SPAWNING OF OCEAN POUT (MACROZOARCES-AMERICANUS L) - EVIDENCE IN FAVOR OF INTERNAL FERTILIZATION OF EGGS

Sperm physiology, in vivo artificial insemination and spawning of the ocean pout (Macrozoarces americanus L.), a marine bottom fish, were st udied. Milt was collected from the reproductive tract of mature males by suction using a catheter. The uncontaminated milt, having a very lo w sperm concentration, contains highly motile spermatozoa and sperm mo tility was retained in vitro at 4 degrees C for at least 24 h in both seminal plasma and ovarian slime collected from the oviduct of pre-spa wning females. instead of activating sperm, dilution in sea water inst antly immobilized the spermatozoa of ocean pout. Osmolarity and pH of ocean pout seminal plasma were in the ranges 365-406 mOsM and 7.2-7.5, respectively. A study of the ionic composition of ocean pout seminal plasma demonstrated the presence of various ions including Na+, K+, Ca 2+, Mg2+, and Cl-, with a remarkably lower K+ concentration compared t o that from other fish species. Since injections of milt containing mo tile sperm into the ovaries of pre-spawning females, which spawned in the absence of males, yielded fertilized ocean pout eggs, it is conclu ded that the ocean pout exhibits internal fertilization. The larvae ha tched after 3 months of egg incubation in ambient sea water (9-10 degr ees C). With proper timing of in vivo artificial insemination of matur e females, fertilized ocean pout eggs can be obtained from fish reared in captivity.