ABSTRACT
Locomotion was studied in seven species of marine diatoms.
A scanning electron microscope was employed to observe frustule
morphology, secretion from the raphe system, and trails.
Active secretion may be involved in locomotion, but to varying
degrees in each species of diatom. It is also possible that
secreted trails are, for the most part, just a by-product of
locomotion in certain species.
Differences in sensitivity to the content of calcium of
sea water may indicate less direct use of secretion for loco¬
motion in Nitzschia Longissima and Bacillaria Paradoxa. In
addition, drugs such as cytochalasin D and movement in sea
water flow seems to confirm the fact that microtubules are
not involved and that at least Navicula Vulpina and Nitzschia
Closterium use only their posterior portions of their raphe
systems during locomotion.
Wing-like extensions of the frustule used in coupling
colonial Bacillaria Paradoxa were observed for the first time.
INTRODUCTION
Diatoms are one of the most abundant plants in the world,
producing 25 to 30 percent of the world's oxygen. It seems
strange that a plant, so basic for our survival, is so
little understood. Moving about in beautiful glass houses,
they reach speeds quite fast relative to their size. The
mechanism for this locomotion is unknown, but it seems to be
unique to these little plants. Theories about how diatoms
locomote have been proposed for over one hundred years and
include ideas from jet propulsion to cytoplasmic capping.
All studies of locomotion now, though, seem to be coupled
to the unique morphology of the diatom frustule (Fig. 1). The
raphe system, gut into the silica frustule, is an integral
part of locomotion. Secretion of mucopolysaccarides are extru¬
ded along this channel and are one of the means by which the
diatoms move. The frustule, or shell, is made of silica and
divided into three parts—two valves and a girdle. The anal¬
ogy to a petri dish can closely be drawn to the frustule if the
two valves are compared to the upper (cover) and lower half of
a petri dish, one fitting into the other and the girdle being
a piece of tape surrounding the outer edges. The raphe sys¬
tem, which usually consists of a single linear channel opening
through to the cytoplasmic wall, is directly in the center of
each valve. Each raphe is then split in half by two central
pores, each ending in two terminal pores.
1 -
There are only four theories that seem plausible as to
the exact method of locomotion in diatoms. These are as fol¬
lows (Fig. 2):
1) Mucilage secreted at the anterior terminal pore and
posterior central pore is driven by undulating actin.
The mucilage is forced out and against the substrate
by the actin. The mucilage then acts to push the
diatom along. (Jarosch, 1962)
2) Trails are secreted through the entire raphe and
expand upon leaving it. The secreted trail then pushes
along the substrate to force the diatom forward.
(Hopkins & Drum, 1966)
3) Trails are secreted from the anterior terminal pore
allowing for locomotion, and secretion on the dorsal
valve creates streaming. Streaming is the observation
of particles being moved along the dorsal raphe rapidly
back and forth. (Harper & Harper, 1967)
4) Capillary flow of a viscous liquid along the raphes
flows outward and becomes trails only at the anterior
central pore and posterior terminal pore. (Gordon &
111
Drum, 1970)
All of these theories cite secretion of some sort of muco¬
polysaccharide as the direct means of locomotion and claim the
presence of secreted trails on the substratum. Drum and Hopkins
(1965) also claimed actin-affecting drugs reacted on diatoms,
indicating that actin may also be involved.
In this study I examined seven diatom species. I was
asking the question whether it is correct to assume that loco¬
motion is exactly the same in every diatom, i.e., whether one
theory suffices for all diatoms. To probe the possibilities
of locomotion in marine diatoms six approaches were used:
1) Morphological studies of diatom frustules.
2) Sensitivity of diatoms to ion changes in sea water.
3) Whether calcium, since it is linked to the secretory
mechanism of pulling vesicles to the cytoplasmic wall
for excretion, is linked to locomotion in diatoms.
Calcium-free water was used in this study.
4) The use of chemical additives for analysis for effects
on secreted trails.
5) Scanning electron microscopy with gentle fixation
methods to carefully analyze the raphe systems during
secretion and the secreted trails.
6) Observations of differences between species with
respect to their speeds and methods of movement in and
out of sea water mainstream flow.
In addition to analyzing the possible methods of locomo¬
tion for each of the seven species, I was able to observe the
coupling mechanism of the diatom Bacillaria Paradoxa. This
mechanism, which is a delicate extension of the silica frus¬
tule has never been observed before.
MATERIALS AND METHODS
I selected seven species of diatoms in which to study
locomotion. They are as follows: Bacillaria Paradoxa,
Navicula Vulpina, Nitzschia Closterium, Eunotia Soleirolii,
Eunotia Carolina, Pleurosigma Elongatum, and Nitzschia
Longissima. These species were chosen because of their abun¬
dance in the populations sampled.
The marine diatoms used in the following experiments
were collected from the indoor salt water pumping system used
by the Hopkins Marine Station in Pacific Grove, California.
The fresh-water diatoms were collected from a nearby stream.
Some of the Nitzschia Longissima were cultured in the labora¬
tory. All diatoms were stored at approximately 20°C at normal
day and night intervals.
All experiments concerning the ionic content of the arti¬
ficial sea water used were repeated 30-65 times depending on
the consistencies of the results. Trials were done at least
30 times on each species. If those 30 results were within
958 of each other, the testing was stopped. No test went
longer than 65 times. Averages of all the trials were then
taken, and the results recorded. Observations were taken at
approximately the same time of day and for each of the seven
species separately.
When changing solutions, during ionic content studies,
three methods were employed:
1) For studies done longer than three hours the diatoms
were transferred from their holding container into a
petri dish with cover-slips resting on the bottom.
After a sufficient amount of time, which usually was
at least one-half hour, the diatoms adhered to the
cover-slips and were transferred via the cover-slips,
They then were rinsed in the new solutions fairly
vigorously and placed in their new solution as free
as possible from any previous liquid.
2) For cruder, long-term studies, diatoms were concentrated
in a single spot on tissue paper with the use of a
pipette and then dried and scraped off into the new
solution.
3) In order to visualize immediate effects of new solu¬
tions on diatoms, solution changes had to be made under
the cover-slip while viewing through a light micro¬
scope. I was able to accomplish this by putting the
diatoms in their original solution on a glass slide.
I then placed a cover-slip, raised on two sides by
vaseline, over them. By placing the new solution on
one side of the cover-slip I was able to "pull" it
through with tissue paper on the other side. This
method effectively allowed for complete changes of
solutions quickly and during visualization.
To observe particle streaming along the raphe of the dia¬
toms, a fine grain charcoal colloid suspension was diffused
under a raised cover-slip while being observed through a
light microscope, or simply added to their solution.
The diatoms were observed in artificial sea water with
varied ionic contents. The base formula for this artificial
sea water, which was used as a control throughout the experi¬
ments, was: 47 millimoles Nacl, 1 millimoles KCl, 5 milli-
moles MgCl., 1 millimoles Cacl,, and 114 grams triss HCl as a
buffer. Distilled water was then added until 100 milliliters
was reached and triss base was added to bring the P.H. up to
7.8. The osmolarity was checked on each solution and kept at
980 milliosmoles.
Diatoms were first tested in chelated and unchelated
calcium-free sea water. The base formula for artificial sea
water was used omitting the calcium. E.G.T.A. at a 10 mM
concentration was incorporated in the chelated formula. The
cover-slip rinsing method was used at first in solution changes
until the effects were determined to be short termed. Disper-
sion under the cover-slip during visualization was then pre¬
ferred. The diatoms were viewed under 100x, 400x, and 1000x.
They were timed with a stop watch over 260 microns. The
microscope ocula were calibrated using an optical stage
micrometer and adjusted for each magnification. Cessation of
motion was determined to be complete when at least 908 of the
movement from a certain species had ceased. Once stopped I
attempted to induce recovery using the base formula artificial
sea water.
Calcium was substituted by either barium chloride or
strontium chloride, of concentrations equal to the calcium
chloride in the control solution. The base formula artificial
sea water was used in recovery, and the short-term techniques
of observing the diatoms were used. Both solutions were non¬
chelated.
I also observed diatoms placed in the artificial sea
water with a calcium ionophore added at a 10 uM concentration.
The calcium ionophore was dissolved in D.M.S.O. [1 ul/mll. A
control of artificial sea water with D.M.S.O. at the same con¬
centration was used. Observations were taken using both long¬
and short-term methods of solution changing.
The effectspof local anesthetic tetracaine were studied.
The anesthetic, a calcium blocker, was added to the sea water
at a concentration of 1 uM and .5 uM. Only the short-term
method of solution changing was used.
To determine whether microtubules were involved in
locomotion, cytochalasin D was applied to diatoms in a 10 uM
concentration. The cytochalasin was dissolved in D.M.S.O.
[1 ul/mll and a control of artificial sea water with D.M.S.O.
at the same concentration was used. Both long- and short-term
methods of solution changing were employed.
Two enzymes, pronase and hemicellulase, and a complex of
abalone entrails were tested on the diatoms to help determine
the structure of the diatom trail. All these chemicals were
dissolved directly in the artificial sea water at concentra¬
tions of .005 g/ml, .0l g/ml, and .001 g/ml, respectively.
Recovery was recorded using artificial sea water. Both the
long- and short-term methods of solution changes were used.
Two other ion substitutions were used to observe their
effects upon the diatoms. These were both sodium substitutions,
one using N-methyl glutamine at the same concentration as
sodium and the other lithium chloride at concentration equal
to the sodium chloride in the control solution. Recovery in
both cases was achieved using artificial sea water and short¬
and long-term solution changing methods.
Potassium-free sea water was also introduced to the dia¬
toms simply by leaving the KCl out while making the artificial
sea water. Osmolarity was held at 980 milliosmoles by remov¬
ing distilled water, and the base formula artificial sea water
was used for recovery. Observations were made with the long¬
term methods of solution changing.
Lastly, the effects of P.H. were examined. Triss HCl
and triss base were used in adjusting the P.H. P.H. was
recorded on an electronic meter. Four solutions (P.H. 6.5,
9.2, 6.0, and a control of 8.08) were used. Rinsing with the
control was employed to examine recovery in the diatoms.
The movements of the diatoms in a flow was observed under
a light microscope using a vacuum suction device. A .5 mm
diameter polyurethane tubing was attached to a small aquarium
vacuum pump. The free end of the tube was placed against a
small piece of tissue paper that extended part of the way
underneath a cover-slip. The cover-slip was raised on a
glass slide on two sides by vaseline. In this manner an
even suction was created to pull water from under the cover¬
slip. The flow of sea water was varied by adjusting the height
of a gravity drip system attached by tubing to the other side
of the cover-slip. Flow speed was taken with an optical microme¬
ter and a stop watch while observing charcoal particle flow,
SCANNING ELECTRON MICROSCOPY
Four different methods of gentle fixation were used to
observe diatoms under the electron microscope:
1) A freeze drying method was used on fresh water diatoms,
the only type that would move in distilled water for
a prolonged period of time. The diatoms were trans¬
ferred to distilled water and allowed to locomote for
one-half hour before being placed in liquid nitrogen.
Distilled water was used to keep salt crystals from
forming during lyophilization, Äfter freezing on
cover-slips the diatoms were placed on a metal slab
which was half emersed in liquid nitrogen. The metal
slab was then placed in a vacuum and all liquids were
sublimed for approximately two days.
2) A second method of fixation was tried using osmium
tetroxide and gluteraldehyde in 18 and 48 solutions,
respectively. Two preparations of diatoms were made,
one with colloid charcoal particles and one without the
10
particles. The marine diatoms were placed on a cover¬
slip, allowed to locomote for one-half hour, and then
placed in 18 osmium tetroxide and 48 gluteraldehyde
fixative (osmolarity of 980) for one-half hour. They
were then transferred to sea water in a solution chang-
ing apparatus, designed by Bill Magruder, which very
slowly changes the osmolarity of the solutions. The
sea water was exchanged for distilled water over a
period of about seven hours. The distilled water was
then exchanged with acetone over approximately the same
period of time. The diatoms were then critical point
dried for two days.
3) The third method of fixation employed the same method
as t2 except the solution changes were stopped at the
distilled water point; no acetone was added. The dia¬
toms were then immersed in liquid nitrogen and all
liguids were sublimed off exactly as in method number
one.
4) The fourth method of fixation was used to observe the
morphology of the silica frustule. Marine diatoms
were centrifuged to concentrate them. They were then
acidified with a solution of concentrated sulfuric
and nitric acids for two days. After two days, they
were rinsed and centrifuged ten times with distilled
water. The water was removed by sublimation in a
vacuum device.
11
After all methods of fixation, the diatoms were coated
with gold and viewed using a Hitachi scanning electron
microscope.
RESULT!
Velocity of Diatoms: (Table 1)
In six of the seven species of diatoms I was able to
record speeds. Bacillaria Paradoxa, being colonial, moves the
whole colony at tremendous speeds relative to each individual,
making it almost impossible to record an individual speed.
The orders Eunotia and Bacillaria Paradoxa were most consis¬
tent, as the other orders tended to have more stop-and-go
motions. Pleurosigma Elongatum was by far the quickest, which
may be because of the extremely large raphe it possesses,
thereby allowing it a larger space for its locomotory mechan¬
ism.
Changes in the Ionic Content of Sea Water:
Calcium-free sea water with E.G.T.A. was introduced to
the diatoms because of calcium's probable relation to secre¬
tion (Fig. 3). Calcium has been cited as being needed for the
fibers that pull the secretory vesicles to the cytoplasmic
wall. Without calcium secretion stops. Cessation of motion
was recorded in all species except Nitzschia Longissima.
Distinct differences between the species Bacillaria Paradoxa
12
and Nitzschia Longissima were recorded in the time required to
stop and to recover.
Calcium-free sea water which was not chelated was also
used (Fig. 4). Significant differences between the species
Bacillaria Paradoxa and Nitzschia Longissima in their sensi¬
tivity to calcium-free water were recorded. Nitzschia
Longissima again being unsensitive. The unchelated calcium¬
free sea water, having a trace of calcium, showed the diatoms
to be sensitive even to slight variations of calcium. The time
required for cessation of motion, in general, was longer and
the time required for recovery was shorter.
Effects of calcium substitutions using barium and stron¬
tium are shown in Figs. 5 and 6. These ions substituted for
calcium for a finite period of time, and their substitution
time was not equivalent. Large differences between the
species Bacillaria Paradoxa, Pleurosigma Elongatum, and
Nitzschia Longissima were again recorded, and these differ¬
ences correlated with the differences found in calcium-free
sea water.
Other ionic changes were examined. The absence of sodium
with N-methyl glutamine substituted and, in a separate test,
lithium chloride substituted (Figs. 7 and 8). Potassium-free
sea water was also tested (Fig. 9). For both substitutions of
sodium-free sea water, large differences were recorded between
the species. Nitzschia Longissima was sensitive to N-methyl
glutamine substituted sea water, but insensitive to the lithium
13
chloride substitution. All species had long-term sensitivity
to potassium-free sea water, again with differences between
the species. Bacillaria Paradoxa never completely stopped
moving even after two days.
Chemical Additives:
Of all the chemicals added to the sea water, only one,
abalone entrails, stopped movement and allowed recover
Cytochalasin D, which inhibits microtubules, had no effect as
did the calcium ionophore and hemicellulase (Table 2).
Scanning Electron Microscope Studies of Frustules and Secretions:
(Figs. 10-22)
The secretion, a mucopolysaccharide, coming from the
raphe systems expands as it leaves the raphe and probably comes
from all along the raphe and not just the pores (Figs. 10-16).
The absence of trails suggests a new theory of secretion in
relation to locomotion. The secretion, many times, also seems
to be filament-like, and not as globular as previously thought
(Figs. 10, 11, and 16)
Movement in Flow:
In flow most diatoms which tried to move lost adherence
and were swept away. The majority of diatoms would immediately
stop when the flow reached 89 microns/sec. Before stopping
the Navicula Vulpina and Nitzschia Closeterium would sway back
14
and forth, attached only by their single posterior terminal
pore. When they did stop and adhered tightly, they would
attach their second anterior terminal pore.
S.E.M. Studies of Coupling in Bacillaria Paradoxa: (Figs. 23-35)
Delicate wing-like extensions of the frustules were observed
on Bacillaria Paradoxa when gentle fixation methods were employed.
Bacillaria move by sliding the large wing-extension of one
diatom into the smaller wing-channel of another. They use
only one of the two raphes on each valve to secrete on their
neighbor and thereby force themselves by. The quick oscilla¬
tions of one Bacillaria sliding past another are very similar
to particle streaming on a non-colonial type diatom. Similar
methods of contracting mucous through the raphe may, therefore,
be used. Bacillaria come to a stop very mechanically when
completely outstretched in the colony. A lip at the end of the
wing extension may explain the consistency of this stopping
mechanism. These extensions on Bacillaria Paradoxa are the
first ever observed. Two theories seem possible from the
evidence which includes a channel hook in which the wing exten¬
sion fits. They are diagrammed in Figs. 36 and 37. A lip on
the end of the wing extension appears to be the stopping
mechanism for their mechanical oscillations (Fig. 26).
DISCUSSION
Of the seven species of diatoms used in studies of
sensitivity to changes in ionic content of sea water, each
species had its own specific response time. With calcium-free
water, in which the response time was relatively short, the
differences between the species of Bacillaria Paradoxa and
Nitzschia Longissima in sensitivity may be related to the role
secretion plays in locomotion. Calcium has been indicated to
be needed in the secretion process of bringing the vesicles
to the cytoplasmic walls. Without calcium secretion stops.
Since secretion, or the production and excretion of poly¬
mucosaccharides, should stop, the great length of time for
Bacillaria to cease movement and Nitzschia Longissima's in¬
sensitivity compared to the relatively quick response times of
the other species indicates production of polymucosaccharides
may play a less direct role in locomotion in some species than
in others. Changes in other ions may not be linked to the pro¬
duction of mucopolysaccharides or locomotion. These tests
show how diatoms are extremely sensitive to almost any ionic
changes which, therefore, may have partially masked the
calcium-free sea water experiment.
Since I have made observations of very quick particle
streaming, back and forth, across the dorsal raphe and even
the "reeling" in of particles from a distance up onto the raphe,
it seems essential that there be some sort of contractile
16
mechanism within the secretion. Simple recoil of outstretched
mucous could not explain the rapid reversing of direction dur¬
ing particle streaming. Since diatoms were affected by actin
inhibiting drugs and negatively by cytochalasin D, it seems
plausible that these fibers be actin.
Trails of secretion have been reported but in relatively
few species. No trails were even observed in the species I
looked at under the S.E.M. Instead, for the first time, secre¬
tions were seen adjacent to the raphes. They were rolled up
along the raphe or strung-out and fiber-like but never laid
upon the glass. These secretions were fiber-like in that
secreted material is usually distinctly globular or smooth
under the E.M. These secretions were much more rough and torn
as if they contained structural fibers. The fiber-like secre¬
tions that were seen were always attached to a particle.
A simple observation that seems to agree with the four
previous theories of locomotion is the action of diatoms in a
flow. Since Navicula Vulpina and Nitzschia Closterium swing
back and forth by their posterior terminal pore while moving
in a fairly slow flow, it seems to be correct to assume that
at least some diatoms are attached only by their posterior ter¬
minal pore and maybe their posterior central pore while mov¬
ing. When immobile, they seem to adhere at least with both
terminal pores.
The collection of data in this study indicates to me that
a new theory for locomotion in diatoms can be introduced. The
17
basis for this theoy should be that production and excretion
of a mucopolysaccharide through the raphe is probably involved,
but, because no trails were observed, to varying degrees
for certain species. In Navicula Vulpina and Nitzschia
Closterium it appears only the posterior terminal pore and
maybe the posterior central pore are used during locomotion.
The remainder of the locomotory activity in Bacillaria and
other species observed particle streaming must reside in some
contractile mechanism, possibly actin fibers. Theories such
as a rotating tractor tread with reusable mucous (maybe leaving
a portion of the mucous down for a trail) or secretion along¬
side the retractable filaments are still possible depending
on the species in question. Certain types of Navicula, for
example, have readily been observed secreting large webs of
mucous which is used only as a substrate in which to live. On
the other hand, Bacillaria Paradoxa, which lives in colonies,
has no trails. The secreted material definitely seems to
expand, though, or appears ribbon-like, in some micrographs.
In any case, a general theory for locomotion seems too broad
to incorporate such highly variable plants as diatoms.
In the study done on coupling in Bacillaria Paradoxa
definite wing-like silica extensions of the frustule have been
observed. I believe the reason these have never been seen
before is because of less mild fixation methods and few rela¬
tively S.E.M. studies done on them. The gentle fixation methods
used in this study seem to have uncoupled the delicate
18
structures without breaking them. Two theories of exactly how
the wing-like extensions are used in coupling have been intro¬
duced, but the exact method needs more thorough study. The
Bacillaria do seem to have two raphes, one of which secretes
or pushes along on the neighboring diatom. The wing extensions
also show a lip on the end which would allow for their behav¬
ior as they slide past each other and become fully outstretched,
Further study is definitely indicated here to show the exact
positioning of the wing extensions in the coupling of the
colony.
ACKNOWLEDGMET
I would like to thank Bill Magruder very much for his
help on the S.E.M. and fixation method. William Gilly, Chuck
Baxter, and Mark Denny also deserve thanks for their advice
throughout the quarter.
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Bretsche, M. S. 1984.
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E. E. 1943. Marine Plankton Diatoms of the West Coast
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[Edl Sverdrup, H. V.
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University of California Press, Ca.
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R. W.; Gordon, R.; Berden, R; and Goel, N. S
Drum,
Weakly coupled diatomic oscillators Bacillarias Paradox
resolved. J. Physol. Supple. 7:13.
R. W. and Hopkins, J. T. 1966. Diatom locomotion, an
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explanation. Protoplasma 62:1-33.
R. W. and Pankratz, H. S. 1964. Pyrenoids, raphes and
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Diatom Locomotion: A Consideration of
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L. A. 1982.
Movement in a Highly Viscous Situation. Brit. Physol.
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Diatom Locomotion Computer Assisted
Edgar, L. A. 1979.
Analysis of cine film. Br. Physol. J. 14:83-101.
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Cellular Secretion. (Methods in Cell Biology, Vol. 23.)
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Harper, M. A. and Harper, J. F. 1967. Measurement of Diatom
Adhesion and Their Relationship with Movement. Br.
Physol! Bull. 3:195-207.
The diatom trail. J. Quekett Microsc.
Hopkins, J. 7
1967.
Club, 30:209-217.
Hendey, N. I. 1964. An Introductory Account of the Smaller
Algae of British Coastal Waters. Her Majesty's Stationery
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Patrick, R. and Reime, C. W. 1966. Diatoms of the United
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Simpson, T. C. and Benjamin, V. E. [Edl. 1981. Silicon and
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Spangle, L. and Armstrong, T. B. 1973. Gliding Motility of
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Fresh-Water Algae. Sparks Press, N.C., 324 p.
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ABLI
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8

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146
FIGURE LEGENDS
Fig. 1: A simple diatom showing the raphe system and terminal
and central pores.
Five theories of locomotion. The fifth theory being
Fig. 2:
newly introduced.
Fig. 3:
Calcium-free sea water with E.G.T.A. The graph shows
definite differences between Bacillaria, Nitzschia
Longissima, and the two Eunotias. Left bar: time
until cessation of motion occurs. Right bar:
recovery time.
Unchelated calcium-free sea water showing differences
Fig. 4:
between Bacillaria Paradoxa and the six other spe¬
cies. Nitzschia Longissima was unaffected. Left
bar: time unt
cessation of motion occurs. Right
bar: recovery time.
Fig.
Barium substituted for calcium showed significant
differences in sensitivity between Bacillaria, Pleuro¬
sigma, and Nitzschia Longissima. Barium substituted
for a finite period of time. Left bar:
time until
cessation of motion occurs. Right bar: recovery time.
Fig. 6
Strontium substituted for calcium for a finite period
of time. Bacillaria deviated significantly from
Eunotia Caroline, Pleurosigma Elongatum, and Nitzschia
Longissima. Left bar: time until cessation of
motion occurs. Right bar: recovery time.
All species were sensitive to sodium-free water sub¬
Fig. 7:
stituted with N-methyl glutamine. Navicula Vulpina
deviated significantly from all the other species in
the time required for cessation of motion. Left bar:
time until cessation of motion occurs. Right bar:
recovery time.
Fig. 8:
Lithium chloride substituted for sodium for a finite
period of time. Bacillaria deviated significantly
Left bar: time until
from the six other species.
cessation of motion occurs. Right bar: recovery time.
Sensitivity to potassium-free sea water was not very
Fig. 9
Bacillaria never completely stopped. Left
acute.
bar: time until cessation of motion occurs. Right
bar: recovery time.
Fig. 10: Filament-like secretion coming from Bacillaria. The
filament was attached to a charcoal particle. Method
+2 fixation.
Ribbon-like secretion. Method +2 fixation.
Fig. 11:
Fig. 12:
Secretion from the raphe of Pleurosigma. Method +2
fixation.
Fig. 13:
Secretion from the underside raphe of Bacillaria.
Method +2 fixation.
Fig. 14:
Secretion along the raphe of Pleurosigma. Fixation
method +3.
Fig. 15:
Secretion along the raphe. Fixation Method +2.
Fig. 16:
Fiber-like secretion from the raphe of Bacillaria.
Secretion was attached below to a particle of char¬
coal.
Fig. 17:
Secretion near the terminal pore. Fixation method
+2.
Fig. 18:
Raphe system behind silica bridges. Fixation method
+4.
Secretion from the terminal pore of a fresh-water
Fig. 19:
diatom. No trail present. Fixation method f1.
Fig. 20: Raphe structure of Pleurosigma. Fixation method #3.
Fig. 21:
Terminal pore and raphe of Navicula Vulpina. Fixa¬
tion method +4.
Terminal pore and raphe of Nitzschia Closterium.
Fig. 22.
Fixation method +4.
Valve view of two coupled Bacillaria.
Wing exten¬
Fig. 23:
sion visible on right diatom. Fixation method #2.
Fig. 24:
Curvature of wing extension visible on Bacillaria.
Fixation method +2.
Coupled Bacillaria with wing extensions broken off,
Fig. 25:
wing hooks very visible. Fixation method +2.
Lip stopping mechanism on wing extension visible on
Fig. 26:
Bacillaria. Valve view. Fixation method f2.
Single Bacillaria with wing extension visible.
Fig. 27:
Fixation method +2.
Fig. 28: Curved wing extensions on Bacillaria. Fixation method
+2.
Fig. 29:
Bridges held wing extension are visible. Fixation
method +2.
Close view of silica extensions. Fixation method
Fig. 30:
+2.
g. 31:
Single Bacillaria with both wing extensions visible.
Fig. 32:
Lip stopping mechanism visible on the end of silica
extension. Fixation method +2.
Fig. 33:
Silica extension. Fixation method +2.
Terminal end of Bacillaria showing wing extension.
Fig. 34:
Fig. 35: Close view of silica wing. Fixation method +2.
Fic
36: Schematic of possible theory of Bacillaria coupling.
Channel hooks are smaller than the wing extensions.
All connections are on the valves.
Schematic of possible theory of Bacillaria coupling.
Fig. 37:
Channel hooks are on the girdle, and wing hooks are on
the valves.
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VALVE
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COLONIAL BACILLARIA PARADOXA
SECRETION
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GRRDLE VIEW
COLONIAL BACILLARIA PARADOXA