Morphology and computed tomography of the larynx in the white-eared opossum (Didelphis albiventris).

The white-eared opossum (Didelphis albiventris) is a Neotropical marsupial that occurs in the Brazilian territory. The larynx is an important organ of vocalization in mammals, although, other laryngeal functions are more fundamental for survival of mammals than phonation. The anatomical knowledge of respiratory structures is pivotal for a better understanding of the species. Thus, this study aimed to examine the larynx of the white-eared opossum by gross anatomy, computed tomography and histological description. For this, 10 adult (six females and four males) white-eared opossums (D. albiventris) were used. The white-eared opossum larynx was formed by epiglottis, thyroid, cricoids and arytenoid cartilages and a corniculate process. There is a similarity between the larynx of this marsupial and those reported in other wild mammals, regarding the number of cartilages and their location. Histologically, the epiglottis consisted of elastic cartilage and thyroid, cricoid and arytenoid cartilages were composed of hyaline cartilage. The epiglottis protruded rostrally into the nasal part of the pharynx, above the soft palate, and this is probably a marsupial characteristic as the fact that the thyroid and cricoid cartilages were ventrally fused. The hyoid apparatus was similar to that of other animals, with the same bony constitution, but with a greatly reduced stylohyoid bone. Histologically, the larynx was similar to those of other species such as koala, armadillo, crab-eating foxes and giant anteaters. The knowledge of the larynx morphology is important for the anatomical features of the species and clinical and surgical procedures, such as endotracheal intubation.

Anatomical characteristics of the bones of the thoracic limb of white-eared opossum (Didelphis albiventris) / Características anatómicas de los huesos del miembro torácico de la zarigüeya oreja blanca (Didelphis albiventris)

SUMMARY: The skeleton of the thoracic limb is one of the key aspects for the understanding of the habits and movement of different mammalian species. Considering the gap about studies related to marsupial osteology, this work proposes to study the aspects inherent to the skeleton of opossums, with emphasis on the detailed anatomical description of the bones that form the thoracic limb. For this purpose, the bones of six specimens of possums of the species Didelphis albiventris were used. These small to medium sized marsupials inhabit a wide range of South America, living in several types of habitats, being commonly described as arboreal omnivores and have anthropic habits. For the execution of this study, the bone accidents perceptible in the specimens were identified by superficial palpation, which were then radiographed. The thoracic limb bones were prepared by boiling and drying in the sun. Finally, from the radiographic images and the prepared bones, a detailed description of the anatomy of the bone components of the thoracic limb of Didelphis albiventris was made, joining the previously obtained data of surface anatomy. These data were compared with data from the literature, discussing the functional significance of the osteological findings of the thoracic limb of Didelphis albiventris.

RESUMEN: El esqueleto del miembro torácico es uno de los aspectos clave para el conocimiento de los hábitos y movimientos de las diferentes especies de mamíferos. Considerando los escasos estudios relacionados con la osteología marsupial, este trabajo se propusoestudiar los aspectos inherentes al esqueleto de la zarigüeya, con énfasis en la descripción anatómica detallada de los huesos que forman el miembro torácico. Para ello se utilizaron los huesos de seis ejemplares de zarigüeyas de la especie Didelphis albiventris. Estos marsupiales de pequeño a mediano tamaño habitan una zona amplia de América del Sur, viven en varios tipos de hábitats, se describen comúnmente como omnívoros arbóreos y tienen hábitos antrópicos. Para este estudio se identificaron mediante palpación superficial los accidentes óseos perceptibles en los especímenes, y posteriormente se tomaron imágens radiológicas. Los huesos de los miembros torácicos se prepararon hirviéndolos y secándolos al sol. Finalmente, a partir de las imágenes radiográficas y de los huesos preparados, se realizó una descripción detallada de la anatomía de los componentes óseos del miembro torácico de Didelphis albiventris, uniendo los datos de anatomía superficial obtenidos previamente. Estos datos se compararon con datos de la literatura, discutiendo la importancia funcional de los hallazgos osteológicos del miembro torácico de Didelphis albiventris.

Osteology and radiology of the vertebral column in the white-eared opossum (Didelphis albiventris).

The white-eared opossum present a higher roadkill number in Brazil, and the vertebral column is often affected when some type of trauma occurs. Thus, this study describes the osteology and radiology of the vertebral column in white-eared opossum to serve as a basis for support in the veterinary clinical care, since the casuistry of care of this marsupial has increased every year. Radiographs of the cervical (C), thoracic (T), lumbar (L), sacral (S) and caudal (Cd) segments of the vertebral column were taken in thirty-five white-eared opossums (Didelphis albiventris). Furthermore, ten opossums without evident vertebral acquired or congenital abnormalities at the radiographic study were selected for anatomical study. Osteology was correlated with the radiographic images. The use of radiographs allowed the identification of congenital and acquired vertebral changes, as well as the identification of anatomical structures, their distribution and morphology and the number of vertebrae. The vertebral formula varied in the white-eared opossum. In 27 of 35 white-eared opossums (77.2%) with normal vertebral morphology, three vertebral formulas were observed: C7/T13/L6/S2 (62.9%), C7/T13/L5/S2 (5.7%) and C7/T13/L7/S2 (8.6%). Most of the specimens presented 27 caudal vertebrae. The anticlinal vertebra was identified as T10 in 77.2% and T11 in 22.8% of opossums. Cervical block vertebra was observed in two animals and sacrocaudal block vertebra in one animal. The haemal arches could be seen from Cd3-Cd4 in 80% and Cd2-Cd3 in 20% of opossums. The white-eared opossum showed a slender vertebral column with a relatively short thoracic region, a relatively long lumbar region and a highly flexible lumbosacral transition, suggesting that this animal is a fast-running and agile opossum. Therefore, these findings may serve as a basis for further research and support the veterinary clinical care, since the casuistry of care for this marsupial has increased every year.

Histomorphometrical study on the skin of different regions of the Caribbean common opossum (Didelphis marsupialis Linnaeus, 1758).

Common opossums (Didelphis marsupialis) are found throughout the Caribbean island of Trinidad and Tobago. The present work was conducted on the fresh normal skin of 10 common opossums and aimed to provide morphometric data and a histological description of the skin in different regions of the body. In the examined regions, the skin presented a typical thin skin morphology, with numerous folds on the surface. The dermis-epidermis junction is smooth, without the occurrence of dermal papillae. The average thickness of the opossum epidermis was 19.5 µm. The cranial region of the back showed the greatest epidermal thickness, and together with the other areas of the back presented an epidermis 2-3 times thicker compared with the other areas examined. To further confirm that the skin changes in the opossum are age- or diet-related, additional studies are required.

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.

Morphology of the vaginal complex in the white-eared opossum (Didelphis albiventris): Gross anatomy and light microscopy.

Opossums, the largest marsupials found in Brazil, are animals of great interest due to their commonality in large urban centres and their frequent use as laboratory animals. Thus, this study was designed to describe the vaginal complex in ten female opossums by gross anatomy and light microscopy. The vaginal complex comprises two lateral vaginae, a vaginal cul-de-sac and a urogenital sinus. No marked morphological contrast of the vaginal complex was observed in the proestrus and metestrus phases of the females studied. The epithelium lining of cul-de-sac was simple columnar and folded. The lateral vagina was lined by a stratified squamous epithelium that was keratinised in its cranial portion and nonkeratinised in the caudal region. The urogenital sinus was also lined by a stratified squamous epithelium. The morphology of vaginal complex of white-eared opossum is similar to those reported for other marsupials, showing similar histological features.

Absence of bony patella in the white-eared opossum (Didelphis albiventris): Morphology and diagnostic imaging.

Patella, the kneecap, is the best known and largest of the sesamoid bones and is present in the quadriceps femoris tendon. Typical patella appears in all extant mammals, with the exception of some marsupials and bats. No description about the white-eared opossum stifle was found in the available literature up to now. Thus, the knee joints of 16 Didelphis albiventris were examined by gross anatomy, histology, radiography and computed tomography images to determine the presence or absence of ossified patella in this animal. The most remarkable observation in white-eared opossum is the absence of a bony patella. The femoral trochlea is shallow, and the lateral gastrocnemius sesamoids are shown up in all opossums. The quadriceps femoris tendon is composed mainly of dense regular connective tissue with a classic fibrocartilage pad on the superficial surface of the tendon. The absence of a true patella seems to be typical for marsupials.

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)

Comparative Myology and Evolution of Marsupials and Other Vertebrates, With Notes on Complexity, Bauplan, and "Scala Naturae".

Opossums are frequent subjects of developmental studies because marsupials share developmental features not seen in placentals and because Didelphimorpha is the sister-group of other extant Marsupialia. But is the adult marsupial muscular system markedly different from that of placentals or is it, like the skeletal system, very similar? We provide, for the first time, a brief description of all head and limb muscles of Didelphis virginiana based on our dissections and using a unifying nomenclature by integrating the data gathered in our long-term project on the development, homologies, and evolution of the muscles of all major vertebrate taxa. Our data indicate that there were many more muscle synapomorphic changes from the last common ancestor (LCA) of amniotes to the mammalian LCA (63) and from this LCA to the LCA of extant therians (48) than from this latter LCA to the LCA of extant placentals (10 or 11). Importantly, Didelphis is anatomically more plesiomorphic (only 14 changes from LCA of extant therians) than are rats (37 changes) and humans (63 changes), but its musculature is more complex (193 muscles) than that of humans (only 180 muscles). Of the 194 muscles of Didelphis, 172 (89%) are present in rats, meaning that their adult muscle anatomy is indeed very similar. This similarity supports the existence of a common, easy recognizable therian Bauplan, but one that is caused by developmental constraints and by evolutionary change driven by the needs of the embryos/neonates, rather than by a "goal" toward a specific adult plan/"archetype," as the name Bauplan suggests. Anat Rec, 299:1224-1255, 2016. © 2016 Wiley Periodicals, Inc.

Which Factors Determine Spatial Segregation in the South American Opossums (Didelphis aurita and D. albiventris)? An Ecological Niche Modelling and Geometric Morphometrics Approach.

Didelphis albiventris and D. aurita are Neotropical marsupials that share a unique evolutionary history and both are largely distributed throughout South America, being primarily allopatric throughout their ranges. In the Araucaria moist forest of Southern Brazil these species are sympatric and they might potentially compete having similar ecology. For this reason, they are ideal biological models to address questions about ecological character displacement and how closely related species might share their geographic space. Little is known about how two morphologically similar species of marsupials may affect each other through competition, if by competitive exclusion and competitive release. We combined ecological niche modeling and geometric morphometrics to explore the possible effects of competition on their distributional ranges and skull morphology. Ecological niche modeling was used to predict their potential distribution and this method enabled us to identify a case of biotic exclusion where the habit generalist D. albiventris is excluded by the presence of the specialist D. aurita. The morphometric analyses show that a degree of shape discrimination occurs between the species, strengthened by allometric differences, which possibly allowed them to occupy marginally different feeding niches supplemented by behavioral shift in contact areas. Overlap in skull morphology is shown between sympatric and allopatric specimens and a significant, but weak, shift in shape occurs only in D. aurita in sympatric areas. This could be a residual evidence of a higher past competition between both species, when contact zones were possibly larger than today. Therefore, the specialist D. aurita acts a biotic barrier to D. albiventris when niche diversity is not available for coexistence. On the other hand, when there is niche diversification (e.g. habitat mosaic), both species are capable to coexist with a minimal competitive effect on the morphology of D. aurita.

Myosin isoform fiber type and fiber size in the tail of the Virginia opossum (Didelphis virginiana).

Muscle fiber type is a well studied property in limb muscles, however, much less is understood about myosin heavy chain (MHC) isoform expression in caudal muscles of mammalian tails. Didelphid marsupials are an interesting lineage in this context as all species have prehensile tails, but show a range of tail-function depending on either their arboreal or terrestrial locomotor habits. Differences in prehensility suggest that MHC isoform fiber types may also be different, in that terrestrial opossums may have a large distribution of oxidative fibers for object carrying tasks instead of faster, glycolytic fiber types expected in mammals with long tails. To test this hypothesis, MHC isoform fiber type and their regional distribution (proximal/transitional/distal) were determined in the tail of the Virginia opossum (Didelphis virginiana). Fiber types were determined by a combination of myosin-ATPase histochemistry, immunohistochemistry, and SDS-PAGE. Results indicate a predominance of the fast MHC-2A and -2X isoforms in each region of the tail. The presence of two fast isoforms, in addition to the slow MHC-1 isoform, was confirmed by SDS-PAGE analysis. The overall MHC isoform fiber type distribution for the tail was: 25% MHC-1, 71% MHC-2A/X hybrid, and 4% MHC-1/2A hybrid. Oxidative MHC-2A/X isoform fibers were found to be relatively large in cross-section compared to slow, oxidative MHC-1 and MHC-1/2A hybrid fibers. A large percentage of fast MHC-2A/X hybrids fibers may be suggestive of an evolutionary transition in MHC isoform distribution (fast-to-slow fiber type) in the tail musculature of an opossum with primarily a terrestrial locomotor habit and adaptive tail-function.

Macroscopic and microscopic analysis of the tongue of the common opossum (Didelphis marsupialis).

We performed a macroscopic and microscopic study of the tongues of common opossums, Didelphis marsupialis, from South America. We studied two males and two females. We collected morphometric data on the tongue with precision calipers. For the light microscopy and scanning electron microscopy analyses, we fixed tissue fragments in 10% formaldehyde and 2.5% glutaraldehyde, respectively. The opossum tongues averaged 5.87 ± 0.20 cm in length, 3.27 ± 0.15 cm in width at the lingual body, and 3.82 ± 0.15 cm in width at the root. The mean thickness of the lingual body was 1.8 ± 0.1 cm, and the thickness of the root was 3.82 ± 0.15 cm. Sharp filiform papillae were scattered across the entire tongue; conical filiform papillae occurred on the lingual body and tongue tip; fungiform papillae were scattered among the filiform papillae on the lingual body and tongue tip; and there were three vallate papillae at the root of the tongue. We found two strands of papillary projections in the tongue root. Despite the low variability observed in the lingual papillae, the morphological data obtained in this study may be related to the opossum's diverse food habits and the extensive geographic distribution of the species throughout America.

DNA barcodes effectively identify the morphologically similar Common Opossum (Didelphis marsupialis) and Virginia Opossum (Didelphis virginiana) from areas of sympatry in Mexico.

Two morphologically similar species of opossum from the genus Didelphis-Didelphis virginiana and Didelphis marsupialis-cooccur sympatrically in Mexico. High intraspecific variation complicates their morphological discrimination, under both field and museum conditions. This study aims to evaluate the utility and reliability of using DNA barcodes (short standardized genome fragments used for DNA-based identification) to distinguish these two species. Sequences of the cytochrome c oxidase subunit I (Cox1) mitochondrial gene were obtained from 12 D. marsupialis and 29 D. virginiana individuals and were compared using the neighbor-joining (NJ) algorithm with Kimura's two-parameter (K2P) model of nucleotide substitution. Average K2P distances were 1.56% within D. virginiana and 1.65% in D. marsupialis. Interspecific distances between D. virginiana and D. marsupialis varied from 7.8 to 9.3% and their barcode sequences formed distinct non-overlapping clusters on NJ trees. All sympatric specimens of both species were effectively discriminated, confirming the utility of Cox1 barcoding as a tool for taxonomic identification of these morphologically similar taxa.

Body size of commom opossum Didelphis aurita Wied-Neuwied 1826 (Didelphimorphia: Didelphidae) on southern brazilian islands.

The body size of vertebrates isolated on islands can undergo changes due to ecological features of these environments. This study aimed to compare the body size of the common opossum, Didelphis aurita, from different insular populations within the same archipelago in southern Brazil. The opossum populations showed corporal variation and different hypotheses were raised to understand the results. This study constitutes the most detailed body size comparison of a marsupial within different insular populations in the Neotropical zone and the data gathered represents an initial contribution for regional fauna biometric knowledge.

Body size of commom opossum Didelphis aurita Wied-Neuwied 1826 (Didelphimorphia: Didelphidae) on southern Brazilian islands / Tamanho corpóreo de gambás Didelphis aurita Wied-Neuwied 1826 (Didelphimorphia: Didelphidae) em ilhas no sul do Brasil

The body size of vertebrates isolated on islands can undergo changes due to ecological features of these environments. This study aimed to compare the body size of the common opossum, Didelphis aurita, from different insular populations within the same archipelago in southern Brazil. The opossum populations showed corporal variation and different hypotheses were raised to understand the results. This study constitutes the most detailed body size comparison of a marsupial within different insular populations in the Neotropical zone and the data gathered represents an initial contribution for regional fauna biometric knowledge.

O tamanho corpóreo de vertebrados isolados em ilhas pode sofrer alterações em função das particularidades ecológicas desses ambientes. O presente trabalho comparou o tamanho corpóreo de gambás, Didelphis aurita, em ilhas costeiras de um mesmo arquipélago no Sul do Brasil e encontrou diferenças de tamanho entre as localidades. Os gambás apresentaram variações para as medidas corporais e diferentes hipóteses foram consideradas para entender os resultados. Esta é a comparação mais detalhada de tamanho corpóreo entre populações insulares de um marsupial neotropical e uma contribuição inicial para o conhecimento da biometria da fauna regional.

Dental eruption in afrotherian mammals.

BACKGROUND: Afrotheria comprises a newly recognized clade of mammals with strong molecular evidence for its monophyly. In contrast, morphological data uniting its diverse constituents, including elephants, sea cows, hyraxes, aardvarks, sengis, tenrecs and golden moles, have been difficult to identify. Here, we suggest relatively late eruption of the permanent dentition as a shared characteristic of afrotherian mammals. This characteristic and other features (such as vertebral anomalies and testicondy) recall the phenotype of a human genetic pathology (cleidocranial dysplasia), correlations with which have not been explored previously in the context of character evolution within the recently established phylogeny of living mammalian clades. RESULTS: Although data on the absolute timing of eruption in sengis, golden moles and tenrecs are still unknown, craniometric comparisons for ontogenetic series of these taxa show that considerable skull growth takes place prior to the complete eruption of the permanent cheek teeth. Specimens showing less than half (sengis, golden moles) or two-thirds (tenrecs, hyraxes) of their permanent cheek teeth reach or exceed the median jaw length of conspecifics with a complete dentition. With few exceptions, afrotherians are closer to median adult jaw length with fewer erupted, permanent cheek teeth than comparable stages of non-afrotherians. Manatees (but not dugongs), elephants and hyraxes with known age data show eruption of permanent teeth late in ontogeny relative to other mammals. While the occurrence of delayed eruption, vertebral anomalies and other potential afrotherian synapomorphies resemble some symptoms of a human genetic pathology, these characteristics do not appear to covary significantly among mammalian clades. CONCLUSION: Morphological characteristics shared by such physically disparate animals such as elephants and golden moles are not easy to recognize, but are now known to include late eruption of permanent teeth, in addition to vertebral anomalies, testicondy and other features. Awareness of their possible genetic correlates promises insight into the developmental basis of shared morphological features of afrotherians and other vertebrates.

Morfologia da glândula pineal de gambás (Didelphis sp) / Morphology of the pineal gland in opossum (Didelphis sp)

A glândula pineal deve ser analisada e estudada em animais da fauna brasileira, para que dados da pesquisa básica possam ser aplicados em novas técnicas de manejo reprodutivo destes animais, inclusive em cativeiro, face à íntima relação deste órgão fotorreceptor com o ciclo reprodutivo. Para este estudo, foram utilizados 10 gambás (Didelphis sp), provenientes do Departamento de Anatomia da USP e da UNIFEOB, já mortos e fixados. Nenhum animal foi submetido a situações de dor/sofrimento e ao sacrifício de sua vida. A glândula pineal foi encontrada em todos animais estudados e apresentou-se com diminutas dimensões, não sendo possível, portanto descrever-lhe características macroscópicas. Através da análise microscópica pudemos localizar a glândula no espaço correspondente ao plano mediano, em relação ao encéfalo, rostral e dorsalmente aos colículos rostrais, ventralmente aos hemisférios cerebrais e caudalmente à comissura habenular. Consiste de uma evaginação do teto do diencéfalo e mostra-se em forma de “U” invertido. Comparativamente a características de glândulas pineais de outras espécies animais, a do Didelphis genus, que estudamos, revela peculiaridades tanto em relação ao seu tamanho, apenas perceptível microscopicamente, quanto ao fato de apresentar células semelhantes às secretoras, dispersas também em áreas vizinhas. Tais peculiaridades motivam reflexões sobre o papel funcional da glândula, na espécie considerada.

The pineal gland must to be analyzed and studied in animals of the Brazilian fauna, to apply the data obtained in the basic research of new techniques at reproductive handling of these animals, including in captivity, in view of the close relation between this photoreceptor organ with the circadian and reproductive cycle. For this study, 10 opossums (Didelphis sp), had been used, already died and fixed, proceeding from the Department of Anatomy of USP and UNIFEOB. None animals were submitted to pain/suffering situations and their no life sacrifice. The pineal gland was found in all studied animals with and smaller dimention, not possessing, therefore goss features. By microscopy analysis we could found the gland in the correspondent space to median plan in relation to the encephalon, rostral and dorsally to the rostral coliculli, ventrally to the brain hemispheres and caudally to the habenular comissure. That consistes like an evagination of the diencephalons tectum showing the “U” shape. Considering other pineal glands and its features in different species, we note the gland is extremely small for it specie, possessing dispersed secretory cells in the nervous parenchyma whose form, sufficiently irregular, suggests a small hormonal performance to them in the Didelphis genus. Comparativelly of the pineal gland feactures in different animals, the Didelphis genus, that was our aim, shows pecualirity as in size relation, only microscopically visible, than the fact to prossessing similar secretory cells also dispased in neighbor areas. All pecualiarites suggest refletion about the function action of the gland at the studied specie.

Marsupials from space: fluctuating asymmetry, geographical information systems and animal conservation.

We report the development of a new quantitative method of assessing the effects of anthropogenic impacts on living beings; this method allows us to assess actual impacts and to travel backwards in time to assess impacts. In this method, we have crossed data on fluctuating asymmetry (FA, a measure of environmental or genetic stress), using Didelphis albiventris as a model, with geographical information systems data relating to environmental composition. Our results show that more impacted environments resulted in statistically higher levels of FA. Our method appears to be a useful and flexible conservation tool for assessing anthropogenic impacts.