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LAB 4: Experiment on Giant Nerve Fibers of a Lumbricus terrestris Showing Threshold
Voltage, All – non Response, Conduct Velocity, Strength – duration Relationship
And Refractory Period
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BIO409-EARTHWORM GIANT NERVE FIBERS
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LAB 4: Experiment on Giant Nerve Fibers of a Lumbricus terrestris Showing Threshold
Voltage, All – non Response, Conduct Velocity, Strength – duration Relationship
And Refractory Period
@Abstract:
This laboratory report presents an investigation and study on Giant nerve fibers of L.
terrestris. This experiment's primary purpose is to compare the medium and lateral giant axons
and how they behave as far as an absolute and relative refractory response towards a stimuli
artifact is concerned.Taxonomic classification of L. terrestris and a brief introduction about it are
discussed in the introduction section before the main objectives and introduction of the
experiment. In the results section table, I show extracellular reading results of both the medium
and lateral giant axons of L. terrestris. In contrast, table II compares the duration of stimuli pulse
and threshold voltage. Here, as the threshold voltage is being adjusted, the stimuli' duration also
changes indirectly. The values obtained in Table II were then plotted on a graph shown in the
results section. Finally, Table III shows the relative and absolute refractory periods of the
medium giant fibers of L. terrestris where they were recorded at 0.9 and 0.3 V, respectively. Data
and results analysis was then done in the discussion section.
Introduction:
Lumbricus terrestris is an earthworm that is large and reddish. The initial thoughts about
Lumbricus terrestris is that it was to Europe, however, it has attained a global distribution
particularly in temperate zones (Dulaurent et al., 2020). Its usefulness comes through the
barrowing of the soil and ground, where it provides an opportunity for soil formation and
fertility. It's also commercially exploited due to its use as fishing bait, education, and model
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organism (Steckley, 2020). Therefore, their distribution can largely be credited to human
activities.
According to Obert and Vdacny, 2019, this type of Lumbricus spp can be classified as:
•
Domain – Eukaryota
•
Kingdom –Metazoa
•
Phylum - Annelida
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Class – Oligochaeta
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Order – Haplotaxida
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Family – Lumbricidae
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Genus – Lumbricus
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Species - L. terrestris
L. terrestris is a hermaphrodite with obligate outcrossing where individual worms seek
mating partners. Additionally, breeding occurs in damper periods of the year where its activities
are reduced by moisture and temperature (Obert and Vdacny, 2019). It consumes dead leaves at
the surface and A – horizon mineral soil. This laboratory report was all about the action potential
of giant earthworm L. terrestris. Axons from most vertebrates are myelinated, with the myelin
acting as an insulator against many things like harsh conditions and for protection purposes
(Mulloney, 1970). Similarly, the myelin increases the action potential conductor velocity
through the big diameter of the axon. On the other hand, in invertebrates like the L. terrestris,
specialized giant axons help in the commencement of many escape behaviors (Vion-Bailly et al.,
2017).
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The escape behaviors in L. terrestrisare by rapid conduction of action potentials. It can
also go to large extents in understanding the roles of the cell membranes in never excitation.
These roles can be well understood by critically looking at the giant axon's roles and functions
(Subaraja and Vanisree, 2019)). The giant axons receive their stimulation through sensory input.
The sensory input is spread throughout the animal's body to the anterior end, where the median
giant axons receive sensory stimulation. In contrast, the lateral giant axon receives its stimulation
from the body's posterior end (Rusanen et al., 2017).
These activities and many more can be investigated through an experiment as conducted
by this laboratory report. Here, the logic should be from the theoretical point of view, where the
amplitude of normal action potential should be around 80 – 100 mV. However, the amplitude can
be smaller if measured and recorded extracellularly (Stough, 1926). An extracellular recording
can only detect a slight potential difference from the extracellular medium's current action flow
around or near the axon. These extracellular currents measurements are in μV other than in mV
because of the instrument used for measuring them externally. However, it should be noted that
the currents produced by giant axons are significant to the extent that they can be measured and
recorded even from the outside of the body of the worm, something that this laboratory report
investigated and presented.
Objective:
This experiment's primary purpose is to examine the threshold of voltage, all – or non-
response, conduction velocity, strength-duration relationship, and the refractory period.
It will also be prudent to measure and record the action currents after attaining the above
objective from an anesthetized L. terrestris.
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Materials and Methods:
The method and procedure used followed strictly the laboratory manual on excitation
never fiber stimulation of Lumbricus species using the materials as shown (Beck et al., 1968).
The equipment's used: Picoscope and laptop computer, Grass instruments stimulator, A-M
systems MODEL 3000 preamplifier, Shielded leads, Dissecting tray, Metal dissecting pins, 10%
Ethanol in earthworm saline, Pipette, Millimeter ruler, Paper tissues and earthworm.
Results:
The table below shows the extracellular reading of stimulated medium and lateral giant axons of
L.terrestris.
Threshold
(Voltage)
Amplitude
Duration
Latency
Median Giant Fiber
1.4
28.5
1.361
5.524
Lateral Giant Fiber
3.8
16.15
2.122
15.18
Table II: Showing comparison in the duration of stimuli pulse (ms) and threshold voltage
(v)
Duration of Stimulus Pulse ( ms)
Threshold Voltage (v)
0.2
1.5
0.4
1.2
0.6
1.19
0.8
1.2
1
1.2
1.2
1.1
1.8
1.1
The values in the table were then plotted, as shown in the graph below.
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Graph of Threshold Voltage (v) against Duration of Stimuli (ms)
The relative and absolute refractory periods were then investigated, and the values obtained were
arranged as in the table below.
Table III showing Relative and Absolute Refractory Periods of Median Giant Fiber
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Relative Refractory Period
Absolute Refractory Period
Median Giant Fiber
0.9 v
0.3 v
Discussion:
From the table I, stimuli artifact was identified using the amplitude, which depending on
it, the higher the amplitude, the greater the stimuli. Artifact. Therefore, it can be easier to show
the magnitude of the stimuli artifact used. The threshold voltage was then determined, which can
then be compared with the stimuli' duration (Beck et al., 1968).
Table II showed the threshold voltage compared to the duration of stimuli. This was done
by changing the time and increasing the voltage each time. From table II, The stimuli artifact was
identified from the threshold. The higher the threshold value, the more effective is the stimuli
artifact. Also, the median fiber was faster because it has a great length in axon size thanthe
lateral axon.
From Table III, the relative refractory period was greater as compared to the absolute
refractory period. The relative refractory period is when the second action potential was initiated
through greater stimulation. In contrast, the absolute refractory period is that time during which
there's no stimuli's second action potential (Subaraja et al., 2019). Additionally, the second
action potential from the median giant axon could not be seen when the stimulus interval was
short. The threshold brought about by the stimuli was not strong enough to cause second action
potential to occur. This could also be because the first excitation could have induced complete
and maximum excitation. To feel again, the second excitation required a more prolonged stimuli
interval to reenergize the axon.
Invertebrates are preferred to vertebrates for this research and experiment instead of
vertebrates because vertebrates have a myelinated axon. This myelin is a protecting cover that
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will require more to reach the vertebrates' axon. Still, once the axons have been reached in
invertebrates, the myelin will provide a cover that has to be broken down.
Consequently, the results tallied with the experiment's hypothesis and objectives, whose
aim was to investigate the median and lateral action potential of the L. terrestris. Though the
values obtained did not tally with actual theoretical values because of errors like calibration and
instrument usage. Therefore, an improvement could be made by comparing already existing data
that can determine the extent of stimuli artifact according to (Bullock et al., 1965) the axon's
length.
Finally, the research-based it is finding on previous data and previous research done by
(Beck et al., 1968), who talked of the importance of action potential in an isolated nerve cord of
earthworms and (Beck et al., 1968) ideas on the action potential in L. terrestris axon.
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References:
Bullock, T.H. and Horridge, G.A. 1965. Structure and function in the nervous systems of
invertebrates, vol. 1. W.H. Freeman and Co., San Francisco, pp. 680-708.
Beck, D.E. and Braithwaite, L.F. 1968. Invertebrate zoology laboratory workbook. Burgess
Publishing Co., Minneapolis, pp. 196-206.
Dulaurent, A. M., Daoulas, G., Faucon, M. P., & Houben, D. (2020). Earthworms (Lumbricus
terrestris L.) mediate the fertilizing effect of frass. Agronomy, 10(6), 783.
Rusanen, J., Vähäkainu, A., Weckström, M., & Arikawa, K. (2017). Characterization of the first-
order visual interneurons in the visual system of the bumblebee (Bombus
terrestris). Journal of Comparative Physiology A, 203(11), 903-913.
Mulloney, B. 1970. Structure of the giant fibers of earthworms. Science 168: 994-96.
Obert, T., & Vďačný, P. (2019). Integrative taxonomy of five astome ciliates (Ciliophora,
Astomatia) isolated from earthworms in Central Europe. European Journal of Taxonomy,
(559).
Steckley, J. (2020). Cash cropping worms: How the Lumbricus terrestris bait worm market
operates in Ontario, Canada. Geoderma, 363, 114128.
Stough, H.B. 1926. Giant nerve fibers of the earthworm. J. Comp. Neurol. 40:409-63.
Subaraja, M., & Vanisree, A. J. (2019). Aberrant neurotransmissional mRNAs in cerebral
ganglions of rotenone-exposed Lumbricus terrestris exhibiting motor dysfunction and
altered cognitive behavior. Environmental Science and Pollution Research, 26(14),
14461-14472.
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Vion-Bailly, J., N'Djin, W. A., Mestas, J. L., & Chapelon, J. Y. (2017, September). Feasibility and
main mechanisms underlying in vivo ultrasound neurostimulation of the ventral nerve
cord's giant axons of lumbricus terrestris. In 2017 IEEE International Ultrasonics
Symposium (IUS) (pp. 1-4). IEEE.
