Morphological characteristics of the uterus and uterine cervix of the plains viscacha (Lagostomus maximus)

Abstract

The plains viscacha is a hystricognathi rodent with special reproductive characteristics. Despite poly‐ovulation of 800 oocytes, it generates a high embryonic mortality since from 10 to 12 implantations only one or two offspring are born. The present work analyses the morphological, morphometrical, histochemical and lectinhistochemical characteristics of the uterus and uterine cervix of pregnant and non‐pregnant viscacha. Anatomically, the uterus has two horns each one continued with a short cervix devoid of glands. The structure of the uterus is like that of other species; however, the proportion and size of its glands varies according to the physiological state. In viscacha, there is no uterine body and cervices cannot be differentiated externally. The formation of two sack bottoms is determined by the presence of a middle raphe in the cranial portion of the vagina. The so‐described anatomy is different from that described in other hystricognathi such as guinea pig and coypu. The cervix presents two microscopically differentiable regions: the endocervix and the ectocervix lined by epithelia with different characteristics. The general characteristics of the uterus of L. maximus do not show specific differences with those of other mammals that might explain its peculiar gestation.

Prenatal development in Lagostomus maximus (Rodentia, Chinchillidae): A unique case among eutherian mammals of physiological embryonic death

“…Considering that the implantation sites located in the cranial and middle regions are resorbed (Flamini et al, 2011; Flamini et al, 2019; Flamini et al, 2020; Weir, 1971a, 1971b), the embryo resorption rate (% ER) was calculated as: where, RI = number of implantation sites in resorption and TI = total number of implantation sites (Clark et al, 2008; Flores et al, 2014).…”

“…The cranial and caudal segments and all the implantation sites of the right uterine horns were processed for paraffin embedding, according to the standard protocols of our laboratory; 3 μm thick slides were used (Acuña et al, 2020; Flamini et al, 2019; Flamini et al, 2020).…”

“…As a negative control, the primary antibody was replaced with PBS. As positive controls previously obtained sections ( Flamini et al, 2011, 2019, 2020 ) of the placenta, and uterus without pregnancy of the species were used, and incubated with each of the abovementioned antibodies, individually.…”

“…Likewise, 7 biotinylated lectins (Lectin Kit I, Vector Laboratories, Cat#BK‐1000, RRID: AB_2336252, Table 1) were used for the determination of specific sugars, using the lectinhistochemical technique (Goldstein & Hayes, 1978). Previously described protocols were followed for both techniques (Acuña et al, 2020; Flamini et al, 2019). As negative and positive controls, ovary sections of the species were used (Acuña et al, 2018).…”

“…Regularly, in this species, 8–10 implantations out of a total of 10–12 (5–6 per uterine horn) are resorbed between 26 and 70 post‐coitum days in the gestation of 154 ± 0.4 days (Roberts & Weir, 1973; Weir, 1971a, 1971b). Only the two implantations located in the caudal segments of both uterine horns are those that will survive (Flamini et al, 2019). In this way, L. maximus constitutes an unconventional mammalian model for the study of early and physiological embryonic death (Acuña et al, 2020).…”