Bacterial communities along parrot digestive and respiratory tracts: the effects of sample type, species and time / Comunidades bacterianas a lo largo del tracto digestivo y respiratorio de los loros: los efectos del tipo de muestra, especie y tiempo

Digestive and respiratory tracts are inhabited by rich bacterial communities that can vary between their different segments. In comparison with other bird taxa with developed caeca, parrots that lack caeca have relatively lower variability in intestinal morphology. Here, based on 16S rRNA metabarcoding, we describe variation in microbiota across different parts of parrot digestive and respiratory tracts both at interspecies and intraspecies levels. In domesticated budgerigar (Melopsittacus undulatus), we describe the bacterial variation across eight selected sections of respiratory and digestive tracts, and three non-destructively collected sample types (faeces, and cloacal and oral swabs). Our results show important microbiota divergence between the upper and lower digestive tract, but similarities between respiratory tract and crop, and also between different intestinal segments. Faecal samples appear to provide a better proxy for intestinal microbiota composition than the cloacal swabs. Oral swabs had a similar bacterial composition as the crop and trachea. For a subset of tissues, we confirmed the same pattern also in six different parrot species. Finally, using the faeces and oral swabs in budgerigars, we revealed high oral, but low faecal microbiota stability during a 3-week period mimicking pre-experiment acclimation. Our findings provide a basis essential for microbiota-related experimental planning and result generalisation in non-poultry birds.(AU)

Acute, fatal Sarcocystis falcatula infection in rose-ringed parakeets (Psittacula krameri).

Sarcocystosis is an important avian disease that affects several intermediate host species. Birds not endemic from Americas, like Old World psittacine species, appear to be more susceptible to lethal infection than New World psittacine species. The aim of this study was to investigate the sudden death of rose-ringed parakeets (Psittacula krameri) in an exotic private parrot's aviary. Macroscopically, the most prevalent findings were severe lung congestion, slight superficial myocardial hemorrhagic lesions, enlarged liver and congestion of meningeal vessels. The initial diagnosis of sarcocystosis was made in all birds by microscopic observations of intravascular pulmonary schizonts, as well hepatitis, myocarditis, and nephritis. Immunohistochemistry for detection of Sarcocystis sp. antigen revealed an intense immunoreactivity in the lungs. Molecular identification of Sarcocystis falcatula were obtained by nested PCR and sequencing of amplified fragments of internal transcribed spacer 1 (ITS1) and three surface antigen-coding genes (SAG2, SAG3 and SAG4). SAG-based phylogenies showed a close relatedness of the isolate described here and S. falcatula previously detected in naturally infected native birds, which suggests that the isolates that affected ringnecks are a common isolate that circulates in Brazil.

Naturally occurring psittacid alphaherpesvirus 3 and probable adenovirus coinfection in an Indian ringneck parakeet in the United States.

Psittacid alphaherpesvirus 3 (PsAHV-3) is a rarely reported virus that has been associated with pneumonia in psittacine birds. A 5-mo-old Indian ringneck parakeet (syn. rose-ringed parakeet; Psittacula krameri) was euthanized after developing torticollis and lethargy. Postmortem examination of the parakeet revealed severe pneumonia with syncytial cells containing eosinophilic intranuclear inclusion bodies (INIBs) in the respiratory epithelium. Gene sequencing of total DNA extraction detected PsAHV-3 in the frozen lung. The pancreas had severe lytic necrosis, with the remaining parenchymal cells expanded by large basophilic INIBs. Electron microscopy of the pancreas revealed intranuclear paracrystalline arrays of viral particles morphologically resembling adenovirus. Although we found 3 PsAHV-3 cases in birds in a literature search, we found no cases with adenoviral coinfection.

Zoonotic Cryptosporidium meleagridis in urban invasive monk parakeets.

Zoonotic Cryptosporidium meleagridis was identified in invasive monk parakeets (Myiopsitta monachus) from Santiago metropolis in Chile. Oocysts were isolated from nestlings' faeces, and a fragment of 18S ribosomal RNA gene was amplified and sequenced. This finding emphasizes the importance of permanent pathogen monitoring in synanthropic species with wide global distribution.

A Novel Dependoparvovirus Identified in Cloacal Swabs of Monk Parakeet (Myiopsitta monachus) from Urban Areas of Spain.

The introduction of invasive birds into new ecosystems frequently has negative consequences for the resident populations. Accordingly, the increasing population of monk parakeets (Myiopsitta monachus) in Europe may pose a threat because we have little knowledge of the viruses they can transmit to native naïve species. In this study, we describe a new dependoparvovirus detected by metagenomic analysis of cloacal samples from 28 apparently healthy individuals captured in urban areas of Madrid, Spain. The genomic characterization revealed that the genome encoded the NS and VP proteins typical of parvoviruses and was flanked by inverted terminal repeats. No recombination signal was detected. The phylogenetic analysis showed that it was closely related to a parvovirus isolated in a wild psittacid in China. Both viruses share 80% Rep protein sequence identity and only 64% with other dependoparvoviruses identified in Passeriformes, Anseriformes, and Piciformes and are included in a highly supported clade, which could be considered a new species. The prevalence was very low, and none of the additional 73 individuals tested positive by PCR. These results highlight the importance of exploring the viral genome in invasive species to prevent the emergence of novel viral pathogenic species.

Fatal Sarcocystis calchasi hepatitis in a captive Indian ringneck parakeet (Psittacula krameri manillensis).

An adult Indian ringneck parakeet (Psittacula krameri manillensis) from an outdoor aviary in Sacramento, California was found dead on the nest box. Postmortem examination showed firm, enlarged, yellow­tinged liver and splenomegaly. Multifocal to coalescing, acute necrosis with macrophages, lymphocytes, plasma cells, and periportal ductular reaction were seen on liver histology with extra- and intracellular schizonts and merozoites. A few schizonts and lymphohistiocytic inflammation were seen in the spleen. Toxoplasma gondii, Sarcocystis neurona, S. falcatula and Neospora caninum were ruled out by immunohistochemistry. PCR of the liver for Sarcocystis spp. Based on the positive amplification/PCR of ITS1 segment and sequencing of 28S rRNA fragment, S. calchasi was confirmed. The splanchnic presentation of S. calchasi in this parakeet resembles the acute infection described experimentally in domestic pigeons (Columba livia f. domestica) and cockatiels (Nymphicus hollandicus). Since large populations of red-tailed hawks (Buteo jamaicensis) and Cooper's hawk (Accipiter cooperi), the likely definitive hosts of S. calchasi in North America, inhabit the Sacramento area, their presence near outdoor aviaries may account for the source of S. calchasi infective sporocysts.

Psittacid alphaherpesvirus 5 infection in Indian ringneck parakeets in southern California.

Four Indian ringneck parakeets (Psittacula krameri; syn. ringneck parrots or rose-ringed parakeets) were submitted by 2 private owners for autopsy following a history of dyspnea and death. Gross findings were varied and included thickening of the left caudal thoracic air sac, white spots throughout the liver, mild dilation of the proventriculus, coelomic effusion, splenomegaly, and pulmonary congestion and edema. Microscopically, the submitted parakeets had significant lesions in the lower respiratory tract, including necrotizing bronchitis, parabronchitis, and interstitial pneumonia with numerous syncytia containing eosinophilic intranuclear inclusions. Electron microscopy of the lungs was compatible with a herpesviral infection and Psittacid alphaherpesvirus 5 (PsAHV5) was detected via PCR and sequencing. There has been inconsistent terminology used with Psittacid alphaherpesvirus 3 and PsAHV5; we attempt here to clarify the reported history of these viruses.

First detection of Psittacid alphaherpesvirus 5 and coinfection with beak and feather disease virus in naturally infected captive ringneck parakeets (Psittacula krameri) in Brazil.

This study describes a case report in captive rose-ringed parakeets (Psittacula krameri) that developed clinical signs and eventually died after introducing new birds without quarantine. Bronchopneumonia and airsacculitis with syncytial cells associated with intranuclear inclusion bodies were found. Herpesvirus was detected in lungs and liver by PCR, and a nearly complete genome sequence of a Psittacid alphaherpesvirus 5 was obtained from the lung of a bird. Metagenomic analysis also identified beak and feather disease virus in the same samples. The study also highlights the importance of quarantine for avoiding the introduction of new diseases in captive aviaries.

Vasculitis Associated with Parrot Bornavirus 4 Infection in a Rose-Crowned Parakeet (Pyrrhurarhodocephala).

A 3-month-old, female rose-crowned parakeet (Pyrrhura rhodocephala) was found dead after a 24-h course of lethargy and passing blood-tinged faeces. Fine white streaks were seen in the pectoral muscles on necropsy. Microscopic examination revealed typical lesions of avian ganglioneuritis and vascular necrosis in the pectoral muscles, myocardium, kidneys, air sacs, adrenal glands, pancreas and thyroid gland. These lesions were characterized by mural fibrinoid necrosis of small and medium-calibre arteries and arterioles, associated with lymphoplasmacytic inflammation, necrosis, atrophy and fibrosis of the surrounding tissues. Parrot bornavirus (PaBV) nucleoprotein was demonstrated by immunohistochemistry in smooth muscle and endothelial cells of many vessels. An avian bornavirus was isolated from kidney tissue and its identity confirmed as PaBV-4 by sequencing and phylogenetic analysis. We postulate that the vascular lesions could have been immune-mediated and that PaBV-4 may have played a role in its pathogenesis.

Apparent Lack of Circovirus Transmission from Invasive Parakeets to Native Birds.

The transmission of pathogens to native species has been highlighted as one of the most important impacts of biological invasions. In this study, we evaluated the presence of psittacine beak and feather disease virus (BFDV) and other circoviruses in native bird species cohabiting with invasive populations of wild rose-ringed (Psittacula krameri) and monk parakeets (Myiopsitta monachus) that were found positive for a particular BFDV genotype in Sevilla, southern Spain. None of the 290 individuals from the 18 native bird species captured showed typical signs of disease caused by BFDV. A sample of 79 individuals from 15 native species showed negative results for the presence of the BFDV genotype previously detected in the sympatric invasive parakeets, as well as any other of the circoviruses tested. Although preliminary, this study suggests a lack of circovirus transmission from invasive parakeets to native birds at the study site. Further research is needed to determine if this apparent absence in transmission depends on the BFDV genotype present in the parakeets, which requires additional screening in other invasive and native populations living in sympatry.

First record of Ornithonyssus bursa (Berlese, 1888) (Mesostigmata: Macronyssidae) parasitizing invasive monk parakeets in Santiago, Chile.

Myiopsitta monachus is an invasive psittacine with wide distribution due to the pet trade. Its large communal nests and synanthropic nature contribute to its successful colonization of cities, from where it seems to be expanding in range and numbers. This is relevant with regard to pathogens that invasive species may harbor, especially when host populations thrive. We aimed to identify an abundant mite found in invasive monk parakeet chicks that had been collected in Santiago during 2017 and 2018. Through morphological and molecular identification of the 18S ribosomal RNA gene, we confirmed the presence of Ornithonyssus bursa. This was the first report of this mite in Chile. This mite is common in native and invasive monk parakeet populations and may affect other birds, including domestic fowl. Further, this mite bites people and can be a potential vector of pathogens such as bacteria or viruses. We conclude that this parasite was likely introduced with the parakeet and discuss possible ecological, health and economic consequences of this new potential pest.

Fine-scale genetic structure reflects limited and coordinated dispersal in the colonial monk parakeet, Myiopsitta monachus.

The genetic structure of animal populations has considerable behavioural, ecological and evolutionary implications and may arise from various demographic traits. Here, we use observational field data and molecular genetics to determine the genetic structure of an invasive population of monk parakeets, Myiopsitta monachus, at a range of spatial scales, and investigate the demographic processes that generate the observed structure. Monk parakeets construct large nests that can house several pairs occupying separate chambers; these nests are often aggregated within nesting trees. We determined patterns of relatedness within compound nests, within nesting trees and between trees. Spatial autocorrelation analyses of pairwise genetic relatedness revealed fine-scale genetic structure with relatives of both sexes spatially clustered within, but not beyond, nesting trees. In addition, males were more related to males sharing their compound nests than to other males occupying the same nesting tree. By contrast, males and females within compound nests were not significantly more closely related than elsewhere in the same tree, and we found no evidence for inbreeding. Adults showed high breeding site fidelity between years despite considerable disturbance of nest sites. Natal dispersal was female-biased, but dispersal distances were relatively short with some natal philopatry observed in both sexes. Sibling coalitions, typically of males, were observed amongst both philopatric and dispersing birds. Our results show significant clustering of kin within compound nests and nesting trees resulting from limited and coordinated natal dispersal, with subsequent breeding site fidelity. The resulting genetic structure has implications for social behaviour in this unusual parrot species.

Making a parrot zygodactyl foot: Osteology and morphogenesis of the tarsometatarsus in the monk parakeet (Myiopsitta monachus).

The tarsometatarsus conformation and foot types in birds are unique traits within vertebrates. We investigate how the tarsometatarsus and the zygodactyl foot are formed during development in the monk parakeet (Myiopsitta monachus). Using bones, whole mount specimens stained for cartilage and bone, and histological sections, we focus on the osteology and morphogenesis of the tarsometatarsus. We also compare the tarsometatarsus development between the altricial monk parakeet with the precocial chicken. The results and conclusions we reached are: (1) the hypotarsus, a character of phylogenetic significance, is monocanaliculate in the adult; (2) digit I retroversion is consequence of the displacement of the articulation site of the metatarsal 1 and its torsion; (3) digit IV retroversion is linked to the development of the trochlea accesoria; (4) in ovo, the ossification and fusion of the metatarsals 2-4 begin in their mid-diaphysis and extends cylindrically to both proximal and distal directions; and (5) the differences in the development of the tarsometatarsus between the monk parakeet and the chicken evidence heterochronies, probably related with their different types of development.

Antimicrobial susceptibility profile of enterobacteria isolated from wild grey-breasted parakeets (Pyrrhura griseipectus) / Perfil de susceptibilidade antimicrobiana de enterobactérias isoladas de periquitos-de-cara-suja (Pyrrhura griseipectus)

The grey-breasted parakeet (Pyrrhura griseipectus) is an endangered psittacine species that have been affected by illegal trade and deforestation. Currently, this endemic species is only found in three areas in Ceará state, in Brazil. This study aimed to investigate the frequency and diversity of Enterobacteriaceae in wild adult grey-breasted parakeets and determine their susceptibility to antimicrobial agents. Cloacal swab samples were collected from 27 individuals and environmental swabs (drag swabs) from five nests used by these birds. Twenty-seven strains from nine species of Enterobacteriaceae were recovered from cloacal swabs, and the most prevalent bacteria strains were Hafnia alvei (22%) and Pantoea agglomerans (22%). From environmental nest samples, seven strains from three bacterial species were isolated, being the P. agglomerans the most frequent species (100%). Twenty-two of the 27 isolates (81.4%) exhibited antibiotic resistance, varying from one to eight of the 12 antimicrobials commonly used. Resistance to amoxicillin was the most prevalent (70.4%), followed by azithromycin (22.2%) and ceftriaxone (18.5%). None of the strains were resistant to gentamicin, tobramycin, ciprofloxacin or tetracycline. The H. alvei was the main species presenting multidrug resistance, including resistance against meropenem, which is an important finding. These results could provide interesting information on the health of these endangered wild grey-breasted parakeets. They could also indicate that the obtained isolates are part of a group of bacteria that are typical components of the enteric microbiota of birds, which present elevated rates of resistance to amoxicillin.(AU)

O periquito-de-cara-suja (Pyrrhura griseipectus) é uma espécie de psitacídeo considerado pela IUCN como ameaçado de extinção, resultado do comércio ilegal e do desmatamento. Atualmente, essa espécie endêmica é encontrada apenas em três áreas no estado do Ceará, Brasil. O objetivo deste estudo foi investigar a frequência e a diversidade de Enterobacteriaceae em periquitos de peito cinza adultos selvagens e determinar sua suscetibilidade a agentes antimicrobianos. Amostras de suabes cloacais foram coletadas de 27 indivíduos e de suabes ambientais (suabes de arrasto) de cinco ninhos utilizados por essas aves. Vinte e sete cepas de nove espécies de Enterobacteriaceae foram isoladas a partir de suabes cloacais, sendo as cepas bacterianas mais prevalentes Hafnia alvei (22%) e Pantoea agglomerans (22%). Das amostras ambientais de ninhos foram isoladas sete linhagens de três espécies bacterianas, sendo P. agglomerans a espécie mais frequente (100%). Vinte e dois dos 27 isolados (81,4%) exibiram resistência a antibióticos, variando de um a oito dos 12 antimicrobianos comumente usados. A resistência a amoxicilina foi a mais prevalente (70,4%), seguida por azitromicina (22,2%) e ceftriaxona (18,5%). Nenhuma das cepas era resistente à gentamicina, tobramicina, ciprofloxacina ou tetraciclina. H. alvei foi a principal espécie que apresentou resistência a múltiplas drogas e que também esteve associada a um outro achado relevante desta pesquisa, que foi a detecção de um caso de resistência ao meropenem. Esses dados fornecem informações relevantes sobre a saúde desses periquitos selvagens ameaçados e permite concluir que os isolados obtidos fazem parte de um grupo de bactérias que normalmente compõe a microbiota entérica das aves, sendo a amoxicilina envolvida em elevadas taxas de resistência.(AU)

First record of Ornithonyssus bursa (Berlese, 1888) (Mesostigmata: Macronyssidae) parasitizing invasive monk parakeets in Santiago, Chile / Primeiro registro de Ornithonyssus bursa (Berlese, 1888) (Mesostigmata: Macronyssidae) parasitando caturritas invasoras em Santiago, Chile

Abstract Myiopsitta monachus is an invasive psittacine with wide distribution due to the pet trade. Its large communal nests and synanthropic nature contribute to its successful colonization of cities, from where it seems to be expanding in range and numbers. This is relevant with regard to pathogens that invasive species may harbor, especially when host populations thrive. We aimed to identify an abundant mite found in invasive monk parakeet chicks that had been collected in Santiago during 2017 and 2018. Through morphological and molecular identification of the 18S ribosomal RNA gene, we confirmed the presence of Ornithonyssus bursa. This was the first report of this mite in Chile. This mite is common in native and invasive monk parakeet populations and may affect other birds, including domestic fowl. Further, this mite bites people and can be a potential vector of pathogens such as bacteria or viruses. We conclude that this parasite was likely introduced with the parakeet and discuss possible ecological, health and economic consequences of this new potential pest.

Resumo Myiopsitta monachus é um psitacídeo invasor amplamente distribuído devido ao tráfico de animais selvagens. Os grandes ninhos comunitários construídos e sua condição de espécies sinantrópicas contribuem para a colonização bem-sucedida das cidades, onde parece estar expandindo sua distribuição e número de indivíduos. Isso é relevante, quando se trata de patógenos que os invasores podem abrigar, especialmente quando as populações hospedeiras prosperam. O objetivo deste trabalho foi identificar um ácaro abundante, encontrado em filhotes de periquitos-monge introduzidos em Santiago, Chile, coletados durante 2017 e 2018. Por meio da identificação morfológica e molecular do gene do RNA ribossômico 18S, foi confirmada a presença de Ornithonyssus bursa, sendo o primeiro registro para o Chile. Esse ácaro é comum em populações nativas e introduzidas de periquitos-monge e pode afetar outras aves, incluindo aves domésticas. Além disso, esse ácaro pode picar pessoas e pode ser um potencial vetor de patógenos, como bactérias ou vírus. Conclui-se que esse parasita provavelmente foi introduzido com o periquito e foram discutidas as possíveis consequências ecológicas de saúde e econômicas dessa nova praga em potencial.

Cytometric blood phenotyping in free-living white-eyed parakeet (Psittacara leucophthalmus) / Fenotipagem citométrica do sangue de maritacas jovens de vida-livre (Psittacara leucophthalmus)

This study aimed at performing cytometric phenotyping of the blood samples from free-living, young white-eyed parakeets (Psittacara leucophthalmus), stained with 3,3-dihexyloxacarbocyanine [DiOC6(3)]. DiOC6(3)-stained whole blood samples from 19 free-living, young white-eyed parakeets were analyzed by flow cytometry and cell types were distinguished by their typical fluorescence in blue laser channel (FL-1) and SSC (side scatter). It was possible to differentiate erythrocytes (58.3±13.6) from leukocytes (32.4±13.1) and some of the leucocyte subpopulations: lymphocytes/thrombocytes (29.7±7.7), monocytes (30.6±8.5), and granulocytes (5.9-26). However, lymphocytes and thrombocytes could not be sorted in the plots. Our study determined that the predominant population in white-eyed parakeet (P. leucophthalmus) was lymphocytes, thrombocytes, and monocytes in the leucocytes gates in comparison to the granulocyte population. The cytometry method and use of DiOC6(3) stain was available for parakeets blood samples and can be studied and applied to other species of parrots.(AU)

Este estudo teve como objetivo realizar a fenotipagem citométrica com 3,3-di-hexiloxacarbocianina [DiOC6 (3)] de amostras de sangue de maritacas jovens de vida-livre (Psittacara leucophthalmus). As amostras de sangue total, coradas com DiOC6(3) de 19 maritacas de vida livre, foram analisadas por citometria de fluxo e os tipos de células foram distinguidos por sua fluorescência típica no canal laser azul (FL-1) e SSC (dispersão lateral). Foi possível diferenciar eritrócitos (58,3±13,6) de leucócitos (32,4±13,1) e algumas subpopulações de leucócitos: linfócitos/trombócitos (29,7±7,7), monócitos (30,6±8,5) e granulócitos (5,9-26), entretanto, linfócitos e trombócitos não puderam ser diferenciados em duas populações distintas. Nosso estudo determinou que a população predominante P. leucophthalmus foi mononuclear agranulocítica em comparação com a taxa de aquisição da população granulocítica. A metodologia de citometria de fluxo com uso da coloração de DiOC6(3) foi aplicável a amostras sanguíneas das maritacas e pode ser estudado e aplicado para outras espécies de psitacídeos.(AU)

Occurrence and Molecular Typing of Giardia psittaci in Parakeets in Germany-A Case Study.

A grey-hooded parakeet (Psilopsiagon aymara) and two budgerigars (Melopsittacus undulatus) from different owners presented with decreased activity, vomitus, and diarrhea. A microscopic examination of feces showed trophozoites of the protozoan flagellate Giardia. A commercial immunochromatographic dipstick test for Giardia sp. antigens confirmed the infection. These findings were assured by PCR of the small subunit ribosomal RNA (SSU rRNA) gene and coproantigen ELISA. Sequencing of PCR products of the SSU rRNA (292 bp) and ß-giardin genes (511 bp) identified Giardia psittaci as the species involved. Therefore, our results show that a GSA 65-based coproantigen ELISA, which was established for diagnosis of Giardia duodenalis is applicable for the detection of G. psittaci. A treatment with ronidazole was started. Additionally, fecal examination and dissection of the dead birds revealed coinfection with the fungal pathogen Macrorhabdus ornithogaster. One budgerigar survived and repeatedly tested negative after treatment with ronidazole. The described cases indicate that a single infection with G. psittaci has a good prognosis, whereas the prognosis is poor when coinfections occur, especially with M. ornithogaster.

Reporte de caso- Presentación y tipificación molecular de Giardia psittaci en periquitos en Alemania: Un estudio de caso. Un periquito catita aimará (Psilopsiagon aymara) y dos periquitos australianos (Melopsittacus undulatus) de diferentes propietarios presentaron actividad disminuida, vómito y diarrea. El examen microscópico de las heces mostró trofozoitos del protozoo flagelado Giardia. Una prueba de tira reactiva inmunocromatográfica comercial para antígenos de Giardia sp. confirmó la infección. Estos resultados fueron confirmados por PCR para el gene de ARN de la subunidad pequeña ribosomal (SSU rRNA) y por ELISA de coproantígeno. La secuenciación de los productos de PCR del ARNr de SSU (292 pb) y los genes de ß-giardina (511 pb) identificaron a Giardia psittaci como la especie involucrada. Por lo tanto, estos resultados muestran que el método de ELISA de coproantígeno basado en GSA 65, que se estableció para el diagnóstico de Giardia duodenalis, es aplicable para la detección de G. psittaci. Se inició un tratamiento con ronidazol. Además, el examen fecal y la disección de las aves muertas revelaron coinfección con el patógeno fúngico Macrorhabdus ornithogaster. Un periquito australiano sobrevivió y dio negativo repetidamente después del tratamiento con ronidazol. Los casos descritos indican que la infección única con G. psittaci tiene un buen pronóstico, mientras que el pronóstico es malo cuando ocurren coinfecciones, especialmente con M. ornithogaster. Abbreviations: GSA = Giardia-specific antigen; OD = optical density; rRNA = ribosomal ribonucleic acid; SSU = small subunit.

The uropygial gland of the monk parakeet Myiopsitta monachus: Histology, morphogenesis, and evolution within Psittaciformes (Aves).

We describe the morphology, histology, and histochemical characteristics of the uropygial gland (UG) of the monk parakeet Myiopsitta monachus. The UG has a heart-shape external appearance and adenomers extensively branched with a convoluted path, covered by a stratified epithelium formed by different cellular strata and divided into three zones (based on the epithelial height and lumen width), a cylindrical papilla with an internal structure of delicate type and two excretory pores surrounded by a feather tuft. Histochemical and lectin-histochemical techniques performed showed positivity against PAS, AB pH 2.5, AB-PAS, and some lectines, likely related to the granivorous feeding habits. Also, we describe the morphogenesis of the UG of the monk parakeet, which appears at embryological stage 34 as a pair of ectodermal invaginations. Heterochronic events in the onset development of the UG when compared with other birds could be recognized. Finally, to examine the phylogenetic occurrence of the UG within the Psittaciformes and infer its evolutionary history, we mapped its presence/absence over a molecular phylogeny. The reconstruction of the characters states at ancestral nodes revealed that the presence of the UG was the plesiomorphic feature for Psittaciformes and its loss evolved independently more than once.