Sexual Conflict and Polyspermy under Sperm‐Limited Conditions: In Situ Evidence from Field Simulations with the Free‐Spawning Marine EchinoidEvechinus chloroticus

• Published in: The American naturalist 2002-10, Vol.160 (4), p.485-496
• Main Authors: Franke, E. S., Babcock, R. C., Styan, C. A.
• Format: Article
• Language: English
• Subjects: Algae; Fertilization; Gametes; Invertebrates; Larval development; Ova; Polyspermy; Proportions; Sperm competition; Spermatozoa
• ISSN: 0003-0147; 1537-5323
• DOI: 10.1086/342075

For free‐spawning organisms that release gametes into the sea, sperm limitation (too few sperm to fertilize all eggs) is a major factor limiting reproductive success. Given such circumstances, the presence of several mechanisms to prevent polyspermy (too many sperm) may seem paradoxical; however, a growing body of data suggests that natural fertilization levels, though variable, can routinely be high. Under such conditions, polyspermy is much more likely. The tension between sperm limitation and polyspermy represents sexual conflict because males, in competing to fertilize as many eggs as possible, can impose lethal costs on eggs if multiple sperm gain entry. Here we present data for a marine invertebrate indicating high levels of polyspermy under sperm‐limited conditions. When the sea urchinEvechinus chloroticuswas induced to spawn in situ, mean rates of polyspermy were \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $17.3\% \pm 3.4\% $ \end{document} , and polyspermy was recorded at rates as high as 62.7%. Polyspermy was nearly always present, even when fertilization rates were