Neale, J.R.
Rheotaxis
Summary of Course Work
Questions to be handeled in paper
Evaluations of the course and my work
Appendix to paper
Bibliography
285
Questions to be Handled in Paper
.) Esteblishment of a basic positive rheotaxis in L. planaxis
2) Effects of starvation on the taxis
One and two will be an elaboration of experiment A cited
in the appendix.
3) Possible sex difference in activity and its reversal during
spring.
More statistecal and laboratory work must be done before
the first draft of the paper may be made.
28
Evaluation
My main criticism of the course, which is minor relative
to its benefits, was the absence of a syllabus. Granted one
of the lessons to learn in life is to take the initiative,
however, I think that it was a relatively expensive lesson.
Had the class definitely known that it was on its own, I think
that we could have organized ourselves for more intercommunica-
tion and consequent benefit
The main fault in my work was that I failed to relate the
potpourrii of experiments soon enough so that one or two
questions could be answered reliably.
C
C
endix
Exploratory Experiments on the Rheotactic Responces of
Littorina planaxis
Introduction and Experimental Constants
Establishment of a Positive Rheotaxis in L.planaxis
Confirmation in L.scutulata
Effect of the depth of the passing current
Effect of flow rate
Length of responce
Effects of starvation
An innate counter clockwise tendency
Physics of the shell alone
Geotexis vs Rheotaxis
Phototaxis vs. Rheotaxis
Responces to Simulated Wave Action
Sex differences and there reversal during spring
Effects of water and dry turbulance
Effects of phototaxis on the experiment
Introduction
The following experiments were carried out at Hopkins
Marine Station during Apri and May, the mating season of
L. planaxis. At the end of May a population survery showed
that L. planaxis were found primarily between :4 and t10.
In one area exposed to the surf, they were found between -1l
and t 21 feet. The L. planaxis used as specimen were taken
from two populations, which were between t3 and + 8 feet.
Most of the L. planaxis at H.M.S. range between 6 and
15 mm in size. The specimen used here were between 9.5 and
13.4 mm. This is a slightly larger collection than thoes in
the intermediate group North ('54) worked with in his maximum
current study. North reports that a current of 230 cm/sec
was sufficient todisloge a majority of the snails studied.
The currents used in these experiments ranged from 5 to 64 cm/sec.
The water temperature varied from 12.6'to 13.2° C, which is
slightly over a degree warmer than the range of the morning sea
temperatures for the same period.
Most of the results reported were obtained from single tests
or isolated observations and should only be used as elementary
guides for further work. Particulars of an experiment may
be obtained from the author, who may be contacted through the
following address:
290
Esteblishment of a Pogitive Rheotezis
The following procedure was used at each of the four tidal
periods, experiment A: 1) A pair of snails taken from the field
and allowed to attach to a glass plate; a current aimed at
their posterior wes then introduced and their behavior recorded
for fifteen to thirty minutes. 2) The linear and angular
movement of the pair was then recorded for fifty minutes while
in a 2 cm glass tube with a water flow of 55 cm/sec. 3) Step
one was then repested.
This was done on 16 specimen for two complete tidal
periods. There were twice as many turns to the left as to the
right in "responce" to the current on the plate. Sixty-four
per cent of 55 trials was as illustrated in diagram I.
This behavior was duplicated by two snails on four trials
mede using a sand substrate of two degrees of coarseness.
The behavior displayed in the flow tube was essentially
uniform. All displayed a positive rheotaxis reguardless of
innitial orientation, except for three: one female went entirely
negative, and two showed no responce. Of the other thirteen,
three showed brief negative responces. A negative geotaxis
occurred durring about 80% of the runs. In dividual rates
were commonly sporatic and varried from O to 15 cm/min.
No correlation between activity and tidal period could be made.
An identicle procedure was begun on L. scutulata. The
four snails tested showed the same positive rheotexis and
negative geotexis. However, seven of the nine turns recorded
on the plate test were to the right.
21
In preliminary investigations, one pair of L. planaxis
showed opposite rheotactic behavior corresponding to the
depth of the passing current. A shallow flow covering the lower
third of the beast elicited a positive taxis, while a flow
covering about two thirds of the beast elicited a negative
taxis. These responces were tested three times in this pair,
although subsequent investigations failed to reproduce these
results.
An hour and a half test on four snails suggested that the
rate of movement might be inversely proportional to current
velocities of 12, 36, and 58 cm/sec. In general whenever the
current became tto great or when fatigue set in, beasts from
both species would withdraw their tentacles. They oriented into
the current unless the innitial force was too great, in which
case a preservation reaction of forming a suction grip with
the foot (Ohsawa ') dominated any rheoztaxis. This is in
agreement with North's observation that L. planaxis were easier
todislodge when posteriorly oriented to the current.
Rheotaxis appears to be a strong responce in both species
of Littorine. In one experiment on four L. planaxis and six
L. scutulata, a representative of each species demonstrated a
strong positive taxis after seven days of a 36 cm/sec current.
Over half, however, either crawled or were washed out of the
apparatus after 48 hours.
In repeating experiment A on the same subjects a month
later, several behavioral tendencies seemed more steriotyped.
Only half the current first used was employed. Even then,
22
activity was appreciably decreased. Linear rates decreased
and angular movement dropped to almost none, except to perform k fad
a negative geotaxis, which occurred only half of the time.
There were , however, no negative rheotactic responces and the
ratio of left to right turns increased to about 3 to 1. This
experimental apparatus was reversed for half of the tests to
act as a control for possible systematic error.
It is possible that there is an innate tendency for counter
clockwise movement in L. planaxis. On several occasions snails,
which were allowed to attach, spontaneously started to turn to
the left. Four snails with tentacles removed, one pair with
right tentacles removed, exhibited the typical responce in
experiment A. A population study was made on 339 large (12-16 mm)
L. plenaxis located on a vertical surface 12 to 22 feet.
Forty-seven per cent were oriented vertically and 44% were
oriented from 5° to 85°, to the left of the vertica.
The asymetricel Littorine shell and its hydrodynamic
properties are of importance in influencing the behavior
of the snails. Two types of experiment were attempted in order
to determinethe physical reaction of the shell alone. In the
first a withdrawn L. planaxis was repeatedly placed in a
current at various angles. The tendency was for the shell
to orient negatively. Directly depending upon the current rate,
an angle of 30° to 75' was formed to the left of the currental
axis. Qualitative estimates of the relative ease this position
was reached from innitial left and right side exposures were also
made (see diagram II). In the second, shells were mounted on
small rods, which were attached at various positions in the
would be foot area. If the attechment si anterior, as would be
the case when the foot first portnudes, the shell orients directly
into the current. If the attachment is more posterior the
shell orients to the left exposing its right side (see diegram
III). Thus, it would be easier for a left turn to be made
when either the tail or right side were facing the current
and a right turn when the left side was facing the current.
Perhaps the physical properties of the shell have conditioned
the L. planaxis to counter clockwise movement.
Geotaxis vs Rheotaxis
Overnight tests on 50 snails and one hour tests on 24
snails indicate that a negative geotaxis dominates the
positive rheotaxis in both species. This holds in L. planaxis
for angles of 8°, 10°, 15°, 30°, 45°, and 90° with a current
of 25 cm/sec. The rates of movement suggest that it might be
Hsuait harte
more difficult to respond to the negative geotaxis when
traveling with the current.
More exceptions were found in the longer esperiments,
especially among L. scutulata, which once responded
positively to a 30' inclination with a positive rheotaxis
in a test made during low low tide.
Phototaxis vs Rheotexis
In controls on experiment A, 20 snails in tubes of still
watter showed a positive phototexis when given a light gredient.
This often, however, tekes several hours to elicit a total
population responce. In one experiment a current of 5 cm/sec
294
drew away 30% of the population in 45 minutes and 70% of the
population in 3 hours.
Controls indicated that general illumination seemed to have
no appreciable effedt on the experiment. Although, changes
in intensity such as lights or shadows will evoke a tentacle
withdrawing responce. During one trial of experiment A done
in general illumination, a beast withdrew its tentacles when
the experimentor moved his hand in front of it 40 cm away.
Responces to Simulated Wave Action
Groups of 10 L. planaxis were subjected to .5, 1.0,1.5,

2.5, and 5 minutes of aireated water turbulence and timed
during their retreat from the bottom of a 30 cm tank. These
population rates were then compafred with the rates of
populations subjected todry turbulence and no turbulence.
There seemed to be no significant effect of turbulence
although the dry turbulence populations were more like the
turbulence populations than the control populations
A sex difference of greater female activity which reversed
during the month of May might have been revieled.
During these experiments the snails showed a preference
for the sides not exposed, to illumination although controlson
on general illumination showed no more effect than would be expected
by chance.
235
0

di4d.
Behavieg
s










H




MA












I






tttttttttt
t
Bibliography
North, W.J. "Size Distribution, Erosive Activities, and Gross
Metabolic Efficiency of the Marine Intertidal Snails
Littorina planaxis and L. scutulata . Bio. Bull. 106:
185-97. 1954.
Ohba, Shigeru. "Analysis of Activity Rhythm in the Marine
Gastropod Nassarius festivus. Annotationes Zoologicae
Japoneneses. Vol. 25, fl & 12. 1952.
Ohsawa, W. and H. Tsukuda. "Extruding Responces of the
Periwinkle Nodilittorina granularis. (Gray). J. Inst.
Polytech. Osaka City U. Ser. D 6:71-96.
Suzuki, Senji. "Notes on the Behavior of Nerita japonica
dunker. Sci. Rpts. Tokoku Imp. U. Ser. 4, Biol. 9
(4): 297-314.
227