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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
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