Plains viscacha were established in the laboratory to Spanish by Llanos & Crespo (), and some details of reproduction were given. Llanos, A. and J. Crespo. Ecología de la vizcacha (Lagostomus maximus maximus Blainv.) en el nordeste de la provincia de Entre Ríos. Rev. Llanos, A. C. and J. A. Crespo. Ecología de la vizcacha (Lagostomus maximus maximus Blainv.) en el nordeste de la Provincia de Entre Ríos. Revista de.

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The two main species for the vizcacha differed among the grasses. Two different regions in the parenchyma were observed proximal region and distal region. Previous reports have shown that Lagostomus maximus displays a peculiar P4 profile during gestation, which is characterized by two well-defined stages: Pigment granules were observed in a random distribution, vizfacha the pigmented cells were frequently found near blood vessels.

The presence of pigment has been demonstrated in different nervous structures such as those of retina, substantia nigraand locus coeruleus. In our study, a low content of pigments were found in pinealocytes as well as in the interstitial cells. View at Google Scholar J. Animals were housed for one week before euthanasia, under a Zaino was the only habitat without a significant difference between availability and diet for these spe- cies Table 2.

Cell and Tissue Research. The pigmented cells were counted in pregnant and nonpregnant viscachas. In the present study, the histochemical and ultrastructural results demonstrate the presence of melanin in the female viscacha pineal gland. Les preferences ali- mentaires et les strategies viacacha expliqueraient pourquoi la viscache restreint son habi- tat aux plaines.

Cette faible qualite des ressources s’expliquerait, quant a elle, par la cespo de pi antes herbacees. All experimental protocols crespi in the present study were reviewed and authorized by the Institutional Committee on the Use and Care of Experimental Animals of Universidad Maimonides, Argentina. Masson-Fontana silver method, counterstained with nuclear fast red.

Molecular and Biomolecular Spectroscopy. Lactating female group LCT was established by selecting those nonpregnant animals whose mammary glands exhibited the histological features already described vizcacya this period [ 2938 ] Table 1.


Seasonal morphological variations and age-related changes of the seminal vesicle of viscacha Lagostomus Maximus Maximus: More studies about herbi- vores dietary overlap, and their capability of habitat modification are needed in Nor- thern Patagonia. Bucher proposes that habitat modification by livestock grazing favours establishment of vizcachas.

IUCN Red List of Threatened Species

The University of Chicago Press; Therefore, the Selective Quality Hypothesis may be applied to vizcachas expressed as: For the availability the two types of microhabitats PI: Two microhabitats, plains and rocky elevations, were distinguished in the study area of each habitat, in order to verify vizcacha’s preference for plains.

The distribution of vizcacha includes savannas, Monte scrubby areas and arid shrubby areas Olrog and Lucerorarely located higher than m Llanos and Crespo The presence of pigment has been demonstrated in different nervous structures such as those of retina, substantia nigraand locus coeruleus [ 6 — 8 ].

Samplings corresponded to winter Julyspring Octobersummer December and Februaryand autumn May. Probable local modulatory action of melatonin.

Differences in the amount of pigmented cells were found between pregnant and nonpregnant viscachas. Some of these cells showed a higher amount of pigment content in their cytoplasm Figure 1. Melanin pigmentation in mammalian skin and its hormonal regulation.

Since the ovaries of the nonpregnant groups of this study LCT and NP exhibited almost the total absence of corpora lutea, the luteal immunoreactivity was analyzed only at the stages of pregnancy.

Vizcacha’s vizcacua behaviour does not agree with the Optimal Foraging Theory OFTwhich predicts a higher selectivity in situations of higher food diversity and abundance.

But what undoubtedly is the most outstanding aspect of its reproductive profile is the atypical gestational hormonal pattern characterized by the release of gonadotropin-releasing hormone GnRH followed by an LH surge around day of gestation. We studied ovarian LHR expression as a key marker of luteinization Figure 1.

Here, we found that the ovarian PRLR expression profile and the P4-circulating levels follow a concordant pattern along the reproductive cycle of adult female vizcachas. Consumption of chamae- phytes was higher in Escoriales, whose plains differed from the others due to the high chamaephytes availability. A more intensive feeding in the plains is justified by their higher plant cover, grasses proportion, and Panicum and Poa availabilities.


However, in the extracellular space, pigment granules were abundant and dispersed throughout the parenchyma, especially in vizcach and late pregnancy. The photomicrograph shows a semithin section with numerous pigmented cells arrowheads in close relation to blood vessels v.

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Biological Series of the Organization of American States, pp. A seasonal and age-related study of interstitial cells in the pineal gland of male viscacha Lagostomus maximus maximus The Anatomical Record.

In female viscacha, melanin granules within lysosome-like dense bodies were also observed. After bleeding, animals were sacrificed by an intracardiac injection of Euthanyle 0. Since PRL has shown to be essential for synthesis and secretion of luteal P4 during pregnancy in both mice and rats, we hypothesized that PRL also plays a role in the luteal steroidogenesis in pregnant vizcachas.

Calculation of P4 level was made by reference to a calibration curve. The relative frequency of occurence of a species in the diet was detelmined for each sample by dividing the number of microscopic fields in which a given species occurred by the sum total of frequencies for all species identified Hole- chek and Gross The use of forbs and phanerophytes increased significantly in summer, according to a higher availability of forbs, and the presence of buds and fruits in phanerophytic shrubs.

Despite livestock might favour vizca- chas establishment, the fact that both herbivores share the use of grasses in the plains suggests not to discard an interspecific competition situation.

Morphological and biochemical study of the pineal gland of pregnant and non-pregnant female vizcachas Lagostomus maximus maximus Neuro Endocrinology Letters. The Northern Patagonia environment has a special interest due to its location in the most arid region and westernmost limit of vizcacha distribution, its altitude higher than 1, m, and its geomorphology characterized by signs of past strong volcanic activity and processes of aeolic and hydric erosion Gonzalez Diaz Indexed in Science Citation Index Expanded.