Eggs of many species are surrounded by extracellular coats that emit ligands to which
conspecific sperm respond by undergoing chemotaxis and changes in metabolism, motility,
and acrosomal status in preparation for fertilization. Here we review methods used to
measure sperm chemotaxis and focus on recent studies of allurin, a 21-kDa protein
belonging to the Cysteine-RIch Secretory Protein (CRISP) family that has chemoattraction
activity for both amphibian and mammalian sperm. Allurin is unique in being the first …