation is one of the unavoidable common practices in the management of Greater Rheas and, as shown in the present study, that it induces a significant 40-fold corticosterone stress response, efforts should focus on helping to generate management transport standards for optimization of the welfare of this ratite.

Effect of age and body weight of Greater Rhea (Rhea americana) females on egg number, size and composition.

1. A study was conducted to evaluate how body weight and age of each female are related to the number and physical and chemical characteristics of the eggs produced throughout a breeding season in a captive-bred population of Greater Rheas (Rhea americana). 2. Reproductive performance of 15 females of three age classes (5 individuals per class) was monitored; female body weight was recorded before laying-onset. All the eggs laid were collected and identified, and different morphometric variables, percentage of components and fatty acid composition were determined. 3. The earlier the female started egg-laying, the longer the laying period and the greater the overall number of eggs produced. The onset of egg-laying in turn seemed to be related to the attainment of a high body weight. 4. Except for length, the values of the morphometric variables of the egg and unsaturated fatty acids (palmitoleic, oleic and linoleic) increased with female age. 5. High body weight was associated with low palmitic and palmitoleic fatty acids and high linoleic, linolenic and total unsaturated fatty acids. 6. Live weight and age of females can determine several physical and chemical characteristics of eggs.

The hindlimb muscles of Rhea americana (Aves, Palaeognathae, Rheidae).

The Greater Rhea is the largest cursorial Ratitae bird native to South America. Due to its increasing importance in farming and therefore in the sustainable use of this species, a comprehensive knowledge of their anatomy is essential. The goal of this study was to provide an anatomical description of the hindlimb muscles of Rhea americana. Six adult birds of both sexes were macroscopically studied analysing the origin and insertion of thigh and shank muscles. The thigh showed the highest number of muscles, whereas the shank showed the lowest number; this feature minimizes inertia and allows achieving high stride frequencies. The muscles of the shank showed long tendons of insertion that reduce the energetic cost during running. The major muscles responsible for extension of the hip and the ankle joints were massive and robust indicating their importance for cursorial locomotion. The pelvic limb muscles of Rhea americana resemble those of other cursorial Ratitae and their features are consistent with specialization for high-speed locomotion.

Modeling habitat suitability for Greater Rheas based on satellite image texture.

Many wild species are affected by human activities occurring at broad spatial scales. For instance, in South America, habitat loss threatens Greater Rhea (Rhea americana) populations, making it important to model and map their habitat to better target conservation efforts. Spatially explicit habitat modeling is a powerful approach to understand and predict species occurrence and abundance. One problem with this approach is that commonly used land cover classifications do not capture the variability within a given land cover class that might constitute important habitat attribute information. Texture measures derived from remote sensing images quantify the variability in habitat features among and within habitat types; hence they are potentially a powerful tool to assess species-habitat relationships. Our goal was to explore the utility of texture measures for habitat modeling and to develop a habitat suitability map for Greater Rheas at the home range level in grasslands of Argentina. Greater Rhea group size obtained from aerial surveys was regressed against distance to roads, houses, and water, and land cover class abundance (dicotyledons, crops, grassland, forest, and bare soil), normalized difference vegetation index (NDVI), and selected first- and second-order texture measures derived from Landsat Thematic Mapper (TM) imagery. Among univariate models, Rhea group size was most strongly positively correlated with texture variables derived from near infrared reflectance measurement (TM band 4). The best multiple regression models explained 78% of the variability in Greater Rhea group size. Our results suggest that texture variables captured habitat heterogeneity that the conventional land cover classification did not detect. We used Greater Rhea group size as an indicator of habitat suitability; we categorized model output into different habitat quality classes. Only 16% of the study area represented high-quality habitat for Greater Rheas (group size > or =15). Our results stress the potential of image texture to capture within-habitat variability in habitat assessments, and the necessity to preserve the remaining natural habitat for Greater Rheas.

DNA test to sex the lesser rhea (Rhea pennata pennata).

1. A polymerase-chain-reaction (PCR)-based test was adapted to sex the lesser rhea. Feathers instead of blood were used as the source of DNA. 2. The primers used allowed the assignment of sex by amplification of Z and W chromosome linked sequences. 3. This method proved to be safe, accurate and non-invasive. 4. The W chromosome linked fragment was sequenced and compared to other ratite sequences.

Rearing greater rhea (Rhea americana) chicks: is adoption more effective than the artificial intensive system?

(1) Survival and weight gain of farmed Greater Rhea (Rhea americana) chicks reared by the adult males that adopted them were compared with those of chicks reared under an artificial intensive system. (2) Both variables were periodically recorded up to the age of 3 months. Gompertz growth curves were fitted to individual growth data using the average adult weight of this population as asymptote. (3) No significant differences in survival rate were detected between systems (adoption=47%, intensive=43%). However, during the first half of the breeding season (mid-spring to mid-summer), the growth rate of adopted chicks (0.01481) was higher than that of intensively reared chicks (0.01296). (4) The adoption system may be more effective in terms of growth, and is probably more efficient in cost/effectiveness than the artificial intensive technique most frequently used. Adoption by males has additional advantages, such as a correct imprinting of the chicks and the selection of more capable individuals. Therefore, it should be used not only commercially but also in conservation projects where individuals are released to the wild.

Physical characteristics and chemical composition of Lesser Rhea (Pterocnemia pennata) eggs from farmed populations.

1. Eggs from 4 farmed populations of Lesser Rhea (Pterocnemia pennata) were studied to determine their physical and chemical characteristics. 2. None of the physical variables (weight of whole egg, yolk, albumen and shell; proportion of yolk based on egg content; proportion of shell based on entire egg weight; volume; density) showed significant differences between populations. 3. Among chemical variables, moisture, both saturated fatty acids (palmitic 16:0 and stearic 18:0), one monounsaturated fatty acid (palmitoleic 16:1), and one polyunsaturated fatty acid (arachidonic 20:4), did not differ between populations, whereas other variables (protein, lipid and ash contents; fatty acids: oleic 18:1, linoleic 18:2, linolenic 18:3; PUFA; PUFA/SFA; cholesterol) differed significantly.

Microbial contamination of artificially incubated Greater Rhea (Rhea americana) eggs.

1. This paper is a report of biological agents that contaminate Greater Rhea (Rhea americana) eggs during artificial incubation. 2. The cleanliness of eggs when collected, and the period of storage prior to incubation, were investigated to assess their effects on microbial contamination and hatchability. 3. A total of 14 bacteria and 4 fungi species were isolated within the egg in the laboratory. 4. Microbial contamination was higher (24%) in very dirty eggs than in eggs which were clean or dirty (16%). Hatching success was lower (30%) for very dirty eggs, compared with 42% for clean or dirty eggs. 5. The percentage of microbial contamination of stored eggs (10%) did not differ significantly from that of non-stored ones (5%). 6. The extreme lower and upper limits of infection rate estimated for artificially incubated Greater Rhea eggs were 4% and 40%, respectively, being higher than in poultry species. 7. It is concluded that collecting eggs soon after laying will reduce the risk of microbial contamination.

Three-dimensional kinematics of skeletal elements in avian prokinetic and rhynchokinetic skulls determined by Roentgen stereophotogrammetry.

Several different types of cranial kinesis are present within modern birds, enabling them to move (part of) the upper bill relative to the braincase. This movement of the upper bill results from movement of the quadrate and the pterygoid-palatine complex (PPC). The taxon Palaeognathae is characterised by a very distinct PPC and a special type of cranial kinesis (central kinesis) that is very different from that found in the Neognathae. This has led some authors to hypothesise that there is a functional relationship between the morphology of the PPC and the type of cranial kinesis. This hypothesis is tested here by analysing the movement pattern of both the upper bill and the PPC in birds with three different types of cranial kinesis: prokinesis, distal rhynchokinesis and central rhynchokinesis. Movement patterns were determined using a Roentgen stereophotogrammetry method, which made it possible to detect very small displacements (0.5 mm) of bony elements in three dimensions, while the jaw muscles and ligaments remained intact. We found that in all types of kinesis investigated the movements of the quadrate, jugal bars and PPC are similar. Movement of the quadrate is transferred to the upper beak by the jugal bar and the PPC, which moves almost exclusively forwards and backwards, thereby elevating or depressing the upper bill. The differences between the types of kinesis lie only in the position of the point of rotation. These findings indicate that there is no correlation between the specific morphology of the PPC and the type of cranial kinesis. Several other factors, including the external forces applied during food acquisition, may influence the morphology of the PPC. Differences in PPC morphology therefore appear to be the result of different functional demands acting on the system simultaneously but with different strengths, depending on the species.