Those Wonderful Worms
Carolina Tips 1996

Charles D. Drewes, PhD
Department of Zoology and Genetics
Iowa State University
Ames, IA 50011

Science fiction writers often tantalize their readers by conjuring up creatures with bizarre combinations of biological traits and powers. Similarly, teachers often muse longingly for the "perfect" animal for their classroom. Imagine for a minute an animal with transparent skin and red blood pulsating in a heart that is as long as the creature's body. This creature can endure being cut up into many pieces without bleeding or dying and can create a new head or tail, or both, from severed body pieces. It swims, without fins or appendages, by making twisting, corkscrew-like motions of its whole body, and it uses its tail to detect an approaching shadow. Conveniently for you, it lives just beneath the water's surface at the edges of murky ponds and marshes-perhaps even near your home or school.

Impossible, you say? Not at all. In fact, the creature I've described is a common freshwater annelid, Lumbriculus variegatus. Also known as a California blackworm, or mudworm, Lumbriculus variegatus. (Fig. 1) is a member of the Order Lumbriculida, a small subgroup of oligochaetes that includes neither earthworms nor freshwater tubifex worms. About 1­2 inches in length, blackworms are found in sediments and submerged organic debris­­especially along the shallow margins­­in ponds, marshes, and lakes throughout North America. Despite being widely distributed and having many interesting features, blackworms seem to have escaped the attention of most biology teachers and researchers.

Figure 1 The California blackworm, Lumbriculus variegatus.

Blackworms are exceptionally hardy and easy to raise at home or in your classroom, making them readily available year long. With a little patience and imagination, keen eyes, and insights from this article, you and your students can discover and share many intriguing aspects of biological organization and behavior. This worm should provide a variety of new insights and simple, enlightening investigations for your class or lab. No extensive training or expensive equipment is needed; in fact, all of the following laboratory activities have been done with little or no special apparatus or dexterity.

Mature blackworms, usually composed of about 150­250 segments, are hermaphroditic (that is, they contain both male and female sex organs). Sexual reproduction, presumed to be rare, involves direct embryonic development within a cocoon. Asexual reproduction by self-fragmentation is common. Under laboratory conditions, this seems to be the worm's sole means of reproduction.

part 2
© Carolina Biological Supply Compagny, Article used by permission