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

SUBLETHAL CHEMICAL EFFECTS IN LUMBRICULUS 

Possible sublethal effects in blackworms include changes in body shape or behaviors such as swelling, coiling, rigidity, convulsions, limpness, paralysis, ataxia, hyperactivity, constrictions, or segment autotomy (body fragmentation).  Some chemicals may cause changes in body color due to circulatory effects such as blood pooling or blood loss in different body regions, especially the tail end.  Also, there may be important and interesting effects on other body functions that are only evident with more detailed inspection and testing of treated and normal worms. 

One function that may be useful and relevant to both ecological and medical toxicity testing is the pulsation rate of the worm’s dorsal blood vessel (Figure 3A).  Just as in humans, pulsation rates in worms may speed up or slow down as a result of toxicant exposure.  Lesiuk and Drewes (1999) describe methods for measuring pulsations rates in the dorsal blood vessel before, during, and after exposure to common pharmacological agents such as nicotine and caffeine. 

Other functions that may be potentially affected by toxicants include locomotor behaviors such as swimming (Figure 3B), crawling, and body reversal -- all behaviors that are easily evoked and readily measured (Drewes, 1999; Drewes and Cain, 1999).   These functions have special environmental relevance because they relate to the worm’s ability to move about within its environment and escape from predators. 

Another biological process that is easily studied and measured is regeneration of head and tail segments (Drewes, 1996a).  Regeneration of lost segments is a key developmental process that has great adaptive significance to worms.  It is a means for restorative growth following loss of segments, which frequently occurs in nature as a result of predatory attack or spontaneous fragmentation; the latter is a normal mechanism for asexual reproduction in these worms.

These are only suggestions for sublethal effects.  Many other effects (physiological, biochemical, and behavioral) likely occur which may also be amenable to study, but there has been very little research study or publication of any such effects.  This should be viewed as a great opportunity and source of motivation for students to make novel and significant contributions using such toxicity assays.