Authors
Kumpitsch, L., Beckmann, L. M., Hanson, S. E., Paredes, E., Gonzalez Fernandez, J., Langer, L., Lifjeld, J. T., Leder, E. H., Havenhand, J. N.
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 under-stood 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 individ-ual males separately (non-competitive treatment) or to a pooled sample from three males (competi-tive 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 (F50), and the fertilization efficiency of the sperm (Fe), 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 F50 compared to non-competitive treatments, suggesting antagonistic effects that may compromise fertilization under sperm-limited conditions in external fertilizers.
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bioRxiv
The authors list and abstract were imported from bioRxiv on 11 Oct 2026.
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