SMART Science

July/August 2008

Are You my “Cousin”?

Sometimes it is pretty easy to tell if people are related to one another. Often the family members have what we call family traits, or characteristics. In the animal kingdom, animals that are “related” have certain characteristics in common as well. As you are exploring outdoors this summer, you may see many different types of living things, or organisms. When organisms are grouped together for study they are grouped based on characteristics. How do you know if they are “related”?

If you tried the Crayfish Search activity in the May/June 2008 issue of Ohio Valley Parent, you may have found one or more examples of arthropods. Arthropods are thought to be the most successful and abundant animals on earth! There may be over 4 million species of arthropods, and we haven’t even identified all of the species.

Crayfish are a type of arthropod. There are many kinds of crayfish, but all of them have certain characteristics in common. Some crayfish live in streams or rivers, but some dig tunnels and live on land (the burrow has some water in it because crayfish have gills). To learn more about digging crayfish, read Zac Loughman’s article in the Spring 2008 issue of West Virginia Wildlife magazine. Zac is the Natural History Research Specialist at West Liberty State College and would appreciate any information you have about where you have seen digging crayfish or evidence of them (such as their burrows). Contact him with this information at WestVirginiaCrayfish@gmail.com or call 336-8923. Photographs of the animal are also very important to the study.

Maggie Marra holding a millipede at the SMART-Center in 2006

How is a crayfish different than the millipede shown in the photo? How is it the same? How is a crayfish different than a grasshopper? How is it the same? How is a crayfish different than a spider? How is it the same? All of these animals are arthropods. What characteristics do you think arthropods have in common with one another?

All arthropods have an exoskeleton. This hard, protective outer covering keeps the arthropod from drying out quickly but helps it in other ways, too. When an arthropod grows too large for its exoskeleton, it molts, or sheds this outer covering. The old exoskeleton often looks exactly like the animal itself, except it is hollow! The animal will have another exoskeleton that is getting hard under the old exoskeleton.

All arthropods have segments, or sections, to their bodies and have jointed legs or feet. The word arthropod actually means “jointed feet”. Arthropods are cold-blooded, meaning they cannot warm up their body temperature when it is cold or cool their bodies when it is hot. They will be the same temperature, or close to the same temperature, as their surroundings. To learn more about arthropods, visit our website at www.smartcenter.org/ovpm/arthropods.

The millipede and the crayfish in the photos are arthropods. Sometimes people (before they look closely) think the millipede may be a worm because it resembles a worm with LOTS of feet! Millipede means “thousand feet” but this species actually only has a couple of hundred feet. Both the millipede and the crayfish have an exoskeleton, jointed feet and a segmented body. They are sort of like “cousins”!

Robert E. Strong is the director of the West Liberty State College SMART-Center, the hands-on science center of the Northern Ohio Valley. Libby Strong is the Program Coordinator at the West Liberty State College SMART-Center and also directs the WV-Handle On Science Program that brings hands-on science kits to the public school classrooms of the Northern Panhandle. Richard Pollack is the assistant program coordinator, webmaster, and technology specialist for the WLSC SMART-Center. Robert, Libby, and Richard invite you to visit the website at www.smartcenter.org