The development of chemoattractant plumes in complex flows and the role of the chemotactic strategies employed by sperm to navigate the plumes to fertilize an egg.

摘要

The ability of benthic invertebrate sperm to utilize chemotaxis and chemokinesis to locate an egg during broadcast spawning is examined under a variety of flow conditions. During the fertilization process, males release a cloud of sperm and females release a cloud of eggs into the ambient flow. The two plumes are brought together due to turbulent stirring. Individual eggs release a mass of chemoattractant into the flow upon being spawned. The motile sperm are tasked with swimming to an egg for fertilization to occur. The sperm are able to sense the concentration of chemoattractant released by a conspecific egg and change their swimming behavior. Chemotaxis, the orientation due to a chemoattractant, and chemokinesis, the increase in speed due to a chemoattractant, aid the sperm in finding and reaching the egg in a flow. The mechanics of this process are not well understood. The flow around an egg in a linear shear flow is modeled for both a constant linear shear rate and for an unsteady turbulent flow where the linear shear changes direction and magnitude. Sperm are placed in a mass at an initial location and advect due to their swimming behavior and the flow. The rate at which the sperm reach the egg is quantified. The efficacy of several possible response behaviors are tested within 5 flows: quiescent flow, two constant linear shear flows with different shear rates and two levels of complexity for the unsteady linear shear flows, and from different initial locations.