Effects of fluid shear on red abalone sperm-egg interactions

摘要

Fertilization rate is an important factor mediating the production of offspring and, hence, population dynamics. For marine organisms that broadcast their sperm and eggs into the sea, surprisingly little is known about the mechanisms controlling sperm-egg interactions. Here, we investigated hydrodynamic effects on fertilization in red abalone (Haliotis rufescens). Experiments were performed in laminar-shear flows that simulated important aspects of small-scale turbulence within natural habitats. Fertilization rates were determined over a wide range of gamete concentration and shears created in a Taylor-Couette flow tank and using a new application of infrared laser and computer-assisted video imaging technologies. For red abalone, shears of < 0.1/s maximized sperm chemotaxis, gamete encounter rates, and fertilization success. Fertilization was subsequently well explained by numerical models that took into account cell shapes, sizes, and propulsive forces generated by sperm swimming, as well as shear forces imposed by the flow. These models, thus, established the relative contributions of active sperm behavior and passive physical transport to sexual reproductive processes. Combined findings have value in forecasting field sites that maximize offspring production, for transplants, or outplants, of adult brood stock.