The spermatozoa of the fissiparous starfish, asterina burtoni

Spermatozoa of the fissiparous starfish Asterina burtoni from the Mediterranean coast of Israel were studied by electron microscopy. The head of the spermatozoon is a spheroid containing the nucleus and the acrosomal complex within a fossa at the anterior pole of the nucleus. The mitochondrion is dome-like; centrioles are located at the periphery of the mitochondrion. The flagellum is coiled, surrounds the head of the spermatozoon and leaves the cell membrane at a position which is at the perimeter of the spermatozoon and not opposite the acrosome pole. The possibility that the Mediterranean population of A. burtoni reproduces only by fissiparity is discussed.