animal reproduction
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For Fish Penises, Bigger Isn’t Always Better
When it comes to reproduction, most fish are external fertilisers, crop dusting eggs in a cloud of sperm. But swordtails (Xiphophorus) aren’t like most fish. These fish fertilise eggs internally and “give birth” to live young. To help this whole operation, males have evolved external genitalia for transferring sperm – a tool not typical among…
