Hydrodynamics of Anthopleura xanthogrammica
-1-
It has been reported that the siphonoglyph of the sea anemone
Metridium marginatum pumps water into the coelenteron (Parker, 1919).
Batham and Pantin (1950) have monitored coelenteric pressures for
Metridium senile. In general however, a limited amount of research
has been devoted to the hydrodynamics of the sea anemone. My inves¬
tigation has been directed at various aspects of the hydrodynamics
of the sea anemone Anthopleura xanthogrammica. Internal pressures have
been measured, flow rates determined and movement of water through the
body wall' monitored.
MATERIALS
The Anthopleura xanthogrammica studied were collected inter-
tidally off of Monterey California and were kept in running sea water
aquaria for no more than three weeks prior to use.
ETHODS AND RESULT:
I.
An Anthopleura xanthogrammica was anaesthetized in MgClo-H20
for one hour. After which an incision was made in the center of the
pedal disk and a 1.5 cm (external diameter) plastic tube was inserted
(see figure 1). The lengths of the incision extending beyond the tube
were sewn with surgical thread to close the tissue around the tube.
The anemone was then allowed to settle on a piece of styrofoam with
the tube extending through a hole in the styrofoam.
With twelve hours allowed for recovery from the MgClo, the
system was inverted and measurements of the hydrostatic head were
Hydrodynamics of Anthopleura xanthogrammica
-2-
taken. Readings were taken daily for ten days and once weekly for the
following three weeks in normal unstimulated situations as well as after
prodding.
-Results-
No leakage around the tube was observed when a solution of
methylene blue in sea water (Fisher Sci. Co. M-291) was injected into
the coelenteron.
1) Resting pressure (unstimulated) varied between 9 and 11 mm
of sea water. The mean was 10.0 mm.
2) In response to prodding (fast closure) the maximum hydro¬
static head measured was 30 mm of sea water.
II. Monitoring of water movement through Anthopleura xanthogrammica
A. An Anthopleua xanthogrammica was cannulated as described in
part I and allowed to settle onto a plexyglass plate. After a 24 hour
period of recovery from the MgClo as well as immediately following the
MgClo exposure the cannula was connected toa flow meter. An air bubble
was introduced into a 1 cc pipette; flow was taken to be the displacement
of the bubble with time (see figure 2). Visual readings were taken
once per minute for 140 minutes.
The anemone and flow meter were in a running sea water aquarium
whose temperature was 11° Centigrade.
-Results-
Rhythmic oscillations are evident in a plot of bubble dis¬
placement versus time (figure 3). The mean period of eight peaks is
18.3 minutes (standard error 0.71). The maximum rate recorded was
6 ml of water per hour
Hydrodynamics of Anthopleura xanthogrammica
-3-
The anemone can move water into its coelenteron but lacks
the mechanism to expell it when its muscles are inactivated with MgClo
(figure 4).
B. In order to monitor flow as well as pressure over a longer period
of time the anemone was connected to a Grass Model 5 Polygraph. A
force transducer was used to measure flow and a pressure transducer
to measure pressure (see figure 5). The response of the animal to
addition and subtraction of coelenteric volume was recorded.
-Results-
Figure 6-a shows the polygraph reading from the pressure trans¬
ducer and figure 6-b readings from the transducer measuring flow.
After 2cc of water were removed from the anemone (x on figures 6-a,b)
therewas an immediate drop in pressure, a result of the change in volume.
Shortly thereafter there was a sharp increase in pressure which reached
an amplitude greater than that of the prestimulus reading. The pressure
then returned to the pre-stimulus value. Following the sharp decrease
in coelenteric volume (figure 6-b, point x) there is a slow positive,
with respect to the change in pressure, flow to the pre-stimulus volume.
Figures 6-c and 6-d show polygraph readings from the pressure transducer.
The increases in pressure at points xo and xl, x2, x3, x4, x5 result
from single and serial injections of 2cc of sea water into the anemone.
Note the return of the pressure values to pre-stimulus levels. Visual
observations revealed no gross posture changes due to water addition or
subtraction fromuthe anemone.
III. Water movement through the body wall
Hydrodynamics of Anthopleura xanthogrammica
-4-
The body wall tissue of an anaesthetized animal was stretched
to about twice its anaesthetized size around the end of a 1.5 cm
internal diameter flanged glass tube. The tissue was securely fastened
and sealed with waxed string. From three to gight tubes were made
per animal. The tube was placed in running sea water for 12-16 hours,
Various modifications were made; 1) tissue Right Side Out (RSO), the
interior portion of the body wall was on the inside of tube B (see
figure 7), with and without a hydrostatic head of 9mm (to approximate
the internal pressure of the anemone), 2) tissue Inside Out (ISO), the
exterior portion of the body wall was on the inside of tube B, with and
without a hydrostatic head.
A series of six experiments were conducted, usually with
replicate tubes in each experiment, see table 1. All tubes in each
experiment were from the same animal. Experiments were performed at
room temperature with sea water filtered through fl filter paper unless
otherwise indicated. Samples taken during -experimentation were taken
from vessel B, after mixing and replaced with equal volumes of sea
water.
-Results-
The results from experiments a through f are summarized in
table 2. These experiments show that there is movement of tritiated water
through the body wall, whether or not the tissue is stretched or un¬
stretched. In every experimental animal (RSO) movement up the hydrostatic
head is greater than movement through the tissue without the pressure
gradient. Movement of water from the inside to the outside of the anem¬
one (ISO) is up to 40% slower. The mean inward flow (RSO) with and
Hydrodynamics of Anthopleura xanthogrammica
-5-
without the pressure gradient is 0.089 ml/m2/hour. The mean ourward
flow (ISO) with and without a hydrostatic head is 0.048 ml/cm/hour.
The difference is significant (student's t-test p£ 0.001). The approx¬
imate surface area of the whole anemone whose flow was previously measured
as 6.5ml/hour is 200 cm2. By extrapolation of these tritium data it
is seen that the anemone had a potential flow through the body wall of
8.2 ml/hour. Data from experiments e and f show that when tritium is
not used as a tracer no net flow across the body wall is observed.
DISCUSSION
The implanted tube and corresponding column of water, acting as
an extension of the anemone offers a means of easily monitoring the
internal pressure of Anthopleura xanthogrammica. The average measurement
of the unstimulated anemone's coelenteric pressure (10.Omm of sea water)
is higher than that recorded for Metridium senile (Batham and Pantin,
1950), 2.6 mm of water. Anthopleura xanthogrammica which inhabits an area
much closer to the zero tide level than does Metridium senile is likely
to experience relatively pronounced surf shock. The selective advantage
of a higher coelenteric pressure could be resistence to flexure under
the forces of the surf.
The posture assumed by a sea anemone is dependent of the balance
between coelenteric volume and muscular tension, i.e. pressure. A decrease
incoelenteric volume results in a decrease in coelenteric pressure (figure
6-a). That the rate of return of the pressure following an addition or
removal of water is large relative to the rate of return of the volume
indicates that for the anemone to maintain a specific posture a specific
pressure must be maintained.
Hydrodynamics of Anthopleura xanthogrammica
-6-
The results summarized in figures 3 and 4 suggest that while
the influx of water is not controlled muscularly, the coelenteric volume
and hence pressure and posture are. When the volume increases to the
upper limits for a specific posture there is muscular contraction and
concomitant deflation. The cyclical activity may in part explain the
rhythmic oscillation observed. A regulatory mechanism is implied for
queing muscular contraction and the accompanying deflation. Perhaps
it is a stretch and/or a pressure receptor in the anemone body wall.
The results from experiments testing the movement of water
through the anemone body wall are somewhat enigmatic. Results from the
tritium experiments indicate that there is undoubtedly movement of
tritiated water through the body wall. Simple diffusion as the sole
mechanism can be discounted as flux through RSO tissue is up to
40% greater than that through ISO tissue. This is further supported by
the fact that there is movement of water up a hydrostatic head. The
assumption was made that tritiated water could be tsûed as a tracer
because it had the same properties as normal water. However, when non¬
This is perhaps
tritiated water was used no net flow was observed.
accounted for by gradients created by unequal ciliary activity on each
side of the tissue.
The following experiments are suggested in hopes that they
will clarify the observed results. 1) Create an apparatus such that
net flow can be monitored by observation of a bubble in a pipette (as
in experiments e and f) and movement of tritium monitored by sample
taking and disintegrations measured. 2) Repeat experiments a through
d while stirring continually and after ciliary activity has been stopped.
It is important for the understanding of anemone biology that
Hydrodynamics of Anthopleura xanthogrammica
-7-
this question be resolved. Differential movement of water suggests that
there is some sort of pump present, sodium perhaps. The role of the
siphonoglyph come into question. Perhaps the use of tritium is inappro¬
priate in such experiments.
SUMMARY
1. Anthopleura xanthogrammica, in an unstimulated stae, maintains a
positive coelenteric pressure whose mean is 10.0 mm of sea water
(n= 13). In response to prodding a maximum pressure of 30 mm of sea water
was measured. This high maintained pressure, relative to that of
Metridium senile, may have adaptive signigicance.
2. Rhythmic oscillations of flow have been observed. Evidence indicates
that deflation is muscularly controlled and inflation not.
3. Evidence suggests that a pressure is important for particular position-
al configuration and that there is some regulatory mechanism, perhaps
stretch of pressure receptors in the body wall.
4.- There is transport (not simple diffusion) of tritiated water through
the body wall into the coelenteron. Possibilities of sodium and/or water
pumps exist. Transport of water through the body wall challenges present
theory of anemone hydrodynamics..
5. A final theory of water movement through the body wall is presently
not submittable because of conflicting results of movement of tritiated
and non-tritiated water.
Hydrodynamics of Anthopleura
thogrammica
xan
FERENCES
Batham, E. J. and Pantin, C.F.A. (1950) J. Exp. Biol. 27, 264
Parker, G.H. (1919) The Elementary Nervous System Philadelphia:
Lippincott
ACKNOMLEDGEMENT.
Thanks to the staff of Hopkins Marine Station, Robin Burnett in
particular, for their guidance and understanding.
L

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A
B
TISSUE

..
Hydrodynamics of Anthopleura xanthogrammica
TABLE I
A. Five tubes were set up, in each instance vessel A contained sea
water to which tritiated water was added (10-2 mci/ml) and vessel B
normal sea water.
tubes 1, 2, 3, were RSO with 9mm hydrostatic head
tubes 4, 5, were RSO without a hydrostatic head
B. Eight tubes were set up. Set-up was as in A
tubes 1, 2, RSO w/o hydrostatic head
Tubes 3, 4*, RSO w/ hydrostatic head
tubes 5, 6, ISO w/o hydrostatic head
tubes 7, 8, ISO w/ hydrostatic head
C. Eight Tubes were set up as in A and B above
tubes 1*, 2*, RSO w/o hydrostatic head
tubes 3, 4, RSO W/ hydrostatic head
tubes 5*, 6, ISO w/o hydrostatic head
tubes 7, 8, ISO w/ hydrodtatic head
D. Six tubes were set up as above
tubes 1, 2, RSO w/o hydrostatic head tissue unstretched
tubes 3*, 4, RSO w/o hydrostatic head tissue stretched
tubes 5, 6, ISO w/o hydrostatic head
E. Five tubes were set up and connected to a lec pipette. Readings
were taken for six hours. For experimental set-up see figure 7.
F. Six tubes were set up, three from one animal and three from another.
Set-up same as E above.
Hydrodynamics of Anthopleura xanthogrammica
TABLE II
ISO w/o
ISO w/o
RSO w/
RSO W/
RSO w/
RSO w/c
Al
o.088
2*
o.092
o.096
o.074
0.073
0.072
5
o.11
Bl
0.096
o.079
o.13
1*
o.037
o.038
o.040
8
C1*
o.10
o.087
0.073
5*
o.047
—
o.o90
DI
o.o99
o.11
3*
0.073
o.062
o.053
o.044
-
El,
2, 3, 4, 5, flow less than o.ool
flow less than o.ool
Fl, 2, 3, 4, 5, 6,
ISO w/
o.032
o.040
o.047
o.049
1S0 w/
0.036
o.048
Hydrodynamics of Anthopleura xanthogrammica
FIGURE CAPTIONS
Figure 1. Cannulated anemone and apparatus used to measure internal
pressures. The mean pressure recorded was lOmm of sea water.
Figure 2. Cannulated anempne connected to a pipette flow meter.
Visual readings of the displacement of the air bubble with time
were taken.
Figure 3. Displacement of the air bubble in the pipette flow meter
versus time. Values of displacement are relative to the base line.
The absolute value of the base line has not been determined. Note
the rhythmin oscillations, with a mean period of 18.3 minutes. A
maximum positive flow rate of 6 ml/hour can be discerned. An upward
trend in the graph indicated flow into the coelenteron.
Figure 4. Displacement of the air bubble in the pipette flow meter
versus time for the animal whose muscles have been inactivated with
MgCl.. Displacement values are relative to the base line. The absol¬
ute value of the base line has not been determined. Point A indicates
the observation of an air bubble leaving the mouth of the anemone.
Figure 5. Anemone and apparatus connected to a Grass Model 5 Poly.
graph. Pressure and flow were measured. A is a vessel attached to a
force transducer-flow into this vessel was used as a means of monitoring
flow into and out of the anemone. B is a pressure transducer.
Figure 6. A--readings from the pressure transducer. B--coincident
readings from the flow meter. X--marks the removal of 2cc of sea
water from the coelenteron. Note relative rates of increase in A
and B after the water removal. C--recordings from the pressure trans¬
Hydrodynamics of Anthopleura xanthogrammica
FIGURE CAPTIONS (continued)
ducer. D--recordings from the pressure transducer. X, marks the
addition of 2cc of sea water into the coelenteron. X,through Xg
mark serial additions of water to the coelenteron. In A, B, C, D,
the return to pre-volume change levels.
Figure 7. 1, Apparatus used to measure flow of tritiated water through
the body wall. Test samples were taken from vessel B. 2, Apparatus
used to measure flow of non-tritiated water through the body wall
* indicates that the tube was not used for such reasons
Table II.
as torn tissue or bad preparation.
Units are ml/m2/hour.