March 16 – Crunchy Crawlers

Today’s Factismal: North America has 330 different species of crawdads, which is twice as many as the rest of the world combined.

Crawdad. Crayfish. Crawfish. Mudbug. Yabbies. Baby Lobsters. No matter what you call them, crawdads are popular critters. And why not? They’ve been around so long that they can remember when the Americas, Europe, and Africa were all part of the same continent. Fossil crawdads have been found going back 30 million years, and fossilized crawdad burrows have been found going back 225 million years. Today, these crunchy crawlers make their homes on five different continents (Africa and Antarctica are the exceptions). Though the vast majority of species in found in North America, there are some 100 species in Australia, and several dozen in Europe.

Where can you find crawdads? (Image courtesy somebody)

Where can you find crawdads? (Image courtesy Crayfish and Lobster Taxonomy Browser)

These arthropods are ubiquitous, with species living in swamps, in lakes, in streams, and even in caves. Crawdads range in size from just over an inch to more than a foot long (and more than eight pounds in weight!). They range in color from pale green to bright red. And their diet varies from dead leaves to dead fish to dead insects, while they serve as the diet for eels, trout, birds, and Cajuns.

A cooked crawdad (Image courtesy Louisiana Crawfish)

A cooked crawdad (Image courtesy Louisiana Crawfish)

About the only constant with crawdads is their body structure. Like their lobster cousins, crawdads have twenty body segments with a head at one end and a tail at the other. Each segment has a set of legs, with different legs being specialized for different activities (eating, walking, swimming, making baby crawdads).

A  crawdad's body structure

A crawdad’s body structure

And some species of crawdads are both invasive and being invaded. North American crawdads were introduced to Europe in an effort to replace native stocks that were being lost to pollution; unfortunately, the new crawdads brought a disease with them that has done far more damage to the locals than pollution did. In many areas, the native, non-burrowing crawdads have been wiped out and the burrowing North American species are now doing extensive damage to river banks. But turnabout is fair play; in many parts of North America the local crawdads are being forced from their homes by invasive crawdads from China; the invaders are thought to be live bait crawdads and refugees from home aquariums, set free by well-meaning idiots.

If you’d like to help track the path of the invaders, then why not join CrayWatch?
http://craywatch.org

2 thoughts on “March 16 – Crunchy Crawlers

  1. Pingback: July 31 – You Otter Know – Little facts about science

  2. Pingback: July 31 – You Otter Know | Little facts about science

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