Topografia dos órgãos abdominais em Didelphis albiventris / Topography of abdominal organs in Didelphis albiventris

O conhecimento da localização dos órgãos nas diferentes regiões do corpo do animal é essencial para a prática clínica, cirúrgica e para o diagnóstico por imagem. O objetivo do estudo foi descrever a anatomia topográfica abdominal do Didelphisalbiventris. Foram utilizados quatro cadáveres (animais jovens), dois destes destinados para o estudo macroscópico em peças a fresco e os outros fixados em solução aquosa de formaldeído a 10%. Os cadáveres foram dissecados e as estruturas anatômicas identificadas, analisadas e fotografadas. A maioria dos órgãos localizados na região abdominal dos cadáveres da espécie D. albiventris apresentou posição similar aos dos caninos, porém, alguns órgãos e a localização de determinadas estruturas apresentaram particularidades importantes, como a presença dos ossos epipúbicos, a ausência do lobo hepático quadrado, a presença de um ceco desenvolvido e o cólon dividido em três segmentos.

The knowledge about localization of organs in different regions of the animal’s body is essential for clinical, surgical and diagnostic imaging practice. The purpose of this study was to describe the abdominal topographic anatomy of Didelphis albiventris. Was used four dead bodys (young animals), two of these was intended for the macroscopic study of fresh pieces and the others fixed in 10% aqueous formaldehyde solution. The corpses was dissected and the anatomic structures was identified, analyzed and photographed. Most of the organs located in the abdominal region of cadavers from species D. albiventris presented structure and position similar to canines, however some of these organs and localization of structures presented important particularities, like the presence of epipubic bones, absence of square hepatic lobe, presence of an developed cecum and colon divided into three segments.

Topografia dos órgãos abdominais em Didelphis albiventris / Topography of abdominal organs in Didelphis albiventris

O conhecimento da localização dos órgãos nas diferentes regiões do corpo do animal é essencial para a prática clínica, cirúrgica e para o diagnóstico por imagem. O objetivo do estudo foi descrever a anatomia topográfica abdominal do Didelphisalbiventris. Foram utilizados quatro cadáveres (animais jovens), dois destes destinados para o estudo macroscópico em peças a fresco e os outros fixados em solução aquosa de formaldeído a 10%. Os cadáveres foram dissecados e as estruturas anatômicas identificadas, analisadas e fotografadas. A maioria dos órgãos localizados na região abdominal dos cadáveres da espécie D. albiventris apresentou posição similar aos dos caninos, porém, alguns órgãos e a localização de determinadas estruturas apresentaram particularidades importantes, como a presença dos ossos epipúbicos, a ausência do lobo hepático quadrado, a presença de um ceco desenvolvido e o cólon dividido em três segmentos.

The knowledge about localization of organs in different regions of the animal's body is essential for clinical, surgical and diagnostic imaging practice. The purpose of this study was to describe the abdominal topographic anatomy of Didelphis albiventris. Was used four dead bodys (young animals), two of these was intended for the macroscopic study of fresh pieces and the others fixed in 10% aqueous formaldehyde solution. The corpses was dissected and the anatomic structures was identified, analyzed and photographed. Most of the organs located in the abdominal region of cadavers from species D. albiventris presented structure and position similar to canines, however some of these organs and localization of structures presented important particularities, like the presence of epipubic bones, absence of square hepatic lobe, presence of an developed cecum and colon divided into three segments.

Anatomical comparison across heads, fore- and hindlimbs in mammals using network models.

Animal body parts evolve with variable degrees of integration that nonetheless yield functional adult phenotypes: but, how? The analysis of modularity with Anatomical Network Analysis (AnNA) is used to quantitatively determine phenotypic modules based on the physical connection among anatomical elements, an approach that is valuable to understand developmental and evolutionary constraints. We created anatomical network models of the head, forelimb, and hindlimb of two taxa considered to represent a 'generalized' eutherian (placental: mouse) and metatherian (marsupial: opossum) anatomical configuration and compared them with our species, which has a derived eutherian configuration. In these models, nodes represent anatomical units and links represent their physical connection. Here, we aimed to identify: (1) the commonalities and differences in modularity between species, (2) whether modules present a potential phylogenetic character, and (3) whether modules preferentially reflect either developmental or functional aspects of anatomy, or a mix of both. We predicted differences between networks of metatherian and eutherian mammals that would best be explained by functional constraints, versus by constraints of development and/or phylogeny. The topology of contacts between bones, muscles, and bones + muscles showed that, among all three species, skeletal networks were more similar than musculoskeletal networks. There was no clear indication that humans and mice are more alike when compared to the opossum overall, even though their musculoskeletal and skeletal networks of fore- and hindlimbs are slightly more similar. Differences were greatest among musculoskeletal networks of heads and next of forelimbs, which showed more variation than hindlimbs, supporting previous anatomical studies indicating that in general the configuration of the hindlimbs changes less across evolutionary history. Most observations regarding the anatomical networks seem to be best explained by function, but an exception is the adult opossum ear ossicles. These ear bones might form an independent module because the incus and malleus are involved in forming a functional primary jaw that enables the neonate to attach to the teat, where this newborn will complete its development. Additionally, the human data show a specialized digit 1 module (thumb/big toe) in both limb types, likely the result of functional and evolutionary pressures, as our ape ancestors had highly movable big toes and thumbs.

Volumetric computed tomography reconstruction, rapid prototyping and 3D printing of opossum head ( Didelphis albiventris ) / Reconstrucción volumétrica por tomografia computarizada, prototipado rápido e impresión 3D de cabeza de zarigüeya ( Didelphis albiventris )

Natural anatomical pieces of wild animals are rare and teachers seek alternatives in satisfactory quantity and quality to inform their students. This article aims to describe the use of multiplanar reconstructions and 3D volume rendering computed tomography (CT) images, rapid prototyping and 3D printing of opossum head to create a biomodel to veterinary education in descriptive anatomy of wild animals. A six-step method study was conducted to construct the biomodel: (1) selection of opossum head from museum; (2) CT scanning of bones structures in veterinary hospital; (3) DICOM visualization medical images in multiplanar reconstructions and 3D volume rendering; (4) .dicom file conversion to .stl; (5) 3D printing of opossum head by rapid prototyping; (6) comparison of 3D model printed with the original anatomical piece. The use of CT images with their different forms of reconstruction can provide a more comprehensive 3D view of opossum craniofacial region and allow a better understanding of head anatomy of this species. The 3D printed biomodel can be a viable alternative to original bone specimens when used in anatomy education. However, further studies must be continued to validate the method in Veterinary Medicine courses.

Las piezas anatómicas naturales de animales salvajes son raras y los profesores buscan alternativas satisfactorias, en cantidad y calidad, para enseñar a sus alumnos. Este artículo tuvo como objetivo describir el uso de la reconstrucción volumétrica por tomografía computarizada, la creación rápida de prototipos y la impresión 3D de la cabeza de zarigüeya para obtener un biomodelo en anatomía descriptiva de animales salvajes para educación veterinaria. Se realizó un estudio en seis pasos para construir el biomodelo: (1) selección de cabeza de zarigüeya del museo; (2) tomografía computarizada de estructuras óseas en hospital veterinario; (3) visualización de las imágenes médicas en DICOM por reconstrucciones multiplanares y renderización de volumen 3D; (4) conversión de archivos .dicom a .stl; (5) impresión 3D de cabeza de zarigüeya mediante prototipado rápido; (6) comparación del modelo 3D impreso con la pieza anatómica original. El uso de imágenes de tomografía computarizada, con sus diferentes formas de reconstrucción, puede proporcionar una vista 3D más completa de la región craneofacial de zarigüeya y permitir una mejor comprensión de la anatomía de la cabeza de esta especie. El biomodelo 3D impreso puede ser una alternativa viable a las muestras óseas originales cuando se utiliza en la educación de la anatomía. Sin embargo, se deben continuar los estudios para validar el método en los cursos de Medicina Veterinaria.

Why to study opossums? / ¿Por qué estudiar las zarigüeyas?

Due to the very important role in Brazilian ecosystems, studying the anatomy of opossums is extremely relevant for their natural preservation and possible clinical and surgical interventions with captive animals. These marsupials occupy diversified niches being well distributed throughout the Brazilian territory. They collaborate in the control of urban and agricultural pests such as rodents and insects. They are also excellent dispersers of seeds through their feces. The conclusion is that opossums can be a great model for the study of the anatomy of wild animals.

Las zarigüeyas desempeñan un papel muy relevante en los ecosistemas brasileños, siendo extremadamente importante estudiar su anatomía para su preservación natural y posibles intervenciones clínicas y quirúrgicas de los animales en cautiverio. Estos marsupiales ocupan nichos diversificados y están bien distribuidos en todo el territorio brasileño. Colaboran en el control de plagas urbanas y agrícolas, como roedores e insectos. También son excelentes dispersores de semillas a través de sus heces. Por lo tanto, se concluye que las zarigüeyas pueden ser un gran modelo para estudiar la anatomía de los animales salvajes.

Unique skull network complexity of Tyrannosaurus rex among land vertebrates.

Like other diapsids, Tyrannosaurus rex has two openings in the temporal skull region. In addition, like in other dinosaurs, its snout and lower jaw show large cranial fenestrae. In T. rex, they are thought to decrease skull weight, because, unlike most other amniotes, the skull proportion is immense compared to the body. Understanding morphofunctional complexity of this impressive skull architecture requires a broad scale phylogenetic comparison with skull types different to that of dinosaurs with fundamentally diverging cranial regionalization. Extant fully terrestrial vertebrates (amniotes) provide the best opportunities in that regard, as their skull performance is known from life. We apply for the first time anatomical network analysis to study skull bone integration and modular constructions in tyrannosaur and compare it with five representatives of the major amniote groups in order to get an understanding of the general patterns of amniote skull modularity. Our results reveal that the tyrannosaur has the most modular skull organization among the amniotes included in our study, with an unexpected separation of the snout in upper and lower sub-modules and the presence of a lower adductor chamber module. Independent pathways of bone reduction in opossum and chicken resulted in different degrees of cranial complexity with chicken having a typical sauropsidian pattern. The akinetic skull of opossum, alligator, and leatherback turtle evolved in independent ways mirrored in different patterns of skull modularity. Kinetic forms also show great diversity in modularity. The complex tyrannosaur skull modularity likely represents a refined mosaic of phylogenetic and ecological factors with food processing being probably most important for shaping its skull architecture. Mode of food processing primarily shaped skull integration among amniotes, however, phylogenetic patterns of skull integration are low in our sampling. Our general conclusions on amniote skull integrity are obviously preliminary and should be tested in subsequent studies. As such, this study provides a framework for future research focusing on the evolution of modularity on lower taxonomic levels.

Anatomical and radiographic study of the white-eared opossum (Didelphis albiventris) skull / Estudo anatômico e radiográfico do crânio no gambá-de-orelha-branca (Didelphis albiventris)

This study was made to investigate the anatomical features of the white-eared opossum skull, by osteology and radiographic anatomy. For this, five animals were used without sexual distinction. The skull was examined by radiographic and macroscopic characteristics. The skulls were then subjected to maceration. The skull was described macroscopically according to standard views, i.e. dorsal and caudal, lateral, ventral, and midsagittal. The skull can be divided into facial (viscerocranium) and cranial (neurocranium) regions. The facial region was elongated and more developed than neurocranium. The supraorbital foramen was absent. The tympanic bulla is not well developed. The zygomatic arch was formed by zygomatic process of the temporal bone, zygomatic process of the maxilla, and temporal process of the zygomatic bone. There was no significant difference between bones found in this study when compared with those described for others mammals. These findings may contribute to the better understanding of the anatomy and biology of the white-eared opossum.(AU)

Este estudo objetivou investigar as características anatômicas do crânio do gambá-de-orelha-branca, através da anatomia óssea e radiográfica. Para tanto, cinco animais foram usados sem distinção sexual. O crânio foi estudado através de análises radiográficas e macroscópicas. Para esta última, os crânios foram macerados. O crânio foi descrito macroscopicamente de acordo com as vistas ou normas rotineiras, isto é, dorsal e caudal, lateral, ventral e sagital. O crânio pode ser dividido em regiões facial (viscerocrânio) e cranial (neurocrânio). A região facial se mostrou alongada e mais desenvolvida que o neurocrânio. O forame supraorbital estava ausente. A bula timpânica não era bem desenvolvida. O arco zigomático era formado pelo processo zigomático do osso temporal, processo zigomático da maxila, e pelo processo temporal do osso zigomático. Não houve diferenças significativas entre os ossos estudados quando comparados com os já descritos para outros mamíferos. Estes resultados podem contribuir com um melhor entendimento da anatomia e biologia deste animal.(AU)

Morfologia e histoquímica das glândulas sexuais acessórias de Metachirus nudicaudatus, Didelphidae-Marsupialia / Morphology and histochemistry of accessory sex glands of Metachirus nudicaudatus, Didelphidae-Marsupialia

São descritas a morfologia e a distribuição de glicogênio e mucossubstâncias na próstata e nas glândulas bulbouretrais de Metachirus nudicaudatus (Geoffroy, 1803), única espécie do gênero. A próstata é envolvida pelas túnicas adventícia e muscular, e o estroma é formado pelo conjuntivo da mucosa uretral. O parênquima é constituído pelos túbulos secretores, disseminados na mucosa uretral, e que diferem histológica e histoquimicamente nos segmentos cranial, médio e caudal. Essas diferenças morfo-histoquímicas também são observadas nas partes externa, média e interna de cada túbulo. De um modo geral, os três segmentos prostáticos secretam mucossubstâncias neutras, porém o segmento caudal produz também glicogênio. Os três pares de glândulas bulbouretrais (laterais, intermédias e mediais) do Metachirus são envolvidas por uma cápsula conjuntiva e músculo estriado esquelético. O maior par é a bulbouretral lateral que é constituída por longos túbulos secretores de mucossubstâncias neutras. As bulbouretrais intermédias são formadas por túbulos ramificados, que produzem mucossubstâncias neutras, ácidas carboxiladas e ácidas sulfatadas. Os túbulo-ácinos ramificados das bulbouretrais mediais secretam mucossubstâncias neutras. O Metachirus não possui glândulas ampulares, vesículas seminais nem glândulas de coagulação.(AU)

This paper describes the morphology and distribution of glycogen and mucous substances in the prostate and the bulbourethral glands of Metachirus nudicaudatus (Geoffroy, 1803), the only species of the genus. The prostate is surrounded by the tunica adventitia, and muscle and stroma is formed by connective urethral mucosa. The glandular parenchyma consists of secretory tubules, scattered throughout the connective tissue of the urethral mucosa which differs histologically and histochemically in cranial, middle, and caudal segments of the prostate. These morpho-histochemical differences are also observed in the outer, middle and inner parts of the tubular epithelium of each prostatic segment. In general, prostatic segments secrete neutral mucous substances, and the caudal segment also produces glycogen. The three pairs of bulbourethral glands (lateral, intermediate and medial) are surrounded by a capsule of dense connective tissue and skeletal striated muscle. The glandular parenchyma is formed by tubules or branched tubuloacinar, covered by simple epithelium which is characteristic for each pair of glands. The lateral bulbourethral glands and the medial bulbourethral glands produce neutral mucous substances and the secretion of the intermediate bulbourethral glands consists of neutral mucous substances, carboxylated acids, and sulfated acids. The M. nudicaudatus does not have ampullary glands, seminal vesicles or coagulating glands.(AU)

Phylogenetic evaluation of taxonomic definition of didelphid mouse opossum of the genus Thylamys from valleys of Coquimbo region, Chile.

Only two species of Didelphidae are currently recognized in Chile, the sister species Thylamys elegans, endemic of Mediterranean ecorregion and Thylamys pallidior, the inhabitant of the Puna and desert canyons. Three subspecies have been described for T. elegans: T. e. elegans, T. e. coquimbensis and T. e. soricinus. However, a recent study based on morphological analyses, synonymized T. elegans coquimbensis from the Coquimbo valleys (30-31° S) with T. pallidior and proposed that T. elegans and T. pallidior could be in sympatry at Coquimbo valleys between Fray Jorge (30°40'S) and Paiguano (30°02' S). We assess the current definition of T. e. coquimbensis and T. e. elegans, as well as this taxonomical conflict among the mouse opossums from the Coquimbo valleys through phylogenetic analyses of cytochrome b mitochondrial gene sequences. In this study, for the first time, we used specimens from the type localities of T. e. coquimbensis and T. e. elegans. In addition, we analyzed diagnostic cranial structures for this taxonomic revision. The results supported two allopatric clades, allowing us to keep the taxonomic definition of T. e. elegans and T. e. coquimbensis as phylogenetic reciprocal monophyletic clades and polyphyletic with T. pallidior. This result corroborates previous morphological analyses, which support that mouse opossums from the Coquimbo valleys are T. e. coquimbensis, thus extending its geographic distribution to the coast of Coquimbo and Atacama regions. We don´t have evidence for sympatric distribution between T. elegans and T. pallidior in the Coquimbo region.

Branching pattern of aortic arch in the white-eared opossum (Didelphis albiventris) / Ramescência do arco aortico no gambá-de-orelha-branca (Didelphis albiventris)

Knowledge of the aortic arch main and collateral branches is important because these arteries supply vital organs found in the head, neck, thoracic cavity and forelimbs of domestic and wild animals. This study aimed to contribute to the anatomical knowledge in opossums and collaborate with veterinary medical and surgical clinics. Thus, the anatomy of aortic arch was described in eighteen opossums. The results indicated that the aortic arch gives off the brachiocephalic trunk and the left subclavian artery in all animals studied. The branching pattern of the aortic arch is similar to that reported in the guinea pig, chinchilla, paca, raccoon, nutria, red squirrel, and ocelot. The brachiocephalic trunk showed as collateral branches, the right subclavian artery and the bicarotid trunk, that originated in the right and left common carotid arteries (77.7%). Bicarotid trunk was absent in four animals (22.2%). The right and left subclavian arteries originated in the vertebral artery, costocervical trunk, internal thoracic artery, and superficial cervical artery. Collateral branches of the subclavian artery showed similarities to that observed in other wild animals such as paca, ocelot and rock cavy.(AU)

O conhecimento do comportamento das artérias que emergem do arco aórtico é importante, pois estas artérias irrigam órgãos vitais encontrados na cabeça, pescoço, cavidade torácica e membros torácicos de animais domésticos e selvagens. Com o objetivo de contribuir com o conhecimento anatômico em gambás e colaborar com a clínica médica e cirúrgica de animais selvagens, descreveu-se neste estudo, a ramescência do arco aórtico em dezoito gambás. Os resultados indicaram que o tronco braquiocefálico e a artéria subclávia esquerda se originaram do arco aórtico em todos os animais estudados. Este padrão de ramescência do arco aórtico é similar ao descrito para a cobaia, chinchila, paca, mão-pelada, nutria, esquilo-vermelho e jaguatirica. O tronco braquiocefálico apresentou como ramos colaterais, a artéria subclávia direita e o tronco bicarotídeo, o qual se bifurcou nas artérias carótidas comuns direita e esquerda (77,7%). O tronco bicarotídeo não apareceu em quatro animais (22,2%). As artérias subclávias direita e esquerda originaram a artéria vertebral, o tronco costocervical e, as artérias torácica interna e cervical superficial. A ramescência encontrada nas artérias subclávias do gambá mostrou similaridades quando comparada com a descrita para outros animais selvagens como a paca, jaguatirica e o mocó.(AU)

Morphological, morphometric and genetic variation among cryptic and sympatric species of southeastern South American three-striped opossums (Monodelphis: Mammalia: Didelphidae).

Monodelphis is the most diverse genus of the family Didelphidae, whose systematics and taxonomy have not yet been well established. Two of the included species, Monodelphis americana and M. iheringi, are difficult to distinguish because both present three dorsal black stripes. Furthermore, they show intra- and interspecific variation related to body size and pelage coloration. Because this variation is not well understood, there are problems in correctly identifying these species, which remain poorly collected and thus rare in zoological collections. This study evaluated the morphological and genetic variations in a sample of striped opossums from a single location in southeastern Brazil to understand if the morphological variation observed in individuals from the same location was indicative of the existence of more than one taxon. The comparative analyses of a series from this single locality with museum specimens of other locations revealed variations in the skin and skull qualitative characters that were related to age and sex. Morphological comparisons led to the identification of two morphogroups, which were corroborated by molecular data; the analysis of cytochrome b sequences indicated the existence of two clades, with an average divergence of 14%. Thus, the results support the existence of two taxa in the sample, defined as M. americana and M. iheringi. We confirmed the sympatry of these two species in a location in southeastern Brazil, presented morphological diagnostic characters to distinguish the two species, provided novel phylogenetic information on the group, and also demonstrated the existence of important intra- and interspecific morphological variations related to sexual dimorphism and ontogeny in the group. These results significantly contribute to information on the systematics of the genus.

Morfologia das glândulas salivares de glironia venusta Thomas, 1912 (didelphimorphia) / Morphology of salivary glands of the glironia venusta Thomas, 1912 (didelphimorphia)

O objetivo deste trabalho foi descrever a morfologia das glândulas salivares de Glironia venusta. Foi utilizado um exemplar coletado no resgate de fauna da Usina Hidroeletrica Teles Pires. Este foi fixado com solução de formaldeído a 10%. Para a análise macroscópica, as glândulas foram dissecadas e fotografadas in situ e para a microscopia foram retirados fragmentos das glândulas. Estes foram desidratados em concentrações crescentes de álcool, diafanizados em xilol, inclusos em parafina e corados com HE. G. venusta apresentou as glândulas mandibulares, parótidas, sublinguais, labiais e zigomáticas. As mandibulares se mostraram como estruturas alongadas, constituídas por lobos não septados e localizadas na porção anterior da região cervical. De formato triangular, a parótida estava localizada na depressão do masseter, ventral à cartilagem auricular. As sublinguais encontravam-se ventrais ao ramo da mandíbula, caudais ao digástrico. Foi observado na porção dorsoposterior à comissura labial, dorsal ao músculo orbicular da boca, as glândulas labiais, que apresentaram formato de "U". Já as glândulas zigomáticas acompanhavam a forma da porção anterior do arco zigomático, na margem infraorbital. As glândulas mandibulares e sublinguais apresentaram ácinos do tipo mucosos, com alguns ácinos serosos. A parótida era constituída por ácinos puramente serosos. Na glândula labial foi observado ácinos do tipo mistos ou seromucosos. Para a glândula zigomática não foi possível a realização da análise microscópica devido problemas de procedimento histológico. As características das glândulas salivares observadas em G. venusta se assemelham a de outros mamíferos onívoros, entretanto, apresentaram pequenas diferenças no que se refere à sua localização e forma.

The aim of this study was to describe the morphology of the salivary glands of Glironia venusta. A sample of G. venusta was collected in fauna rescue of hidroelectric usine of Teles Pires was used. This exemplar was fixed with formaldehyde solution 10%. For macroscopic analysis, the glands were dissected and photographed in situ and for the microscopy fragments of the glands were removed, that were dehydrated in increasing alcohol concentrations, diaphanizated in xylene, included in paraffin and stained with hematoxylin and eosin. G. venusta presented the mandibular, parotid, sublingual, labial and zygomatic glands. The mandible is shown as elongated structures, composed of non-septated lobes and located in the anterior cervical region. With a triangular format, the parotid was located in the depression of the masseter, ventral an auricular cartilage. The sublingual were located ventral to the mandible, caudal to the digastric muscle. In the posterior dorsal portion, until the labial commissure, dorsal to the orbicularis muscle of mouth was observed the labial glands, which showed a "U" shape. The zygomatic glands was accompanied the shape of the anterior portion of the zygomatic arch at the infraorbital margin. The mandibulars and sublinguals glands showed acini of mucous type, with some serous acini. The parotid one was made up purely by serous acini. In the labial gland was observed acini of mixed types mixed or seromucosous. Related the zygomatic gland was not possible to perform the microscopic analysis because of histological proceeding problems. Characteristics of the salivary glands observed in G. venusta resemble other omnivores mammals, but showed small differences as regards their location and shape.

Development of the ethmoid in Caluromys philander (Didelphidae, Marsupialia) with a discussion on the homology of the turbinal elements in marsupials.

Homology of turbinals, or scroll bones, of the mammalian ethmoid bone is poorly known and complicated by a varied terminology. Positionally, there are two main types of ossified adult turbinals known as endoturbinals and ectoturbinals, and their cartilaginous precursors are called ethmoturbinals and frontoturbinals, respectively. Endoturbinals are considered to be serially homologous due to similarity in their developmental patterns. Consequently, endoturbinals from mammals with differing numbers of elements cannot be individually homogenized. In this study, the development of the ethmoid of Caluromys philander, the bare-tailed woolly opossum, is described based on serial sections of six pouchlings ranging in age from 20 to 84 days postnatal (PND-84), and computed tomography images of an adult skull. I found that four ethmoturbinals initially develop as seen in PND-20 and PND-30 individuals but by PND-64 an interturbinal (corresponding to endoturbinal III in adults) is present between ethmoturbinals II and III. This developmental pattern is identical to that of Monodelphis domestica, the gray short-tailed opossum, and is probably also present in the marsupials Didelphis marsupialis, and Thylacinus cynocephalus based on work of previous authors. These data suggest that endoturbinal III has a developmental pattern that differs from other endoturbinals, and the name interturbinal should be retained for the adult structure in recognition of this difference. These results may prove useful for homologizing this individual turbinal element across marsupials, the majority of which have five endoturbinals as adults. This might also explain the presumed placental ancestral condition of four endoturbinals if the marsupial interturbinal is lost.

Myosin isoform expression in the prehensile tails of didelphid marsupials: functional differences between arboreal and terrestrial opossums.

Prehensile tails are defined as having the ability to grasp objects and are commonly used as a fifth appendage during arboreal locomotion. Despite the independent evolution of tail prehensility in numerous mammalian genera, data relating muscle structure, physiology, and function of prehensile tails are largely incomplete. Didelphid marsupials make an excellent model to relate myosin heavy chain (MHC) isoform fiber type with structure/function of caudal muscles, as all opossums have a prehensile tail and tail use varies between arboreal and terrestrial forms. Expanding on our previous work in the Virginia opossum, this study tests the hypothesis that arboreal and terrestrial opossums differentially express faster versus slower MHC isoforms, respectively. MHC isoform expression and percent fiber type distribution were determined in the flexor caudae longus (FCL) muscle of Caluromys derbianus (arboreal) and Monodelphis domestica (terrestrial), using a combination of gel electrophoresis and immunohistochemistry analyses. C. derbianus expresses three MHC isoforms (1, 2A, 2X) that are distributed (mean percentage) as 8.2% MHC-1, 2.6% 1/2A, and 89.2% 2A/X hybrid fibers. M. domestica also expresses MHC-1, 2A, and 2X, in addition to the 2B isoform, distributed as 17.0% MHC-1, 1.3% 1/2A, 9.0% 2A, 75.2% 2A/X, and 0.3% 2X/B hybrid fibers. The distribution of similar isoform fiber types differed significantly between species (P < 0.001). Although not statistically significant, C. derbianus was observed to have larger cross-sectional area (CSA) for each corresponding fiber type along with a greater amount of extra-cellular matrix. An overall faster fiber type composition (and larger fibers) in the tail of an arboreal specialist supports our hypothesis, and correlates with higher muscle force required for tail hanging and arboreal maneuvering on terminal substrates. Conversely, a broader distribution of highly oxidative fibers in the caudal musculature is well suited for tail nest building/remodeling behaviors of terrestrial opossums.

Functional and evolutionary aspects of axial stability in euarchontans and other mammals.

The presence of a stable thoracolumbar region, found in many arboreal mammals, is considered advantageous for bridging and cantilevering between discontinuous branches. However, no study has directly explored the link between osteological features cited as enhancing axial stability and the frequency of cantilevering and bridging behaviors in a terminal branch environment. To fill this gap, we collected metric data on costal and vertebral morphology of primate and nonprimate mammals known to cantilever and bridge frequently and those that do not. We also quantified the frequency and duration of cantilevering and bridging behaviors using experimental setups for species that have been reported to show differences in use of small branches and back anatomy (Caluromys philander, Loris tardigradus, Monodelphis domestica, and Cheirogaleus medius). Phylogenetically corrected principal component analysis reveals that taxa employing frequent bridging and cantilevering (C. philander and lorises) also exhibit reduced intervertebral and intercostal spaces, which can serve to increase thoracolumbar stability, when compared to closely related species (M. domestica and C. medius). We observed C. philander cantilevering and bridging significantly more often than M. domestica, which never cantilevered or crossed any arboreal gaps. Although no difference in the frequency of cantilevering was observed between L. tardigradus and C. medius, the duration of cantilevering bouts was significantly greater in L. tardigradus. These data suggest that osteological features promoting axial rigidity may be part of a morpho-behavioral complex that increases stability in mammals moving and foraging in a terminal branch environment.

Integration of the mammalian shoulder girdle within populations and over evolutionary time.

Morphological integration has the potential to link morphological variation within populations with morphological evolution among species. This study begins to investigate this link by comparing integration among shoulder girdle elements (e.g. scapular blade, glenoid, coracoid, etc.) during the origin and evolution of therian mammals, and within modern bat, opossum and mouse populations. In this study, correlations among skeletal elements and patterns of allometry are used as proxies for integration. Results suggest that shoulder girdle elements tended to vary and evolve independently during the origin of mammals and subsequent radiation of placentals, consistent with the elements' distinct developmental and evolutionary origins. This finding suggests that skeletal element correlations, and therefore integration, can be conserved over large taxonomic and temporal scales. However, marsupials display a different pattern in which shoulder girdle elements tend to be more integrated, with the exception of the coracoid. This finding is consistent with a shift in the pattern of skeletal element integration coincident with the appearance of the marsupial mode of reproduction. This finding provides further evidence that development can play a significant role in the establishment of patterns of skeletal element correlation and that patterns of skeletal element correlation can themselves evolve when faced with sufficient selective pressures.

Marsupial morphology of reproduction: South America opossum male model.

This study aims to describe the morphology of Didelphis sp. male genital organs (penis, testes, epididymis, ductus deferens, prostate, and bulbourethral gland). Ten male animals were used, eight for macroscopic and light microscopy analysis, and two for scanning electron microscopy. The testes and epididymis showed similarity to other eutherian mammals. The bifid penis showed the urethra ending in the medial region where the bifurcation begins, occurring in each segment extension of the urethral groove until the beginning of the glans. Histologically, the penis consists of a cavernous and spongy body, covered by stratified squamous epithelium with loose connective tissue. The urethra was lined by transitional stratified epithelium. In the prostate, prostatic segments were found consisting of tubular glands in a radial arrangement around the urethra, coated externally by a dense connective tissue associated with a relatively thick layer of smooth muscle arranged in two layers that surround the glandular tissue. The animals had three pairs of bulbourethral glands placed at the membranous and cavernous urethra junction with descending and parallel excretory ducts ending caudally in the urethral lumen.

Morphological and morphometric study of the opossum's dorsal root ganglia neurons.

The ultrastructural characteristics and the morphometric evaluation of the different types of neurons present in the dorsal root ganglia (DRG) of the South American opossum (Didelphis albiventris) were studied. Four adult male animals were used and the neurons from cervical and lumbar DRG were removed and processed for histological and transmission electron microscopy observations. The morphometric data were obtained from serial sections stained by H/E and Masson's trichrome. The number of neurons in cervical and lumbar DRG was 22 300 and 31 000, respectively. About 68% of the cervical neurons and 62.5% of the lumbar neurons presented areas up to 1300 µm(2) and were considered as the small neurons of the DRG. The ultrastructural observations revealed two morphological types of neurons: clear large neurons and dark small neurons. The nuclei of both cell types are spherical and the chromatin is disperse and rarefected. The cytoplasm of the dark small neuron is more electron dense and shows a regular distribution of small mitochondria and many rough reticulum cisterns in the periphery. A small Golgi apparatus was close to the nucleus and many disperse neurofilaments occupy most parts of the cytoplasm. Smooth reticulum cisterns are rare and lipofucsin-like inclusions are present at some points. In the clear large neurons, the organelles are homogenously scattered through the cytoplasm. The neurofilaments are close packed forming bundles and small mitochondria and rough reticulum cisterns are disperse. Lipofucsin-like inclusions are more frequent in these cells.

Skull modularity in neotropical marsupials and monkeys: size variation and evolutionary constraint and flexibility.

An organism is built through a series of contingent factors, yet it is determined by historical, physical, and developmental constraints. A constraint should not be understood as an absolute obstacle to evolution, as it may also generate new possibilities for evolutionary change. Modularity is, in this context, an important way of organizing biological information and has been recognized as a central concept in evolutionary biology bridging on developmental, genetics, morphological, biochemical, and physiological studies. In this article, we explore how modularity affects the evolution of a complex system in two mammalian lineages by analyzing correlation, variance/covariance, and residual matrices (without size variation). We use the multivariate response to selection equation to simulate the behavior of Eutheria and Metharia skulls in terms of their evolutionary flexibility and constraints. We relate these results to classical approaches based on morphological integration tests based on functional/developmental hypotheses. Eutherians (Neotropical primates) showed smaller magnitudes of integration compared with Metatheria (didelphids) and also skull modules more clearly delimited. Didelphids showed higher magnitudes of integration and their modularity is strongly influenced by within-groups size variation to a degree that evolutionary responses are basically aligned with size variation. Primates still have a good portion of the total variation based on size; however, their enhanced modularization allows a broader spectrum of responses, more similar to the selection gradients applied (enhanced flexibility). Without size variation, both groups become much more similar in terms of modularity patterns and magnitudes and, consequently, in their evolutionary flexibility.