Ultrastructure of the mature spermatozoon of the bivalve Scapharca broughtoni (Mollusca: Bivalvia: Arcidae).
The ultrastructure of mature spermatozoa of the giant clam bivalve Scapharca broughtoni was investigated by transmission electron microscopy for the first time. The mature spermatozoon consists of a head which is composed of a cone-shaped acrosome, a round nucleus, and a tail region. A subacrosomal space contains an axial rod and a basal plate, the latter lying between the acrosome and the nucleus. Although the nucleus lacks an anterior invagination, an inverted shallow V-shaped posterior invagination is present within the nucleus. Within the middle portion of the spermatozoon lie five spherical mitochondria while the long whip-like end portion is composed of an axoneme with the typical 9+2 structure. Our conclusion is that the spermatozoon of S. broughtoni is of the type I anacrosomal "aquasperm", and the morphology of acrosome and nucleus are an adaptation to external fertilization.
Zhu
Jun-Quan
JQ
Faculty of Life Sciences and Biotechnology, Ningbo University, Zhejiang 315211, China.
Dahms
Hans-Uwe
HU
Yang
Wan-Xi
WX
D000177:Acrosome / Q000648:ultrastructure; D000818:Animals; D002467:Cell Nucleus / Q000648:ultrastructure; D008297:Male; D008928:Mitochondria / Q000648:ultrastructure; D049894:Scapharca / Q000648:ultrastructure*; D013094:Spermatozoa / Q000648:ultrastructure*