SPERMATOZOA MOTILITY OF TROUT (ONCORHYNCH US-MYKISS) AND CARP (CYPRINUS-CARPIO)

In the past fifteen years, teleost spermatozoa and seminal plasma were studied with the aim of understanding the mechanical and chemical pro cesses which regulate motility. Trout and carp spermatozoa were partic ularly studied; their flagella are classic, with ''9+2'' microtubule d oublets and outer and inner associated dynein arms. Flagellar beating results from hooking/unhooking cycles from the dynein arms of one micr otubule to the one adjacent through ATP hydrolysis. A protease coupled to a ligase is probably also involved. Spermatozoa undergo drastic st ructural change when shed in freshwater but not in an activating salin e solution; however, in both cases, motility is short, 30 sec. in trou t and one minute in carp. Trajectories are circular; flagellar beat fr equencies are high at the beginning of the motility (50-60 Hz), and de crease to 10-20 Hz: one observes that sperm head stop, whereas flagell a of carp spermatozoa continue beating at low frequency (< 10 Hz). The velocity decreases with frequency; the mean duration of displacement is 3 mm in trout and 5 mm in carp. Trout and carp spermatozoa motility are influenced by the ionic external environnement. A high concentrat ion of K+ ions in trout and a high osmotic pressure in carp inhibit mo tility. Other ions like H+, Ca2+, Mg2+ also interfere with the motilit y regulation. At the time of trout spermatozoa movement initiation, ad enylate cyclase activity and cAMP concentration increase. cAMP is like ly a factor involved in the initiation of motility, which may also inv olve the phosphorylation of a protein 15 Kd through a Tyrosine protein kinase activity. cAMP may also be involved in the acquisition of sper m motility in vivo. When carp spermatozoa are immotile in the activati ng, solution, they can undergo a ''maturation in vitro'' (i.e. the acq uisition of the capacity to move) by incubation in a medium with high concentration of K+ and with a high osmotic pressure (400 m Osm/kg). A fter initiation of movement in the activating solution, intracellular ATP decreases rapidly in the spermatozoa of the two species. ATP regen eration occurs spontaneously within fifteen minutes following the arre st of movement in trout. In carp there is no AT regeneration in activa ting saline solution, but replacing spermatozoa in an immobilizing sol ution (high osmotic pressure) results in a recovery of the intracellul ar ATP content. It was shown that demembranated trout spermatozoa can be reactivated with ATPMg2+ and cAMP; in contrast, cAMP was not necess ary in carp.