ULTRASTRUCTURE OF THE SPERMATOZOA AND EGGS OF THE OCEAN POUT (MACROZOARCES-AMERICANUS L), AN INTERNALLY FERTILIZING MARINE FISH

Ultrastructure of sperm and eggs of the ocean pout (Macrozoarces ameri canus L.), an internally fertilizing marine teleost, was examined by s canning and transmission electron microscopy. The results showed that the sperm do not have an acrosome but have a very long mid-piece (one to two times the sperm head length) containing numerous well-developed elongated mitochondria. The sperm also have two tails (is biflagellat e) each consisting of nine peripheral and one central pair (9 +/- 2) o f microtubules. This long mid-piece and the biflagellate nature of the sperm appear to be associated with the long life-span of the sperm an d with sperm dispersal in the ovary to fertilize the eggs internally. The ocean pout eggs are enveloped by a porous chorionic membrane simil ar to that found in other teleosts but have two microphles, a conditio n likely related to a mechanism of egg fertilization which increases t he egg fertlity in the presence of low sperm numbers. Following insemi nation, some biochemically undefined excretions appeared on the surfac e of fertilized eggs and led to the acquisition of adherent capability of the eggs which formed a tightly associated egg mass in sea water. (C) 1995 Wiley-Liss, Inc.