What is going on with non-pregnant horn in plains viscacha?

FLAMINI MA; PORTIANSKY EL; FAVARON PO; MARTINS DS; AMBRÓSIO CE; MESS A; MIGLINO MA; BARBEITO CG.

Santiago de Chile. Chile

Simposio; Meeting 2010 International Federation of Placenta Associations; 2010

Plains viscacha Lagostomus maximus maximus (Rodentia, Hystricognathi, Chinchillidae) belongs to Argentine wild faune.  Various studies so far deal with their very distinct characteristics of reproductive parameters and endocrine organs. In particular, female viscachas produced around 300-800 ova at each cycle, but only 10% were fertilized, resulting in 2 offspring with advanced developmental status (Mossman & Duke, 1973). In its natural environmental plains viscacha had a monoestrous cycle, but in captivity they could be polyoestrous. However, there are still only few data on the reproductive system itself. We therefore investigated structural parameters of the early developmental processes. Four female reproductive apparatus were obtained from Estación de Cría de Animales Silvestres, Buenos Aires, Argentine; the necropsy was performed at the Faculty of Veterinary Science, La Plata University, and fixed in 4% paraformaldehyde. Samples were processed for light microscopy in the Faculty of Veterinary Medicine and Animal Science, University of Sao Paulo, Brazil. Sections of 5µm were stained with haematoxylin and eosin. Female reproductive system was composed by two ovaries, two uterine tubes, a bicornuate uterus, and one vagina. After the mean cycle, early embryologic stages were present in both uterine horns. Multiple implantations were observed in the uterine horns, in a variable number and shape, but not exceeding 6 for each horn. These implantations showed a clustered appearance while proceeding pregnancy. Implantations near to uterine tube were associated with a dark color of the uterine body as well as amorphous appearance and irregular shape. Larger implantations showed light color with a circular cavity. When studied late stages of pregnancy were only found embryos near to the uterine body, while the others had disappeared. Data suggest the position of the implantating eggs in uterine horns is crucial for its developmental success and the uterine tissue has the power to regulate implantation processes.