The Impacts of Inbreeding and Hybridization on Sperm Quality in Felids and Canids.

• Main Author: Huffmeyer, Audra Alexandra
• Other Authors: Wayne, Robert K
• Format: Other/Unknown Material
• Language: English
• Published: eScholarship, University of California 2021
• Subjects: Ecology; Genetics; Canids; Felids; Gene expression; RNA0Seq; gray wolf
• Online Access: https://escholarship.org/uc/item/2fv0g0dz

Normal sperm form and function is essential to fertilization of oocytes and species reproduction. Large carnivores, particularly large cats, experience reduced sperm quality at higher rates than other mammals due to genetic isolation caused by habitat loss and urbanization. Reduction in home ranges for large carnivores is the primary consequence of habitat loss and urbanization that leads to inbreeding and genetic isolation.In this dissertation, we explore the impacts of inbreeding and hybridization on sperm quality in two felid species, the domestic cat and mountain lion (Felis domesticus and Puma concolor) and two canid species, wolf and coyote, (Canis lupis and Canis latrans). To assess the extent to which inbreeding, and hybridization reduces sperm quality in felid and canid species, we focused our investigation on three systems. (1) We completed a comparative study using a single cell RNA-Seq approach to identify differentially expressed genes between morphologically normal and abnormal sperm from domestic cats with normospermia (< 60% abnormal sperm production per ejaculate) and teratospermia (> 60% abnormal sperm production per ejaculate) to elucidate genes and pathways associated with abnormal sperm function. We found normal sperm from cats with teratospermia have a gene expression profile similar to abnormal sperm from males with teratospermia. There was also downregulation of cGMP pathways and kinase phosphorylation pathways. (2) We surveyed male mountain lions for abnormalities associated with inbreeding depression during live captures, after mortality events, and from images collected from camera traps between December 2019 and December 2020 in California (Santa Monica Mountains, Santa Susanna Mountains, Santa Ana Mountains, and Eastern Peninsula). Specifically, we looked for evidence of teratospermia, cryptorchidism, and distal tail kinks. For teratospermia, we extracted testes from five males (postmortem). Epididymal sperm evaluations revealed all males were teratospermic. Across all samples, on average, 93% of observed spermatozoa were abnormal. Further, we found 4 individuals exhibited distal tail kinks, one unilaterally cryptorchid male and one male with testes that differed greatly in size - likely reflecting asynchronous migration of the testes during puberty. Finally, (3) we assessed gene expression patterns between the coyote (Canis latrans) and gray wolf (C. lupus) whose potential to hybridize may underlie the origins of the red wolf (Canis rufus) and Eastern wolf (Canis lycaon). Here we examined ejaculates from gray wolves and F1 and F2 hybrids between a western coyote and a western gray wolf and employed a comparative RNA-Seq approach to assess expression differences between ejaculates from gray wolf males and their wolf-coyote hybrid offspring. Our RNAseq analyses identified 9 transcripts between wolves and F1 and F2 offspring that were differentially expressed (DE). However, we found 425 DE transcripts between F1-F2 offspring suggesting the potential for reproductive incompatibility between hybrid generations.