Prenatal development of the digestive system in the horse.

Since the horse has a highly precocial reproductive strategy, most organs are functionally well developed at birth and thus, embryonic and fetal life is interesting. Data on the development of important organs are very limited. Here, we detailed macroscopically and histologically the equine digestive system, focusing on the first third of gestation.

Ultrastructure of the bullfrog (Lithobates catesbeianus-Shaw, 1802) oviduct in different seasons.

The bullfrog (Lithobates catesbeianus) is an exotic animal that adapted perfectly to the climatic conditions of Brazil after introduction in the country. These climatic conditions favor the reproduction and fattening of bullfrogs. However, the development of the bullfrog is significantly reduced in colder regions because low temperatures affect the secretion of gonadotropins and change the sensitivity of the germinal epithelium to gonadotropic hormones.

Placentation in the anteaters Myrmecophaga tridactyla and Tamandua tetradactyla (Eutheria, Xenarthra).

Background: Since Xenarthra are serious candidates for being basal to Eutheria, their characteristics, e.g. the placental system, influence perceptions of evolution.

The subplacenta of the red-rumped agouti (Dasyprocta leporina L).

Background: Hystricognath rodents have a lobed placenta, comprising labyrinthine exchange areas and interlobular trophoblast. These correspond to the labyrinthine and spongy zones of other rodent placentae. Beneath them, however, is a structure unique to hystricognath rodents called the subplacenta.