Ultrastructure of the turtle spermatozoon

The turtle spermatozoon is vermiform in shape with a narrow pointed head that is curved. In general, the turtle sperm contains a typical head, midpiece and tail, similar in morphology to that of birds, amphibians and other reptiles. However, several structures are unique. These unusual features include (1) a perforatorial cap over the proximal end of the nucleus, which contains 2–3 rods that are contiguous with intranuclear tubules; (2) a connecting collar of dense material that surrounds the base of the nucleus; (3) a distal centriole containing central microtubules that extend its entire length and having outer triplicate microtubules that open toward the central cavity of the centriole; and (4) unusual spherical mitochondria containing 7–8 outer laminated membranes.