Sperm chemotaxis: egg peptides control cytosolic calcium to regulate flagellar responses

The chemoattractant sea urchin egg peptide catalyzes high increases in intracellular calcium (Cai) concentration in an extracellular calcium-, and 3-isobutyl-1-methylxanthine (IBMX)-dependent manner for mediating sperm chemotaxis and modulating flagellar responses. Increase in Cai results in the tight circular configuration of the swimming paths and a 40% improvement in the flagellar waveform. Repetitive additions of the peptide speract for simulating the concentration gradient of sperm as it nears the egg show that the sperm is capable of responding to a broad Cai concentration.