Cavitation and impact forces by the Peacock mantis shrimp (Stomatopoda: Odontodactylus scyllarus)

Transcription

1 Cavitation and impact forces by the Peacock mantis shrimp (Stomatopoda: Odontodactylus scyllarus) This is a brief presentation about the morphology, impact forces and cavitation phenomena of the mantis shrimp s raptorial strike. Most pages contain an image and reference to a video clip (in turquoise text) that is also uploaded to the biomechanics site. Sheila Patek Dept. of Integrative Biology University of California, Berkeley

2 scyllarussnail shot Odontodactylus scyllarus (Peacock mantis shrimp) uses its raptorial appendages (second thoracic appendages) to hammer hard-shelled prey.

3 The raptorial appendage is built of the typical crustacean appendage segments. merus carpus V (merus) propodus Lateral view of the peacock mantis shrimp s raptorial appendage dactyl For complete CT scan images showing videos of internal and external anatomy, check out Digimorph s website:

4 The raptorial appendage is built of the typical crustacean appendage segments. Lateral view of the peacock mantis shrimp s raptorial appendage dactyl For complete CT scan images showing videos of internal and external anatomy, check out Digimorph s website:

5 The raptorial appendage is built of the typical crustacean appendage segments. propodus Lateral view of the peacock mantis shrimp s raptorial appendage For complete CT scan images showing videos of internal and external anatomy, check out Digimorph s website:

6 The raptorial appendage is built of the typical crustacean appendage segments. carpus Lateral view of the peacock mantis shrimp s raptorial appendage For complete CT scan images showing videos of internal and external anatomy, check out Digimorph s website:

7 The raptorial appendage is built of the typical crustacean appendage segments. merus V (merus) Lateral view of the peacock mantis shrimp s raptorial appendage For complete CT scan images showing videos of internal and external anatomy, check out Digimorph s website:

8 The raptorial appendage is built of the typical crustacean appendage segments. merus V (merus) Lateral view of the peacock mantis shrimp s raptorial appendage For complete CT scan images showing videos of internal and external anatomy, check out Digimorph s website:

9 STAB SMASH rotatinglimb The raptorial appendage can be used for smashing (with the dactyl heel) or stabbing with the tip of the dactyl.

10 HSVsnailsmash Here a peacock mantis shrimp strikes a snail wired to a stick. This video was filmed at 5000 frames per second and is played back at 15 fps. Even slowed down >300x, the movement is extremely rapid; the dactyl heel can reach speeds of over 20 m/s. Note the formation of a bright bubble between the dactyl heel and snail shell. More details can be found in: Patek, S. N., Korff, W. L. and Caldwell, R. L. (2004). Deadly strike mechanism of a mantis shrimp. Nature 428,

11 20Kstrike Here is a closer look at the formation of bubbles between the snail and dactyl heel. This video was filmed at 20,000 frames per second (played back at 15 fps). These bubbles are known as cavitation. Cavitation bubbles are formed because of extremely low pressure in the water between the snail and dacty heel such that the water vaporizes (like boiling water, but without the application of heat). The collapse of the cavitation bubbles is like a small explosion, and causes the emission of heat, light and sound. This is an extremely destructive phenomenon it can destroy rapidly rotating metal boat propellers.

12 hsvloadcellgamma The forces generated by the limb s impact and the collapse of cavitation bubbles were measured using a force sensor (a waterproof piezoelectronic load cell). This is a video of a mantis shrimp striking the force sensor, filmed at 5000 frames per second, played back at ~15 fps.

13 Note the cavitation bubble forming between the dactyl heel and force sensor.

14 load cell heel of appendage 100Kstrikeincolor 1 mm Because these processes occurred over such short time scales, it was necessary to film the strike with extremely high speed video - 100,000 frames per second (10 μs per frame), played back here at ~15 fps.

15 forceandvideo By synchronously recording force and video, one can see that mantis shrimp generate two force peaks with every strike the first force peak is due to the impact of the limb on the sensor and then the second is caused by the collapse of cavitation bubbles. Thus, peacock mantis shrimp use two forms of force generation one due to the limb s direct impact, and the other due to the potent cavitation processes caused by the extreme speeds of the strike. This video shows synchronously recorded force sensor output and high speed images (100,000 frames per second; played here at 10 frames per second). More details: Patek, S. N. and Caldwell, R. L. (2005). Extreme impact and cavitation forces of a biological hammer: strike forces of the peacock mantis shrimp (Odontodactylus scyllarus). Journal of Experimental Biology 208,

16 References Burrows, M. (1969). The mechanics and neural control of the prey capture strike in the mantid shrimps Squilla and Hemisquilla. Zeitschrift fur vergleichende Physiologie 62, Burrows, M. and Hoyle, G. (1972). Neuromuscular physiology of the strike mechanism of the mantis shrimp, Hemisquilla. Journal of Experimental Zoology 179, Caldwell, R. L. and Dingle, H. (1976). Stomatopods. Scientific American, Patek, S. N. and Caldwell, R. L. (2005). Extreme impact and cavitation forces of a biological hammer: strike forces of the peacock mantis shrimp (Odontodactylus scyllarus). J Exp Biol 208, Patek, S. N., Korff, W. L. and Caldwell, R. L. (2004). Deadly strike mechanism of a mantis shrimp. Nature 428, Patek, S. N., Baio, J. E., Nowroozi, B. N., Caldwell, R. L. and Summers, A. P. (2007). Linkage mechanics and power amplification of the mantis shrimp's raptorial strike. J Exp Biol 210,