No abstract

BackgroundSeveral studies have shown that the corpus luteum is the principal source of progesterone during the gravidity period in reptiles; however, its participation in the maintenance of gestation in the viviparous squamata is in dispute. The effects of ovariectomy or luteectomy vary according to the species and the time at which the procedure is performed. In this paper, we describe the effects of luteectomy during early pregnancy on the maintenance of gestation and progesterone concentrations in the temperate Mexican viviparous lizard Barisia imbricata imbricata.MethodsTwenty-four lizards were subjected to three different treatments: luteectomy, sham luteectomy or non-surgical treatment, and blood samples were obtained before and after surgical treatment at different stages of gestation to determine the effects of luteectomy on the maintenance of gestation and progesterone concentrations.ResultsSpontaneous abortion was not observed in any of the females. However, luteectomy provoked abnormal parturition and a significant reduction in the number of young born alive. Parturition was normal in untreated females as well as those submitted to sham luteectomy. The surgical treatment also caused a significant reduction in progesterone concentrations in luteectomised females during early and middle gestation. However, no significant differences in hormone concentrations were observed among the three groups during late gestation or immediately post-parturition.ConclusionsOur observations indicate that the presence of the corpus luteum is not necesary for the maintenance of gestation, but that it does participate in parturition control. Moreover, the corpus luteum of the viviparous lizard B. i. imbricata produces progesterone, at least during the first half of pregnancy, and that an extra-ovarian source of progesterone must maintain gestation in the absence of luteal tissue.

Luis-Díaz, J., Cárdenaz-Vázquez, R., Villalpando-Fierro, I., Martínez-Torres, M. and Merchant, H. 2008. Follicular development in the volcano mouse ( Neotomodon alstoni alstoni , Rodentia: Muridae) from birth to maturity: a morphological approach. -Acta Zoologica (Stockholm) 89 : [185][186][187][188][189][190][191][192] The present study describes the morphology and ultrastructural features of postnatal follicular development in the volcano mouse ( Neotomodon alstoni alstoni ), an endemic Mexican rodent. By the first week of age, germ cells were organized in clusters within the ovigerous cords, and only 51.8% of them were associated with somatic cells. At the ultrastructural level, pairing chromosomes and cellular junctions between germ and pregranulosa cells, such as desmosomes, were observed. At this time, the zona pellucida could not be detected in the formed follicles. From 15 to 28 days postpartum, growing follicles were located at the medulla and inner cortex of the ovary, but most were atretic. The first preovulatory follicles were seen at 40 days. Likewise, corpora lutea were observed at this stage of development, which shows that the volcano mouse is a spontaneous ovulator. The follicular development of the volcano mouse shows strong similarities with that of the golden hamster, particularly during the first week. The morphological changes observed during postnatal follicular development of the volcano mouse follow the same general histological pattern as reported for other mammals, although the timing of these events is species-specific.