daphnia - OpenStudyassets.openstudy.com/...1439920894851-daphnia.pdf · Daphnia’s heart rate. The experiment also validated our hypothesis would yield the similar effects to human’s

DAPHNIA MAGNA

BIO110-923; SEPT. 25, 2011

CHRIS PANLASIGUI

SEBASTIAN MORENO

LUKE ZOTTOLI

GENIE

this paper may be redistributed for educational purposes [email protected]

CHRIS PANLASIGUI

BIO110-923 Daphnia Magna

Abstract

This laboratory experiment was done on Daphnia Magna, a type of “fresh water

flea,” to observe how it responds to neurotransmitters and temperature changes.

The Daphnia was examined and observed to document its heart rate (HR). Then

tests were conducted to determine its heart rate responses to neurotransmitters –

Epinephrine and Acetylcholine (ACh), low and room temperatures. A microscope

and stopwatch were used to measure the changes in the Daphnia’s heart rate.

The results showed that the Daphnia’s heart rate increased when induced with

Epinephrine, and it decreased with Acetylcholine and when it was kept at a low

temperature.

Introduction

This experiment was done to test the effects of neurotransmitters and low

temperature on the heart rate of animals. The Daphnia was used to see how they

respond to Epinephrine, Acetylcholine (ACh) and low temperature. As students in a

Biology class, it is imperative to know the effects of environmental conditions -

such as low temperature, and neurotransmitters on a different species other than

human.

Before the experiment, a brief group discussion was conducted to hypothesize

some Daphnia responses by identifying some distinguishable effects on humans.

As discussed, the following notable human heart rates effects were identified -

Epinephrine causes an increase, Acetylcholine causes a decrease and so is the low

(cold) temperature. This prior knowledge, allowed us to hypothesize that similar


CHRIS PANLASIGUI


effects would be seen in the Daphnia experiment it also gives us a more specific

objective to continue with the experiment.

Materials & Methods

Materials The materials used were Acetylcholine, cotton, Daphnia, Epinephrine,

microscope, paper towel, pipette, pond water, crushed ice, and a stopwatch.

Methods The Daphnia was observed under a microscope with magnification power of

forty times. Then the speed of its heart beat or heart rates (HR) were recorded

and had assigned “beats per minute” or “bpm” as the unit.

There were times when Daphnia moved a lot and sometimes violently,

particularly when the Acetylcholine was applied; this made it difficult to get a

precise count of the Daphnia’s heartbeat to a minute length. As a solution, the

group decided to restrain the Daphnia’s movements by surrounding it with

cotton, and then obtained a record of the heartbeat count for fifteen seconds and

then multiplied the value by four to maintain a minute count.

The parameter for the first test was assigned as baseline; the controlled experiment

included five parameters in the following order: first, with the Pond water;

second, with Acetylcholine; third, Epinephrine; fourth with low temperature;

and the last was the recovery.

For accuracy, we tested all parameters - baseline and controlled experiments – twice

then, calculated the average for each. And lastly, the group used pipette and


CHRIS PANLASIGUI


paper towel to drain the fluid and also allowed the Daphnia to rest for two

minutes every after test.

Observations

Baseline Experiment The first baseline experiment showed that the Daphnia’s heart beat one hundred

forty four times (144 bmp). The second baseline test yielded the same result. So

the average heart rate for both baseline testing was one hundred forty four beats

per minute (144 bpm).

Controlled Experiment Pond water was used in the first controlled experiment. The first HR recorded was

one hundred sixty beats per minute (160 bpm) and the second HR was one

hundred forty four beats per minute (144 bmp). The average HR on the pond water

parameter was calculated to about one hundred fifty two beats per minute (152

bpm), a very slight increase, but an insignificant one.

On the second experiment, the Daphnia’s HR on the Acetylcholine was one

hundred twenty beats per minute (120 bpm) and its second HR was one hundred

sixteen beats per minute (116 bmp). This gave us an average of one hundred

eighteen beats per minute (118 bmp). In addition to the decrease of the Daphnia’s

heartbeat, we also noticed an increased activity in its stomach. Though this is

irrelevant with the experiment, it’s worth documenting it, because it may be of

use in the future.

The third controlled experiment – Epinephrine - showed rather a significant

increase in the Daphnia’s heart rate. The initial HR was two hundred forty beats


CHRIS PANLASIGUI


per minute (240 bmp) and the second HR was two hundred thirty six beats per

minute (236 bmp). This gave us an average of two hundred thirty eight beats per

minute (238 bpm).

Cold temperature, the fourth controlled experiment, gave us an initial HR of one

hundred twenty beats per minute (120 bmp) and the second HR was about one

hundred sixteen beats per minute (116 bpm). The average HR for this experiment

was one hundred eighteen beats per minute (118 bpm). The results reflected

similarity to the results of Acetylcholine experiments.

Recovery, the last parameter in the controlled experiment, gave us an initial HR of

one hundred sixty beats per minute (160 bpm) and the second HR was one

hundred fifty two beats per minute (152 bpm). The results showed near similarity

to the baseline experiment, something that we actually would expect to obtain, as

the Daphnia is to resume to its normal state.

Below is a tabular and graphical representation of the observations:

1st HR (x4) 2nd HR (x4) Average

Baseline 144 144 144 bpm

Pond Water 160 144 152 bpm

ACh 120 116 118 bpm

Epinephrine 240 236 238 bpm

Cold Temperature 120 116 118 bpm

Recovery 160 152 156 bpm


CHRIS PANLASIGUI


Analysis

The results of the experiment showed that neurotransmitters - particularly

Epinephrine and Acetylcholine - and low temperature have chronotropic effects on

Daphnia’s heart rate. The experiment also validated our hypothesis would yield

the similar effects to human’s. As seen in the tabular and graphs, Epinephrine has

a positive chronotropes or increases the heart rate, while Acetylcholine and cold

temperature have negative chronotropic or decreases the heart rates.

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Baseline! Pond Water! ACh! Epinephrine! Cold Temp! Recovery!

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daphnia - OpenStudyassets.openstudy.com/...1439920894851-daphnia.pdf · Daphnia’s heart rate. The experiment also validated our hypothesis would yield the similar effects to human’s