Incidence of cystic ovaries and reproductive performance in the Mongolian gerbil, Meriones unguiculatus

The incidence and severity of ovarian cysts were stongly age dependent, increasing from 7% in 89 female gerbils aged 135-399 days to 47% in 45 females aged 400-899 days. Cysts varied in size from less than 1 mm up to 50 mm in diameter, and accounted for from 1 to 16% of the female's live weight.

Litter sizes were reduced in the presence of ovarian cysts, and reproduction ceased prematurely. Ovulation and formation of corpora lutea could still occur in cystic ovaries but the proportion of eggs developing normally was reduced from 90 to 29%, probably because of impaired gamete transport.