![]() In this paper we review the structure of the subplacenta and examine possible functional correlates. Beneath this is a structure known as the subplacenta that is unique to the hystricognath rodents. The lobules are separated by interlobular trophoblast that is the counterpart of the spongy layer found in the placenta of other rodents. The exchange area or labyrinth is lobulated, an adaptation that allows an increase in the total exchange area and helps to support the larger fetus at the end of gestation. The hystricognath placenta has a number of distinctive features. This reproductive strategy requires a lower rate of energy consumption and is well suited to an herbivorous diet. The newborn is well developed with open eyes and a full coat of hair. They differ from other rodents in giving birth to precocial young. At this time they were able to capitalize upon the emergence of grasslands for which they were well adapted in a number of ways. The hystricognath rodents (Suborder Hystricomorpha, Infraorder Hystricognathi ) appeared in the Eocene and underwent an extensive radiation in the Miocene. Our findings are consistent with this interpretation, but suggest that hormone secretion is directed towards the fetal circulation rather than the maternal tissues. The functions that have been attributed to the subplacenta include hormone production. Within it the vessels pursue a tortuous course with sinusoidal dilatations and constrictions. The subplacenta is supplied entirely from the fetal circulation. This is probably the amylase-resistant PAS-positive material identified by histochemistry. The syncytial cytoplasm contains electron-dense granules. Microvilli project into these lacunae from the plasma membrane of the syncytiotrophoblast. The syncytiotrophoblast surrounds an extensive system of lacunae. The basal membrane of these cells is often close to fetal blood vessels. There are prominent intercellular spaces between the cytotrophoblast cells. Clusters of multinuclear giant cells occur in the transition zone between the subplacenta and decidua. Beneath this is found syncytiotrophoblast. In the subplacenta, lamellae of connective tissue support a layer of mononuclear cytotrophoblast cells. In addition, to study the microvasculature of the subplacenta, vessel casts were inspected by scanning electron microscopy Results Placentae were collected from early in midgestation to near term of pregnancy and examined by standard histological techniques, immunohistochemistry and transmission electron microscopy. We here describe the subplacenta of the red-rumped agouti and examine the possible functional correlates of this structure. Beneath them, however, is a structure unique to hystricognath rodents called the subplacenta. These correspond to the labyrinthine and spongy zones of other rodent placentae. Hystricognath rodents have a lobed placenta, comprising labyrinthine exchange areas and interlobular trophoblast. Red Rumped Agouti | National Zoo & Aquarium. To obtain food the red-rumped agouti may follow a group of monkeys and eat any fruits which they drop from the trees.īy Postdlf – Digital photo by Postdlf, CC BY-SA 3.0, īy Bernard DUPONT from FRANCE – Red-rumped Agouti (Dasyprocta leporina) in the garden …, CC BY-SA 2.0, They will bury nuts to eat and if they do not return to eat them these will grow in to new trees. As such they are an important distributor of the seeds of these nuts through the environment. They are the only animal in their habitat which is able to break through the shell of a brazil nut without tools. To eat food they have incisors which grow throughout their life and are stronger than those of other rodents. When food is scarce they have been known to eat insects. They will feed on fruits, nuts, shoots, leaves. An average red-rumped agouti will measure 49-64cm (19-25in) long and weighs 3-5.9kg (6.6-13lbs). The legs are long.Īt the end of the body they have a short tail which measures 6cm (2.4in) long.įemale red-rumped agoutis are typically larger than males. Each foot ends with a sharp, hoof like claw. On the front foot they have four toes and on the back foot they have three. Their name comes from the orange or red patch of fur on their rear. On their underside they have orange-brown fur with a white stripe which runs down the centre. The red-rumped agouti is covered with coarse, short fur which is glossy green-brown across the back.
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