Species Of Didelphis Research Articles

Ontogeny of the masticatory muscles in the opossum Didelphis albiventris (Marsupialia, Didelphimorphia, Didelphidae).

Opossums (marsupials of the Didelphidae family) retain a generalized masticatory apparatus and tribosphenic molars, often used as models to understand the evolution of mastication in early therian mammals. Like all marsupials, their growth goes through a stage when pups complete their development while permanently attached to the mother's teats before weaning and starting feeding on their own. Yet, while the masticatory muscles of adults are known, as is the ontogeny of the cranium and mandible, the ontogenetic changes in the masticatory muscles remain unknown. Here we describe for the first time the changes in the masticatory muscles observed in lactating pups, and weaned juveniles, subadults, and adults in the White-eared opossum, Didelphis albiventris, through dissection of 25 specimens and quantification of relative muscle masses, lines of actions and mechanical advantages whenever possible. We also assessed the scaling patterns of muscle masses and mechanical advantages through ontogeny. The main changes, as expected, were found between suckling and weaned specimens, although some changes still occurred from juveniles to adults. The adult adductor musculature is similar to the other Didelphis species already known, with a dominant m. temporalis that originates on the lateral wall of the skull, up to the sagittal and nuchal crests, and fills the zygomatic arch when inserting into the lateral and medial surfaces of the coronoid process, respectively through the pars superficialis and pars profunda. The m. masseter is also subdivided in superficial and deep bundles which originate posteriorly in the maxilla and zygomatic arch, and insert into the angular process and masseteric fossa in the mandible. The m. pterygoideus medialis originates from the palatine, the pterygoid bone and the alisphenoid, and it inserts on the angular process medially. Suckling pups showed muscles with more restricted attachments, reduced muscle lines of action, and less diversity in the fiber orientation. The absence of the postorbital constriction also resulted in a distinct morphology of the m. temporalis pars profunda, through two bundles, one anterior and one posterior, which insert more inferiorly into the mandible. These major changes can be related to the onset of mastication and to size-related changes in growing weaned age classes. In general, all adductor muscles grew with positive allometry, and increased their fixation areas through, in part, the development of specific regions of the cranium and mandible. Their lines of action also increase and diversify along ontogeny. These changes can be related to the functional requirements for fixation during lactation, which shift to adduction and mastication movements after weaning.

A novel Babesia sp. of the “Western Babesia group”, detected in opossums from Guatemala

Babesia spp. are tick-borne protozoans that involve birds and mammals in their transmission cycles and cause babesiosis, a severe hemolytic malaria-like disease. Opossums of the genus Didelphis are recognized hosts of tick-borne pathogens. Therefore, exploring tick-borne agents in Didelphis species is important to understand the circulation of pathogens in areas where opossums occur. In this study, we targeted Anaplasmataceae, Babesia, Borrelia and Hepatozoon DNA in ticks, blood and organ samples collected from three hunted Didelphis marsupialis specimens in eastern Guatemala. While the samples were negative for Hepatozoon and bacterial DNA, sequences of Babesia 18S rDNA, cox1 and cytb genes were retrieved from two opossums. Ticks collected on the animals included Amblyomma parvum and an undetermined Ornithodoros sp. The Babesia sp. detected in this study (Babesia sp. THB1–2) clusters phylogenetically within the “Western Babesia group”, which includes pathogenic species such as Babesia conradae, Babesia duncani, and Babesia negevi. Our results represent the first record of a Babesia sp. in Guatemala and highlight the importance of D. marsupialis as potential spreaders of ticks and pathogens in Central America.

Identification and characterization of repetitive DNA in the genus Didelphis Linnaeus, 1758 (Didelphimorphia, Didelphidae) and the use of satellite DNAs as phylogenetic markers.

Didelphis species have been shown to exhibit very conservative karyotypes, which mainly differ in their constitutive heterochromatin, known to be mostly composed by repetitive DNAs. In this study, we used genome skimming data combined with computational pipelines to identify the most abundant repetitive DNA families of Lutreolina crassicaudata and all six Didelphis species. We found that transposable elements (TEs), particularly LINE-1, endogenous retroviruses, and SINEs, are the most abundant mobile elements in the studied species. Despite overall similar TE proportions, we report that species of the D. albiventris group consistently present a less diverse TE composition and smaller proportions of LINEs and LTRs in their genomes than other studied species. We also identified four new putative satDNAs (sat206, sat907, sat1430 and sat2324) in the genomes of Didelphis species, which show differences in abundance and nucleotide composition. Phylogenies based on satDNA sequences showed well supported relationships at the species (sat1430) and groups of species (sat206) level, recovering topologies congruent with previous studies. Our study is one of the first attempts to present a characterization of the most abundant families of repetitive DNAs of Lutreolina and Didelphis species providing insights into the repetitive DNA composition in the genome landscape of American marsupials.

Reactivity of Horse Sera to Antigens Derived From Sarcocystis falcatula-Like and Sarcocystis neurona.

Sarcocystis neurona and Sarcocystis falcatula are protozoan parasites endemic to the Americas. The former is the major cause of equine protozoal myeloencephalitis, and the latter is associated with pulmonary sarcocystosis in birds. The opossum Didelphis virginiana is the definitive host of these parasites in North America. Four Didelphis species are found in Brazil, and in most reports in this country, Sarcocystis species shed by opossums have been classified as S. falcatula–like. It is unknown whether reports on S. neurona–seropositive horses in Brazil are also derived from exposure of horses to S. falcatula–like. The aim of this study was to test the sera reactivity of 409 horses in Brazil using antigens derived from a Brazilian strain of S. falcatula–like (Sarco-BA1) and from a North American strain of S. neurona (SN138). Samples were examined by immunofluorescent antibody tests (IFATs) at start dilutions of 1:20, and a selected number of samples was tested by Western blot (WB). Sera from 43/409 (10.5%) horses were reactive to S. falcatula–like and 70 of 409 (17.1%) were reactive to S. neurona antigen; sera from 25 animals (6.1%) were positive for both parasites by IFAT. A poor agreement was observed between the two employed IFATs (κ = 0.364), indicating that horses were exposed to more than one Sarcocystis species. Horse sera evaluated by WB consisted of four sera reactive to S. falcatula–like by IFAT, six sera positive to S. neurona by IFAT, two sera that tested negative to both parasites by IFAT, and a negative control horse serum from New Zealand. Proteins in the range of 16 and 30 kDa were recognized by part of IFAT-positive sera using both antigen preparations. We concluded that Brazilian horses are exposed to distinct Sarcocystis species that generate different serological responses in exposed animals. Antigens in the range of 16 and 30 kDa are probably homologous in the two parasites. Exposure of the tested horses to other Sarcocystis species, such as Sarcocystis lindsayi, Sarcocystis speeri, and Sarcocystis fayeri, or Sarcocystis bertrami cannot be excluded in the current study.

LEISHMANIA SPP. IN DIDELPHIS SPP. FROM NORTHEASTERN BRAZIL.

The synanthropic behavior of marsupials of the genus Didelphis in endemic areas of leishmaniasis suggests that these animals may play an important role in the epidemiology of this infection. The aim of the present study was to detect Leishmania spp. DNA in Didelphis albiventris (white-eared opossum) and Didelphis aurita (big-eared opossum) living in forested and peridomestic areas of northeastern Brazil. Blood samples were collected from 25 animals (23 D. albiventris and 2 D. aurita ) by cardiac puncture and then analyzed via PCR. Leishmania (Viannia) braziliensis DNA complex was detected in 4 (16%) of the 25 samples, whereas no samples scored positive for Leishmania (Leishmania) donovani complex. Our data suggest that D. albiventris participates in the wild enzootic cycle of the L. (V.) braziliensis complex. Therefore, humans living in this area are at risk of infection, because Didelphis species are in constant movement between wild and urban environments.

Morphometrics of the largest New World marsupials, opossums of the genus Didelphis (Didelphimorphia, Didelphidae)

Opossums of the genus Didelphis include the largest living species of New World marsupials. Although species of the genus have been morphometrically analyzed separately in several studies, size and shape variation within the genus has never been assessed with all species simultaneously. Here I provide the first comprehensive analysis of diversification in size and shape in the skull and mandible in the living species of Didelphis. I established a set of landmarks to capture the size and shape of the skull and mandible, using a sample of ca. 350 specimens, and compared species in size, and assessed the major axes of shape variation and differentiation through Principal Components and Canonical Variates analyses of the Procrustes coordinates of these landmarks. Additionally I assessed the effect of size on shape variation by regressing PC and CV scores onto centroid sizes. This analysis shows that almost all species can be distinguished in size, except for two species of white-eared opossums. Shape variation and diversification is also highly driven by size effects, as the most distinctive species in size, D. virginiana, is also the most distinctive species in shape, due to allometric shape changes. Major axes of shape variation are correlated with size, indicating that size plays a major role in the morphological diversification of the genus Didelphis, and these correlations are shared and conserved across species.

Forrajeo de Didelphis pernigra (Mammalia: Didelphidae) en un área suburbana de la Sabana de Bogotá, Colombia

Introduction: In Colombia, there is widespread transformation of natural ecosystems, especially in the Andean region. However, the impacts of those transformations have been poorly studied. Optimal patch theory was used to evaluate the foraging behavior and movement patterns in the white-eared opossum ( Didelphis pernigra ) in the Sabana de Bogota, a plateau at about 2,600 m in the Colombian Andes. The study site was dominated by an exotic grass (Cenchrus clandestinum), and little is known about possible impacts of this exotic species on native fauna.Thus, we analyzed whether this grass the foraging behavior and movements of D. pernigra . To test this, we used the giving up density (GUD) technique, which uses the amount of food left in a feeding patch to assess the forager’s habitat perception. We also tested whether this exotic grassland acted as a barrier to movements to and from an area of native and exotic trees. Finally, we measured the influence of moon illumination, air temperature, and precipitation on the oppossum’s foraging behavior. Methodology: We established two approximately parallel transects in a suburban area (Fig. 1). Foraging stations were located 30 to 40 meters apart on each transect. Each station consisted of a feeder made of a cylindrical plastic container with 150ml of sugar water in a 1:3 proportion. Each container also contained 60 glass spheres to generate diminishing returns on the harvest rate. The oppossums were habituated to the feeders for 15 days, and then GUDs were measured for 30 days. Feeders were filled before sunset and checked the following morning. Results: Oppossums foraged at least 240 m into the grasslands from the trees along the river. Air temperature and precipitation did not influence their foraging behavior (Fig. 2). There was, however, temporal variation in foraging activity, and at least some of this was due to a negative effect of lunar illumination (Fig. 3). Discussion and Conclusions: Our results indicate that the white-eared opossum is a tolerant species able to exploit human-created habitats. This finding is in agreement with reports on other species of Didelphis that they are tolerant of moderate human interventions. We surmise that this species’ ability to exploit the open ecosystems of the paramo has made it possible for it to effectively use the grasslands on the study site. The only abiotic factor that was found to be influential was moon illumination. Darker nights gave lower GUD’s indicating that the foragers perceived decreased predation risk. Finally, we argue that efforts should be made to prevent the local extinction of this opossum in disturbed areas of Bogota since it could aid in the conservation of ecological functions in those areas. Key words: Andes, giving-up density (GUD), habitat selection, optimal patch use, urban ecology.

Turgida turgida (Nematoda: Physalopteridae) parasitic in white-bellied opossum, Didelphis albiventris (Marsupialia: Didelphidae), state of Mato Grosso do Sul, Brazil

Turgida turgida have been largely reported parasitizing Didelphis species in North and South America based on light microscopy observation. However, the features that differentiate T. turgida from other physalopterid species should be observed using scanning electron microscopy (SEM). A female white-bellied opossum, Didelphis albiventris, arrived dead at the Centro de Reabilitação de Animais Silvestres (CRAS) in the municipality of Campo Grande, state of Mato Grosso do Sul, Brazil. During the necropsy, adult nematodes were collected from stomach and intestine. The nematodes were determined to be adult specimens and submitted to SEM for the species determination. This is the first report of T. turgida confirmed by SEM in the Neotropical region and the first report in an urban area in the state of Mato Grosso do Sul, Brazil.

Variation in the latitudinal reproductive patterns of the genus Didelphis (Didelphimorphia:Didelphidae)

Abstract: The data published on reproduction of the species of the genus Didelphis (Didelphimorphia, Didelphidae) were compiled and analysed to identify general patterns. The duration of the breeding season for the Didelphis species varied from 12 months near the Equator to 6 months at latitude 25°S and varied inversely with latitude and litter size. The mean litter size varied from 4.2 in Colombia to 9.4 in New York and was positively associated with latitude and negatively with the duration of breeding season. We propose that the higher investment in production at higher latitudes was compensated by increased mortality owing to the seasonal variation in food availability and environmental variables in theses latitudes.

Origins of Chagas disease: Didelphis species are natural hosts of Trypanosoma cruzi I and armadillos hosts of Trypanosoma cruzi II, including hybrids

Trypanosoma cruzi, the causative agent of Chagas disease, has at least two principal intraspecific subdivisions, T. cruzi I (TCI) and T. cruzi II (TCII), the latter containing up to five subgroups (a–e). Whilst it is known that TCI predominates from the Amazon basin northwards and TCII to the South, where the disease is considered to be clinically more severe, the precise clinical and evolutionary significance of these divisions remains enigmatic. Here, we present compelling evidence of an association between TCI and opossums ( Didelphis), and TCII and armadillos, on the basis of key new findings from the Paraguayan Chaco region, together with a comprehensive analysis of historical data. We suggest that the distinct arboreal and terrestrial ecologies, respectively, of these mammal hosts provide a persuasive explanation for the extant T. cruzi intraspecific diversity in South America, and for separate origins of Chagas disease in northern South America and in the southern cone countries.

Mitochondrial DNA-like sequences in the nuclear genome of the opossum genus Didelphis (Marsupialia: Didelphidae).

This study reports the occurrence of mtDNA-like sequences in the nuclear genome of the opossum genus Didelphis (Didelphidae, Marsupialia). A specific primer pair designed to amplify a region encompassing a 3' terminal 118 bp region of the cytochrome b gene, the Thr and Pro tRNA genes, and a 489 bp region of the D-loop of the D. virginiana mtDNA, was used in highly stringent PCR reactions. These PCR reactions resulted in several fragments per individual varying in size from 259 bp to 1 kb. The sequencing of some of these fragments showed the occurrence of paralogous mtDNA-like sequences among the PCR amplified fragments. Analyses of qualitative aspects of these sequences, their transition/transversion ratios, and phylogenetic relationships were conclusive in showing the occurrence of mtDNA-like sequences in the nuclear genome of the genus Didelphis. Comparisons and phylogenetic analysis of orthologous mtDNA from the four Didelphis species and paralogous nuclear sequences suggested that mtDNA migration to the nuclear genome occurred more than once in Didelphis evolution.

DNA/DNA hybridization studies of carnivorous marsupials. III. Relationships among species ofDidelphis (Didelphidae)

We report three sets of DNA hybridization experiments conducted to determine relationships among species ofDidelphis (D. albiventris, D. marsupialis, D. virginiana). The 1989 and 1991 sets had fewer replicates per cell than the 1990 series (3.4 and 5.4 vs 9), but in 1991 we distinguished two populations ofD. marsupialis and utilized several individuals for each heterologous comparison. BothPhilander opossum andLutreolina crassicaudata were used as outgroups in 1989, but onlyLutreolina was included in subsequent sets. For each set, we calculated all four standard indices of thermal stability (Tmode,Tm,T50H, and NPH) and constructed trees by least-squares (FITCH) and neighbor-joining methods, both before and after correction for asymmetric reciprocal cell values. Subsets of the 1989 data lacking eitherPhilander orLutreolina were analyzed similarly. To explore measurement imprecision, the corrected and uncorrected matrices for each of the four indices were bootstrapped 100 times for the 1989 set and subsets and 1000 times for the 1990 and 1991 sets. Again, for the 1990 and 1991 data, an additional 100 bootstrapped distances were fitted to user trees representing the three possible pairings ofDidelphis spp. to determine the significance of the FITCH branch lengths. The successive experimental sets generated increasingly consistent evidence for pairingD. marsupialis withD. albiventris. The 1989 experiments involved just 85 comparisons, and only ΔTmode's pairedD. marsupialis withD. albiventris (at bootstrap percentages of 70% or above), but did so whetherPhilander orLutreolina or both were included as the outgroup(s). FITCH and neighbor-joining trees had identical topologies for ΔTmode's but sometimes differed for the other measures. In contrast, all but one of the corresponding FITCH and neighborjoining trees matched for the 1990 and 1991 data, and three of the four distance measures (ΔTmode, ΔTm, and ΔT50H) unitedD. marsupialis withD. albiventris at bootstrap percentages averaging 81%; ΔNPH gave a different result for 1990, associatingD. marsupialis withD. virginiana. Further, all but 2 of the 16 matrices for 1990 and 1991 gave mean bootstrapped branch lengths for a consensus pairing that were positive and at least one standard deviation from zero, despite the very short internodes recovered. These results illustrate that the potential of DNA hybridization for resolving very close relationships depends on both the index and the experimental design employed. We conclude that of the three species,D. albiventris andD. marsupialis shared a more recent common ancestor and estimate thatDidelphis spp. have diverged at about 0.39% in nucleotide sequence per myr.

Anatomy of the epididymis of the South American opossum (Didelphis azarae)

The epididymides of eight South American Didelphis azarae were examined gross anatomically after in situ preservation with formalin. The shape and division into head, body and tail correspond to those of domestic mammals. The attachment of the vascular portion of the spermatic cord to the middle of the body of the epididymis is similar to conditions in other marsupials. The runica vaginalis parietalis is pigmented as found in other species of didelphis.

The chromosomes of the Didelphidae (Marsupialia) and their evolutionary significance

One hundred and seventy-seven specimens of American didelphids, representing 9 genera and 22 species have been studied for their chromosomal constitution. Didelphids are very conservative in chromosomal complements. All of the studied species can be sorted into one of three kinds of karyotypes: 2n= 14 (three species of Didelphis, one of Lutreolina, two of Philander, and one of Chironectes), 2n = 14 (eight species of Marmosa, one of Metachirus, three of Caluromys, and one of Dromiciops), and 2n= 18 (three species of Monodelphis). These karyotypes are stable, showing only minor variations within each basic pattern. It is concluded that chromosomals evolution in the Didelphidae proceededs from low numbers to higher numbers by a process of centromeric fissioning complemented by some pericentric inversions and/or translocations. The pattern of karyotypic stability is consistent with bradytely at the organismic level of evolution. This is explained by a low rate of regulatory genetic evolution promoted by epistatic selection favouring the retention of chromosomal arrangements highly advantageous for overall adaptation.

XI. Description of two new Species of Didelphis from Van Diemen's Land.

XI. Description of two new Species of Didelphis from Van Diemen's Land.