Effects of Drugs on Pulsation Rate of Lumbriculus variegatus ...

This article reprinted from: 

Bohrer, K.E. 2006. <strong>Effects</strong> <strong>of</strong> drugs on pulsation rate <strong>of</strong> Lumbriculus variegatus 

(blackworms). Pages 127-146, in Tested Studies for Laboratory Teaching, Volume 27 

(M.A. O'Donnell, Editor). Proceedings <strong>of</strong> the 27th Workshop/Conference <strong>of</strong> the 

Association for Biology Laboratory Education (ABLE), 383 pages. 

Compilation copyright © 2006 by the Association for Biology Laboratory Education (ABLE) 

ISBN 1-890444-09-X 

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<strong>Effects</strong> <strong>of</strong> <strong>Drugs</strong> on Pulsation Rate <strong>of</strong> Lumbriculus 

variegatus (Blackworms) 

Kelly E. Bohrer 

Department <strong>of</strong> Biology 

University <strong>of</strong> Dayton 

300 College Park 

Dayton, OH 45469-2320 

bohrerke@notes.udayton.edu 

Abstract: In this investigative lab, students observe blackworm pulsation rate in normal conditions and 

observe how pulsation rate is affected by drugs. This lab stresses the circulatory system, but can also be 

used for homeostasis, behavior, toxicology, and nervous system labs. Part I guides the student through 

blackworm handling procedures and initial observations <strong>of</strong> the blackworm’s behavior and circulatory 

system. Part II is a student-led investigation in which the students design and run their own experiments 

to test drug effects on pulsation rate. The students write their investigations as an informal report and 

orally present their design, results, and conclusions. 

Keywords: blackworms, Lumbriculus variegatus, pulsation rate, circulatory system, blood vessels, 

student designed investigations 

©2006 Kelly Bohrer 

This major workshop paper is dedicated to and in memory <strong>of</strong> Dr. Charles Drewes. 

Contents: 

Introduction 128 

Student Outline 130 

Materials 138 

Notes for Instructor 139 

Acknowledgements 143 

Literature Cited 143 

About the Author 143 

Appendix A: Recipes for Drug Solutions 144 

Appendix B: Preparation Notes 145 

Association for Biology Laboratory Education (ABLE) 2005 Proceedings, Vol. 27:127-146

128 ABLE 2005 Proceedings Vol. 27 Bohrer 

Introduction 

Background 

Blackworms (Lumbriculus variegatus) are excellent organisms for studying the circulatory system 

and the effects <strong>of</strong> drugs on this system for three main reasons: their skin is transparent making it easy to 

observe pulsation rates, drugs quickly diffuse through the skin <strong>of</strong> blackworms thus providing immediate 

effects, blackworms are easy to maintain in a laboratory. In blackworms, the dorsal blood vessel pumps 

oxygenated blood from the posterior to the anterior end by muscular contractions in each segment. At 

any time, several pulsation waves travel the length <strong>of</strong> the worm at a constant rate. Much like in humans, 

the pulsation rate is regulated by the nervous and endocrine systems. Since many drugs affect these 

systems (e.g. nicotine mimicking natural neurotransmitters), they can affect the rate <strong>of</strong> pulsation in 

bloodworms. In this investigative lab, students observe blackworm pulsation rate in normal conditions 

and observe how pulsation rate is affected by drugs. 

In addition to the blackworm circulatory system, this lab stresses the following skills: scientific 

process/inquiry, collaborative group work, critical thinking, verbal and written, data collection and 

analysis, and working with live animals. Part I is designed to teach blackworm handling and viewing 

procedures and to guide the student through initial observations <strong>of</strong> the blackworm’s behavior and 

circulatory system. Part II is a student-led investigation in which the students develop their own 

hypotheses and design and run their own experiments. The students write up their investigations as an 

informal report and orally present their design, results, and conclusion at a later date. 

In its current context, this lab exercise is completed in a two hour, non-major’s lab course. The lab 

course is an introduction to biology that is meant to supplement the lecture course material. When this 

lab exercise is performed, the students are learning about the human organ systems in lecture, including 

the circulatory system. Prior to this lab exercise, the students have learned about the scientific process 

and have designed a mini-investigation, including formulating an hypothesis, identifying a control, 

identifying independent and dependent variables, analyzing results, and drawing conclusions. 

Therefore, the lab content and process is not difficult for the students to understand; however, the 

handling <strong>of</strong> the blackworms and the counting <strong>of</strong> the pulsation rate can be tricky. Therefore, it is 

necessary that students are given sufficient practice with calculating pulsation rate before coming to lab 

(by visiting the website indicated in the student outline) and given some time at the beginning <strong>of</strong> lab to 

handle the worms (15-20 minutes). Other prerequisite knowledge and skills required for this lab include 

microscope usage and evaluating outside sources <strong>of</strong> information on the internet. 

This lab can easily be modified and/or expanded to a three hour and/or advanced biology lab (see 

instructor notes). It can be adapted for lab exercises focused on homeostasis, toxicology, environmental 

biology, behavior, or physiology. For example, students could calculate the Q 10 <strong>of</strong> blackworms’ 

pulsation rate, test one or more physiological responses to external stimuli (pollution, acid rain, exercise, 

salinity, etc.), observe regeneration <strong>of</strong> blackworm fragments, or explore acute and chronic exposure to a 

toxicant. 

There are many resources available for learning about blackworms and learning how to handle them 

and experiment with them. In addition to the background information and reference publications in the 

literature cited, you can also find a lot about blackworms on websites, especially Dr. C. Drewes website: 

http://www.eeob.iastate.edu/faculty/DrewesC/htdocs. Additionally, teachers attending the 1996 

Woodrow Wilson National Leadership Program have developed many similar blackworm lab activities, 

which can be found on various websites.

Pulsation rate <strong>of</strong> blackworms 129 

Lab Exercise Objectives 

1. Identify blackworms. 

2. Explain and identify key features and functions <strong>of</strong> the blackworm’s circulatory system. 

3. Describe blood vessel pulsations <strong>of</strong> a blackworm. 

4. Measure pulsation frequency and velocity. 

5. Explain the effect <strong>of</strong> drugs on the circulatory system <strong>of</strong> blackworms. 

6. Design and implement an investigation using blackworms. 

7. Present results and conclusions both in writing and orally. 

Timeline for Lab Activities 

Culturing/buying worms 

Cutting worms 

Making solutions 

Time needed for preparing lab 

In-lab timing: 


Selecting and Handling worms 

Determining Baseline Rate (Part I) 

Designing Experiment (Part II) 

Running Experiment 

Start culturing 2-4 weeks in advance 

24-48 hours in advance 

24 hours in advance 

~5 hours if viewing slides have been 

previously made 

10 minutes 

15 minutes 

30 minutes 

20 minutes 

45 minutes 

History <strong>of</strong> Blackworms in Biology Teaching Labs 

Prior to 1996, Lumbriculus variegatus was well known among fish hobbyists. Thanks to Dr. Charlie 

Drewes, the wonderful world <strong>of</strong> blackworms was introduced to biology teachers all over the nation by 

Dr. Drewes’ Carolina Tips article in 1996 and by his guest appearance (as an instructor) at the 1996 

Woodrow Wilson Institute at Princeton. Teachers from this institute have developed and shared many 

blackworm related lab ideas, which has made this lab exercise possible. Additionally, much information 

about culturing, handling, and viewing blackworms was gained through Dr. Drewes’ website and other 

compositions.



Student Outline 

Purpose for This Lab 

This lab activity serves three purposes: to introduce you to the circulatory system <strong>of</strong> blackworms, to 

demonstrate the effects <strong>of</strong> drugs on the circulatory system <strong>of</strong> blackworms, and to provide additional 

experience in designing and performing your own lab investigation. By the end <strong>of</strong> this lab, you will be 

able to identify blackworms, explain and identify key features and functions <strong>of</strong> the blackworm’s 

circulatory system, describe blood vessel pulsations <strong>of</strong> a blackworm, measure pulsation frequency and 

velocity, explain the effect <strong>of</strong> drugs on the circulatory system <strong>of</strong> blackworms, design your own 

investigation using blackworms, and present your results and conclusions both in writing and orally (due 

at the end <strong>of</strong> the semester). 

Function <strong>of</strong> a Circulatory System 

A circulatory system is needed by any animal that is too large and/or complex to obtain essential 

chemicals by the process <strong>of</strong> diffusion alone. Most importantly, a circulatory system quickly transports 

nutrients, oxygen, and other important chemicals to all body cells. Circulatory systems have three 

components: circulating fluid (blood or hemolymph), a heart or pulsating vessel which pumps the fluid, 

and vessels through which the fluid travels. There are two types <strong>of</strong> circulatory systems, closed and 

open. Open circulatory systems have vessels that are open at one end allowing hemolymph fluid to 

flow out among the cells. Most mollusks and arthropods have an open circulatory system. In a closed 

circulatory system, the fluid is called blood and this blood remains within the vessels as it rapidly 

circulates the body. Vertebrates and annelids have a closed circulatory system. The pumping <strong>of</strong> blood 

or hemolymph in a circulatory system is achieved by regular muscular contractions. The rates <strong>of</strong> these 

contractions can be regulated either by hormones or by neurotransmitters released by nerve cells. 

Lumbriculus variegatus 

Blackworm is the common name for Lumbriculus variegatus, a freshwater oligochaete worm in the 

phylum Annelida (earthworms and leeches are also in this phylum). Blackworms can be found 

naturally in stagnant water along edges <strong>of</strong> marshes and ponds where they feed on small living and 

decaying organisms. You can also find these worms at local tropical fish stores since they are great food 

for pet fish. Blackworms are small worms, ranging from 4-6cm in length (~150 body segments with 

head region containing 7-8 segments) in lab conditions, and up to 10cm in length in their natural 

habitats. 

Blackworms have several complex organ systems including a closed circulatory system, which 

transports nutrients and oxygen; a complete digestive tract; and a nervous system, which includes a brain 

and a nerve cord. Using their nervous system, the blackworm can respond very quickly to shadows, 

touch, and vibrations by swimming, crawling, or performing a body reversal (rapidly coils and uncoils to 

turn itself around). These worms obtain oxygen through their skin on their tail; hence the reason they 

can <strong>of</strong>ten be found with their tails hanging out at the water surface. Unlike many other animals, sexual 

reproduction is rare in blackworms; instead, it commonly multiplies by fragmentation and 

regeneration. The worms will simply split into two or more sections, and each section will grow a new 

head and/or tail. You may notice that some blackworms are darkly pigmented at one end compared to 

the rest <strong>of</strong> the worm – the dark area is the original fragment (Drewes, 2003; Drewes 1996).


Pulsation Rate <strong>of</strong> Lumbriculus variegatus 

Today you will be observing the pulsation rate <strong>of</strong> blackworms. The blackworm has a large dorsal 

blood vessel that is very easy to see using a microscope because the skin <strong>of</strong> the worm is transparent. 

This dorsal blood vessel pumps oxygenated blood from the tail (which is usually kept towards the 

surface <strong>of</strong> water) to the head <strong>of</strong> the worm by using rhythmic muscular contractions. The blood returns 

to the posterior end <strong>of</strong> the tail via the ventral blood vessel, which is not pulsatory and is connected to the 

dorsal blood vessel via small vessels in the first 1-18 body segments <strong>of</strong> the worm. In addition, to aid in 

the pumping <strong>of</strong> the blood, most body segments have a pair <strong>of</strong> lateral, pulsatory vessels that do not 

connect to the ventral blood vessel. 

At any one time, you can see several pulsation waves along the length <strong>of</strong> the worm. Blood vessel 

pulsation rate in blackworms is partially controlled by neurotransmitters that are secreted by nerve cells 

(very similar to control <strong>of</strong> human heartbeats). The frequency (how many beats/waves per minute) and 

the velocity (distance traveled per minute) <strong>of</strong> the pulsations can easily be calculated by observing the 

pulse in the middle section <strong>of</strong> the worm (Lesiuk and Drewes, 1999). Because the rate <strong>of</strong> pulsation is 

easily seen and calculated and some chemicals can easily diffuse through the worm’s thin skin, it is easy 

to test the effects <strong>of</strong> exposure to different chemicals on the cardiovascular system <strong>of</strong> the blackworms. 

This is what you will be doing for the second part <strong>of</strong> today’s lab. During the first part <strong>of</strong> today’s lab you 

will be performing baseline observations <strong>of</strong> the behavior and pulsation rate <strong>of</strong> blacworms. 

Safety Precautions, Disposal, and other Notes 

1. Dispose <strong>of</strong> glass waste in the glass boxes 

2. Handle organisms with care 

3. Handle microscopes with care. 

4. Report broken equipment, slides, etc. to the TA. 

5. Making slides and cutting worms can result in minor wounds. Please take the necessary 

precautions to avoid injury and report all cuts, however minor, to the TA. 

Pre-Lab Assignment 

1. Before lab begins, you will need to become familiar with blackworms and how to accurately measure 

the dorsal blood vessel pulsation rate for the worms. Below is the URL for a website (Drewes, 2001) 

that you should access before lab this week. This website provides a close up view <strong>of</strong> a blackworm 

body segment (these are segmented worms) and shows you how blood pulsation occurs in a worm. 

Read the directions and answer the questions for BOTH the posterior end <strong>of</strong> the worm and the mid-body 

section <strong>of</strong> the worm. 

http://www.eeob.iastate.edu/faculty/DrewesC/htdocs/INT-ANIMA-LvDBV-mid.htm 

2. What types <strong>of</strong> chemical compounds affect the heart rate <strong>of</strong> humans Perform an internet search to 

find the names <strong>of</strong> at least two chemical compounds that affect the heart rate <strong>of</strong> humans. In what way 

does the heart rate change when humans are exposed to these compounds (increase or decrease) and 

how does that change occur Please remember to cite the name <strong>of</strong> any websites, books, articles, etc. that 

you use.


Part One: Baseline Observations 

In this part <strong>of</strong> the investigation, you will observe “normal” behavior and basal pulsation rate for 

living blackworms. Make careful observations, sketch what you see, and record relevant data. Make 

sure that both people get the chance to observe the worms’ pulsation rates using the microscope! At the 

end <strong>of</strong> this initial investigation, you will be combining class data. 

Important Notes 

• The basal pulsation rate is generally greater at the tail end <strong>of</strong> the worm because many pulsations 

starting at the tail end never make it all the way to the other end <strong>of</strong> the worm. Therefore, when 

you observe the pulsation rate <strong>of</strong> the dorsal blood vessel, make sure to observe a mid-body 

section <strong>of</strong> the worm and to always view the same segment throughout the entire investigation. 

• Never use tap water with these worms! The chlorine in the tap water is toxic to the worms. Use 

spring water and/or aged tap water for all parts <strong>of</strong> this experiment. 

• Never use forceps or sharp objects to touch the worms – they are very fragile! 

• Several factors can affect the behavior and the viewing <strong>of</strong> the worms = temperature, age, health, 

direct light exposure, etc. Therefore, talk to your lab instructor if you have problems with a 

particular worm. 

Procedure 

1. Fill both <strong>of</strong> your specimen bowls with spring water to a depth <strong>of</strong> approximately 2cm. 

2. You will now select 5-10 worms that are equal in size. Avoid picking any worms that have 

recently regenerated (worms that have a dark pigmented area and a lighter pigmented area). To 

remove your worm from the water, you will need to use a plastic pipette. Gently suck up the 

worm with a little bit <strong>of</strong> water and place into your specimen bowl. 

3. You will also need to select 5-10 cut worms from the bowl at the TA desk. The anterior third 

and the posterior third <strong>of</strong> the worm were cut <strong>of</strong>f yesterday and placed in another bowl for 

regeneration. You will be using the middle third <strong>of</strong> the worm for the second half <strong>of</strong> this lab since 

this is easier to work with than a whole worm. The worms were cut yesterday to give the ends 

time to heal for today’s lab. Before using these worm segments for the second part <strong>of</strong> today’s 

lab, you will need to determine if the pulsation rate <strong>of</strong> the middle third is similar to the pulsation 

rate <strong>of</strong> the mid-body segments <strong>of</strong> a whole worm. Why do you think we need to determine 

this 

4. Obtain 5-10 middle third worm segments and place them in the second specimen bowl. 

5. Watch the whole worms – what are they doing How are they moving Are they clumpled 

Swimming Record in your notes what you observe. Can you identify the head end <strong>of</strong> your 

worms The head segments are generally darker, wider, and more blunt than the tail end. When 

you observe these worms with the microscope, you should also be able to tell the difference 

between the head and tail ends by how the blood vessel pulse moves (from tail to head). 

6. Remove a whole worm from your bowl with a plastic pipette. 

7. Place the worm into the trough on the well slide. Gently remove any excess water with a 

chemwipe and place a coverslip over the worm. Wait a minute or two for the worm to adjust to 

the trough (stop wiggling).


8. Place the slide on the microscope and observe the worm at scanning power (4x) or using a 

stereoscope. 

*NOTE: Since intense light exposure can fry your worms and/or make them hyperactive, use a 

low amount <strong>of</strong> light and avoid exposing your worms for long periods <strong>of</strong> time to the light. 

9. Find a segment as close to the middle <strong>of</strong> the worm as possible. Count the number <strong>of</strong> pulsations 

that pass through this point on the worm over 30 seconds. Multiply this by two to get rate per 

minute. Repeat this procedure two more times. Then, find the average pulsation rate per minute 

(record data in Table 1). 

10. Place this worm into a weigh boat containing a small amount <strong>of</strong> spring water (just enough to 

cover the worm). Label the weigh boat so that you can recall which worm is where. 

11. Obtain another worm and have your partner run through #6-9 with this worm. This worm should 

be placed in a different weigh boat. Record the data in Table 1. 

12. Run through #6-9 using a third worm. Place this worm into its own weigh boat too. Record 

your data in Table 1. 

13. Now, run through #6-9 using three <strong>of</strong> the middle third segment worms. Record your data in 

Table 1. 

Table 1. Basal Pulsation Rate for Uncut and Cut Blackworms 

Uncut Blackworms 

1 

Average Pulsation Rate 

2 

3 

Average Rate for Uncut: 

Cut Blackworms 

1 

2 

3 

Average Rate for Cut: 

Discussion 

1. Put your results on the board. Your TA will calculate the average pulsation rate for both the cut 

and uncut worms for the entire class. What is the class average for the cut worms For the uncut 

worms 

2. How did the class average pulsation rate for the cut worms compare to the class average for the 

uncut worms


3. Explain why the results are different or similar. What could have caused a difference if there is 

one 

4. For data to be reliable, your data need to be accurate and reproducible. How have you achieved 

this 

Part Two: Investigating the <strong>Effects</strong> <strong>of</strong> <strong>Drugs</strong> on Pulsation Rate in Lumbriculus variegatus 

In this part <strong>of</strong> the lab, you will get the chance to design your own investigation. Certain chemicals 

and drugs can greatly affect organ system function. Today, we will be looking at the effect <strong>of</strong> drugs on 

the circulatory system <strong>of</strong> blackworms. Based on the research you performed for pre-lab and the 

chemical compounds that your TA has available, you will design an investigation to see how pulsation 

rate changes in response to exposing your worms to drugs. You have several options on how to design 

this – you can investigate the effects <strong>of</strong> one or more drugs, investigate the effect <strong>of</strong> different 

concentrations <strong>of</strong> a drug, investigate the effect <strong>of</strong> the length <strong>of</strong> exposure time to the drug, and/or you can 

investigate the length <strong>of</strong> time it takes for the worms to recover from the effects <strong>of</strong> the drug. 

Before beginning your investigation, please review information about setting up an investigation, 

paying close attention to the necessary factors for a sound investigation (control, limiting variables, etc.). 

Also, before you begin your procedures, talk to your TA about hints and suggestions for running this 

type <strong>of</strong> investigation. 

For your investigation, use the pre-cut worms (the middle body segments that you used in the 

baseline observations earlier). If you need to use more worm segments, remember to first obtain a 

baseline pulsation rate for each worm! Also, make sure to rinse your worms before placing them in the 

trough and/or rinse your trough between observations so that you do not contaminate other worms. 

Design Your Experiment 

Before you begin, describe your experiment below and show your description to your TA. Do not 

proceed with your experiment until your TA has given you the go-ahead. 

• What would you like to investigate 

• What is your hypothesis 

• What is your dependent variable (what will you measure) 

• What is your independent variable 

o Why do you think this independent variable will affect the pulsation rate 

o How do you think this variable will affect the pulsation rate 

• What is your control Be very specific! 

• How will you include replications


• What results would support your hypothesis 

• Describe your methods: 

• What materials will you need 

• What do you predict will happen 

Perform Your Experiment 

As you carry out your experiment you will want to record your procedures, results (including table/s 

to collect data and observations), and conclusions in a notebook. Be thorough and detailed as you 

record your results. If you have problems, questions, and/or errors during the experiment, be sure to 

write these down. Use the following information to guide you in writing your results and your 

conclusions: 

• Results - Describe your results in general. Do not explain why you got these results yet. Decide 

how best to present your results – as a table and/or as a graph – and then complete your tables 

and/or graphs before you interpret your results. You can use excel to design graphs. 

• Conclusions – 

o Look back at your hypothesis and look at your tables and graphs. Do your results support 

or refute your hypothesis Explain by using your data as evidence. 

o Do your results match what you predicted above Why or why not Explain. If they are 

not what you predicted, explain what may have occurred. 

o If you had an opportunity to redo this experiment, how might you do it differently to 

make it more convincing 

o Answer the summary questions below 

Summary Questions 

1. What was the reason for using more than one animal for each test Did all animals respond in 

the same way Why or why not What factors might influence individual response What 

implications does this have for the effects <strong>of</strong> drugs on humans 

2. Describe how the drug affected pulsation rate. Why do you think your results occurred 

3. Would your drug be classified as a depressant or a stimulant Why 

4. What behavior characteristics did you note Are they different than the behavior <strong>of</strong> the 

unexposed worms


Cleanup 

1. Return all worm segments exposed to chemicals to the recovery bowl (do not dump chemicals 

into this bowl –rinse your worms in spring water first). 

2. Return all unexposed worm segments to the regeneration bowl. 

3. Return all unexposed whole worms to the other bowl. 

4. Dispose <strong>of</strong> chemical waste appropriately 

5. Clean <strong>of</strong>f all slides really well 

6. Turn <strong>of</strong>f your microscope, clean the lenses with microscope lens paper, and put away your 

microscopes 

Poster Presentation Information 

Refer to Table 2 for grading information. You should present the sections <strong>of</strong> the poster on one 

posterboard. You may use illustrations, pictures, drawings, etc. – be creative but don’t include irrelevant 

information! Use a large font – something that can be read from 5 feet away. Single spacing is fine. 

Label each part well (and in bold). All written parts should be in complete sentences and in paragraphs 

(no bulleting). 

Introduction: 

The purpose <strong>of</strong> this section is to explain why you are performing this experiment and to provide 

background information necessary to understand the framework <strong>of</strong> the experiment. Here you want to 

describe the role <strong>of</strong> the cardiovascular system and discuss factors that can influence it (including “how” 

and “why” these factors may change the pulsation rate). You also want to describe the organism we are 

studying in lab and why we chose to use this organism. Then, you want to provide information about 

the chemical you chose to test. Explain what is known about the chemical and then state what you 

expected to see when you tested the chemical. Why did you expect this The last paragraph typically 

states your original question. 

Materials and Methods: 

This section should describe in moderate detail how the experiment was performed, and should 

include the explanation <strong>of</strong> controls and the number <strong>of</strong> replicates performed. 

Results: 

This section is where the data is presented. Data should be presented as tables and graphs with 

titles/brief explanations. No conclusions should be in this section. 

Conclusions: 

The conclusion should explain the results that you obtained and if your hypothesis was or was not 

supported. This section should also include answers to any summary questions from the lab. 

References: 

Cite any outside information that you used when writing the introduction, material and methods, 

and/or conclusions. See examples in book for correct format.


Reflection Paper 

Describe what you learned from this lab/process. Discuss what you liked about the lab and any ways 

that this lab might be improved. 1-2 pages double-spaced. 

Prelab 

Assignment 

Question 

Investigated 

Experimental 

Design 

Poster 


Materials and 

Methods 

Results 

Conclusions 

References 

Grammar 

Organization 

Creativity 

Reflection Paper 

Table 2. Grading Rubric for Investigation, Poster Presentation, and Reflection Paper 

1 point 2 points 3 points 4 points Score 

In complete in Partially incomplete, Does not thoroughly discuss Completed on time, 

more ways no effort shown, no #2, does not have accurate correct information, #2 

than one references 

answers for #1, and/or does not thoroughly discussed and 

Not related to 

topic and not 

testable 

Lacking 3 or 

more <strong>of</strong> the 

criteria for a 

good 

experiment 

Question not 

identified 

and/or 

summary 

incomplete 

Not sequential, 

most steps are 

missing or 

confusing 

Incomplete 

information 

including other 

problems 

Presents an 

illogical 

explanation <strong>of</strong> 

findings and 

doesn’t address 

original 

question 

Missing 

citations and 

not in correct 

format 

Very frequent 

grammar or 

spelling errors 

Disorganized, 

incorrect 

placement <strong>of</strong> 

parts, not neat 

Lacking 

creativity 

Incomplete, no 

depth, not 

interesting 

Addresses too many 

variables and/or not 

related 

Lacking 2 <strong>of</strong> the 

criteria for a good 

experiment 

Summary <strong>of</strong> 

background 

information is not 

complete 

Some <strong>of</strong> the steps are 

clear, most are 

lacking detail and are 

confusing 

Mostly complete 

information, but 

inaccuracies, 

mislabeling, and 

confusion 

Presents an illogical 

explanation <strong>of</strong> 

findings 

Missing citations but 

in correct format 

reference websites 

Not in correct format, but is 

testable and related 

Lacking one <strong>of</strong> the criteria for a 

good experiment 

Identifies question. Summary 

<strong>of</strong> background information 

complete, but not clear and/or 

concise 

Most <strong>of</strong> the methods are 

understandable, some lack 

detail or are confusing 

Information accurate. Labels 

missing and/or information is 

not clear 

Presents an explanation <strong>of</strong> 

findings and addresses original 

question, but is not clear and/or 

complete 

Citations not in correct format 

referenced 

Directly related to prelab 

research findings, testable, 

correct format 

Includes control, only one 

experimental variable, 

design directly answers 

original question, other 

variables kept constant 

Identifies question 

investigated. Provides a 

clear and concise 

summary <strong>of</strong> necessary 

info (see below) 

Clear and concise 

summary <strong>of</strong> methods used 

with adequate detail 

Tables and graphs 

complete, accurate, well 

labeled, and clear. Clearly 

written summary <strong>of</strong> trends 

Presents a clear, complete, 

and logical explanation <strong>of</strong> 

findings, with evidence, 

and addresses the original 

question 

Everything outside source 

is cited, citations are in 

correct format 

More than 2 errors Only one or two errors All grammar and spelling 

are correct 

Somewhat organized, 

lacking flow, 

incorrect placement 

<strong>of</strong> parts 

Creative, but the 

creativity causes 

design problems 

Somewhat 

incomplete and 

lacking depth 

Mostly organized, some parts 

are out <strong>of</strong> place or do not flow 

well 

Poster and question 

investigated somewhat creative 

Complete, but lacking depth 

and/or creativity 

Very well organized, 

everything in correct 

place, good transitions, 

neat 

Poster is creative and 

question investigated is 

unique and/or innovative 

Complete, interesting, 

creative, well thought out


Materials 

Materials listed are for a class size <strong>of</strong> 20 students working in pairs. There are two student pairs at each 

lab bench. 

Culturing Blackworms 

• Lumbriculus variegatus (need approximately 10-20 worms per group). These can be ordered from 

Carolina Biological Supply (# CE-14-1720), Flinn Scientific, Inc (#LM1220), or can be purchased at a 

local aquarium store. See appendix B for culturing instructions. 

o “Starve” worms at least 2 weeks in advance <strong>of</strong> the lab 

• Spring water or aged, dechlorinated water (let tap water sit in an open container for ~2 weeks) 

o Worms are very sensitive to chlorine 

• Small aquaria or buckets, large finger bowls, or 2 liter pop bottles for holding worms 

• Brown paper towels 

• Sinking fish food pellets 

Prep Materials 

• Single edge razor blades (new) 

• Disposable petri dishes, Ward’s Biology (#19-7100) 

• Filter paper, 90mm diameter, Ward’s Biology (#15-2815) 

• Dissecting microscope 

• Finger bowls to separate worms 

• Standard Plastic pipets, Ward’s Biology (#18-2971) 

Labroom supplies (front or back bench) 

• Lumbriculus variegatus, uncut worms in one bowl, cut worms in another bowl 

• Nicotine, caffeine, alcohol, and/or other drug solutions (labeled) (see Appendix A for recipes) 

• Labeled plastic pipets 

• Large finger bowl labeled “Rehab” and one labeled as “Regeneration” 

• Graduated cylinders (1-ml and 10-ml) 

• Latex gloves 

• Spring water or aged, dechlorinated water 

• Computer with internet access 

Supplies at lab bench 

• Parafilm trough slides or Tape well slides, 2 per group. (See Appendix B) 

• Coverslips – heavy transparency or plastic preferable 

• Chemwipes 

• Weigh boats, 10 per pair, Ward’s Biology (#18-1453) 

• Several standard plastic pipets 

• Compound microscope and/or stereoscope, 1 per group 

• Petri plates to raise worms away from light <strong>of</strong> stereoscope 

• Widgets, 1 per group (See Appendix B) 

• Eye droppers for solutions 

• 100-ml beakers for solutions 

• Stop watch – one per pair 

• Cotton swabs 

• Microrulers (See Appendix B)


Notes for Instructors 

Lab Design Information 

The prelab assignment included in the student outline is a way for students to start making 

observations about the blackworm’s circulatory system and about how drugs can affect heart rate. 

Before this assignment is given, however, the students will need instruction on how to evaluate outside 

sources <strong>of</strong> information on websites. They will also need to be reminded to cite all websites that they 

reference. Coming to the class with the observations and background research complete, and an idea <strong>of</strong> 

what type <strong>of</strong> drug they would like to test, saves time and prepares the students to make their hypotheses. 

After Part I, the students formulate these hypotheses based on their observations, research, and supplies 

available. The students will need guidance during this part so that their hypotheses are specific and 

testable. 

Before Part I begins, which is performed and discussed as a class, you may need to review basic 

information about circulatory systems <strong>of</strong> annelids, “heart” rate, blackworms, designing a hypotheses and 

making predictions, writing up lab results and conclusions, safety issues (see above), and the purpose for 

the day’s activities. It will be important for the instructor to do background research before teaching this 

lab to help guide students and work out issues that come up with using the worms. Refer to the 

literature cited section <strong>of</strong> this paper for some <strong>of</strong> the best references on blackworms. 

Purpose for Part I: 

• To have baseline data (rates before treatment) to compare with experimental data. 

• To practice handling and observing blackworms. Students will observe both behavior <strong>of</strong> the 

worms and dorsal vessel pulsation. 

Purpose for Part II: 

• To design and run an investigation to test the effects <strong>of</strong> “x” on pulsation rate. Purpose is not 

to kill the worms, but to determine the effects <strong>of</strong> sublethal concentrations <strong>of</strong> a drug on dorsal 

vessel pulsation rate (and behavior). 

Before having the students make their hypotheses for Part II, ask them what they found out about 

drugs and the effects they have on heart rate. How do drugs affect heart rate Is it dependent on 

concentration and/or exposure time How might exposure to several drugs change the effect Can 

blackworms recover from exposure How long does it take Can blackworms die from exposure 

Would acute exposure affect the pulse rate differently than chronic exposure These are all good 

questions for the students to consider in making their hypotheses for their experiment (Part II). 

You can have the students proceed with their hypotheses and experiments in one <strong>of</strong> several ways: 

• You pick which drug they test and how they test it. 

• You pick which drug they test, but they choose what they want to test (concentration, type <strong>of</strong> 

drug, exposure time, recovery time, etc.). 

• Students pick which drug they test, but each group has to pick a different drug. 

• Students pick which drug they test and it doesn’t matter if they possibly end up all picking the 

same drug (you could have results about other drug effects available for them to see). 

• Either <strong>of</strong> the last two option above, but you choose how they test it.


Possible Extension Activities: 

• Calculating vessel diameter and pulsation velocity using microrulers (See Appendix B) 

• Calculating Q 10 <strong>of</strong> pulsation rate 

o Q 10 = rate at Temperature 1 + 10 degrees/rate at Temperature 1 

• Chronic versus acute exposure to drugs 

• Lethal and sublethal levels <strong>of</strong> drugs 

o Students can determine the concentration <strong>of</strong> a particular drug that would evoke the 

following responses: 

Low concentration = little to no response in pulsation rate 

Medium concentration = near maximum response 

High concentration = no increase response, but still sublethal 

Viewing Blackworm pulsations 

Look for worms that are healthy (wriggling), not recently regenerated (colorful), and “starved” (guts 

are not dark). Use a plastic pipet to transfer the worms to their viewing slides (either the parafilm 

troughs or the tape wells). Immediately after placing the worms on the slides, suck up extra water with a 

fine tipped pipet. The water level should be even with the top <strong>of</strong> the well. Use tissue paper to soak up 

extra water around the edges <strong>of</strong> the well. If the worm is not quite in the well or is wiggling out, 

encourage it back in with the widget. Wait a minute or two for the worm to settle down. Then, place 

the slide on the microscope and view using scanning power. Use a minimal amount <strong>of</strong> light so the worm 

does not get overheated. Discern which way (to the left or to the right) that the pulse is moving so that 

you can determine which end is the posterior end (remember, blood flows from posterior to anterior). 

Pulsation rates may be higher at the posterior end <strong>of</strong> the worm because some <strong>of</strong> the dorsal vessel 

contractions die out before reaching the anterior end <strong>of</strong> the worm. Therefore, it is important to monitor 

the pulsation rates at the same location for each worm and for each time on the same worm. 

Typical Data for Cut Vs. Uncut 

Each number is an average for pulses/minute <strong>of</strong> three worms counted by each student group: 

• Cut = 22, 13, 12, 16, 21 = 17 pulses/minute 

• Uncut = 17, 13, 13, 13, 27 = 17 pulses/minute 

• Cut = 18, 18.7, 14.6, 12, 17, 15 = 15.9 pulses/minute 

• Uncut = 21.7, 10.6, 16, 14, 13.8 = 15.2 pulses/minute 

How drugs affect the pulsation rate <strong>of</strong> Blackworms 

Different chemicals (drugs) can have different effects on the pulsation rate <strong>of</strong> the dorsal blood 

vessel. Their effect can occur by mimicking natural neurotransmitters that bind to “heart” receptors, 

changing the propagation <strong>of</strong> action potentials, changing the amount <strong>of</strong> neurotransmitters released, 

changing the amount and type <strong>of</strong> hormones that are released, blocking ion channels, or by directly 

affecting muscular contractions. Most drugs enter the bloodstream <strong>of</strong> blackworms by diffusion through 

the skin. Thus, they also wash out <strong>of</strong> the bloodstream once placed back in a dilute environment. 

• Just like many other drugs taken recreationally, nicotine mimics a neurotransmitter that controls 

pulsation rate. Nicotine is an acetylcholine agonist, so it increases the pulsation rate <strong>of</strong> the dorsal 

blood vessel (depending on the concentration <strong>of</strong> nicotine).


• In humans, caffeine inhibits the enzyme phosphodiesterase, thus allowing cAMP levels to go up 

and ultimately increasing the heart rate. In blackworms, it is not clear if the increase in pulsation 

rate due to caffeine is a direct or indirect effect. 

• Alcohol acts as an ion channel blocker, thus decreasing the pulsation rate <strong>of</strong> the dorsal vessel. 

Blackworm responses to solutions 

• Response to caffeine – At low concentrations, worms may clump. As concentration increases, 

worms become very active. They may curl up and stretch out at higher concentrations. 

Pulsation rate will increase. Most worms recover within 15 minutes and all recover within one 

day. 

• Response to alcohol – Worms will become inactive as concentration increases and will be less 

likely to clump. Worms may straighten out, with their ends curled, in higher concentrations. 

They will not be able to swim as well. Their pulsation rate will decrease. Worms at the lower 

concentrations will begin to recover within 15 minutes. Most all worms will recover within one 

day. 

• Response to nicotine – Worms become more active, but do not clump. At moderate doses, the 

worms may be less active and twitch. In high doses (0.1 mM), paralysis (worm will be stretched 

out and motionless) may occur. The pulsation rate may not show an increase at the lowest 

concentration, but will increase at the middle and high concentrations. Most worms begin to 

recover within 15 minutes and all recover within one day. 

Tips for Instructors 

• Suggestion for beginning the lab (to engage)- 

o Have the students locate their pulse and ask them what they are sensing. Then, ask them 

how they could change the rate <strong>of</strong> their pulse. Once they start bringing up many types <strong>of</strong> 

drugs, ask them how drugs might affect the rate. 

• When students first obtain their worms, have them place them in a weigh boat with just spring 

water. Tell them to take some time making initial observations – which end is the tail end How 

do you know What is the behavior <strong>of</strong> the worm Does the worm swim How How is the 

worm responding to its new environment Etc. Lead a class discussion about their observations. 

• To get the worm to stay in the well and to coax it into a good position for viewing, gently use the 

widget or a piece <strong>of</strong> hair. 

• Have one person view worm and count pulses while the other keeps track <strong>of</strong> time. Switch roles 

<strong>of</strong>ten and make sure both students are relatively consistent when completing the baseline rate 

count. 

• Students can mix their own dilutions <strong>of</strong> the stock solution, or you can have dilutions already 

made for them. They could also try other dilutions than just the ones recommended in the 

recipes in Appendix A. 

• Tell students to be careful not to transfer liquid from one container to the next as they move the 

worms. Students also need to discern between pipets to reduce contamination. 

• Wells need to be rinsed thoroughly with distilled water between worms


• Encourage students to thoroughly think about their control for their experiment. Moving worms 

to and from dishes and slides could affect them; thus, it may be necessary to do the same for 

control worms. 

• You may want to check students’ procedures they have written down before letting them proceed 

with their experiment. They may need a little guidance. Avoid telling them what to do; instead, 

ask leading questions to help them develop a more sound experiment. Or, let them make 

mistakes and talk about sources <strong>of</strong> errors and mistakes at the end <strong>of</strong> lab. 

• If comparing pulsation rate <strong>of</strong> cut to uncut worms in Part I, have students put data on board. 

• If students end up experimenting with more than just the few specimens they used for finding the 

baseline rate in Part I, you will need to encourage them to find the baseline rate for all <strong>of</strong> the 

other worms that they are going to use. 

• Students may think that a very small change in pulsation rate is meaningless. Remind them that 

even very small changes in an organisms’ body can have significant consequences. For example, 

slight changes in body temperature, calcium levels, blood pressure, etc. 

• Potential pitfall – Students will not notice a change or will have a myriad <strong>of</strong> problems resulting 

in poor results. For these reasons, have the students also note changes in behavior so that, worse 

comes to worse, they can write about behavior changes in their lab reports. 

• If using statistics to analyze results, students will need to use at least 5 worms per treatment. 

Students can use a paired difference t-test to compare before and after exposure. 

• To save time, be strict about allotted times. Also, have data for the control group (worms that 

are never treated but are transferred back and forth) already available. 

After Lab Notes 

• Rinse <strong>of</strong>f worms well. Cut worms that were in treatments go into “Rehab” bowl (do not dump 

treatment chemicals into this bowl!). Untreated cut worms can go into “Regeneration” bowl. 

• Rinse <strong>of</strong>f and dry viewing slides, weigh boats, and other containers. 

• Throw away plastic pipets. 

• Wipe microscope lenses with lens paper and turn <strong>of</strong>f microscopes.


Acknowledgements 

I first want to thank Dr. Charles Drewes for all the help he <strong>of</strong>fered me in preparing for this major 

workshop. He was an incredible advice giver, a great support, and a friend – he will be missed. In 

honor and in memory <strong>of</strong> him, I am dedicating this laboratory investigation write-up to him and the many 

students that he has influenced throughout the years. I would like to thank both Charlie Drewes and the 

teachers attending the 1996 Woodrow Wilson National Leadership Program for their work in 

disseminating information about the use <strong>of</strong> blackworms in biology labs and for their lab investigation 

ideas. I also would like to thank Dan Johnson from Wake Forest University for additional ideas and 

feedback on this lab exercise and for Bunny for first encouraging me to use blackworms in the labs. 

Literature Cited 

Drewes, CD. 2003. A toxicology primer for student inquiry: Biological Smoke Detectors. The Kansas 

School Naturalist, Emporia State University, 50(1):3-14. 

Drewes, CD. 2001. Lumbriculus variegatus: A Biology Pr<strong>of</strong>ile. 

www.eeob.iastate.edu/faculty/drewesc/htdocs 

Drewes, CD. 1996. Those wonderful worms. Carolina Tips, 59(3), 17-20. 

Lesiuk, NM and Drewes, CD. 1999. Blackworms, blood vessel pulsations and drug effects. The 

American Biology Teacher, 61(1), 48-53. 

About the Author 

Kelly Bohrer received a B.S. in Environmental Biology and an M.S. in Biology from The 

University <strong>of</strong> Dayton, where she is currently the Biology Lab Coordinator. As such, she 

coordinates the activities <strong>of</strong> 4 lab courses per semester; teaches biology labs, introductory 

courses, and a graduate course on pedagogy for teaching assistants (TA’s); supervises TA’s and 

prep assistants; and develops innovative lab curricula. Her research interests include wetland 

ecology and laboratory pedagogy. She has recently received several grants to enhance laboratory 

experiences for non-majors and pre-service teachers and to develop a university wide graduate 

teaching assistant orientation.


Appendix A: Recipes for Drug Solutions 

Make all solutions with spring water or aged, dechlorinated water. Use all solutions within 24 hours. Solutions 

can be stored at room temperature. The dilutions are designed to give a small effect at the “low” concentration 

and a more pronounced effect at the “medium” solutions. The “high” solutions should show that either the 

threshold concentration has been reached or that the exposure response has reached maximum (but still sublethal). 

Actual responses will vary depending on other factors. 

Caffeine Stock Solution 

• Use Vivarin tablets, NOT NoDoz! 

• 200-mg caffeine/tablet 

• Make a 5mM stock solution by crushing 2 caffeine tablets and add 412-ml <strong>of</strong> spring water (or aged 

water). Dissolve tablets with stirring and heating if necessary. 

• Use appropriate amounts <strong>of</strong> the stock solution to make 500-ml quantities <strong>of</strong> 0.1 (low), 1 (medium), and 5 

mM (high) solutions. 

Nicotine Stock Solution 

• Cigarettes - regular length and strength, NOT menthol, 100’s, or ultralights 

• 1.1mg nicotine/cigarette 

• Make a 0.1mM stock solution by stirring the tobacco from 10 cigarettes in 680-ml <strong>of</strong> very warm spring 

water for 20 minutes. Filter the solution. You will lose about 50-ml <strong>of</strong> the solution when filtering. 

• Use appropriate amounts <strong>of</strong> the stock solution to make 500-ml quantities <strong>of</strong> 0.01 (low), 0.05 (medium), 

and 0.1 mM (high) solutions. 

Alcohol Stock Solution 

• Vodka = 40% alcohol 

• 1 mM alcohol = 2.6% 

• Mix 32.5-ml <strong>of</strong> vodka and 467.5-ml <strong>of</strong> spring water to make the stock solution. 

• Use appropriate amounts <strong>of</strong> the stock solution to make 500-ml quantities <strong>of</strong> 0.1 (low), 0.5 (medium), and 

1 mM (high) solutions. 

Other Possible Drug/Toxicant Solutions 

• Diet pills, cold medicine, Tylenol, acetylcholine, epinephrine, lidocaine, glucose, sugar substitutes, saline 

solution, detergents, pesticides, etc. 

• Crush and dissolve tablets in spring water. Make a high, medium, and low solution. Groups could work 

to find the concentrations that lead to little response and maximum response.


Appendix B: Preparation Notes 

Culturing Blackworms 

Fill a bucket, small aquarium, or large finger bowl with 2-3 inches <strong>of</strong> aged, dechlorinated water (or spring 

water). Add healthy worms (about 100) to the water and then layer the water with several small pieces <strong>of</strong> brown 

paper towel. Every week add one to two (depending on size <strong>of</strong> aquarium) pellets <strong>of</strong> sinking fish food. Do not 

overfeed! As water evaporates, add spring water to the original level. When the water begins to appear cloudy 

and/or starts to stink, slowly pour <strong>of</strong>f as much <strong>of</strong> the water as possible without losing the paper towel pieces or the 

worms. Rinse the worms and paper towel once (with aged water) and then refill the aquarium (to 2-3 inches) with 

fresh water and a few new pieces <strong>of</strong> brown paper towel. If you are not using the worms for a while, split the 

culture or feed some <strong>of</strong> the extra worms to fish (the culture should double every 2-3 weeks and more quickly with 

slight agitation). This culture should live for a long time following these procedures. 

Handling Blackworms 

Worms are best handled by sucking them up with a plastic disposable pipet. Blow out the air in a pipet, place 

the pipet at a 45 degree angle, lower it to the bottom, and quickly suck up 1 or 2 worms at their head ends. If you 

dismember any <strong>of</strong> the worms in the process, just leave the pieces in the culture to regenerate. 

Using Cut Blackworms 

Blackworms that have been fragmented tend to move around less. Typically, the pulsation rate <strong>of</strong> a newly 

fragmented worm is close to the pulsation rate <strong>of</strong> a whole worm. At UD, we have the students actually verify this 

before “choosing” to use cut worms for their experiment. Each student group measures the pulsation rate <strong>of</strong> three 

cut and three whole worms (in approximately the same region <strong>of</strong> the worms), and then pool their data with the rest 

<strong>of</strong> the class. Then, as a class, we can decide if the pulsation rates are close or not. To save time, it may be best to 

either tell them that this is so or to have data available for whole worms and have the students see for themselves. 

If you do choose to use cut worms, these worms should be cut at least one day in advance so that the ends are 

healed. Select whole worms that are healthy and full-sized and cut them into thirds by placing them on a piece <strong>of</strong> 

saturated filter paper in a petri dish and cutting them with a clean, sharp razor blade. Keep the middle segments 

for the experiments and put the other two segments back into your culture so they can regenerate. Keep the 

middle segment worms separate from the whole worms and place both into separate bowls with fresh spring water 

for the lab exercise (label the bowls as “cut” and “whole”). 

Making “Widgets” (for moving worms) 

The following directions for making widgets is adapted from “A Toolbox for Working With Living 

Invertebrates,” by Dr. Charlie Drewes. This article can be found in ABLE’s 2004 proceedings. 

1. Materials: applicator stick (handle <strong>of</strong> a probe works well), rubber band, scissors, and tape. 

2. Cut, at an angle, a piece <strong>of</strong> rubber band that is one inch long. 

3. Attach the rubber band to one end <strong>of</strong> the applicator stick with tape, leaving _ inch <strong>of</strong> rubber band beyond the 

end <strong>of</strong> the stick. 

Making Viewing Slides 

The procedure for making tape well slides is also presented in the article listed above. You can also find 

directions, and pictures, for both widgets and slides at 

http://www.eeob.iastate.edu/faculty/DrewesC/htdocs/ (scroll down to “Gadgets & Technical Information”) 

Tape Well Slides: 

1. Materials: clear plastic tape (Scotch Colored Plastic Tape, Clear, 0.75” X 125”); forceps; single edge 

razor blade; heavy scissors; heavy-duty, flexible clear plastic (or glass microscope slides); pen; ruler 

2. Using a pen and a ruler, mark <strong>of</strong>f desired size slides on the plastic sheet.


3. Place a long strip <strong>of</strong> tape over the plastic sheet, ensuring that there are no bubbles 

4. Add multiple layers <strong>of</strong> tape (4-5). 

5. Using a ruler and razor blade, make vertical cuts to define the well sizes for holding the blackworms 

(3-mm deep and wide and 4-cm long) 

6. Using a forcep, carefully lift the tape layers covering the desired well. 

7. Cut out the “slides” from the plastic sheet. 

8. On another piece <strong>of</strong> clear plastic, mark <strong>of</strong>f and cut out rectangles to act as cover slips for your slides 

(make them a little smaller than your slides). 

Parafilm Trough Slides: 

1. Materials: single edge razor blade, parafilm, glass microscope slides, ruler, metal surfaced hot plate, 

glass plate (~same size as hot plate), forceps, glove for hot items 

2. Put hot plate on low. 

3. Lay out glass slides, side by side, on glass plate to about 6” long. 

4. Cut out pieces <strong>of</strong> parafilm that are 4” X 6”. 

5. Place several layers <strong>of</strong> parafilm (6-8) on the glass slides and press down on the parafilm to make sure 

the sheets stick to each other and the glass slides. 

6. Put glass plate on hot plate and let it warm up for ~5-10 minutes. During this time, use parafilm 

backing to press the s<strong>of</strong>tened parafilm against the slides. Try to remove all air bubbles and make sure 

everything is sticking together. 

7. Once the parafilm just begins to get clear and s<strong>of</strong>t, remove the glass sheet (with gloves) and carefully 

place it on the counter. 

8. Using a ruler and razor, make cuts in parafilm to define the well sizes for holding the blackworms (3- 

mm deep and wide and 4-cm long). Make long wells for whole worms and short wells for cut worms. 

You can put two short wells and one long well on each slide. 

9. Use forceps to remove the parafilm from the cut wells. 

10. If part <strong>of</strong> the parafilm lifts during this time, simply reheat the slide on the hot plate and press down on 

the parafilm. 

Making Microrulers 

• Visit www.eeob.iastate.edu/faculty/DrewesC/htdocs/microruler-links.htm 

Safety Issues 

• Clearly label the contents and concentrations <strong>of</strong> all chemical solutions, including stock solution and 

dilutions (remind students to do this). 

• Read the Material Safety and Data Sheets (MSDS) for chemicals being used. For chemicals that are 

health hazards, including nicotine, wear gloves and minimize contact. 

• Properly dispose <strong>of</strong> all solutions and all materials exposed to solutions. 

• Scrub and clean all glassware and wipe down all benches with ethanol at the end <strong>of</strong> lab. 

• If accidentally cut, wash the area thoroughly. 

• Handle microscopes appropriately. Use lens paper to clean lenses before and after use.

Effects of Drugs on Pulsation Rate of Lumbriculus variegatus ...

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