Sperm Motility Initiation in Pacific Herring
Pp. 208-224 (17)
Gary Cherr, Carol A. Vines, Edmund H. Smith, Murali Pillai, Frederick Griffin and Ryuzo Yanagimachi
Pacific herring (Clupea pallasi) are estuarine fish that spawn in reduced
salinity water. The spermatozoa are virtually motionless upon spawning into water of
varying salinities and only initiate motility upon contact with a chorion-bound
glycoprotein. Sperm can remain in the water column for up to 24 hrs, yet are still
capable of fertilizing eggs. Immotility in the environment is maintained as a result of
herring sperm utilizing reverse sodium (Na)-calcium (Ca) exchange (Ca2+ in, Na+ out)
as a mechanism for increasing intracellular calcium at motility initiation. The primary
initiator of motility, Sperm Motility Initiation Factor (SMIF) requires protein kinase C
activation that in turn appears to increase the reverse Na-Ca exchanger. A nondiffusible
chemoattractant, Micropylar Sperm Attractant (MSA) is also present on the
chorion immediately surrounding the micropyle opening in herring (as well as other
fish and insects) that induces a rapid increase in intracellular Ca2+ when sperm come in
contact with it and this causes sperm to make sudden turns toward the canal opening.
As such, herring sperm appear to undergo at least two increases in intracellular Ca2+:
one at motility initiation by SMIF, and a further increase as they contact MSA at the
Circular motility, Flagellar bending, Herring, Micropylar Sperm
Attractant, Micropyle, Motility initiation, PKC, Sodium-calcium exchange, Sperm
Motility Initiation Factor.
Departments of Environmental Toxicology and Nutrition, University of California Davis, Davis, CA USA.