Download Planaria and their Aggregation Response to Injured Conspecifics

Fun With Flatworms!
Alyssa Morazé,
Natalie Moloney,
and Ethan Yip
Fun With Flatworms!
Planaria spp. aggregation response to
injured conspecifics
Alyssa Morazé,
Natalie Moloney,
and Ethan Yip
“Fun” Flatworm Facts
 Free living aquatic worms
 Class Turbellaria
 Acoelomate
 Two eye spots called ocelli that
are photoreceptors
 Negatively phototactic
 Abundant tactile and
chemoreceptor cells
BRIAN D. WISENDEN & MELISSA C. MILLARD
• Tested whether Planarians showed any response
when chemical cues from injured conspecifics
were introduced (in Dugesia dorotocephala)
•Crushed up a conspecific
and placed in ‘Danger Zone’
•Test worm immediately
turned 180 when in the
‘Danger Zone’
•Did control test with water
and found significant
differences
So… WHY?
• Found other studies that showed natural aggregation
in flatworms
• Thought back to schooling in fish lab and how social
grouping can be a predation response
• Found no prior studies linking aggregation to
antipredator response in flatworms
• We hypothesized that we would see a difference in the
tightness of aggregation in response to IC stimulus
Materials and Methods
Three tests to accomplish our goal:
1. Do they actually aggregate?
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5 flatworms in a petri dish
5 minutes to Acclimate
Photograph taken
Image J software measuring
3 trials
2. Do individuals respond to injured conspecifics?
 Single flatworm given 5 minutes to acclimate
 Photos taken starting at 5 minute mark
every 15 seconds
 Single planarian crushed
 Added to edge of Petri dish
 Behaviour of flatworm noted for two minutes
at 15 second intervals
 3 trials of Injured Conspecifics and 3 trials
of Control of water also used as stimuli
 Distance from planaria to edge of Petri dish
calculated
*Attempting to recreate the results of the Wisenden and Millard Study
3. Is there group response to injured conspecific?
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5 flatworms/Standard Petri dish
1 minute acclimation, photo every 15s for 1min
Injured conspecific solution added
Photo every 15s for 2mins
Average Nearest Neighbour Analysis
Results
1. Do they actually aggregate?
Average nearest neighbor distance (cm)
 Found no significant differences between trials
 Showed no tendency towards aggregation or dispersal
2
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0
1
2
3
Trial Group
Figure 1: The mean ± SEM between each flatworm and their
nearest neighbour in three different replicates (N=15).
2. Do individuals respond to injured conspecifics?
 Could not replicate the findings of Wisenden and Millard
 No significant difference between acclimation period and stimulus
 No significant difference between treatment and control
Average Distance from Point of Stimulus (cm)
8
Control
7
Injured Conspecific
6
5
4
3
2
1
0
1
2
3
Trial Group
Figure 4: Side by side comparison of post stimulus response of the control
(tank water as stimulus) and the treatment (injured conspecific solution)
3. Is there group response to injured conspecifics?
Table 2: Average group response (nearest neighbour values in
cm) before and after introduction of tank water as stimulus
Pre-Stimulus
Post-Stimulus
ANN
S.D.
ANN
S.D.
p=
Group 1
1.57
0.188
1.43
0.373 0.3469
Group 2
1.00
0.373
1.33
0.281
1.349
Group 3
x
x
0.996
0.181
x
Table 3: Average group response (nearest neighbour values in
cm) before and after introduction of ICS as stimulus.
Pre-Stimulus
Post-Stimulus
ANN
S.D.
ANN
S.D.
p=
Group 1
1.23
0.407
1.36
0.405 0.582
Group 2
1.34
0.420
1.28
0.323 0.791
Group 3
0.946
0.170
1.12
0.344 0.233
No significant difference in ANN analysis
before/after introduction of stimulus
No significant difference between control
and treatment
Discussion
 ANN values around 1… threshold for clumping/dispersal
 Directly contradicted findings of Wisenden & Millard (2001)
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Said organisms avoided areas where injured chemical cues present
 Directly contradicted findings of Reynierse et al. (1967)
- Tested anitpredator response in Dugesia dorotocephala
 This flatworm species doesn’t show antipredator
aggregation response
Future Avenues
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Red light – too intense?
Larger sample size?
Larger area
Single, well identified species of flatworm