Hypergravity
resistance experiment
on shrimps and crabs
Experimental setup:
A round iron tank was used to hold the water. The tank was about 35.1 cm deep
and had a diameter at 53 cm. Due to balance adjustment of the centrifuge about
6 cm sand was added to the bottom of the iron tank and salt water was added
until the water level was 6 cm above the sand.
The test animals would
rotate at a radius of 2.51 m at the various rpm's.
A video camera was placed so that once the tank swung up the test animals
would be visible from above. (The tank came into view between 2G and 6G) The
camera was connected to a computer to record the experiment.
2 crabs and 4 shrimps were added to the tank.
The experiment:
The camera started recording at time 0:00 with 1 fps.
At time ~6:00 the centrifuge was started and set to an acceleration of 10
G
At time 8:00 the centrifuge
was rotating at 58.6 rpm. ( 9.6 G)
The shrimps and crabs were moving around and seemed unaffected by the acceleration.
The vibrations of the entire system was quite low. This could be seen on the
flatness of the water surface.
At time 13:00 the centrifuge
was rotating at 87.6 rpm. (21.5 G)
Noticeably more vibration visible on the water surface.
Animals seemed to be stressed a bit by this, as there was an increased movement.
The shrimps jumped quite frequently around in the tank.
At time 16:00 the centrifuge
was rotating at 103.2 rpm. (29.9G)
No changes from the previous description at 87.6 rpm.
At time 22:00 the centrifuge
was rotating at 117.2 rpm. (38.5 G)
Slightly less activity. Still, all the animals were moving around freely.
One of the crabs seemed a bit slowed down.
At time 27:00 the centrifuge
was rotating at 129.2 rpm. (46.8 G)
Like at 117.2 rpm, there was slightly less activity, but both the crabs and
shrimps
seemed ok.
At time 31:00 the centrifuge
was rotating at 143.5 rpm. (57.8 G)
No changes from the previous description at 129.2 rpm
At time 34:30 the centrifuge
was rotating at 160 rpm. (71.8 G)
Quite strong vibrations.
No other changes from the previous description at 143.5 rpm
37:00 a shrimp jumps vigorously around for a few seconds. (picture to come)
39:00 a shrimp jumps vigorously around for a few seconds. (picture to come)
At time 40:00 the centrifuge
was rotating at 167,8 rpm. ( 79.0 G)
Quite strong vibrations. - This is close to the maximum velocity for the centrifuge.
The crabs are lying quite still.
42:05 a shrimp jumps vigorously around for a few seconds. (picture to come)
At time 45:00 the process
of stopping the centrifuge starts and the rotation begins to slow down from
the 167.8 rpm.
At time 50:00 the centrifuge has come to a full stop.
All the animals are still alive, and seem to be doing fine.
A one hour break is then
taken, and after a total of 1.5 hours the same shrimps and crabs are taken
for another spin.
They are still alive and doing ok. The maximum rotation reached in this second
test run was 172.0 rpm (83 G). All the test animals were still alive afterwards.
Two crabs stopped mating after passing 30G, not sure if they were done, or
if they thought the surrounding conditions became problematic.
The shrimps and crabs were then kept alive for 3 more hours before they were boiled and eaten.
Conclusion:
The first 30 G seemed not to affect the animals at all. The vibrations were
low so this was a small stress factor.
At around 40 G the activities slowed down, and the vibrations were quite high.
The slow down in activity could be due to exhaustion from the stress of the
vibrations, or from the effects of the hyper gravity.
At 79 G a shrimp jumped around for a few seconds, and showed the ability to
move quickly around in the water.
How much acceleration the shrimps and crabs actually can sustain is still unknown, but it is obviously more than 83 G.
I think it is reasonable to expect fish to be able to sustain similar acceleration, but the airbladder would become a greater and greater problem as the acceleration increase.
Curiosity: If the animals were accelerated linearly instead of circularly the velocity they would have reached during the 5 minutes at 83G would have been 235 000 m/s or around 700 times the speed of sound.
Participants:
Bendik Stang
Prof. Gunnar Bagge
PhD & DSc, Assoc. Prof Knud Erik Heller
MSc. Rasmus Kirkegård Sørensen
Special thanks to Lars
Skou Olsen at Denmark's Aquarium for
providing the shrimps and crabs.
Bendik Stang Copenhagen Sept. 22. 2002
http://bendik.stang.com