odontodactylus-scyllarus

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Peacock Mantis Shrimp: a true marine breaker

Commonly known as Peacock Mantis Shrimp, Odontodactylus scyllarus (Stomatopoda - Odontodactylidae) could well be called the marine breaker, because it is a true biological hammer when it comes to breaking the shells of its lunch. These shrimps are renowned for their unusual method of breaking shells with brief, powerful strikes of their raptorial appendages. 

It has been discovered that each strike of Odontodactylus scyllarus generates two brief, high-amplitude force peaks, typically 390–480 μs apart. Based on high-speed imaging, force measurements and acoustic analyses, it is evident that the first force peak is caused by the limb’s impact and the second force peak is due to the collapse of cavitation bubbles. Despite their small size, O. scyllarus can generate impact forces thousands of times their body weight. Furthermore, on average, cavitation peak forces are 50% of the limb’s impact force, although cavitation forces may exceed the limb impact forces by up to 280%.

The rapid succession of high peak forces used by mantis shrimp suggests that mantis shrimp use a potent combination of cavitation forces and extraordinarily high impact forces to fracture shells. The stomatopod’s hammer is fundamentally different from typical shell-crushing mechanisms such as fish jaws and lobster claws, and may have played an important and as yet unexamined role in the evolution of shell form.

Reference: [1]

Photo credit: ©Benjamin Naden | Locality: Bali (2013) | [Top] - [Bottom]

Made with Flickr
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MANTIS SHRIMP SIGHT

Even though the eye-catching mantis shrimp has 12 different color receptor cones (compared to humans’ three for red, blue, and green), it may be worse at discerning colors.

The dark areas of the eye are called the pseudopupil, is created by the facets of the eye that are looking directly at you. You will notice that the mantis shrimp often has three separate pseudopopils in each eye looking at you, this gives them trinocular depth perception in each eye independently. You will also sometimes see the pseudopupils get very large. This is when the animal points the acute zone of the eye at you. The acute zone has much greater resolution than the rest of the eye, and is analogous to our fovea.

  • Gif 1 footage by Michael Bok
  • Gif 2: showing pseudopupils in the eyes of a male Odontodactylus scyllarus. The right eye is damaged by RoyLCaldwell
  • More: Nature
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Implosion Punch!!

Rather than the pincers employed by its more well-known crustacean cousins (the crabs and lobsters), the front appendages of ‘smasher’-type mantis shrimps are modified into clubs.

These clubs are formidable, high-speed weapons used for punching or smashing prey, as demonstrated by this peacock mantis shrimp (Odontodactylus scyllarus). Notice how its punch actually breaks the crab’s pincers in the 3rd and 4th clip.

The mantis shrimp’s punch moves so fast, that water at the point of impact vaporizes, forming small bubbles of gas in a process called ‘cavitation’.These cavitation bubbles implode, producing heat, light, and sound, and causing small shock-waves that further damage the shrimp’s target.

Therefore, the strike of the mantis shrimp is effectively a four-stage attack—the impact of the first punch, followed by the collapse of the first cavitation bubble, then the impact of the second punch, and the collapse of the second cavitation bubble.

If that does not qualify as a secret kung fu technique or finishing move or something, I don’t know what does.

video source: Kharn Stomatopods on Youtube

reference: Patek Lab, authors of this journal article.

“The eye of the peacock mantis shrimp has led an international team of researchers to develop a two-part waveplate that could improve CD, DVD, blu-ray and holographic technology, creating even higher definition and larger storage density.

Peacock mantis shrimp are one of only a few animal species that can see circularly polarized light—like the light used to create 3-D movies. Some researchers believe the mantis shrimp’s eyes are better over the entire visual spectrum than any man-made waveplates.

A waveplate is a transparent slab that can alter the polarization of light because it is birefringent—exhibits double refraction. The mineral calcite, which sometimes is used as a waveplate, is birefringent. This print viewed through a calcite lens appears as doubled and slightly offset letters.” [more.]

I’m not sure where this study ended up, but look how cute he is.

[Photo by Vinny Turner.]

Peacock Mantis Shrimp (Odontodactylus scyllarus)

Mantis shrimps have the strongest strike of any animal, relative to their size. Large peacocks can hit with a force equal to a .22 caliber bullet. They also have the fastest strike of any animal. Their strike is so fast that they vaporize the water at the point of impact, causing a small implosion. This makes their strike even more destructive, and stuns their prey. Mantis shrimp are also one of the only predators of the Blue-Ring Cctopus. They smash the octopus until the venom glands burst, and after the venom dissipates in the water, they eat the octopus.

The Peacock Mantis Shrimp (Odontodactylus scyllarus) is fondly known as “Thumb Splitter” by the fishermen who catch them. This is due to its incredibly powerful claws, which are used for both defence and for feeding. The Mantis Shrimp is also known for its incredible vision. While we humans have three types of colour receptors in our eyes, the Mantis Shrimp has twelve, allowing it to detect light from the infrared to ultraviolet areas of the spectrum. Additionally, it has circularly polarised vision, the function of which is unclear but is thought to be related to mate selection and reproduction.

(Source: Tyler Huston)

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モンハナシャコ
学名:Odontodactylus scyllarus
分類:シャコ目 ハナシャコ科
分布:東南アジア、ミクロネシア、インド洋、台湾の海域。日本では相模湾以南。

[memo(アクア・トトの解説より引用)]
モンハナシャコはエサとなるヤドカリやカニの仲間、貝類などを、捕脚(エビやカニのハサミ脚に相当する部分)を使って一撃で打ち砕いて食べます。そのため、捕脚の関節が硬く球状になっています。この捕脚の打撃力は凄まじく、自然界では大型のホラガイも一撃で割ってしまうほどです。


アクア・トトぎふ 1F マンスリー水槽 2012年7月『トトリンピック開催!』