Volume 50, Number 1, December 2003:
A Toxicology Primer for Student Inquiry: Biological Smoke Detectors

Text-only version

ISSUE HOME PAGE

ABOUT THIS ISSUE
- about KSN
- about the author
- acknowledgements

IN THIS ISSUE
- disclaimer, objectives
- "biological smoke detectors"
- purpose of invertebrate toxicity testing
- lethal and sublethal effects
- some wormy ideas for toxicity testing
- sublethal chemical effects in lumbriculus
- selecting the chemical(s)
- safety
- exposure methods
- preliminary experiments and concentration range-finding
- final stages of toxicity testing
- typical equipment and supplies
- other organisms, other ideas
- obtaining background information
- references
- glossary of toxicological terms

A Toxicology Primer for Student Inquiry:
Biological Smoke Detectors
by Charles Drewes

SOME WORMY IDEAS FOR TOXICITY TESTING

Freshwater organisms, such as aquatic oligochaetes are good choices for toxicity testing because: (1) they are important parts of aquatic ecosystems and food chains, (2) they are exposed to many chemicals that contaminate water and sediments, and (3) certain freshwater species, such as Lumbriculus variegatus (the blackworm or mudworm; Figure 3A), have been used previously for studying toxicity effects.  Lumbriculus is cheap (commercial or field sources), easily cultured in the lab (asexual reproduction), and simple to handle (Drewes, 1996b).  Most important, there are interesting aspects of this worm’s biology that may be useful indicators of toxicity (Rogge and Drewes, 1993; Drewes, 1997; Lesiuk and Drewes, 1999). 

[Note that the genus Lumbriculus is very different from the mud-dwelling genus Tubifex.  Lumbriculus displays unique locomotor behaviors, such as helical swimming (Figure 3B) and reversal (Drewes, 1999; Drewes and Cain, 1999).  Tubifex are much less acrobatic and display neither of these behaviors.]   

Figure 3.  The segmented oligochaete, Lumbriculus variegatus, is widely distributed throughout the U. S. and easily cultured in the laboratory.  Several behavioral and physiological features of this worm may be sensitive indicators of sublethal toxicity effects.   A)  Diagram of an untreated, whole worm showing prostomium (P) and dorsal blood vessel (D).  B)  Two freeze-frame images of the cork-screw shape of a worm’s body during helical swimming -- a normal response to tail touch when the worm is in open water.  Note that the first wave (B1) has a counter-clockwise, or left-handed helical orientation.  The second wave, occurring about 1/10 sec later, has a clockwise, or right-handed, orientation.  [For details, see Drewes, 1999; Drewes and Cain, 1999].