Understanding the Amazon’s Plethora of Freshwater Stingray Species

To the casual observer, the rivers of the Amazon rainforest could be mistaken for the ocean. They teem with stingrays, pufferfish, and needlefish – all more commonly associated with marine environments.

Where did the Amazon’s dozens of freshwater stingray species come from?

All species that first originated in the sea, they may appear decidedly out of place in freshwater. South America’s rivers even play host to once exclusively ocean-dwelling dolphins that have fully adapted to life there.

However, the Amazon today ultimately has just a few different species of pufferfish and the like. Yet, at the same time, there are 38 separate species of freshwater stingrays. Purely in terms of outright diversity, that’s frankly extraordinary.

Freshwater stingrays now exist in almost every major river basin in South America, where they take on an array of appearances and body types.

For João Pedro Fontenelle, an evolutionary biologist at the Institute of Forestry and Conservation at the University of Toronto in Canada, this raises an important question: “What happened there?”

Continue reading: Where Did All These Freshwater Stingrays Come From? via Defector