The tree shrew ( Tupaia belangeri chinensis
) is a small non-rodent mammal, which is a relatively new
experimental animal in medicine due to its close evolutionary relationship to primates and its rapid propagation. Sperm
characteristics and cryopreservation in the tree shrew were the main contents of our spermatological research. Epididymal
sperm were surgically harvested from male tree shrews captured from the Kunming area. The rate of testis weight to body
weight was (1.05±0.07)%, volume of both testis was (1.12±0.10) mL, total sperm from epididymis and vas deferens were
, and sperm motility and acrosome integrity were (68.8±3.9)% and (90.0±2.1)%, respectively. Sperm
ultrastructure of the tree shrew was examined by scanning electron microscopy and transmission electron microscopy.
Tree shrew sperm had a round or oval shaped head of approximately 6.65×5.82 μm, and midpiece, principal piece, tail,
and total sperm lengths were 13.39, 52.35, 65.74, and 73.05 μm, respectively. The mitochondria in the midpiece
consisted of approximately 48 gyres and had a 9+9+2 axonemal pattern. After freezing and thawing, sperm showed partly
intact acrosomes and plasma membrane defects, and sperm breakages, twists, and swellings were found. The tree shrew
had similar ultrastructure with other mammalians except for the mitochondria number and the sperm size. Ultrastructural
alteration is still the main cause resulting in poor sperm after cryopreservation.