When the uterus is a vagina Intra-horn insemination in the alpaca and consequences to genital morphology coevolution and 3-D shape

January 3 – Febuary 28, 2021

Meeting Abstract

S3-2  Mon Jan 4 10:30 – 11:00  When the uterus is a vagina: Intra-horn insemination in the alpaca and consequences to genital morphology coevolution and 3-D shape Brennan, PLR*; Sterett, M; DiBuono, M; Klo, K; Marsden, R; Schleinig, P; Tanner , L; Purdy, S; Mount Holyoke College pbrennan@mtholyoke.edu http://www.pattybrennan.com/

Alpacas are among the few mammalian species where insemination is reportedly transcervical. Transcervical insemination is expected to be be rare in mammals, because the penis can be a vehicle for disease transmission, and female upper reproductive tract immunity is typically downregulated for pregnancy to succeed. However, evidence for transcervical insemination in alpacas was only circumstantial. Here we performed mating experiments with females that were going to be culled at a meat farm, and determined that the penis tip of the male enters not only the cervix, but travels the entire length of the reproductive tract all the way to the end of the uterine horns. We further studied the 3-D morphology of male and female genitalia and report oddities of their morphology that may be associated with this unusual insemination mode. The cranial vagina varies between bulbous and straight, while the caudal vagina is typically narrower. The cervix consists of a series of 2-3 spirals, and it is in an open state most of the time. The uterus and uterine horns have a complex shape with multiple constrictions. The male alpaca has a cartilaginous penis tip and a keratinized nail that may help to push against these constrictions, resulting in extensive damage to the female tract. In effect, the entire female reproductive tract of the female is behaving like a vagina, and its modifications likely extend beyond the morphology, into immune adaptations to manage uterine wounding, and potential pathogen exposure.

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