Natures wonders: mantis shrimp clubs prey (Introduction)

by David Turell @, Wednesday, January 17, 2018, 18:04 (688 days ago) @ dhw

How its construction is now understood:

"In research published this week in the journal Advanced Materials, researchers from the University of California at Riverside, US, have identified a unique structure that wraps around the shrimp's club to protect it from self-inflicted damage as it crushes hard-shelled prey.


"Mantis shrimp, marine crustaceans of the order Stomatopoda, are aggressive hunters known for killing their prey using a predatory strike that is among the fastest known animal movements. Stomatopods are divided into two groups: "spearers", which attack soft-bodied prey using a harpoon-like structure, and the more recently evolved "smashers", which crush hard-shelled prey using a hammer-like appendage called a dactyl club.

"The researchers uncovered how the mantis shrimp uses its smasher to carry out such rapid underwater attacks, which can occur at speeds of up to 23 meters per second. The profile of the club, together with an adjoining region called the propodus, is a hydrodynamic teardrop design that reduces drag resistance.

"This teardrop design allows the club to accelerate so quickly that it shears the water, creating imploding bubbles – an effect known as cavitation – to yield a secondary impact on prey.


"In previous research, Kisailus and his team found that the dactyl club is a composite made of mineralised chitin – the same as found in the shells of other crustaceans and insects – but arranged in several unique structures. The exterior of the club, called the impact region, has a hard, crack-resistant coating that enables the mantis shrimp to inflict incredible damage to its prey by transferring its momentum upon impact.

"The interior of the club comprises the periodic region, an energy-absorbing structure that dissipates cracks along a series of long, spiral-like fibres; and the striated region.
In the current paper, the researchers show that the striated region has a series of highly aligned fibres that wrap around the club and stop it from expanding upon impact.

“'We believe the role of the fibre-reinforced striated region in the smasher's club is much like the hand wrap used by boxers when they fight: to compress the club and prevent catastrophic cracking,” Kisailus says.

“'Together, the impact, periodic and striated regions form a club of incredible strength, durability and impact resistance.”

"He says a similar striated architectural element is seen in the smasher's more ancient cousin, the spearer, where it is thought to prevent the long, thin barbs from becoming deformed during penetrating strikes.

"The study suggests the presence of this structure in the spear likely enabled the advent of the smasher and its biological hammer, a diversification that coincided with the appearance of hard-shelled prey with more sophisticated defences.

"The researchers also found a similar structure in the tibia of the land-based praying mantis, suggesting biology has used this design for similar functions."

Comment: Nature always comes up with ingenious designs. Why not recognize the designer, God?

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