Interspecific variation in structural organisation of the spermatozoon in the Asian bandicoot rats, bandicota species (family muridae)

Abstract

<jats:title>Abstract</jats:title><jats:p>The structural organisation of the spermatozoon from two species of bandicoot rats <jats:italic>Bandicota bengalensis</jats:italic> and <jats:italic>Bandicota indica</jats:italic> was investigated by light and electron microscopy together with the effect of incubation in Triton‐X 100 and sodium dodecyl sulphate. The sperm head of <jats:italic>B. bengalensis</jats:italic> is invariably falciform, has a uniform electron‐dense nucleus capped by an acrosome with a posteriolateral equatorial segment, a subacrosomal cytoskeleton with a large rostral perforatorium, and a sperm tail, attached to the lower concave surface of the sperm head, with typical coarse fibres and fibrous sheath. By contrast, the sperm head shapes of <jats:italic>B. indica</jats:italic> are generally conical or bulbous, the nucleus contains a few large vacuoles, the acrosome lacks an equatorial segment, no recognisable perforatorium occurs, and the sperm tail, which is attached basally, is very short with only modest development of coarse fibres and fibrous sheath. These results indicate that, within the genus <jats:italic>Bandicota</jats:italic>, huge interspecific differences in morphology of the spermatozoon have evolved. The spermatozoa of <jats:italic>B. bengalensis</jats:italic> are similar to those of <jats:italic>Rattus</jats:italic> and many other murids and thus presumably represent the ancestral condition, whereas those of <jats:italic>B. indica</jats:italic> (and <jats:italic>B. savilei</jats:italic>) are unlike spermatozoa from any other eutherian mammal so far described. © 1998 The Royal Swedish Academy of Sciences. Published by Elsevier Science Ltd. All rights reserved</jats:p>