This study aimed to determine if trematode infection causes behavioral changes in Helisoma trivolvis snails. Snails were collected from the field with naturally varying infection intensities and placed in experimental tanks. Their locations over 20 hours were recorded. Upon dissection, the number of trematode cysts in each snail was counted. The results showed infection intensity did not seem to influence snail behavior. Possible explanations given were that the infection may not affect Helisoma behavior, intensities were not high enough, or the experiment was not sensitive enough to detect real behavioral alterations.

1. Background
Parasites
can
manipulate
the
behavior
of
their
hosts
in
order
to
increase
the
probability
of
transmission.
When
parasites
are
transmi8ed
trophically
(by
one
host
ea:ng
another),
parasites
may
change
the
behavior
of
their
host
to
increase
the
probability
that
the
host
is
consumed.
For
instance,
trematode
infec:on
in
Physa
integra
snails
can
alter
whether
the
snails
use
cover
in
the
presence
of
fish
and
crayfish
predators
(Bernot
2003).
Similarly,
trematode-­‐infected
freshwater
snails
behave
differently
than
uninfected
snails
in
morning
hours,
when
waterfowl
(defini:ve
host)
are
feeding
(Levri
&
Lively
1996).
Purpose
of
Study:
Determine
if
trematode
infec:on
causes
behavioral
changes
in
Helisoma
trivolvis
snails.
Research
Ques8ons:
(1)
Does
high
infec:on
intensity
cause
snails
to
spend
more
:me
feeding
and
less
:me
in
covered
areas?
(2)Does
infec:on
intensity
affect
the
depth
where
snails
forage?
(3)
Are
infected
snails
clumped
together
in
space
to
increase
transmission
to
defini:ve
hosts?
Results
Conclusion
The
intensity
of
infec:on
did
not
seem
to
influence
snail
behavior.
There
are
several
possible
explana:ons.
• Metacercarial
infec:on
doesn’t
influence
Helisoma
behavior.
• Infec:on
intensi:es
were
not
high
enough
to
induce
behavioral
changes.
• The
experiment
was
not
sensi:ve
or
realis:c
enough
to
elicit
or
detect
real
behavioral
altera:ons.
The
addi:on
of
defini:ve
host
cues,
predator
cues,
or
host-­‐seeking
trematode
cercariae
could
be
improvements
for
the
future.
Experiment
• Helisoma
trivolvis
snails
collected
from
field
site
in
Riner,
VA,
with
naturally
variable
infec:ons
• Five
snails
in
each
of
twenty
tanks,
replicated
in
four
trials
• Each
tank
had
four
:les
covered
with
algae
+
four
covered
refugia
• 24
cm
water
depth
• Loca:on
recorded
over
20
hours
• Snails
were
dissected
to
count
trematode
metacercarial
cysts
(a
larval
form)
acquired
in
the
field
before
the
experiment
Acknowledgments/
Literature
Cited
This
work
was
supported
by
the
Na:onal
Science
Founda:on
through
grants
#DEB-­‐0918656
(to
JMW)
and
DEB-­‐0918960
(to
LKB).
Bernot
R.
2003.
Trematode
infec:on
alters
the
an:predator
behavior
of
a
pulmonate
snail.
Journal
of
the
North
American
Benthological
Society
22:241-­‐248.
Levri
EP,
Lively
CM.
1996.
The
effects
of
size,
reproduc:ve
condi:on,
and
parasi:sm
on
foraging
behaviour
in
a
freshwater
snail,
Potamopyrgus
an;podarum.
Animal
Behaviour
51:891-­‐901.
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
2
8
16
32
60
120
240
480
1200
Null
Propor8on
of
snails
in
each
habitat
Minutes
High
infec8on
(>100
cysts)
Side
Covered
Top
algae
Printing Supported by the Office of Undergraduate Research and Scholarship
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
2
8
16
32
60
120
240
480
1200
Null
Propor8on
of
snails
in
each
habitat
Minutes
Low
infec8on
(<100
cysts)
Side
Covered
Top
Algae