Crayfish and salamanders and Hickory Horned Devils — OH MY! What a time we had today at our weekly Nature Study class! We visited a mountain stream at the foot of Bays Mountain in Kingsport, Tennessee to learn about crayfish. But we learned about so. much. more.
The greatest diversity of crayfish species is found in southeastern North America, especially Appalachia (that’s us), with over 330 species.
Crayfish are detritivores (they eat detritus = decomposing plant and animal parts) but they also eat living plants and animals such as worms and insects. Raccoons, snakes, opossums and muskrats are the crayfish’s most dangerous predators.
The crayfish breathe through feather-like gills and tend to inhabit water bodies that don’t freeze all the way through to the bottom. Some species are found in brooks and streams where there is fresh water running, while others thrive in ponds, swamps and ditches. Most crayfish cannot tolerate polluted water, so if they are present the water is probably pretty clean.
Crayfish burrow during the late summer, and spend most of the fall and winter underground in water-filled tunnels. Everywhere you see a crawfish chimney, there is a crawfish living in a burrow underneath. Their tunnels may extend down into the earth 3 feet or more and are full of water. Sometimes the color and texture of the chimney mud is different at different levels of the chimney. Why might this be? This is a sign that there are different types of soil layers below the surface, and the crayfish has burrowed through several layers.
As the crawfish burrows down, it brings up soil from different layers and deposits the pellets of mud at the top of the chimney. https://www.youtube.com/watch?v=DSIY5oUaUr4
During droughts, crayfish routinely plug the openings of their burrows with mud. As the water table drops, or when the temperature drops, the animal moves further down to warmer water levels. Over time, oxygen may be depleted in the burrow water. When this happens, the crayfish may position itself just above the water, thus keeping the gills wet and absorbing oxygen from the air in the burrow.
Crayfish also lay eggs in their burrows. After they mate in open water, (the male depositing sperm into a special sac on the female’s abdomen) the female (and sometimes the male as well) will dig a burrow where the female will lay the eggs, fertilize them with the stored sperm, and hold them attached to little appendages under the tail called swimmerets.
Once the eggs are laid, the male typically stays near the entrance and the female remains deeper in the burrow. As long as oxygen levels in the burrow water are high, the female keeps the eggs under water and swishes them back and forth to ensure aeration (air circulation). As the oxygen drops, the female keeps the eggs moist, but gets them out of the water, thus allowing them to absorb oxygen from the air. https://www.youtube.com/watch?v=XHCWiISnu_4
The eggs usually hatch in the burrows and begin to grow. Since there is a restricted amount of food available in the burrow, the babies eat infertile eggs and the bodies of dead babies. They will even kill each other to survive.
After the hatching, with her brood still attached, the female emerges from the burrow to find food. Once she is in open water, the hatchlings detach from their mother and begin living independently.
A young crayfish molts 11 times before becoming an adult. This takes about a year. They will live another year to mate and produce young. In this video, the carapace (shell) completely detaches about 5 minutes in: https://www.youtube.com/watch?v=mF6NgMBcNCM
In 2011 a new species of giant crayfish was discovered in Shoal Creek, a tributary of the Tennessee River. “A new species of giant crayfish [has] literally crawled out from under a rock in Tennessee, proving that large new species of animals can be found in highly populated and well-explored places,” Reuters reported. Aquatic biologists had been studying life in that little waterway for decades, but it appears these crayfish are not common (only 5 have ever been caught) and their preference for living under large rocks in deep water may have made them easy to overlook, especially in times of high water. After DNA testing and studying a ridge and unique spine between the crayfish’s eyes, the biologists knew they were looking at something entirely new, and named it Barbicambarus simmonsi (after TVA scientist Jeffrey Simmons — the guy who first spotted this giant).
Here’s a video about the discovery which gives some interesting insight into how these creatures are measured and catalogued. https://www.youtube.com/watch?v=e05nqc1ygYg
We spread out along the length of the creek. We haven’t had much rain lately so the water was low. Within 15 minutes the class had collected about 30 samples of crayfish at all different stages of development and a couple of baby salamanders.
Then a shout went up: Look what was found crawling along on the creek bank!
It’s a Hickory Horned Devil Caterpillar that will dig a hole in the ground and after pupating through two winters will emerge as a beautiful, huge Royal Walnut Moth!
And if that’s not enough, look who else came to call: