Left–right ovarian laterality during gestation in the northern mountains viscacha

Previous studies in Lagidium peruanum and Lagidium viscacia reported strict right-sided dominance in ovulation and embryo implantation, although bilateral ovarian functionality may represent an intrinsic reproductive strategy to the genus. Here, we analyzed the morphology, histochemistry (periodic acid-Schiff [PAS] and Alcian blue [AB]) and lectin histochemistry of both ovaries in L. peruanum (Chinchillidae) during early, middle, and late gestation. Through gestation, the ovarian cortex contained follicles at different developmental and atretic stages, as well as interstitial glands. The medulla was composed mainly of vascularized connective tissue. Embryonic remnants, including cortical and medullary cords, were found in the cortex and the medulla during all gestational stages. A single persistent primary corpora lutea (CL) was observed in the left ovary at all gestational stages, while a secondary CL was detected only during early stages. These findings differ from previous reports describing the primary CL in the right ovary. The zona pellucida of some follicles was PAS and AB positive, and lectin histochemistry revealed dynamic glycosylation patterns in the follicles between both ovaries and throughout gestation. The ovarian morphology of L. peruanum supports the hystricomorph ovarian bauplan. However, variable ovarian laterality, persistence of embryonic structures, and differences in the number and distribution of CL among chinchillids (which includes Lagidium, Chinchilla, and Lagostomus) suggest previously unrecognized diversity in ovarian organization and reproductive strategies within the clade.