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Mantis shrimp

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Mantis shrimp are highly specialized carnivorous marine crustaceans belonging to the order Stomatopoda.

Mantis Shrimp at the National Aquarium (Baltimore) - July 2017
Mantis Shrimp at the National Aquarium (Baltimore) - July 2017

They are essential predators within shallow tropical and subtropical marine habitats. These creatures have a very ancient lineage, having branched off from other Malacostraca about 400 million years ago. All living species belong to the suborder Unipeltata, which emerged roughly 250 million years ago. Today, scientists recognize more than 520 extant species of mantis shrimp.

Stomatopoda (10.1590-2358-2936e2018005) Figure 4
Stomatopoda (10.1590-2358-2936e2018005) Figure 4

Because many species spend most of their lives hiding in burrows, they remain poorly understood by researchers.

The most famous feature of the mantis shrimp is its raptorial appendages.

MantisShrimpLyd
MantisShrimpLyd

These are specialized second pairs of thoracic appendages used for close-range combat and hunting. Mantis shrimp are primarily classified into two functional groups based on these limbs: spearers and smashers. Spearers possess spiny appendages with barbed tips, which they use to stab and snag soft prey like fish or cephalopods. Smashers, however, possess heavily mineralized, club-like appendages. These clubs are divided into three distinct subregions: the impact region, the periodic region, and the striated region.

20220123 stomatopod strike mechanics spearing en
20220123 stomatopod strike mechanics spearing en

Some species, like those in the family Hemisquillidae, are considered unspecialized "spike smashers" because their limbs lack spines except at the very tip.

The mechanics of a smasher's strike are among the fastest movements in the animal kingdom. When a smasher attacks, it rapidly unfolds its raptorial claws with incredible acceleration. This acceleration can reach 10,400 g, which is 102,000 m/s². This speed causes the appendage to generate vapor-filled bubbles in the water, known as cavitation bubbles. When these bubbles collapse, they produce a secondary shock wave. This means the prey is struck twice: first by the physical impact of the club, and second by the collapsing bubbles. This impact can reach forces of 1,500 newtons. The collapse of these bubbles can even produce light, a phenomenon called sonoluminescence.

Beyond hunting, the mantis shrimp possesses perhaps the most complex visual system ever discovered.

Odontodactylus scyllarus eyes
Odontodactylus scyllarus eyes

Their eyes are mounted on mobile stalks and can rotate in all three dimensions. Each eye is a compound eye made of tens of thousands of ommatidia, which are clusters of photoreceptor cells. The eye is divided into two flattened hemispheres by a specialized row of ommatidia called the midband. This midband contains between two and six rows of cells. This unique structure allows for trinocular vision, providing depth perception for objects near the eye's mid-plane.

Mantis shrimp eyes
Mantis shrimp eyes

This allows them to perceive shapes and motion with extreme precision.

The diversity of their photoreceptors is staggering when compared to humans. While humans possess only four types of photoreceptor cells, some mantis shrimp have between 12 and 16 types.

Pseudosquilla
Pseudosquilla

This diversity is believed to have resulted from ancient gene duplication events. These cells allow them to perceive a massive range of light, from deep ultraviolet at 300 nm to far-red at 720 nm. They can also detect polarized light. In certain superfamilies, the midband is specialized: rows 1 through 4 process color, while rows 5 and 6 detect circularly or linearly polarized light. This complex array of sensors allows them to navigate and hunt in diverse environments.

Some species exhibit a remarkable ability called spectral tuning. This is a species-specific phenomenon where they adjust the sensitivity of their long-wavelength color vision to match their environment. For example, the species *Neogonodactylus wennerae* shows more pronounced tuning than *N. oerstedii* because it lives in habitats with higher ecological diversity. This ability is likely linked to mutations in the retinal binding pocket of the opsin, which is a light-sensitive protein. By tuning their vision, these crustaceans can adapt to different depths and light conditions. This ensures they can maintain high-speed processing of their surroundings, which is vital for territorial combat.

The biological complexity of the mantis shrimp has significant implications for modern science. Researchers are currently studying their powerful, robust claws as microscale analogues for new macroscale material structures. Their ability to withstand such intense physical forces is a subject of great interest. Additionally, the way their visual information is processed into parallel data streams provides insight into efficient sensory systems. From the physics of cavitation to the biology of advanced optics, the mantis shrimp remains a subject of intense scientific study.

They represent a perfect intersection of mechanical power and sensory sophistication.

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🖼️ Images & Media (12)
File:MantisShrimpLyd.jpg
MantisShrimpLyd.jpg
File:20220123 stomatopod strike mechanics spearing en.gif
20220123 stomatopod strike mechanics...
File:Odontodactylus scyllarus eyes.jpg
Odontodactylus scyllarus eyes.jpg
File:Mantis shrimp eyes.jpg
Mantis shrimp eyes.jpg
File:Mantis Shrimp at the National Aquarium (Baltimore) - July 2017.jpg
Mantis Shrimp at the National Aquarium...
File:Pseudosquilla.JPG
Pseudosquilla.JPG
File:Careful now... (29866247452).jpg
Careful now... (29866247452).jpg
File:Stomatopoda (10.1590-2358-2936e2018005) Figure 4.jpg
Stomatopoda (10.1590-2358-2936e2018005)...
File:Daidal.png
Daidal.png
File:Hai san Hau Loc05.JPG
Hai san Hau Loc05.JPG
File:Banhkhotomtit.JPG
Banhkhotomtit.JPG
File:Harpiosquilla harpax SeaDonuts.jpg
Harpiosquilla harpax SeaDonuts.jpg
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