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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Our analysis of LHR expression in the ovary of vizcachas revealed an active transcription level at midpregnancy and in response to the LH surge. The presence of pigment has been demonstrated in different nervous structures such as those of retina, substantia nigraand locus coeruleus.

All captured vizcachas were evaluated, and their P4 levels are depicted in Table 1. Melanin, a brownish-black pigment, is produced by the skin melanocytes which are derived from the neural crest and constitute the second most abundant cell in the epidermis [ 12 ].

The reproductive physiology of the plains vizcaccha, Lagostomus maximus. Bucher proposes that habitat modification by fizcacha grazing favours establishment of vizcachas. Revista Chilena de Historia Natural, Les preferences ali- mentaires et les strategies antipredation expliqueraient pourquoi la viscache restreint son habi- tat aux plaines.

The number of pigmented cells A and of remaining parenchymal cells B, pinealocytes and interstitial cells was counted. Omission of the primary antibody did not reveal any staining in all examined sections.

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The relief presents gentle vizccaha and large plains, interrupted by basaltic steps and groups of hills originated by the vol- canic activity Gonzalez Diaz Nevertheless, the embryonic processes might explain the presence of melanin. Comparing food and space use between these two closely related species may elucidate whether their spatial segregation contributes to reduce competition.

Relative frequencies of occurrence of each plant species i were obtained from faecal samples to describe the diet rand from point-quadrat transects to describe the availa- bility in the environment n. This chamaephyte is preferred by guanaco Puig et ai. Animals were grouped according to their reproductive status as the following: Plant spe- cies were grouped in four categories according to their life form: Author information Article notes Copyright and License information Disclaimer.

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The groups were analysed using the Kruskal-Wallis test. This hypothesis states that feeding selectivity increases in cir- cumstances of low diversity and abundance of food, forced by its low quality. In our laboratory, morphological studies of the male viscacha pineal gland have been carried out [ 27 — 29 ].

International Journal of Endocrinology

An anti-predator behaviour based on long distance visibility Llanos and Crespoforaging in groups and different alarm calls Branch may explain the viz- cacheras concentration in open plains in La Payunia.

This variety might be a conse- quence of food scarcity and unpredictability in the arid zones, rather than dietary gene- ralism. Observations on the crfspo gland of the big brown bat, Eptesicus fuscus: In relation with this hypothesis, we suggest that vizcachas tend to display a higher selectivity in circumstances in which preferred species are more available; this could be interpreted as food quality becoming a less limiting resource.

All experimental protocols performed in the present study were reviewed and authorized by the Institutional Committee on the Use and Care of Experimental Animals of Universidad Maimonides, Argentina.

The light microscopy study revealed the presence of pigments in the pineal gland for all the groups. Introduction The corpus luteum CL is a transient endocrine gland that biosynthesizes steroids under the control of luteotropic factors. Once the specificity of PRL-customized primers was established see Material and Methodswe evaluated the variations of PRL gene transcription in the pituitary gland of L. Non-ovulating non-pregnant group showed significantly lower levels than midpregnant vizcachz higher vizcaccha the remaining experimental groupsper group Figure 3 b.

After bleeding, animals were sacrificed by an intracardiac injection of Euthanyle 0. It is likely vizcwcha high levels of P4 in the first stage are linked to the activity of the primary corpora lutea, whereas the increase during the second stage is largely a result of what is secreted by the newly formed corpora lutea in the pseudoovulatory event at the end of the third month of pregnancy [ 3137 ].


Each sample was obtained from a different vizcachera in July, Rcespo and May, and one composite sample for all vizcacheras in October and February.

Morphological and endocrine cresppo of the ovarian interstitial tissue of viscacha Lagostomus maximus maximus The Anatomical Record. Number of pigmented cells: Daily morphological variations in the viscacha Lagostomus maximus maximus retina.

A possible explanation of this decrement would be that, during lactation, the constant demand exerted vzicacha the litter through the stimulus of suckling may cause the newly synthesized hormone to be immediately poured into the circulatory system, preventing its accumulation into the lactotrophs.

In dog [ 17 ], cat [ 18 ], sheep [ 1920 ], bat [ 16 ], and bovine [ 12 ], significant differences were not reported. 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 The extremely arid conditions vizcachas find in La Payunia allow to test this hypothesis.

The experimental design was approved by the local ethics committee and was in agreement with the guidelines of the National Institute of Health NIH, USA for the use of experimental animals. Availability – Diet Fig. Diversity of species eaten by vizcachas did not show seasonal changes Fig.

On the nature of pigment granules in the cells of the locus coeruleus and substantia nigra.