Post on 28-Jan-2023
Marine biology lab report- Mitchell Ray Pranata
Title: The effect of different salinities on the rate of
activity, physique and mortality of sandworms and
bloodworms.
Abstract:
This report presents the effects of changing different
salinities (20 ppt, 30 ppt and 40 ppt) on two species of
worms, the bloodworm (Glycera dibranchiata) and the sand worm
(Nereis Virens). All worms were placed in six different
aquariums (three tanks for each species, with each tank
containing 35 worms) that were filled with different
salinities and were weighed using a precision scale after
several time periods (at 0 hour, 4th hour, 8th hour and 24th
hour). Their activity levels and mortalities were also taken
into account. The values obtained were prone to inaccuracy
corresponding to the difference in removal of free surface
water off the worms before weighing them. However, the
results were supportive of the hypothesis. The sandworm,
being osmoregulators, is shown to be returning to a 0%
1
(normal) weight change whereas the bloodworm, being
osmoconformers (low tolerance), is shown to be drifting
further apart from the 0% (normal) weight change mark as
time increases. Analysis shows that sandworms have a lower
mortality rate and are able to withstand different
salinities in comparison to the bloodworms, vice versa. It
also shows that the sandworms, being osmoregulators, are
returning to their normal weight whereas the bloodworms are
drifting further apart from its initial weight as time
progresses.
Introduction:
Each organism has a set of individual requirements and
adaptations needed in order to thrive in its environment.
For instance, the musk ox that lives in the vast Alaskan
Tundra is well adapted to the harsh, cold environment by the
presence of its thick fur-coat that shields the ox from
frigid temperatures. However, significant changes in the
environment can affect an organism and different organisms
may react at variance.
Estuaries, by definition, are partially enclosed water
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bodies that form at the transitional areas between
freshwater and seawater. Despite of being interconnected,
estuaries and oceans are dissimilar environmental
ecosystems. Safeguarded from the ocean’s rough oceanic
forces by peninsulas, estuaries, or ‘nurseries of the sea’
are highly productive environments with a rich ecosystem for
various organisms.
Salinity, as the word suggests, is the measure of
concentration of salt in a solution of water. The more
saline a water solution is, the more salt it contains, vice
versa. Some organisms are well suited and can only survive a
certain level of salinity, while other organisms are able to
tolerate and adapt to different salinity levels.
In the open ocean, the salinity is measured at a
constant 35 ppt (parts per thousand), while in estuaries,
salinities range from 0-35 ppt depending on each estuary.
The highest salinity is recorded where the ocean water flows
in, and lowest where freshwater flows in. The salinity, or
concentration of salt in freshwater is so low that it’s
close to zero.
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Organisms that reside in the ocean are generally
‘stenohaline’, meaning that they are unable to tolerate wide
fluctuations in salinity levels. On the other hand, since
estuaries have an unstable salinity level, organisms that
live in estuaries are generally ‘euryhaline’, meaning that
they are able to tolerate wide fluctuations in salinity.
Poikilosmotic organisms (also known as osmoconformers) match
their body’s osmolarity with the environment through
osmosis, which in turn provides identical salinity with the
organism’s surrounding environment. On the other hand,
homoiosmotic organisms (also known as osmoregulators)
regulate an independent osmolarity in their bodies
regardless of the environmental conditions, therefore
keeping a constant salinity level inside their bodies.
Oysters for example, are Poikilosmotic organisms and
stenohaline as well because a huge fluctuation in salinity
levels would affect their growth and activity negatively. On
the other hand, the salmon fish is euryhaline organism which
is able to self-regulate its body to suit both ocean and
fresh water.
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Two species of worms from different genus will be
experimented on; the sand worm (Nereis virens) and the blood worm
(Glycera dibranchiata). Both these worms live alongside one
another in estuaries, but are different from one another.
They are both annelids (segmented bodies). The sand worm has
more than 200 segments that have parapods (similar to legs)
on each segment that allow them to squirm and limp in order
to move themselves. Sand worms can be found on both sides of
the North Atlantic, France and the United States east coast.
These carnivorous worms feed on tiny invertebrates and on
organic waste material (such as glutamic and aspartic acid).
These worms are capable of inflicting a bite through two of
their sharp jaws found in their mouth, painful even for a
human. Furthermore, they have a pair of antennae and two
pairs of eyes and prefer to reside in muddier environments.
They are euryhaline and are able to tolerate various
salinities, even one ranging to near zero. (*See figure 5)
In contrast, bloodworms are osmoconformers and
stenohaline organisms. Each one has over 300 segments in its
body with less developed parapods compared to the sandworm
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and an eversible proboscis which houses four sharp jaws that
can inflict a poisonous bite. Bloodworms receive their names
due to their translucency, which enables its red body fluids
to be visible through the naked eye. Like the sand worms,
they are also carnivores and will prey upon invertebrates.
They can be found from Florida to the Atlantic, and on the
West Coast of United States. Another similarity with the
sand worm is that bloodworms prefer the mud and burrow
themselves so deep within that oxygen and salinity levels
are low. By exposing these two estuarine worms in three
different salinities, we can measure their weight loss or
gain. The loss or gain in their weights meant that osmosis
had taken place and water had either entered or exited the
worms. (*See figure 6)
Hypothesis: This experiment serves to study the effects of
various salinities on the two species of estuarine worms by
placing them in different saline solutions. The sand worms,
being osmoregulators (rather tolerant to changes in salinity
by regulating their own suitable salinities), will have a
higher mortality rate than the bloodworms. On the other
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hand, the bloodworms will have more deaths as they are
osmoconformers (low tolerance level) and will adjust to
their surrounding salinities, which may not be suitable for
their survival. Furthermore, the sand worm (euryhaline)
should not experience any weight changes, if any, little, as
they are regulating their own osmolarity. Contradictory, the
bloodworm (stenohaline) will initially increase or decrease
in weight and will maintain that weight, if not increase or
decrease more throughout the time period. The bloodworm’s
weight will continue to get further away from its initial.
Bloodworms will experience higher weight changes in
comparison to the sand worms because they will take in salt
from their surrounding through osmosis as to synchronize
themselves with their surrounding environment. Sand worms
are going to be more active in comparison to the bloodworms,
as they will not get affected by the different salinity
levels and will function normally. However, the bloodworms
will have difficulties, as they are unable to tolerate the
change in salinity levels, therefore they will become less
active.
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Rationale: By conducting this experiment, we will learn the
bloodworm and sand worm’s reaction towards different
salinities, and study their physical and psychological
status accordingly. It will show the range of effectiveness
of both euryhaline and stenohaline organisms on their
mortality rate. Through this experiment, we can learn about
the different mechanisms that these different species of
worms use in order to thrive in their environment, and how
they adjust to new ones. By knowing this, we will know the
approximate level of salinities that these worms are able to
tolerate and which ones they are unable to tolerate. We are
also able to predict the approximate internal salinities of
the worms through the weight changes and observing the
osmotic gradient trends.
Materials and method:
Setup: This experiment was done in the museum of
comparative zoology laboratory room 5088, at Oxford St,
Cambridge. It was done under normal room temperature and
conditions. The constant variables were the water saline
water used throughout, the worms, light, temperature and
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pressure in the room. There were six aquariums set up, of
which three are for sand worms and the other three are for
bloodworms. For each species, out of the three tanks, one
was filled with 20 PSU (practical salinity units) artificial
seawater, the other with 30 PSU and the final one with 40
PSU. This was done for both species of worms. There were 35
worms in each of the tank. We had been provided a precision
scale, plastic gloves and tissue in order to dry out the
worm before weighing it. Furthermore, we had a considerable
size plastic jar to move the worm from the aquarium to the
table where we were to weigh and observe them. Finally, we
had a small glass plate to place the worms after measuring
their weights, as to separate them from the worms that have
not been weighed yet. The worm’s weight at 0 hour (initial
hour, before placing them in the saline solutions) was
already measured. We were to measure the weight of the worms
at the 4th hour of submersion. Additionally, the weight of
the worms had to be measured at the 8th and 24th hour.
Method: My group consisted of three people. Initially, we
put on plastic gloves on both hands as a precaution from the
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worm’s potential danger, as both worms are capable of biting
and bloodworms have poisonous bites. Then, we chose a
designated tank (in this case, we chose the 40 PSU tank of
sand worm) and filled the plastic jar with the water from
the tank, not too much, but enough for the worms to be
submerged. Subsequently, we picked up the sand worms with
our gloved hands from the aquarium and moved it to the
plastic jar. We then took it to our table for our
observation. Before weighing out the worms, we had to blot
them on tissue paper to dry them of excess water. This was
done by gently patting the worms with tissue paper, and not
by drying them thoroughly. After removing the surface water
from the worm, we weighed the worm using the precision scale
to the nearest 0.1-gram. Before weighing the first worm, we
pressed ‘tare’, and did so after weighing every subsequent
worm. To make sure that we did not re-weigh the same worm
again, we did not rejoin the worm we had weighed back to the
plastic jar. Instead, we placed them on a dry glass plate.
Before placing them on the glass plate, we also noted down
their activity rate which ranged from being less active,
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moderately active, active and very active. We also took into
account whether there are dead worms during the observation.
We used statistical analysis and put the means into a t
test to find out the trend in weight change of the worms in
different salinities and to find out the p values.
Results:
This section provides the data collected from the sand
worm and bloodworm experiment. The experiment was conducted
with success and had very little errors in data collection.
At 0 hour, the worms were weighed as a reference to
calculate the change in weight from the 4th hour onwards.
Changes in actual percentage weight of the sandworms and
bloodworms on the 4th hour were roughly similar (in general
context). For instance, in 20 ppt, the sandworms had 40.9%
increase in their weight at the 4th hour and the bloodworms
had 46.3% increase in their weight as well (*see figure 1
and 2). Furthermore, in 30 ppt (at the 4th hour), the sand
worms had an increase of 6% in weight, while the bloodworms
had 8.2% increases in their weight (*see figure 1 and 2).
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At 40 ppt at the 4th hour, the sand worms had a decrease of
10% in their weight and the bloodworms had a decrease of 11%
in their weight (*see figure 1 and 2). The increases and
decreases at the 4th hour for all salinities on both species
of worms were similar to each other.
However, the data starts to change at the 8th hour. As
per the data, the sandworm’s actual percent change is
nearing to normal weight (0) as time progresses (*see figure
1) At the 8th hour, the sandworm’s change in weight at 20
ppt had become 38.1% and drops again to 24% in the 24th
hour. This is in line with the other salinities as well. In
30 ppt salinity, the sandworm’s percent change in weight
dropped to 4.5% in 8th hour and then to a further 1.6% in
the 24th hour time period. Lastly, at 40 ppt, the decrease
of weight in the sandworm is becoming lesser and nearing
normal weight; at the 8th hour, it only decreased by 8.1%
and at the 24th hour, it decreased by a mere 3.1% (in
comparison with the 4th hour, at which the sandworm lost 10%
in weight). This shows that after the 4th hour, the
sandworm’s change in weight is returning to an equilibrium
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and will eventually have 0 change in percent weight if
recorded over more time.
On the other hand, the data shows an opposed trend for
the species of bloodworms as the change is shown to become
further apart from 0 as time progresses (at 8th and 24th
hour- *see figure 2) Case in point, in 20 ppt solution, the
bloodworms had 48.2% change in weight at the 8th hour, and
47.1% change in weight at the 24th hour. The percentage
weight change increased from the 4th hour and it shows that
it is not returning to 0% (normal) weight change (as it is
on the species of sandworms). Additionally, in 40 ppt, the
decrease in weight for the 8th hour and 24th hour is becoming
larger and further apart from normal weight (0%). At the 8th
hour, it increased from 1.1% (4th hour) to 1.3% and then on
to 1.5% in the 24th hour.
However, some results were inconsistent. For instance,
for the species of bloodworms, the 20 ppt solution (at the
24th hour), the change in weight dropped from 48.2% (in 8th
hour) to 47.1%, although it was meant to further apart from
0 (*see figure 2). Furthermore, for the species of
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bloodworms in 30 ppt, the changes in weight generally
decreased as time progresses. It should be increasing,
however it is shown to be decreasing. There may be a logical
explanation to this and will be talked about later on in
discussion (*see fig 2, red line)
In addition to that, there was more mortality in
bloodworms than in sandworms. It is shown that in all
salinity levels, the first four hours experienced no
mortalities whatsoever. However, at the 8th hour, there was
one sandworm dead in the solution of 40 ppt. As for the
bloodworms, at the 8th hour, there was one death at 20ppt
and another two at 40 ppt. Furthermore; there were two more
sandworm deaths after 24 hours in the 40 ppt solution.
Finally, there are six more bloodworm mortalities after 24
hours, two of which belong to the 20 ppt and the other four
belonging to the 40 ppt. (*see figure 3 and 4 of mortality).
This shows that the bloodworms have a higher mortality rate
compared to the sandworms as more deaths occurred at the end
of 24 hours.
Standard deviation for the sandworms under all
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salinities is shown to decrease as time progresses. For
instance, at 30 ppt, it was 4% at the 4th hour, and then
drops to 31% in the 8th and to a further 2.8% in the 24th
hour. Contrastingly, the bloodworm’s standard deviations
were increasing as time progresses. At 20 ppt, standard
deviation at the 4th hour was 2.9%, then rose to 4.5% in the
8th hour and lastly, 5.7% in the 24th hour.
P values are less than 0.05 for both species at the 4th
hour, and are much larger than 0.05 during the 8th hour. In
the 24th hour, P values for the sandworms became smaller
than 0.05 (with one exception, which was valued at 0.075)
whereas P>0.05 in the 24 hour bloodworm category. There were
a total of 3 sandworm deaths (one died in the 40 ppt during
the 8th hour, and the other two died in 40 ppt during the
24th hour). A total of 9 bloodworm deaths were recorded
(one died in 20 ppt during the 8th hour, two in the 40 ppt
during the 8th hour, and the other 6 died during the 24th
hour, two in 20 ppt and the other four in 40 ppt).
Discussion:
The results clearly bring forth the effects different
15
salinities had on the two species of worms. It was in line
with the hypothesis. As the sandworms are euryhaline
creatures, and are also osmoregulators, they are rather
tolerant and were expected to be more resistant and in turn,
have a lower mortality rate. This was shown to be true, as
the results show that at the end of the experiment, the
sandworms have less death count than the bloodworms. The
sandworm’s total death was only three. This is because they
regulate their osmolarity regardless of the unsuitable
environment outside. On the other hand, the bloodworms are
stenohaline organisms, and are also osmoconformers.
Bloodworms will match their surrounding salinity, as they do
not have control of their own osmolarity. If the salinity on
the outside is unsuitable for their survival, and it enters
their bodies, there would be mortalities. This particular
hypothesis was also accurate. There are as many as 9
bloodworm deaths in total (*see figure 3 and 4).
In both species, most of the worms are shown to be
tolerant to changes in salinity levels. However, the deaths
were irreversible damage and points out that if the salinity
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was further increased or decreased to an extreme level, it
may cause a significant increase in the mortality. Even
though bloodworms are osmoconformers and are only suited to
30 ppt salinity, they are able to tolerate both 20 ppt and
40 ppt (excluding the few deaths, which is but a small
number in comparison to the amount of worms experimented
on).
At the first 4 hours, the sandworms and the bloodworms
experienced similar weight gains and losses. It was
predicted that the sandworm, being osmoregulators, should
not experience any weight changes or just a slight change.
However, it is shown that the sandworms did experience
weight changes, even as high as 40.9%. Moreover, the
sandworms did begin to show signs of weight change
retractions, as they are slowly returning to a 0% weight
change (which is the normal weight; due to their
osmoregulation).
On the contrary, the bloodworms were expected to
regulate their salinities according to the environment they
were provided with, as they are osmoconformers. This meant
17
that they would experience a constant weight change (either
decrease or increase) and will maintain that weight change,
or become further apart than the 0% weight change. It should
diverge away from the normal weight. As soon as they take in
a salinity they’re not suitable with, they will have
difficulty adjusting and might die out. At the 4th hour,
they were shown to experience weight changes. For the 20 ppt
and 40 ppt, the hypothesis was followed as they are
diverging away from normal weight as time progresses.
However, at 30 ppt, the bloodworm’s weight change is shown
to be decreasing as time progresses (8.2% to 6.9% to 5.3%),
although not as fast as the sandworm’s decrease in weight.
This was initially thought to be an error, however it is
decreasing because of the fact that 30 ppt is very close to
normal ocean salinity. As bloodworms do live in the open
ocean, they would be very used to this salinity and adjust
easily. Therefore, their weight change is decreasing and
nearing normal weight as time progresses. Furthermore, this
also explains why the mortality rate of bloodworms at 30 ppt
is 0, whereas in 20 ppt its 2 and in 40 ppt its 4. It is
18
because the bloodworms are suited to the 30 ppt and thus
will survive. On the other hand, if we changed the salinity
to 20 ppt and 40 ppt, there would be a few mortalities as
they are osmoconformers and are stenohaline.
Sandworms are very tolerant to the change in salinity
and therefore there are lesser deaths, although it is shown
that a total of 3 sandworms have died, its possible that it
is because some of them take a longer time to regulate their
bodies, as they could be weaker, or younger specimens. The
deaths could also result from psychological issues such as
stress. It is also plausible that the worms might attack one
another, resulting in their deaths.
Moreover, the sandworms are shown to be undergoing
recovery as shown in figure 1. Initially, their weight has
increased and decreased significantly under different
salinities, which means that at that point of time, there
are not yet regulating their body osmolarity. This in turn,
fashion that their body’s salinity is the same as the
environment’s salinity and might not be suitable for them.
However, since sandworms are tolerant to different
19
salinities, they do not get much affected even though they
experience a weight change (change in body’s salinity) and
it is shown in figure 1 that they are returning back to
normal weight change as time progresses.
At the 4th hour, both species had P values smaller than
0.05 in all three salinities, therefore meaning that it is
statistically significant and did not occur by chance.
However, at the 8th hour for both species, the P values were
larger than 0.05. Nonetheless, this does not mean that it is
not statistically significant, for the data is reliable and
did not happen by chance, there is just lack of strong
evidence. Furthermore, at the 24th hour, the P values for
the sandworms were much smaller than the P values of the
bloodworms. (At 20ppt 24 hour, the sandworm had P value of
0.002 whereas the bloodworm had a high 0.513). There is a
huge variance in the p values.
For both species, the rate of inflow during the first
four hours for both 20 and 30 ppt were more than the
outflow, as there was an increase in weight (positive
change). For 40 ppt during the first four hours, the rate of
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outflow was more than the rate of inflow, as a decrease of
weight is shown (negative change). The sandworm, in the 8th
hour, experienced 38.1% in weight change, which means that
the rate of inflow is still more than the rate of outflow.
However, it is smaller in comparison with the 4th hour,
which had a bigger rate of inflow that caused 40.9% change
in body weight. In 40 ppt, the sandworm’s rate of outflow
was greater than the rate of inflow throughout the time
period as the change is continuously negative. Nevertheless,
the rate of outflow in 40 ppt sandworm is becoming lesser as
the time progresses. For the bloodworms, the rate of inflow
at 20 and 30 ppt were greater than the outflow. At 40 ppt
however, the rate of outflow was greater.
The negative values in 40 ppt for both species suggests
that the osmolarity of both estuarine worms were less than
40 ppt, because they are losing weight to their environment,
which can only occur through osmosis from a lower
concentration to a higher concentration. It means that their
osmolarity is somewhere between 30-40ppt. A reasonable
assumption would be 35 ppt, which is normal seawater
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salinity. Therefore, the difference in the direction and
rate of water flow between these salinities depends on the
salinity contained in the worms. If the worm has a higher
concentration than the saline solution, it will gain weight,
meaning that the change will be positive. On the opposite
side, if the worm has a lower concentration than the saline
solution, it will lose weight, as water will go out to the
aquarium due to the osmotic gradient; thus it will cause
negative values in change. Bloodworms would be found mostly
near the ocean, as the salinity would be 35 ppt. Sandworms
would be found in both near ocean sites (where salinity is
quite high), and in other places (nearer to freshwater) as
well (where salinity is lower).
As to improve the accuracy of the experiment, we have
to make sure that most of the extra surface water from the
worms are removed prior to weight measurement. During the
experiment, some worms were dried more thoroughly than
others; some worms were just given a light pat.
Furthermore, the time at which the weights are recorded
could be extended to 48 hours instead of 24. This would
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allow greater visibility in data trends and validate the
hypothesis to a greater extent. More worms could also be
taken as to provide a wider range from which averages can be
taken and will reduce sampling error. Weight (in grams)
should not be rounded off, and taken as they are shown on
the scale as to improve accuracy. Each worm could be weighed
several times; as to make sure the readings are consistent.
Devoting all our attention towards the experiment can also
reduce human errors and making sure that every step taken is
necessary and done correctly.
The sandworms that my group recorded were from the 40
ppt (high salinity) aquarium and were observed to be
generally active. None of the worms were observed to be
inactive, and there were no mortalities. This may be because
sandworms are osmoregulators and do not get bothered by the
change in salinity. However, bloodworms may be less active
in 40 ppt conditions because they are osmoconformers and are
not suitable to live in that salinity (although most
tolerate it, they could potentially start to die out if they
were exposed for more than 24 hours).
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Urination is not only a process of removing metabolic
waste, it is also a technique used for osmoregulation. The
worm’s parapods move in rhythm and draws fluid inside the
tubular system, which enters the nephridia. These tubular
structures reabsorb essential substrates such as amino
acids, and removes excess water, metabolic waste and ions.
This process allows the worms to osmoregulate themselves.
In conclusion, both the estuarine worms were able to
tolerate the different salinities, even though there were
mortalities. The bloodworm has less tolerance and hence had
more deaths; opposite goes for the sandworm. I learnt that
although the worms co-exist alongside each other in the same
environment, they are completely different in the sense that
one is a euryhaline and another is stenohaline. Each species
adjusted to the different salinities, and some died because
they couldn’t adjust to the new saline environment. The
bloodworm, although used to living in 35ppt, could well
adjust to 30ppt condition. However, when it is pushed too
far from the comfort zone (say, 40 ppt), then the worms
start to die out. This shows that osmoconformers are able to
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adjust to slight changes in environment, but if pushed too
extensively, they will not be able to adjust. It applies to
the sandworm, if they were placed in a saline solution that
is much too high or low in concentration, they might be
shocked and die out before self-regulation kicks in.
To further this investigation, an experiment should be
done with different and more extreme salinities (ranging
from 0-70ppt). More estuarine animals (other than worms)
should also be experimented on, such as fishes or crabs as
to further the research and see its application and effects
on different types of organisms. Overall, the experiment was
successful and yielded the results that were laid out in the
hypothesis.
Table and Figures:
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Figure 1. Shows the sand worm’s change in weight over time (0
hour, 4 hour, 8 hour and 24 hour). Y-axis shows the change in
weight, and X-axis shows the time in hours. Measurements were
taken at 20ppt, 30ppt and 40ppt. The graph shows the weight is
nearing normal weight.
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0 5 10 15 20 25 30
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
Sand Worm's change in weight with respect to time
20 PPT30 PPT40 PPT
Time (hours) cha
nge
in w
eigh
t
Figure 2. Shows the bloodworm’s change in weight over time (0 hour, 4 hour, 8 hour and 24 hour). Y-axis shows the change in weight, and X-axis shows the time in hours. Measurements were taken at 20ppt, 30ppt and 40ppt.
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0 5 10 15 20 25 30
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
Bloodworms
20 PPT30 PPT40 PPT
Time (hours)
change in weight
Figure 3 shows the mortality of bloodworms after being exposed to the three different salinities. Mortalities are recorded from 0 hour, 4 hour, 8 hour and finally 24 hour. The x-axis shows the time in hours, and the Y-axis shows thenumber of worms that have died.
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0 4 8 240
0.51
1.52
2.53
3.54
4.5
Mortality of Bloodworm
20 ppt30 ppt40 ppt
Time (hours)
Worm Deaths
Figure 4 shows the mortality of bloodworms after being exposed to the three different salinities. Mortalities are recorded from 0 hour, 4 hour, 8 hour and finally 24 hour. The x-axis shows the time in hours, and the Y-axis shows thenumber of worms that have died.
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0 4 8 240
0.5
1
1.5
2
2.5
Mortality of Sandworm
20 ppt30 ppt40 ppt
Time (hours)
Worm Deaths
Figure 5 shows a bloodworm with its transparent skin that allows its red color to be exposed to our naked eye. It hasparapods, four jaws jaws and over 300 segments.
Figure 6 shows a sandworm with its greenish brown skin colorand its much more developed parapods that enables it to limpfaster. It has two jaws and over 200 segments.
Literature cited:
Manual:
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Laboratory Manual. Science of living systems 22. Human influences on life in the Sea. 2011, Harvard University, Cambridge, MA.
Text:
Wilson, W.H, Jr, and R.E Ruff. 1988. Species profiles: Life histories and environmental requirements of coastal fishes and invertebrates (North Atlantic)—sandworm and bloodworm. U.S Fish. Wildlife. Serv.Biol. Rep. 82(11.80) U.S Army Corps of Engineers, TR EL-82-4. 23 pp.
Internet:
Kenneth S. Saladin. Osmoregulation. Retrieved from http://www.biologyreference.com/Oc-Ph/Osmoregulation.html
Restore America’s estuaries (est. 1995) what is an Estuary. Retrieved from http://www.estuaries.org/what-is-an-estuary.html
United States Environmental Protection Agency (EPA, est. Dec1970) what is an estuary. Retrieved from http://www.epa.gov/owow_keep/estuaries/kids/about/what.htm and http://water.epa.gov/type/oceb/nep/about.cfm
Laney P. Austin. May 2011. Nereis Virens. Retrieved from http://wiki.hicksvilleschools.org/groups/hsbiology/wiki/ebe67/Nereis_virens.html
Pictures:
Figure 5 (bloodworm) retrieved from http://zottoli.files.wordpress.com/2011/01/glycera-dibranchiata-coiled-worm-orrs-island-bridge-mud-flat-october-5-2006-054.jpg?w=576&h=499
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