Lumbriculus is a small oligochaete worm which has easily visible internal organs and behaviors that can be observed. Their skin is thin and lets chemical through quickly. They are also easy to grow in a lab.

Lumbriculus variegatus (also called mudworms or blackworms) are tiny segmented worms found in shallow marshes and ponds throughout North America and Europe. They eat dead and decaying leaves or animals and have a complete digestive tract with a mouth and an anus. Their respiratory system is very simple—they have no lungs or gills but instead breathe through their skin.

Lumbriculus have a nervous system with a nerve cord, made up of many neurons, that runs along the entire length of the body, just below the intestines. This nerve cord controls the worm’s muscles and allows it to move. You can tell that the nervous system in Lumbriculus worms is working because they pull their head or tail quickly when it is touched—you should try this in the lab! Interestingly, Lumbriculus worms may also quickly withdraw their tail if a shadow suddenly occurs— they can sense the shadow with lots of tiny eyespots in their tail segments.

In this lab, you are going to examine the Lumbriculus circulatory system. The nervous system controls the circulatory system. Like our circulatory system, blood flows in blood vessels and capillaries. But unlike our circulatory system, you can easily see the dorsal blood vessel rhythmically pulsing to pump blood through the body. This makes Lumbriculus a model organism that is often used in laboratory investigations.