Chorioallantoic and yolk sac placentation in the plains viscacha (Lagostomus maximus) – A caviomorph rodent with natural polyovulation

Abstract

The principle processes of placentation in caviomorphs follow an extraordinarily stable pattern that is independent of specializations, such as polyovulation.

Placental Evolution within the Supraordinal Clades of Eutheria with the Perspective of Alternative Animal Models for Human Placentation

“…The capybara represents the largest species of recent Caviomorpha, which approximates human dimensions with an adult body mass of around 50 kg [223,224]. Likewise, specialized reproductive traits in other caviomorphs such as polyovulation in the plains viscacha (Lagostomus maximus) do not affect the set of placental features typical for the caviomorphs [35], supporting indeed their appropriateness as animal models.…”

“…Thus, several taxa including rare or wildlife species have been studied by means of histology and modern methods like immunohistochemistry or proper fine structural investigations by electron microscopy. Among 2 Advances in Biology them are nonmurine rodents native to South America and Africa [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40], as was shown by Figure 2, bats [41][42][43], anteaters and armadillos [44,45], and some other taxa [46][47][48][49][50][51]. Also, there were several promising attempts to reinvestigate historical histological material from museum collections such as neotropical primates [52] or great apes [53][54][55][56] in order to answer open questions.…”

“…Also a very stable pattern of fetal membrane and placental characters has evolved on the stem lineage of hystricognath rodents [26-30, 171, 172] that is relatively similar to the placental fine structure in the human [27,28,71,101]. Inside the placenta, proliferating trophoblast cells are situated on bands of fetal mesenchyme, lined by syncytial trophoblast facing towards the maternal blood spaces [27,28,34,35,222,223]. In near term pregnancy, the exchange area consists of a single, very thin layer of syncytiotrophoblast (Figure 2(d)) as does the mature human placenta [26,171].…”

“…Implantation is invasive or superficial [172]. The guinea pig and other hystricognaths have a unique structure called a subplacenta from which extravillous trophoblast migrates to invade deeply inside the decidua (Figures 2(e) and 2(f)) and transform the maternal arteries [10,26,29,34,35,171,172,223], in parallel to the structure and function of the human cell columns [120]. Other derived character conditions of hystricognaths are the ring-shaped placenta with radial flow of maternal blood in order to increase the capacity for passive diffusion [26].…”

Chorioallantoic and yolk sac placentation in Thrichomys laurentinus (Echimyidae) and the evolution of hystricognath rodents

“…Data so far indicate that key characters are largely independent from size dimensions in medium to large‐sized species up to the capybara Hydrochaeris hydrochaeris with around 50 kg body mass, which approximated the condition in humans (Kanashiro et al, 2009). Likewise, other aspects of reproduction, such as the obscure superovulation in the plains viscacha ( Lagostomus maximus , Chinchillidae), do not affect placental development (Flamini et al, 2011). The situation in smaller species is ambiguous, because data are deficient for important taxa.…”