Here are some notes on a presentation I attended yesterday. It's about fast motion in zoology, specifically looking at creatures that use elastic energy to snap at things, like Mantis Shrimp and Trap-jaw ants. It was wonderful. The notes are not too well organised, but I am happy that taking them with org-mode in emacs let me easily export them to an HTML I could pretty simply embed. :D
Sudden and Swift
Table of Contents
1 Sudden and Swift: Extreme Movements in Biology, with Sheila Patek
Dr. Sheila Patek, Zoology, University of Massachusetts Amherst, Duke University
- Mantis Shrimps
- introduced by teacher of Invertebrate Zoology
- isopod crustaceans underrepresented in his course, in favour of Mantis Shrimp
- What is fast?
- not about cheetahs or diving falcons, which are slower than MS
- fast in physics, evolutionary history
- research spectrum
- basic research (fun and satisfying, building knowledge)
- applied research
- Catalina island
- Rachel Carson, 1950, The Sea Around Us quote
- "One of the most extraordinarily widespread sounds of the undersea is the crackling, sizzling sound, like dry twigs burning or fat frying, heard near beds of the snapping shrimp... The shrimp are forever clicking the two joints of this claw together."
- snapping shrimp Alpheus heterochaelis
- Rachel Carson, 1950, The Sea Around Us quote
2 Snapping Shrimp
- in 2000, they were able to watch at 40,500 frames per second, the snapping of the shrimp, creating a cavitation bubble
- this is speed, underwater
- the sound is the cavitation bubble collapsing, not claws snapping
- how do fungal seeds get off of stem? e.g. jelly fungus Auricularia auricula
- surface tension catapult propels ballistopores
- spore + water droplet, theory of surface tension catapult
- droplet fuses with spore
- in yeast, 1000,000fps
- energy from surface tension of water,
- occurs <10us, 120,000 m/s2, ~300,000 occur within eye blink, average acceleration of missiles
- related to microdrop technologies
- engineers did a lot of physics to control inkjet printers
- math from inkjet printers informed understanding of spore dispersal
- includes photo of daughter because she wants her to
- faster things, turtles, jely fish, etc.
- basic research: how can we apply it? // missed something important here
- organisms
3 Mantis Shrimp
- Stomatopoda
- Odontodactylus scyllarus, peacock mantis shrimp
- Australia, Indonesia, size of cigar
- durable snail destroyed with a single blow
- Sheila works on sound production (not even caring about noise of impact)
- you can hear the cavitation bubble's collapse, louder than the shell cracking
- 1.8ms, 150 within a blink, acceleration 105 m/s2
- mechanics of strike
- muscle holds latch that prevents hammer from swinging; elastic energy stored
- the effect is stronger than any muscle contraction known
- same mechanism used across all 5000 known mantis shrimps (some using different things like spears)
- Cavitation bubble kind of spreads out
- mandibles degrade due to them, but molting replaces them
- impact forces used to be hard to measure, new technology with
piezoelectric crystals to record force and hydrophones to also
record cavitation
- measured over 400Newtons
- two force peaks, limb impact and cavitation impact or second hit
- had to record at 100,000 fps
- appendage not hitting twice
- pairing video with force sensor
- cavitation bubble here is half as strong as the limb impact (typically, cavitation bubbles can be 2-3x stronger than original impact)
- compared impacts against horn shark, Horn Shark has longer sustained
force, and it's about the same force as a Mantis shrimp, latter working in a few microseconds, former in almost one second
- but the horn shark is 3kg an the shrimp 40g
- informs snail shell's evolution
- Maya deVries looked at Lysiosquillina maculata, spearing strikes, longer reach, slower speeds, no cavitation
- 25ms, 10 within a blink, 0.3m/s2
- connected to other shrimps, co-evolved, same mechanism
- not that fast, don't need to be super fast to hunt; need minimum speeds
- so no cavitation
- extreme speeds usually the byproduct of some other goal
- evolved as early as ~300 million years ago
4 Speed
- nematocysts, jelly fish, smallest duration action is 0.7us
Duration
| Duration (us) | Species |
|---|---|
| 10 | fungal spores |
| 25 | termite jaws |
| 100-300 | trap-jaw ants, dogwood spores, bladderworts |
| 1-6ms | mantis shrimp |
Speed
| Speed (m/s) | Species |
|---|---|
| 67 | trap-jaw ants, termite jaws |
| 58 | gyrfalcon dive |
| 28-29 | cheetaw sprint |
…
5 Trap-jaw Ants
- Trap-jaw ant, Odontomachus bauri, trigger hairs, scale bars = 0.5mm for size of mandibles, trigger hairs near mouth bypass the brain and trigger jaws immediately.
- truly fast movement requires spring+latch, can't just use muscles
- latches block closing, latches moved away and jaws snap
- these are slightly faster than things she studied, but they do it in air so it doesn't count
- they have horrible stingers
- can be viewed when slowed by 1000x, occur in <0.13ms, 2000 within an eyeblink
- jump with their jaws, how much force can they produce?
- each jaw generates 400x body weight of ant
- Patek et al. 2006, PNAS
- prey on prey that is defended, they get to knock out prey before being sprayed by acid
- she studied these ants jumping
- video is beautiful, 100x slowed
- new result => many new questions
- creates a sense of wonder
- http://www.youtube.com/watch?v=G89IcZ3PluE, 46s
- use it during battles
- these jaws have evolved in 4 separate groups, two species have evolve jumping
- Mystrium, Myrmoterus, Myrmecia, Strumigenys, Anochetus, Acanthognathus, Orectognathus
- fast?
- it's about producing high forces in hunting, speed is a by-product
- basic research?
- how are they produced? how do they evolve? multipl origins, similar selective regimes
- applied research
- strong, lightweight materials, store elastic energy, withstand high impacts; mineralisation strengthening
- back to Mantis Shrimp
6 Cavitation
- fast boat propellers were disintegrating
- fast flow meeting slow flow, you get low pressure, bubbles form and
collapse, generating heat 6700°C (sun surface), light, and sound
- wears away boat propellers
- wears away shrimp appendages, thank good for molting
7 Conclusions
basic research
- mechanism used in a lot of different contexts, like Jelly Fish propulsion, poison stuff, etc.
application
- Ninja Bot, robotic Mantis Shrimp, biomicicry, Susanna Cox; trying to replicate (e.g. to create more durable propellers)
- why do shrimp hammers not break? Mollusk shells used to be thought
of as the most fracture-resistant things, but Mantis Shrimps break them!
- hammers have impact region and periodic region that help dissipate force
- hard materials crack easily, but you need hard to generate hard impact
- harder outer surface, layering dissipates it well, propagates crack energy into other areas to prevent cracking
philosophical
- can kill things with single blows
- need solution to not destroy themselves
- they have tail plates (telson), that they can target instead of the body of
another, so that they don't go off killing the rest of their species (found by Jennifer Taylor)
- telson absorbs energy, like a punching bag
8 Questions
- what do you think about Canada's refocus on research funding
- plant exploding scene
- relationship between water depth and probability of cavitation, harder in lower depths; no smashing mantis shrimp at 100m (close to the max depth for them)
- are there smashers that don't cavitate?
- all smashers cavitate
- spring in Mantis Shrimp; what's the issue?
- It's exoskeleton
- energetic costs of this movement?
- huge ones, you can see their gills moving; they can only do 10 in a row before they stop and you observe their gills flapping, panting
- prey preference: bigger, more shell but more meat; smaller, less meat but less shell? middle
- molting, after can they act right away?
- they start pounding glass at her lab
- gave her daughter nightmares for 6 months after banging glass in front of her
- had to devise her antishrimp spray
- so, eventually they are too soft pre-molting, and they can't stop all together, so instead of actually striking, they display and bluff, and it's effective
- time to recharge?
- muscle contraction takes over 100ms
- now has a neurobiologist studying the neuro basis
- longer sarcameres: more force to produce, longer to contract
- smashers have really long ones, take a long time to load
- spearers have can't contract so much, but reload faster; they hunt faster, evasive pray
- how to house mantis shrimp
- urban legend says you can't store them in glass tanks
- has stored 1000s in glass tanks, and they've never broken them
- they've broken other things, like Nalgene bottles
- why?
- size component to the amount of force in a cavitation bubble
- doesn't know, but she should have measured it she says
- guesses there isn't a scaling
- actually, size of animal => size of force
- yes!
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