Ovarian dysgenesis in an alpaca with a minute chromosome 36.

A 4-year-old female alpaca (Lama pacos [LPA]) was presented to the Oregon State Veterinary Teaching Hospital for failure to display receptive behavior to males. Although no abnormalities were found on physical examination, transrectal ultrasonographic examination of the reproductive tract revealed uterine hypoplasia and ovarian dysgenesis. Cytogenetic analysis demonstrated a normal female 74,XX karyotype with 1 exceptionally small (minute) homologue of autosome LPA36. Chromosome analysis by Giemsa staining and DAPI- and C-banding revealed that the minute LPA36 was submetacentric, AT-rich, and largely heterochromatic. Because of the small size and lack of molecular markers, it was not possible to identify the origin of the minute. There is a need to improve molecular cytogenetic tools to further study the phenomenon of this minute chromosome and its relation to female reproduction in alpacas and llamas.