Mutations in SLC45A2 lead to loss of melanin in parrot feathers.

Bird plumage coloration is a complex and multifactorial process that involves both genetic and environmental factors. Diverse pigment groups contribute to plumage variation in different birds. In parrots, the predominant green color results from the combination of 2 different primary colors: yellow and blue. Psittacofulvin, a pigment uniquely found in parrots, is responsible for the yellow coloration, while blue is suggested to be the result of light scattering by feather nanostructures and melanin granules. So far, genetic control of melanin-mediated blue coloration has been elusive. In this study, we demonstrated that feather from the yellow mutant rose-ringed parakeet displays loss of melanosome granules in spongy layer of feather barb. Using whole genome sequencing, we found that mutation in SLC45A2, an important solute carrier protein in melanin synthetic pathway, is responsible for the sex-linked yellow phenotype in rose-ringed parakeet. Intriguingly, one of the mutations, P53L found in yellow Psittacula krameri is already reported as P58A/S in the human albinism database, known to be associated with human OCA4. We further showed that mutations in SLC45A2 gene affect melanin production also in other members of Psittaculidae family such as alexandrine and plum-headed parakeets. Additionally, we demonstrate that the mutations associated with the sex-linked yellow phenotype, localized within the transmembrane domains of the SLC45A2 protein, affect the protein localization pattern. This is the first evidence of plumage color variation involving SLC45A2 in parrots and confirmation of associated mutations in the transmembrane domains of the protein that affects its localization.

Unique oestrogen receptor ligand-binding domain sequence of native parrots: a possible link between phytoestrogens and breeding success.

The New Zealand (NZ) native parrots kakapo, kaka and kea are classified as critically endangered, endangered and vulnerable respectively. Successful reproduction of kakapo and kaka is linked to years of high levels of fruiting in native flora (mast years). To assess a possible hormonal link between native plants and reproductive success in these parrots in mast years, we examined the ligand-binding domains (LBD) of the progesterone receptor (PR), androgen receptor (AR), estrogen receptor 1 (ESR1) and estrogen receptor 2 (ESR2) in NZ native (kakapo, kaka, kea and kakariki) and non-native (Australian cockatiel) parrots and compared them with those in the chicken. The amino acid sequences for PR, AR, ESR1 and ESR2 shared >90% homology among the NZ parrots, the cockatiel and, in most cases, the chicken. The exception was for the ESR1 LBD, which contained an extra eight amino acids at the C-terminal in all the parrots compared with the chicken and with published sequences of non-parrot species. These results support the notion that the ESR1 LBD of parrots responds differently to putative oestrogenic compounds in native trees in NZ during times of intermittent masting. In turn, this may provide important information for generating parrot-specific bioassays and linkages to steroidogenic activity in native plants.

Pharmacokinetics of meloxicam after intravenous, intramuscular and oral administration of a single dose to African grey parrots (Psittacus erithacus).

Meloxicam is a nonsteroidal anti-inflammatory drug commonly used in avian species. In this study, the pharmacokinetic parameters for meloxicam were determined following single intravenous (i.v.), intramuscular (i.m.) and oral (p.o.) administrations of the drug (1 mg/kg·b.w.) in adult African grey parrots (Psittacus erithacus; n = 6). Serial plasma samples were collected and meloxicam concentrations were determined using a validated high-performance liquid chromatography assay. A noncompartmental pharmacokinetic analysis was performed. No undesirable side effects were observed during the study. After i.v. administration, the volume of distribution, clearance and elimination half-life were 90.6 ± 4.1 mL/kg, 2.18 ± 0.25 mL/h/kg and 31.4 ± 4.6 h, respectively. The peak mean ± SD plasma concentration was 8.32 ± 0.95 µg/mL at 30 min after i.m. administration. Oral administration resulted in a slower absorption (tmax  = 13.2 ± 3.5 h; Cmax  = 4.69 ± 0.75 µg/mL) and a lower bioavailability (38.1 ± 3.6%) than for i.m. (78.4 ± 5.5%) route. At 24 h, concentrations were 5.90 ± 0.28 µg/mL for i.v., 4.59 ± 0.36 µg/mL for i.m. and 3.21 ± 0.34 µg/mL for p.o. administrations and were higher than those published for Hispaniolan Amazon parrots at 12 h with predicted analgesic effects.

Resposta endócrina à contenção física e isolamento em papagaios-verdadeiros / Endocrine response to physical restraint and isolation in blue-fronted parrots

O objetivo deste trabalho foi analisar a resposta dos papagaios-verdadeiros aos procedimentos de contenção e separação física por método não invasivo, como a dosagem das concentrações de metabólitos de glicocorticoides nas excretas. Para tanto, foram utilizadas 24 aves, 17 machos e sete fêmeas, inicialmente mantidas em viveiros amplos e adjacentes, separadas por sexo. Após captura e contenção de três minutos, 13 aves voltaram para os viveiros coletivos e 11 foram alojadas em gaiolas individuais no mesmo recinto dos viveiros, de modo a permitir que as aves isoladas mantivessem contato visual e auditivo com as demais. Para avaliar se os animais responderiam de maneira diferente quando fisicamente isolados ou em grupo, amostras de excretas foram coletadas sequencialmente em intervalos de três horas durante 24 horas para avaliação dos metabólitos de glicocorticoides por enzimaimunoensaio. Não houve efeito significativo de sexo (P=0,5850), tratamento (P=0,6805) e tempo (P=0,2293), e as concentrações de metabólitos de glicocorticoides mantiveram-se dentro da variação diurna esperada para esta espécie. Portanto, ambos os grupos responderam endocrinologicamente de forma semelhante e o estresse de captura e separação física não foi significativo para as aves.(AU)

The aim of this study was to evaluate the response of blue-fronted parrots to restraint procedures and separation by non-invasive methods such as measurement of glucocorticoid metabolites in droppings. For this, we utilized 24 birds, 17 males and 7 females, initially kept in large adjacent aviaries, separated by sex. After capture and 3 minutes of manual contention, by random, 13 birds returned to the aviary and 11 animals were housed in individual cages in the same facility of the aviaries allowing the maintenance of auditory and visual contact between them. In order to evaluate if the physically isolated birds isolated or in groups would react in different ways, all droppings samples were collected at 3-hours intervals during 24 hours to evaluation of excreted glucocorticoid metabolites by enzimeimmunoassay. There were no significant effects of sex (P=0.5850), treatment (P=0.6805) and time (P=0.2293) and the glucocorticoid metabolites concentrations were within the diurnal range expected for this specie. Therefore, the endocrine response of both groups was similar and stress of capture and physical separation was not significant for the birds.(AU)

Molecular and cellular changes associated with the evolution of novel jaw muscles in parrots.

Vertebrates have achieved great evolutionary success due in large part to the anatomical diversification of their jaw complex, which allows them to inhabit almost every ecological niche. While many studies have focused on mechanisms that pattern the jaw skeleton, much remains to be understood about the origins of novelty and diversity in the closely associated musculature. To address this issue, we focused on parrots, which have acquired two anatomically unique jaw muscles: the ethmomandibular and the pseudomasseter. In parrot embryos, we observe distinct and highly derived expression patterns for Scx, Bmp4, Tgfß2 and Six2 in neural crest-derived mesenchyme destined to form jaw muscle connective tissues. Furthermore, immunohistochemical analysis reveals that cell proliferation is more active in the cells within the jaw muscle than in surrounding connective tissue cells. This biased and differentially regulated mode of cell proliferation in cranial musculoskeletal tissues may allow these unusual jaw muscles to extend towards their new attachment sites. We conclude that the alteration of neural crest-derived connective tissue distribution during development may underlie the spatial changes in jaw musculoskeletal architecture found only in parrots. Thus, parrots provide valuable insights into molecular and cellular mechanisms that may generate evolutionary novelties with functionally adaptive significance.

Effects of UVB radiation on calcium metabolism in psittacine birds.

The effects of providing ultraviolet (uv) radiation (285 to 315 nm, ultraviolet B) on calcium metabolism in two groups of 20 healthy grey parrots (Psittacus e erithacus) fed either a seed or pellet-based diet were investigated. There was a significant increase in the concentration of ionised calcium in the plasma of both groups, independent of the calcium and vitamin D(3) content of the diets fed, and a significant increase in the plasma concentration of 25-hydroxycholecalciferol in only the seed-fed group. In a separate study there were no significant increases in plasma ionised calcium or 25-hydroxycholecalciferol between March and August in a group of 28 South American parrots (Pionus species) exposed to unfiltered natural sunlight.

Distribution of iron in the parrot brain: conserved (pallidal) and derived (nigral) labeling patterns.

The distribution of iron in the brain of a vocal learning parrot, the budgerigar (Melopsittacus undulatus), was examined using iron histochemistry. In mammals, iron is a highly specific stain for the dorsal and ventral pallidal subdivision as well as specific cell groups in the brainstem, including the substantia nigra pars reticulata [Neuroscience 11 (1984) 595-603]. The purpose of this study was to compare the distribution of iron in the mammalian and avian brain focusing on pallidal and nigral cell groups. The results show that in the avian brain, iron stains oligodendrocytes, neurons and the neuropil. Cell staining changes dramatically along the rostrocaudal axis, with neuronal labeling confined to regions caudal to the thalamus and oligodendrocyte labeling denser in regions rostral to the dorsal thalamus. Many sensory forebrain regions contain appreciable iron labeling, including telencephalic vocal control nuclei. The dorsal and ventral subdivision of the avian pallidum, along with the basal ganglia component of the vocal control circuit, the magnicellular nucleus of the lobus parolfactorius, stain heavily for iron. Several brainstem regions, including nucleus rotundus, the medial spiriform nucleus (SpM), the principle nucleus of the trigeminal nerve, nucleus laminaris and scattered cell groups throughout the isthmus and pontine reticular formation stain intensely for iron. Within SpM neuronal labeling is more intense in the medial division while oligodendrocyte labeling is more intense in the lateral division. surprisingly no nigral iron staining was observed. Our results imply that iron is a conserved marker for the pallidum in birds and mammals, but that patterns of nigral staining have diverged in birds and mammals. Differences in iron staining patterns between birds and mammals may also reflect the relatively greater importance of the collothalamic visual pathways, pretectal-cerebellar pathways and specialized vocal learning circuitry in avian sensory and motor processing.