Didelphis Marsupialis Research Articles

Eco-epidemiological study of an endemic Chagas disease region in northern Colombia reveals the importance of Triatoma maculata (Hemiptera: Reduviidae), dogs and Didelphis marsupialis in Trypanosoma cruzi maintenance.

BackgroundIn Colombia, Rhodnius prolixus and Triatoma dimidiata are the main domestic triatomine species known to transmit T. cruzi. However, there are multiple reports of T. cruzi transmission involving secondary vectors. In this work, we carried out an eco-epidemiological study on Margarita Island, located in the Caribbean region of Colombia, where Chagas disease is associated with non-domiciliated vectors.MethodsTo understand the transmission dynamics of Trypanosoma cruzi in this area, we designed a comprehensive, multi-faceted study including the following: (i) entomological evaluation through a community-based insect-surveillance campaign, blood meal source determination and T. cruzi infection rate estimation in triatomine insects; (ii) serological determination of T. cruzi prevalence in children under 15 years old, as well as in domestic dogs and synanthropic mammals; (iii) evaluation of T. cruzi transmission capacity in dogs and Didelphis marsupialis, and (iv) genetic characterization of T. cruzi isolates targeting spliced-leader intergene region (SL-IR) genotypes.ResultsOut of the 124 triatomines collected, 94 % were Triatoma maculata, and 71.6 % of them were infected with T. cruzi. Blood-meal source analysis showed that T. maculata feeds on multiple hosts, including humans and domestic dogs. Serological analysis indicated 2 of 803 children were infected, representing a prevalence of 0.25 %. The prevalence in domestic dogs was 71.6 % (171/224). Domestic dogs might not be competent reservoir hosts, as inferred from negative T. cruzi xenodiagnosis and haemoculture tests. However, 61.5 % (8/13) of D. marsupialis, the most abundant synanthropic mammal captured, were T. cruzi-positive on xenodiagnosis and haemocultures.ConclusionsThis study reveals the role of peridomestic T. maculata and dogs in T. cruzi persistence in this region and presents evidence that D. marsupialis are a reservoir mediating peridomestic-zoonotic cycles. This picture reflects the complexity of the transmission dynamics of T. cruzi in an endemic area with non-domiciliated vectors where active human infection exists. There is an ongoing need to control peridomestic T. maculata populations and to implement continuous reservoir surveillance strategies with community participation.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-015-1100-2) contains supplementary material, which is available to authorized users.

Molecular characterization and development of Sarcocystis speeri sarcocysts in gamma interferon gene knockout mice.

The North American opossum (Didelphis virginiana) is the definitive host for at least three named species of Sarcocystis: Sarcocystis falcatula, Sarcocystis neurona and Sarcocystis speeri. The South American opossums (Didelphis albiventris, Didelphis marsupialis and Didelphis aurita) are definitive hosts for S. falcatula and S. lindsayi. The sporocysts of these Sarcocystis species are similar morphologically. They are also not easily distinguished genetically because of the difficulties of DNA extraction from sporocysts and availability of distinguishing genetic markers. Some of these species can be distinguished by bioassay; S. neurona and S. speeri are infective to gamma interferon gene knockout (KO) mice, but not to budgerigars (Melopsittacus undulatus); whereas S. falcatula and S. lindsayi are infective to budgerigars but not to KO mice. The natural intermediate host of S. speeri is unknown. In the present study, development of sarcocysts of S. speeri in the KO mice is described. Sarcocysts were first seen at 12 days post-inoculation (p.i.), and they became macroscopic (up to 4 mm long) by 25 days p.i. The structure of the sarcocyst wall did not change from the time bradyzoites had formed at 50-220 days p.i. Sarcocysts contained unique villar protrusions, 'type 38'. The polymerase chain reaction amplifications and sequences analysis of three nuclear loci (18S rRNA, 28S rRNA and ITS1) and two mitochondrial loci (cox1 and cytb) of S. speeri isolate from an Argentinean opossum (D. albiventris) confirmed its membership among species of Sarcocystis and indicated an especially close relationship to another parasite in this genus that employs opossums as its definitive host, S. neurona. These results should be useful in finding natural intermediate host of S. speeri.

The Chagas disease domestic transmission cycle in Guatemala: Parasite-vector switches and lack of mitochondrial co-diversification between Triatoma dimidiata and Trypanosoma cruzi subpopulations suggest non-vectorial parasite dispersal across the Motagua valley

Parasites transmitted by insects must adapt to their vectors and reservoirs. Chagas disease, an American zoonosis caused by Trypanosoma cruzi, is transmitted by several species of triatomines. In Central America, Triatoma dimidiata is a widely dispersed vector found in sylvatic and domestic habitats, with distinct populations across the endemic region of Guatemala. Our aim was to test the strength of association between vector and parasite genetic divergence in domestic environments. Microsatellite (MS) loci were used to characterize parasites isolated from T. dimidiata (n=112) collected in domestic environments. Moderate genetic differentiation was observed between parasites north and south of the Motagua Valley, an ancient biogeographic barrier (FST 0.138, p=0.009). Slightly reduced genotypic diversity and increased heterozygosity in the north (Allelic richness (Ar)=1.00–6.05, FIS −0.03) compared to the south (Ar=1.47–6.30, FIS 0.022) suggest either a selective or demographic process during parasite dispersal. Based on parasite genotypes and geographic distribution, 15 vector specimens and their parasite isolates were selected for mitochondrial co-diversification analysis. Genetic variability and phylogenetic congruence were determined with mitochondrial DNA sequences (10 parasite maxicircle gene fragments and triatomine ND4+CYT b). A Mantel test as well as phylogenetic, network and principal coordinates analyses supported at least three T. dimidiata haplogroups separated by geographic distance across the Motagua Valley. Maxicircle sequences showed low T. cruzi genetic variability (π nucleotide diversity 0.00098) with no evidence of co-diversification with the vector, having multiple host switches across the valley. Sylvatic Didelphis marsupialis captured across the Motagua Valley were found to be infected with T. cruzi strains sharing MS genotypes with parasites isolated from domiciliated triatomines. The current parasite distribution in domestic environments can be explained by multiple parasite-host switches between vector populations and selection or bottleneck processes across the Motagua Valley, with a possible role for didelphids in domestic transmission.

Phylogenetic measures applied to the conservation of Mexican marsupials

The didelphimorphs in Mexico are found all over the country except for the Baja California Peninsula. The aim of this study was to use three methods to assess the phylogenetic diversity of the species: Marmosa mexicana, Tlacuatzin canescens, Caluromys derbianus, Chironectes minimus, Didelphis marsupialis, Didelphis virginiana, Metachirus nudicaudatus and Philander opossumdistributed in the Mexican biogeographic provinces, and to determine the potential conservation areas for these mammals. Phylogenetic information was included to execute the taxonomic weighting, taxonomic dispersion and taxonomic distinctness within the Mexican biogeographic provinces. In addition a gap analysis was performed to show which protected areas contain the didelphimorphs under a conservation category. Considering phylogenetic diversity with the former analysis, results indicate that the biogeographic provinces most important for conservation of didelphimorphs are the Gulf of Mexico, the Pacific Coast and Oaxaca but also have to be considered Soconusco and Sierra Madre del Sur. We also observed that not all of the richest sites corresponded with current protected areas. This study is important because it employed different conservation approaches based on phylogenetic measures and was focused on Mexican marsupials from which one species is endemic and two are under conservation concern.

Phylogenetic measures applied to the conservation of Mexican marsupials

The didelphimorphs in Mexico are found all over the country except for the Baja California Peninsula. The aim of this study was to use three methods to assess the phylogenetic diversity of the species: Marmosa mexicana, Tlacuatzin canescens, Caluromys derbianus, Chironectes minimus, Didelphis marsupialis, Didelphis virginiana, Metachirus nudicaudatus and Philander opossum distributed in the Mexican biogeographic provinces, and to determine the potential conservation areas for these mammals. Phylogenetic information was included to execute the taxonomic weighting, taxonomic dispersion and taxonomic distinctness within the Mexican biogeographic provinces. In addition a gap analysis was performed to show which protected areas contain the didelphimorphs under a conservation category. Considering phylogenetic diversity with the former analysis, results indicate that the biogeographic provinces most important for conservation of didelphimorphs are the Gulf of Mexico, the Pacific Coast and Oaxaca but also have to be considered Soconusco and Sierra Madre del Sur. We also observed that not all of the richest sites corresponded with current protected areas. This study is important because it employed different conservation approaches based on phylogenetic measures and was focused on Mexican marsupials from which one species is endemic and two are under conservation concern.

Características Morfológicas de un Grupo de Zarigüeyas (Didelphys marsupialis) del Suroccidente Colombiano

La familia Didelphidae representa la mayoría de los marsupiales americanos ampliamente distribuidos en América del Sur, ocupando casi todo tipo de hábitats a excepción de zonas altas y zonas desérticas. Los marsupiales de la familia varían de tamaño y algunos autores los describen como medianos y grandes, mientras que otros los describen de tamaño pequeño y mediano. El presente trabajo aporta una descripción morfológica de las zarigüeyas ubicadas en una región del suroccidente colombiano.

Endogenous Life Cycle of Eimeria marmosopos (Apicomplexa: Eimeriidae) from the Opossum, Didelphis marsupialis (Didelphimorphia: Didelphidae) in Costa Rica.

The endogenous life cycle of Eimeria marmosopos was studied in experimentally infected young opossums, Didelphis marsupialis . All the endogenous stages were located in the epithelial cells of villi in the small intestine. Giemsa-stained mucosal scrapings and histological sections were studied for the diagnosis of all the life cycle stages. Eimeria marmosopos has 3 generations of meronts (M) that differ by size, shape, and number of merozoites (m), which also differ in their size, shape, and location of their nuclei within the cytoplasm of the meronts. The 3 meront types, M(1)-M(3), respectively, had 8-15 (m(1)), 4-9 (m(2)), and 22-30 (m(3)) merozoites. Macrogametocytes and microgametocytes, as well as macrogametes and microgametes, completed the sexual cycle, finishing with the formation of unsporulated oocysts. This parasite's endogenous development produced severe intestinal lesions in experimentally infected opossums. There are 56 Eimeria species known from all marsupials worldwide, but this is the first complete life cycle in which both the asexual and sexual stages have been documented.

Evidence that the house finch (Carpodacus mexicanus) uses scent to avoid omnivore mammals

The detection of predator chemical cues is an important antipredatory behaviour as it allows an early assessment of predation risk without encountering the predator and therefore increases survival. For instance, since chemical cues are often by-products of metabolism, olfaction may gather information not only on the identity but also about the diet of predators in the vicinity. Knowledge of the role of olfaction in the interactions of birds with their environment, in contexts as important as predator avoidance, is still scarce. We conducted two two-choice experiments to explore 1) whether the house finch Carpodacus mexicanus can detect the chemical cues of a marsupial predatory mammal, the common opossum (Didelphis marsupialis), and 2) whether its response to such cues is influenced by the recent diet of this omnivorous predator, as this would increase the accuracy with which the risk of predation is assessed. House finches avoided the area of the apparatus containing the scent of the predator, and this effect did not depend on the recent diet (bait used to lace the traps) of the predator. Our results provide clear evidence that house finches detect and use the chemical cues of predators to assess the level of predation risk of an area and avoid it.

Association patterns of ticks (Acari: Ixodida: Ixodidae, Argasidae) of small mammals in Cerrado fragments, western Brazil.

The present study describes ticks associated with small mammals and analyzes the aggregation patterns according to seasonal and host variations in the Cerrado biome, central-western Brazil. Small mammals were systematically captured in 54 woodland fragments from February 2012 to July 2013. A total of 1,040 animals belonging to eight marsupial and 12 rodent species were captured; 265 animals were parasitized by eight tick species (in decreasing order of abundance): Ornithodoros mimon, Amblyomma coelebs, Amblyomma sculptum, Amblyomma ovale, Amblyomma parvum, Amblyomma dubitatum, Amblyomma parkeri, and Ixodes amarali. With few exceptions, collected ticks were larvae and nymphs. Among the more abundant animals, the marsupial Didelphis albiventris showed the highest tick prevalence (84.4 %), mean abundance (19.2), mean intensity (22.8), richness of ticks species (n = 7), and total abundance of ticks (n = 2,457). Amblyomma sculptum and O. mimon were the most generalist species, collected on four host species. Fifteen new tick-host associations are reported for the first time. Most ticks showed higher prevalence and mean intensity in the dry season, regardless of host species. Overall, tick prevalence and mean intensity of infestation were significantly associated with host gender. Finally, the importance of the large number of records of the argasid O. mimon is discussed.

The Araguaia River as an Important Biogeographical Divide for Didelphid Marsupials in Central Brazil.

The riverine barrier model suggests that rivers play a significant role in separating widespread organisms into isolated populations. In this study, we used a comparative approach to investigate the phylogeography of 6 didelphid marsupial species in central Brazil. Specifically, we evaluate the role of the mid-Araguaia River in differentiating populations and estimate divergence time among lineages to assess the timing of differentiation of these species, using mitochondrial DNA sequence data. The 6 didelphid marsupials revealed different intraspecific genetic patterns and structure. The 3 larger and more generalist species, Didelphis albiventris, Didelphis marsupialis, and Philander opossum, showed connectivity across the Araguaia River. In contrast the genetic structure of the 3 smaller and specialist species, Gracilinanus agilis, Marmosa (Marmosa) murina, and Marmosa (Micoureus) demerarae was shaped by the mid-Araguaia. Moreover, the split of eastern and western bank populations of the 2 latter species is consistent with the age of Araguaia River sediments formation. We hypothesize that the role of the Araguaia as a riverine barrier is linked to the level of ecological specialization among the 6 didelphid species and differences in their ability to cross rivers or disperse through the associated habitat types.

Eimeria marmosopos(Coccidia: Eimeriidae) from the OpossumDidelphis marsupialisL., 1758 (Didelphimorphia: Didelphidae), in Costa Rica

ABSTRACT: Oocysts of a coccidium found in the small intestine of a road-killed opossum, Didelphis marsupialis (Didelphimorphia: Didelphidae), are described and identified as Eimeria marmosopos. Sporulated oocysts (n = 57) were subspherical to spherical and measured 21.9 × 22.1 (20–25 × 20–25); oocyst wall rough and striated, yellowish and bilayered; micropyle, polar body, and oocyst residuum all absent, but some oocysts have a polar granule. Sporocysts were ovoidal, 9.8 × 8.7 (8–13 × 7–12), with both a conspicuous Stieda body and sub-Stieda body, but para-Stieda body was absent. The sporocyst residuum was composed of 2–5 globules (1–4 wide) and several smaller ones. Sporozoites (n = 10) were comma-shaped, ~7 × 2.7 and had 1 refractile body at their wider end and a centrally located nucleus. These morphological characters were compared with other Eimeria species found in related genera of New World marsupials; based on oocyst morphology, we identified this species as Eimeria marmosopos Heckscher, Wicke...

Evolution of molar shape in didelphid marsupials (Marsupialia: Didelphidae): analysis of the influence of ecological factors and phylogenetic legacy

The diversity of items consumed by modern didelphids, varying from mostly fruits in Caluromys Allen to mostly small vertebrates in Lutreolina O. Thomas, may cause changes in molar size and shape. We evaluated the morphometric variation of the first and third upper and lower molars of 16 genera of didelphid marsupials, with the aim of assessing the relationship between molar shape change, diet and phylogeny. We used a geometric morphometric approach to analyse how shape changes with diet. We mapped shape onto the phylogeny of the group to reconstruct ancestral states and analyse the evolution of molar shape. Finally, we statistically estimated the effect of size, diet and phylogeny on molar shape. All the analyses indicated little correlation between diet and molar shape and a strong correlation between the position of each genus on the phylogeny and molar shape. We believe that the wide ecological niche used by most of the groups (at least regarding diet) makes the evolutionary changes not strong enough to override pre-existing differences that occur among clades, and the absence of highly diet-specialized species (e.g. hypercarnivory or obligate folivory) causes the need for retaining a molar shape that can be useful to process different kinds of food items. © 2014 The Linnean Society of London

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.

Common opossum (Didelphis marsupialis Linnaeus, 1758): food and medicine for people in the Amazon.

BackgroundIn the Amazon rainforest, biodiversity is a significant resource for traditional communities, as it can be used as a relevant source of protein and it has a promising zootherapeutic potential. Studies on knowledge and ways how local peoples use the fauna are still incipient. This paper presents both the knowledge on and food and medicinal uses of common opossum (Didelphis marsupialis) by riverine communities in an Amazon floodplain region.MethodsThe study was conducted with riverine communities in the municipality of Abaetetuba, Pará, Brazil. The main methods used were structured and semi-structured interviews, the “snowball” technique, and participant observation.ResultsThe study showed that D. marsupialis has an undeniable cultural significance for the local community, both in terms of food and medicine. Its meat is prized by inhabitants as it is classified as tasty, soft and, in some cases, it is designated as the best bushmeat in the region. The interviewees have demonstrated a thorough knowledge on various aspects of the animal’s biology, such as its diet, behavior, and places of occurrence. The hunting activity is practiced by men, but the preparation of meat and medicinal oil are tasks mainly performed by women. In medical terms, common opossum is used in the treatment of various diseases, such as rheumatism, asthma, sore throat, and inflammation. Given the importance of this species, its meat or live individuals are often sold in the city fair at prices that can reach R$ 40.00 (U$D 18,00) per individual.ConclusionsD. marsupialis is an important source of protein for riverine communities in the region studied. Its fat is used as a traditional medicine and it is indicated for many types of diseases. Although the species concerned is treated with hostility in various Brazilian regions, in the case of Abaetetuba this animal is strongly prized due to the good quality of its meat. However, despite the value assigned to the species, its consumption should be the subject of further studies, as this marsupial species has been described as a reservoir for parasites that cause severe diseases.

Trypanosoma cruzi transmission in a Colombian Caribbean region suggests that secondary vectors play an important epidemiological role.

BackgroundColombia, as part of The Andean Countries Initiative has given priority to triatomine control programs to eliminate primary (domiciliated) vector species such as Rhodnius prolixus and Triatoma dimidiata. However, recent events of Trypanosoma cruzi transmission in localities where R. prolixus and T. dimidiata are not present suggest that other species are involved in the T. cruzi transmission cycle.MethodsWe studied T. cruzi transmission on Margarita Island, located on the Magdalena River in the Colombian Caribbean region, where a high number of non-domiciliated triatomines infected with T. cruzi inside human dwellings have been observed. A cross-sectional survey including serological studies in humans and parasitological and molecular methods in vectors and reservoirs was conducted. We investigated risk factors for human infection and house infestation, and evaluated the association between abundance of wild triatomines in palm trees (Attalea butyracea) across municipalities, seasons and anthropogenic land use.ResultsThe T. cruzi seroprevalence rate in humans was 1.7% (13/743) and autochthonous active T. cruzi transmission was detected. The infection risk was associated with the capture of triatomines in human dwellings. Five wild mammal species were infected with T. cruzi, where Didelphis marsupialis was the main reservoir host with an 86.3% (19/22) infection rate. TcIb was the only genotype present among vectors. Triatomine abundance was significantly higher in Ecosystem 2, as well as in the dry season. Despite the absence of triatomine domiciliation in this area, T. cruzi active transmission was registered with a human seroprevalence rate similar to that reported in areas with domesticated R. prolixus.ConclusionsThis study illustrates the importance of secondary and household invading triatomines in Chagas disease epidemiology in the Caribbean lowlands of Colombia.

Coccidial dispersion across New World marsupials: Klossiella tejerai Scorza, Torrealba & Dagert, 1957 (Apicomplexa: Adeleorina) from the Brazilian common opossum Didelphis aurita (Wied-Neuwied) (Mammalia: Didelphimorphia).

Klossiella tejerai Scorza, Torrealba & Dagert, 1957 is a primitive coccidian parasite reported from the New World marsupials Didelphis marsupialis (Linnaeus) and Marmosa demerarae (Thomas). The current work describes K. tejerai from the Brazilian common opossum Didelphis aurita (Wied-Neuwied) in Southeastern Brazil, evidencing the coccidial dispersion across opossums of the same family. The sporocysts recovered from urine samples were ellipsoidal, 20.4×12.7µm, with sporocyst residuum composed of scattered spherules and c.13 sporozoites per sporocyst, with refractile bodies and nucleus. Macrogametes, microgametes, sporonts, sporoblasts/sporocysts were identified within parasitophorous vacuoles of epithelial cells located near the renal corticomedullary junction. Didelphis marsupialis should not have transmitted K. tejerai to D. aurita because they are not sympatric; however M. demerarae is sympatric with D. marsupialis and D. aurita. Therefore, D. aurita becomes the third host species for K. tejerai in South America.

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AbstractPrehensile 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. Anat Rec, 297:1364–1376, 2014. © 2014 Wiley Periodicals, Inc.

Neurometric evaluations on the brain of the opossum (didelphys marsupialis cancrivora (linnaeus 1758) - a case for cognitive skill -brain development capacity

Abstract Introduction: The Opossum is a marsupial related wild life species belonging to the order Didelphimorphia. They inhabit the swampy forest zones in Nigeria but could inhabit drier regions. Some are arboreal and digitigrades, characterized by long bare tails and opposable thumbs modified for climbing and grasping respectively, they are known to be deficient in comparative sociality, peculiar brain morphology and a short life span. Our aim was to correlate through macro-neuromorphometry as well evaluate for the influence of head and brain weight, sex, adaptation, and behavioral ecology on the brain dimensions in comparison with other marsupials. Method: This study utilized thirteen animals (didelphys marsupialis cancrivota) consisting of four (6) males and seven (7) females and employing statistical methods in making inferences among the categories. Results: The mean overall head weight was 256.17 ±54.11g, 250.60± 51.62g for females and 269.16 ±139.22g for males, the whole brain weight was 30.43 ±10.19g. The brain /head weight ratio was 0.05± 0.02 while the maximum cerebral diameter, length and height were 46.97 ±13.84mm, 48.01±19.72mm and 30.48 ±2.90mm. cerebellar weight was 1.81 ±1.09g, and the cerebellar height and width were 2.39 ± 0.38mm and 2.44 ± 1.59mm respectively, cerebrum/ whole brain length index was 0.86± 0.04mm while mean endo-cranial volume was 19.75 ±30.11mls.The sexually dimorphic variables include whole brain length (59.87± 9.56mm and 57.12± 12.01mm), cerebral length (49.93± 10.17mm and 41.12± 15.57mm) and cerebral diameter (35.91± 13.55mm and 43.54± 29.96mm) for females and males respectively, suggesting better encephalization in females of this species compared to the males. Also, dimorphic parameters function for purposes such as predatory instincts, nursing of the young, spatial orientation, migrations and ecologic adaptations. Conclusion: In addition, this investigation suggests the enhanced possibility of cerebro-vascular accident in this species partly due to the cerebral length and height ratio in relation to the endo-cranial volume and shape in the likelihood of shorter lifespan in the males.

The role of fragmentation and landscape changes in the ecological release of common nest predators in the Neotropics.

Loss of large mammalian carnivores may allow smaller mesopredators to become abundant and threaten other community members. There is considerable debate about mesopredator release and the role that other potential factors such as landscape variables and human alterations to land cover lead to increased mesopredator abundance. We used camera traps to detect four mesopredators (tayra, Eira barbara; white-nosed coati, Nasua narica; northern raccoon, Procyon lotor; and common opossum, Didelphis opossum) in a biological corridor in Costa Rica to estimate habitat covariates that influenced the species’ detection and occurrence. We selected these mesopredators because as semi-arboreal species they might be common nest predators, posing a serious threat to resident and migratory songbirds. Pineapple production had a pronounced positive effect on the detectability of tayras, while forest cover had a negative effect on the detection of coatis. This suggests that abundance might be elevated due to the availability of agricultural food resources and foraging activities are concentrated in forest fragments and pineapple edge habitats. Raccoon and opossum models exhibited little influence on detection from habitat covariates. Occurrence models did not suggest any significant factors influencing site use by nest predators, revealing that all four species are habitat generalists adapted to co-existing in human altered landscapes. Furthermore, fragmentation and land cover changes may predispose nesting birds, herpetofauna, and small mammals to heightened predation risk by mesopredators in the Neotropics.

Home range and shelter preferences of marsupial Didelphis aurita (Wied-Neuwied, 1826) in a fragmented area in southeastern Brazil

Abstract(Wied-Neuwied, 1826) is a marsupial common in the Atlantic Forest and Cerrado but understudied. Thus, we estimated the size of the home range and shelter preferences for three individuals (one male and two females) of