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How do male horseshoe crabs fertilize eggs?
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horseshoe crab
Horseshoe crab (Limulus polyphemus).
Male horseshoe crabs fertilize eggs externally during the spawning process.12
When female horseshoe crabs crawl onto sandy beaches to spawn, they dig depressions and deposit their eggs in clusters. Males, which often attach themselves to the backs of the females, then cover these egg clusters with sperm. This external fertilization occurs after the eggs have been laid in the sand.12