This study examined the movement and aggregation behaviors of fluted giant clams. The purpose was to determine if clams move randomly or are attracted to each other. Clams were observed in aquarium tanks with different light conditions and on coral reefs. Results showed clams moved more through rotation than translation and were more aggregated near live clams than inanimate objects. This indicates clams exhibit positive chemotaxis toward each other rather than moving randomly, helping enhance their survival.
3. INTRODUCTION
Inhabit shallow waters of tropical Indo-Pacific
coral reefs
Traditional food source
Locomotion is crucial for the survival of bivalves
Bivalve may orientate and move according to
several abiotic factors (light, gravity)
Aggregation between conspecifics is one of the
possible outcomes of movement and is a major
determinant of survival in animals
Movement and Aggregation in the
Fluted Giant Clam
4. Movement and Aggregation in the
Fluted Giant Clam
INTRODUCTION
Possible proximate causes of this behavior:
Clumping could be a result of individuals
moving randomly, stopping when groups are
formed
Gregariousness among individuals, especially
chemotic attraction
5. PURPOSE OF STUDY
Aggregation
of clams
occur in
aquarium
tanks and in
the field
Clam
movement
is affected
by byssal
attachment
Clams are
attracted to
one another
and exhibit
positive
intraspecific
chemotaxis
Movement and Aggregation in the
Fluted Giant Clam
6. MATERIALS AND METHODS
1. General experimental
procedures
Study location : Marine
aquaculture facility in
TMSI (Tropical Marine
Science Institute) on St
John’s Island,
Singapore
Duration : July 2005 to
March 2006
Test organism :
Juvenile (23-63mm)
from spawning in
March 2004
Movement and Aggregation in the
Fluted Giant Clam
7. MATERIALS AND METHODS
2. Clam movement and phototaxis
Movement and Aggregation in the
Fluted Giant Clam
Mark initial position.
Data collected in 7
days. Pearson Chi-
square was applied
Acrylic sheets in the
control treatment &
PVC ring were removed
slowly
Placing
PVC ring
around
each
animal
8. MATERIALS AND METHODS
Movement and Aggregation in the
Fluted Giant Clam
Three light treatments were set up using wide-spectrum
SYLVANIA F36/GRO fluorescent tube :
1. Light from one direction
2. Light from two opposite directions, A and B
3. No light
9. MATERIALS AND METHODS
3. Aggregation in Giant Clam
Movement and Aggregation in the
Fluted Giant Clam
Analysing distribution
by 30 x 30 cm
Cartesian coordinates of the
clams’ final positions were
recorded after three days
Microsoft Excel 2003,
ANOVA, SNK (Student-
Newman-Keuls) test
Laboratory work
10. MATERIALS AND METHODS
3. Aggregation in Giant Clam
Movement and Aggregation in the
Fluted Giant Clam
Field experiment 80x80cm enclosures on the
reef flat of St John’s Island
using SCUBA
Similar to aquarium
experiment
ANOVA
11. MATERIALS AND METHODS
4. Attraction and chemotaxis among giant clam
I. Live clam
II. Fouled clam shell
III. Foul-free clam shell
IV. Random inanimate object
V. None (empty ring)
Movement and Aggregation in the
Fluted Giant Clam
12. MATERIALS AND METHODS
5. Data analyses
Pearson Chi-square
test
T-test
ANOVA
ANCOVA
SNK test
Movement and Aggregation in the
Fluted Giant Clam
13. RESULTS
1. Clam movement and
phototaxis
• High significant
associaton between
type of movement and
presence of attachment
• 30.8% of bysally
attached clams moved.
26.6% rotation and
4.2% translation
Movement and Aggregation in the
Fluted Giant Clam
14. 2. Aggregation in giant
clam
• SNK comparisons
showed that clams
were more aggregated
in the live
clam run than both
random walk
, mean
clumpy was higher in
the live clam run than
the stimulations
Movement and Aggregation in the
Fluted Giant Clam
RESULTS
15. 3. Attraction and chemotaxis among
giant clams
• The proportion of clams moving
toward the live clam target (80%)
was greater than movement away
from it (10%) & occur more than
with other object
• For , 1 clam moved
away from the effluent of
conspecifics with majority (80%)
moving toward water emerging
from the source container
• Control treatment: similar
numbers moving in both
directions (towards 33.3%, away
36.7%, center 30%)
Movement and Aggregation in the
Fluted Giant Clam
RESULTS
16. DISCUSSION
Movement & aggregation
do occur
Combination of
movement (foot action &
valve contraction) could
be a consequence of
reduction in foot size
relative to the enlarging
shell
Locomotive behavior in
bivalve to enhance their
survival
Ability to move
determines its fitness
Movement and Aggregation in the
Fluted Giant Clam
17. No significant association
between direction of light
source & clam movement
pattern
Clumping appears to be
more pronounced in the
field than in tanks
Greater movement ability
in younger because
decrease of foot size to
shell-weight ratio as clam
size increase
Movement and Aggregation in the
Fluted Giant Clam
DISCUSSION
