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This episode of DNews features guest host Luiz Rocha from California Academy of Sciences in San Francisco talking with Trace about shark sex! Shark reproduction is of particular interest to marine biologists because despite the fact that they are ancient (450 million years old) and boneless fish, they actually birth live young. Most fish from that era are egg-laying (or oviparous), as opposed to viviparous sharks.
Sharks also have the reputation of being able to reproduce asexually. What actually's happening is that shark sperm can last outside the body for extremely long periods of time -- as long as 45 months in one study. Human sperm, by contrast, can only last for about five days maximum.
Rocha hypothesizes that this evolved so that a female shark could either produce in the absence of males, or when conditions are better for reproduction, like when they have access to more more food, or have better survival chances.
450 Million Years of Sharks (Sharksavers.org)
"Sharks have swum in the oceans for almost 450 million years. But longevity is only part of the story."
Animal Sex: How Great White Sharks Do It (Live Science)
"Despite the intense public and scientific attention the predatory fish has gained these past few decades, there's still a lot we don't know about great white sharks, especially when it comes to their mating behavior."