In article . com,
Raphanus wrote:
While Homo sapiens usually have 46 chromosomes there are individuals
with 45 chromosomes (Turner's syndrome), 47 chromosomes (Down,
Klinefelter's, XYY and XXY syndromes) and even 48 chromosomes (XXYY
syndrome). Most of these variants are fertile and able - with
individuals with the "normal" complement of 46 chromosomes - to produce
children.

Actually, with the exception of XYY, most of these variants are infertile,
usually due to defective development of the reproductive system, among
other physical defects. Trisomies of other chromosomes are known in
humans, but they are invariably fatal either before birth or shortly
after. In general mammals seem to be too finely tuned to work as
aneuploids or polyploids, although some amphibians have complicated
systems of interbreeding between species that result in fertile
polyploids.

Polyploid plants are often more robust than the originals, and seem
to be fertile as long as it's an even numbered ploidy. Many domestic
plants are polyploids -- selected for that robustness over millenia
of domestication. Polyploidy is a well known method of speciation
in plants.

Are there other species also with a variant chromosome count? Or do we
know? Homo sapiens is, no doubt, the species we know most about and
maybe such variation has eluded detection in other species?

Ah, the mystery of the male calico cat, very rare and usually infertile,
These animals are XXY (or mosaics) -- they have Klinefelter's syndrome.