Background: The nutria (Myocastor coypus) is a medium-size, semi-aquatic rodent, valued in skin and meat industry. The brain circulation has been well studied in rodents but not in nutria. To understand and compare the phylogenetic development of the arteries of the base of the brain in rodents, this paper aims to describe and systematize these arteries, establishing a standard model and its main variations in nutria.Materials, Methods & Results: Following approval by the Ethics Committee of Federal University of Rio Grande do Sul, thirty nutrias from a commercial establishment authorized by Brazilian Institute of Environment and Natural Resources (IBAMA) were studied. For euthanasia, was applied heparin (10000 U.I for animal), intraperitoneally, and after thirty minutes the animals ware sedated with acepromazine (0.5 mg/kg) and meperidine (20 mg/kg), intramuscularly. After sedation, they were euthanized with thiopental sodium (120 mg/kg) and lidocaine (10 mg/mL), intraperitoneally. The heart was accessed, the cardiac apex was sectioned, the aorta was cannulated via the left ventricle and clamped close to the diaphragm, and the arterial system was washed with saline solution and filled with latex. The animals were submerged in water for latex polymerization, the trunk was sectioned, the skin removed and a bony window was opened in the skull vault. The pieces were fixed in formaldehyde. The brains were removed, and schematic drawings of the arteries from the base of the brain were made for elaboration of the results. The nutria’s brain was vascularized by the vertebro-basilar system. The terminal branches of the right and left vertebral artery were anastomosed on the ventral surface of the medulla oblongata, forming the basilar artery, and caudally the ventral spinal artery. The basilar artery formed collateral branches, the caudal and middle cerebellar and trigeminal arteries, and at the height of the rostral pons groove, divided into its two terminal branches, the rostral cerebellar and cerebral caudal arteries. The terminal branches of the basilar artery projected rostrally, forming the hypophyseal and rostral choroid arteries. The basilar artery passed the optic tract and bifurcated in the middle cerebral artery, its last collateral branch, and in the rostral cerebral artery, its terminal branch. The rostral cerebral artery formed the medial branch, closing the cerebral arterial circle caudally in 40% of the cases.Discussion: In rodents, variability of the cerebral arterial circle was observed due to the degree of atrophy of the internal carotid artery. The basilar artery was a rectilinear vessel of great caliber in all described rodents, and in rodents with a vertebro-basilar system, it was divided into its terminal branches after crossing the pons, forming the rostral cerebellar, hypophyseal, rostral choroid, caudal, middle and rostral cerebral arteries. The caudal cerebellar artery had variation of origin and sometimes duplication. The median cerebellar artery, a collateral branch of the caudal cerebellar artery, was a branch of the basilar artery in capybara. The caudal cerebral artery had variations between rodents. In capybara, chinchilla and nutria the middle cerebral artery was the collateral branch of the terminal branches of the basilar artery, and distributed on the convex surface of the cerebral hemisphere. The rostral cerebral artery, a branch of the terminal branch of the basilar artery, was a branch of the internal carotid artery in other rodents, forming the medial branch, which was anastomosed with that of the opposite antimer, when present, forming the rostral communicating artery. In nutria, the cerebral arterial circle was closed caudally in all cases, as in other rodents, however, it was opened rostrally in 60% of cases, compared to 70% in chinchilla and 10% in capybara.

Background: This member of the Didelphidea family, commonly known as opossum, is widely distributed in the American territory, with species found from southern Canada up to northern Argentina. Similarly to all marsupials, they are characterized by a short gestational period, followed by a long development period. Opossums are arboreal, terrestrial slow animals of lonely and nocturnal habits. They are omnivore animals, eating from small rodents, birds, eggs and amphibians to fruits and vegetables. These general characteristics have drawn in the interest and curiosity of the scientific community to this animal, which is now the object of study in several knowledge areas. In order to find morphological information that could assist in discussions from a functional point of view and that could offer support for measures that aim at protecting opossums in their natural environment, the objective of the present study is to divulge the anatomical behavior of their celiac artery and its branches, including its distribution areas, considering the importance of these vessels in the blood supply of several digestive organs. Materials, Methods & Results:In this study, the celiac artery of 24 opossums (Didelphis albiventris), of which 17 were females and 7 were males, was systematized. For the purpose, their arterial system was filled with colored latex 603. The abdominal aorta gave off its first visceral collateral branch, the celiac-mesenteric trunk, which originated the celiac artery and the cranial mesenteric artery in 87.5% of the samples, but in 12.5% of the samples, the abdominal aorta gave off these arteries individually. The celiac artery gave off the lienal and hepatic arteries. The lienal artery gave off the left gastric artery to the lesser curvature of the stomach, supplying its parietal and visceral side, also giving off esophageal branches. The lienal artery reached the splenic hilum, giving off several pancreatic branches during its path. Once it reached the splenic hilum, it gave off its own lienal branches and then continued as left gastroepiploic artery towards the greater stomach curvature. The hepatic artery was projected cranially, giving off the gastroduodenal artery and cranial pancreaticoduodenal artery reaching the portal fissure, where hepatic branches arose towards the liver. The gastroduodenal artery gave off the right gastroepiploic artery towards the greater curvature of the stomach, also giving off the right gastric artery towards the lesser curvature of the stomach and then became divided into one branch to the visceral side and one branch to the parietal side, also giving off esophageal and pyloric branches. The cranial pancreaticoduodenal artery branched to the cranial duodenum and right lobe of the pancreas. Discussion: In the majority of opossums (87.5%), the celiac artery had origin in a common trunk with the cranial mesenteric artery, but in 12.5% of the animals, this origin took place separately. In opossums (Didelphis albiventris), regardless of its origin, the celiac artery was a sing...

A novel polyomavirus (PyVs) comprising 5,422 bp was identified by high-throughput sequencing (HTS) in pooled organs of nutria (Myocastor coypus). The new genome displays the archetypal organization of PyVs, which includes open reading frames for the regulatory proteins small T antigen (sTAg) and large T antigen (LTAg), as well as for the capsid proteins VP1, VP2 and VP3. Based on the International Committee on Taxonomy of Viruses (ICTV) Polyomaviridae Study Group criteria, this genome comprises a new PyVs species for the Alphapolyomavirus genus and is putatively named "Myocastor coypus Polyomavirus 1" . The complete genome sequence of this Myocastor coypus Polyomavirus 1 (McPyV1) isolate is publically available under the GenBank accession no. MH182627.

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The nutria (Myocastor coypus) is a medium-sized, semi-aquatic rodent valued by the skin and meat industry. This study aimed to describe and systematize the caudal cerebral artery on the brain surface in nutria, establishing a standard model and its main variations in this species. The thirty animals used were euthanized according to animal welfare rules. The vessels were filled with latex stained with red pigment and the samples were fixed in formaldehyde. In nutria, the brain was vascularized by the vertebral basilar system. The terminal branches of the basilar artery originated the rostral cerebellar, caudal cerebral, rostral choroidal and middle cerebral arteries, and its terminal branch, the rostral cerebral artery. The terminal branch of the basilar artery projected the caudal cerebral artery, which is usually a single medium-caliber vessel, into the transverse fissure of the brain. The caudal cerebral artery was presented as a single (66.7% of the cases to the right and 76.7% to the left) and double vessel (33.3% of the cases to the right and 23.3% to the left). It originated the rostral mesencephalic artery, the proximal component, and the caudal inter-hemispheric artery. The terminal branches of the rostral and caudal tectal mesencephalic arteries formed a typical anastomotic network. The caudal inter-hemispheric artery emitted central branches, the caudal choroidal artery, hemispherical occipital arteries, rostral tectal mesencephalic branches and distal components, and anastomosed “in osculum” with the terminal branches of the rostral inter-hemispheric artery. The caudal choroidal artery anastomosed with the rostral choroidal artery, where it branched out on the thalamic mass, vascularizing all diencephalic structures and the hippocampus. The caudal cerebral artery and its terminal branches anastomosed with the terminal branches of the rostral and middle cerebral arteries in a restricted region of the caudal pole of the cerebral hemisphere. The vascularization area of the caudal cerebral artery and its central branches in the paleopallial of the piriform lobe is extremely restricted, caudomedially.

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