Experimental evidence for antagonistic effects of sperm competition in two sea urchin species
Year: 2026
Type: preprint
Abstract: Sperm competition can occur when sperm from two or more males compete for fertilization of a batch of eggs. While it has been extensively studied in internal fertilizers, it remains poorly understood in external fertilizers. To investigate how sperm competition affects fertilization under sperm limitation, we conducted controlled experiments on two sea urchin species: Paracentrotus lividus and Dendraster excentricus . Eggs from a single female were exposed to sperm from three individual males separately (non-competitive treatment) or to a pooled sample from three males (competitive treatment). We measured fertilization success as proportion of eggs fertilized after two hours and assessed sperm motility as percentage of motile sperm and curvilinear velocity. For P. lividus , we estimated the sperm concentrations where fertilization success was 50% of maximum observed fertilization success ( F 50 ), and the fertilization efficiency of the sperm ( F e ), i.e. the likelihood that a sperm - egg encounter results in a fertilizing contact, using the fertilization kinetics model of Styan (1998). For D. excentricus , fertilization success was measured at a sperm concentration expected to produce 50% fertilization success. Sperm competition reduced fertilization success and increased F 50 compared to non-competitive treatments, suggesting antagonistic effects that may compromise fertilization under sperm-limited conditions in external fertilizers.
Language: English
Subfield: Aquatic Science
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7221455195