Progesterone and estradiol-17β as a potential method for pregnancy diagnosis in the collared peccary (Pecari tajacu)

Evolutionary Patterns of Maternal Recognition of Pregnancy and Implantation in Eutherian Mammals

The implantation of the embryo into the maternal endometrium is a complex process associated with the evolution of viviparity and placentation in mammals. In this review, we provide an overview of maternal recognition of pregnancy signals and implantation modes in eutherians, focusing on their diverse mechanisms and evolutionary patterns. Different pregnancy recognition signals and implantation modes have evolved in eutherian mammals, reflecting the remarkable diversity of specializations in mammals following the evolution of viviparity. Superficial implantation is the ancestral implantation mode in Eutheria and its major clades. The other modes, secondary, partially, and primary interstitial implantation have each independently evolved multiple times in the evolutionary history of eutherians. Although significant progress has been made in understanding pregnancy recognition signals and implantation modes, there is still much to uncover. Rodents and chiropterans (especially Phyllostomidae) offer valuable opportunities for studying the transitions among implantation modes, but data is still scarce for these diverse orders. Further research should focus on unstudied taxa so we can establish robust patterns of evolutionary changes in pregnancy recognition signaling and implantation modes.

Reproductive monitoring of collared peccary females (Pecari tajacu) by analysis of fecal progesterone metabolites

The measurement of fecal progesterone metabolites (fPM) by enzyme immunoassay analysis is a non-invasive technique that permits gathering reproductive information from wildlife without the stress associated with restraint. In the collared peccary (Pecari tajacu), a high correlation between serum progesterone and fPM levels (r² = 0.783) suggests that fPM can be used to monitor their reproductive function. We monitored fPM during the estrous cycle of 15 collared peccary females. Estrous cycles averaged 27.9 ± 4.5 days (n = 28), ranging from 21 to 36 days. The luteal phase was 22.2 ± 4.8 days and the inter-luteal phase was 4.3 ± 1.4 days. Mean concentration of fPM across pregnancy were not different from those found during the luteal phase (1230 ± 718 and 1265 ± 584 ng/100 mg dried feces, respectively), however, significant differences were found when luteal phase concentrations were compared only against fPM concentrations during late pregnancy. In addition, late pregnancy fPM concentrations (1893 ± 551 ng/100 mg) were also significantly higher than those in the early (639 ± 339 ng/100 mg) and mid (1134 ± 449 ng/100 mg) pregnancy. For females during the early post-partum period, fPM concentrations were significantly increased (243 ± 118 ng/100 mg) than those of non-cycling females (103 ± 89 ng/100 mg). The analysis of fPM is a simple, non-invasive methodology to detect the ovarian activity in the collared peccary; moreover, it provides a husbandry tool, which may be used to help understand how social structure may impact reproduction.