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How are ostariophysan eggs usually fertilized?
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ostariophysan
Knifefish, or featherback (Xenomystus nigri)
In the vast majority of ostariophysan species, eggs are fertilized externally in the water.1
While external fertilization is the standard, there are notable exceptions. Internal insemination occurs in auchenipterid catfishes and South American characins belonging to the subfamily Glandulocaudinae.1
Regardless of the method of fertilization, all ostariophysans are oviparous, meaning they lay eggs rather than giving birth to live young.1