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Sexual conflict and polyspermy under sperm-limited conditions : in situ evidence from field simulations with the free-spawning marine echinoid Evechinus chloroticus

journal contribution
posted on 2002-10-01, 00:00 authored by E Franke, R Babcock, Craig Styan
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 urchin Evechinus chloroticus was induced to spawn in situ, mean rates of polyspermy were 17.3% ±3.4%, and polyspermy was recorded at rates as high as 62.7%. Polyspermy was nearly always present, even when fertilization rates were <50%, confirming predictions that it should be present under sperm‐limited conditions. Both sperm limitation and polyspermy imposed substantial reproductive costs, and we conclude that both sexual conflict related to polyspermy and sperm limitation have been simultaneous strong selective forces shaping the evolution of reproductive traits in the sea.

History

Journal

American naturalist

Volume

160

Issue

4

Pagination

485 - 496

Publisher

University of Chicago Press

Location

Chicago, Ill.

ISSN

0003-0147

eISSN

1537-5323

Language

eng

Publication classification

C1.1 Refereed article in a scholarly journal

Copyright notice

2002, University of Chicago

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