Impairment of sea urchin sperm quality by UV-B radiation: Predicting fertilization success from sperm motility

Sperm quality of the sea urchin, Anthocidaris crassispina, after exposure to environmentally realistic UV-B irradiances, was assessed by changes in sperm motility (measured by the computer-assisted sperm analysis (CASA) system), and related to subsequent fertilization success. Percentage motile sperm of A. crassispina declined significantly after exposure to a UV-B dose of 16.2 kJm^-2, while sperm motion velocity as measured by curvilinear velocity (VCL), straight line velocity (VSL), and average path velocity (VAP) showed significant reduction after exposure to a UV-B dose of 5.4 kJm^-2. A parallel study showed that fertilization success was significantly reduced after sperm were exposed to UV-B doses ≥5.4kJm^-2. Notably, the four sperm motility parameters were strongly correlated with fertilization success (P<0.001), followed the increasing order: VSL (r=0.8)<%motilesperm(r=0.804)<VCL(r=0.912)<VAP(r=0.928). Fertilization success is best predicted by VAP using the exponential model: y=8.678+90.202/[1+exp(82.83-x)/10.27)] (r²=0.95). Thus, impairment of sperm motility of sea urchin, as measured by the CASA method, can be used to predict reproductive success and ecological effects. Copyright © 2002 Elsevier Science Ltd. All rights reserved.