Marmosops Incanus Research Articles

ECOLOGY AND HOST SPECIFICITY OF LAELAPINE MITES (ACARI: LAELAPIDAE) OF SMALL MAMMALS IN AN ATLANTIC FOREST AREA OF BRAZIL

Mesostigmatic mites of the Laelapinae Berlese, 1892 (Acari: Laelapidae) are nidicolous arthropods that commonly occur in the fur of Neotropical small mammmals. In this 2-yr study, the laelapine acarofauna associated with the small mammal community in an area of Atlantic forest on Ilha Grande, Rio de Janeiro State, was examined, including observations on patterns of host specificity, mite dispersal, ecology, and food habits. A total of 1,347 laelapines was sampled from the pelage of 6 species of small mammals (Marmosops incanus, Nectomys squamipes, Oryzomys russatus, Rhipidomys n. sp., Oxymycterus dasytrichus, and Trinomys dimidiatus), all of which occurred exclusively in monoxenous associations with their hosts. No evidence of a blood meal was observed in the gut of the mites. With the exception of the 2 species of Tur, mite populations on hosts were entirely or nearly restricted to adult females. These results, together with some morphological characteristics of laelapines, reinforce the hypotheses that Neotropical laelapine mites are not ectoparasitic, and that females disperse by phoresy.

Mapping the distribution of the interstitial telomeric (TTAGGG)n sequences in eight species of Brazilian marsupials (Didelphidae) by FISH and the correlation with constitutive heterochromatin. Do ITS represent evidence for fusion events in American marsupials?

The C-band pattern and the distribution of the (TTAGGG)_n sequence after fluorescence in situ hybridization (FISH), were studied in eight species of Didelphidae marsupials: four species with 2n = 14 (Marmosops parvidens, Marmosops incanus, Marmosa murina and Metachirus nudicaudatus), two species with 2n = 18 (Monodelphis domestica and M. americana), and two with 2n = 22 (Didelphis marsupialis and Lutreolina crassicaudata). The hybridization signals were observed at both termini telomeres of all chromosomes. In addition, interstitial sequences were detected in the pericentromeric region of all chromosomes of Marmosops parvidens, in five chromosome pairs of M. incanus, and in the first pair of Monodelphis domestica. These sites always occur in the region of constitutive heterochromatin, even though C-band positive regions do not always present interstitial telomeric sequences (ITS). We suggest that the interstitial (TTAGGG)_n sequences are associated with satellite DNA and do not necessarily arise through chromosomal rearrangements.

Androlaelaps marmosops (Acari: Laelapidae), a new species associated with the mouse opossum, Marmosops incanus (Lund, 1840) in the Atlantic forest of Rio De Janeiro State, Brazil.

Androlaelaps marmosops, a new species of laelapid mite, is described from the pelage of the mouse opossum, Marmosops incanus (Lund, 1840) (Mammalia: Didelphidae), in two areas of Atlantic Forest of Rio de Janeiro State. Measurements and illustrations are included for females only.

Land fauna composition of small mammals of a fragment of Atlantic Forest in the State of Sao Paulo, Brazil

The Atlantic Forest small mammal land fauna, except bats, and the abiotic factors that might have an influence on its composition, were studied in the Itapevi County, State of Sao Paulo, a forested region, partly altered by antropic action, from January, 1995 to June, 1996. The trapping effort consisted of 2,888 trap-nights, resulting in a 4.6% trapping success and consisted of monthly trappings, for five consecutive days. During this period, 134 specimens were captured, of which 46.3% were Didelphimorphia and 53.7% were Rodentia. Eleven species were registered: two Didelphimorphia: Didelphis marsupialis (Linnaeus, 1758) and Marmosops incanus (Lund, 1841), and nine Rodentia: Akodon cursor (Winge, 1887), Bolomys lasiurus (Lund, 1841), Oxymycterus hispidus Pictet, 1843, Oxymycterus nasutus (Waterhouse, 1837), Oligoryzomys nigripes (Olfers, 1818), Oryzomys angouya (Fischer, 1814), Raltus norvegicus (Berkenhout, 1769), Euryzygomatomys spinosus (G. Fischer, 1814) and Cavia aperea Erxleben, 1777. The relative density indices were correlated with meteorological data by Spearman and Pearson coefficients. For marsupials these correlations were not significant. For rodents, the correlations were significant and directly related to lower temperature and rainfall indices (p<0.05). During the dry season the occurrence of small mammals was 50% greater than during the wet season, probably due to foraging strategies in the studied fragment of Atlantic Forest.

A comparative study of lymph node mast cell populations in five marsupial species

In order to determine whether different subpopulations of mast cells exist, mast cells of mandibular and axillary lymph nodes from five species (Didelphis aurita, Metachirus nudicaudatus, Philander opossum,Marmosops incanus and Gracilinanus agilis) of South American marsupials were studied. Our results showed that mast cells present in the connective tissue of the capsule and septa (CTMC) were similar to those described for eutherian mammals. However, a population of mast cells that was present in the lymphatic sinuses and bathed by the lymph, plus in direct contact with granulocytes, lymphocytes, macrophages, and reticular cells, were morphologically and histochemically different from the CTMC. In the five species studied, these cellular types, called lymphatic-sinus mast cells (LSMC), had a lower concentration of intragranular heparin and, in four of the five species, the cytoplasmic granules appeared to be larger than those in CTMC. Although LSMC have been rarely described in eutherian mammals, it was verified, in this study, that LSMC are nevertheless present in lymphatic sinuses of the five metatherian species studied. These observations suggest that the presence of LSMC may be a characteristic of the marsupials and important in the immune response and adaptive success of the Didelphidae.

Paraneoplastic erythromelalgia

Seasonal reproduction during the time when food availability is high is a widespread strategy in marsupials, which maximizes offspring survival. In Australian marsupials, reproduction is commonly synchronous among co-occurring species, the onset of reproduction being triggered by photoperiodic cues. In a subset of these species, partial semelparity with high mortality of males after reproduction is a common pattern. For Neotropical marsupials, however, environmental triggers of reproduction have been poorly studied despite some evidence of a seasonal synchronous reproduction, and semelparity has been described in few species. Using a capture–recapture dataset of co-occurring marsupials in the Atlantic forest sampled for two years, we aim to investigate the timing and triggering of reproductive activity as well as the occurrence of semelparity in Neotropical small marsupials. We evaluated which environmental cues (rainfall, photoperiod and temperature) best explain the age structure of the populations of Gracilinanus microtarsus, Marmosops incanus, Marmosops paulensis, Monodelphis americana, Monodelphis scalops and Monodelphis iheringi. For the most common species we also tested for the occurrence of semelparity by assessing if survival rate is affected by sex and mating period. Our results indicate that reproduction onset seems to be synchronous among species and driven by photoperiod cues. In all species, reproduction is seasonal with juveniles being born and lactation occurring in the period of highest food availability, the warm–wet season. Further, semelparity is likely to be the cause of a high population turnover in Marmosops incanus, and probably also in co-occurring marsupials.