The reproductive microbiome and maternal transmission via eggs in Sceloporus virgatus

Maternal transmission of microbes occurs across the animal kingdom and is
vital for the  development and long-term health of offspring. The
mechanisms of this transfer are most well studied in humans and other
mammals, but are less well understood in egg-laying animals, especially in
those with no parental care. Here we investigate the transfer of maternal
microbes in Sceloporus virgatus, an oviparous spiny lizard. We compared
three maternal tissue microbiomes – oviduct, cloaca, and intestine – to
three offspring sample types: egg contents and eggshells on the day of
oviposition, and hatchling intestinal tissue on the day of hatching. We
found that dam ID is an important factor in hatchling microbiome
composition, indicating that maternal transmission is occurring. The
maternal cloacal and oviductal communities contribute to offspring
microbiomes in all three sample types, but there was minimal influence of
maternal intestinal microbes. This indicates that the maternal
reproductive microbiome is more important for microbial inheritance than
the gut microbiome, and that the tissue-level variation of the adult S.
virgatus microbiome must develop as the hatchling matures. Despite
differences between adult and hatchling communities, the offspring
microbiome was still dominated by Enterobacteriaceae and Yersiniaceae,
consistent with past studies of adult S. virgatus microbiomes.