Saturday, June 27, 2009

Do stingrays lay eggs?

I got a phone call from Sofi today with a very specific question: Do stingrays lay eggs? It seems that she was playing in the pool, pretending she was swimming with stingrays who were about to have babies. But she needed to stop the story short because she was not sure if stingrays lay eggs or give birth to live young. What a great question!

While researching to find her answer, I came across conflicting information to what I thought should be a pretty simple answer. It turns out it is all about semantics. There are approximately 500 species of rays, and though stingrays are a type of ray, not all rays are "sting" rays. Some stingray species, such as devil rays, don't posses stinging spines. There are also other ray species, including as guitarfish, sawfish, electric rays, and skates, which belong to different phylogenetic families.

Even though stingrays, skates and sharks are a closely-related group of fish (called elasmobranchs), there are key differences between them. Namely, the biggest difference between a stingray and a skate is how they give birth. All stingrays give birth to live young, while skates lay eggs and attach them to the reef in hard pouches sometimes called "mermaid's purses".

So, Sofi, true stingrays give birth to fully-developed live young (called pups) which look just like miniature versions of the adult.

Click this link to watch a video about a family of stingrays at the Houston Zoo:

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