Posts Tagged 'Biomechanics'

The Fastest Claw in the West

I’m surprised that I haven’t gotten around to posting this yet. Here is one of my favorite mantis shrimp videos of all time.

This segment was a bit of humor produced for ‘The Fastest Claw in the West,’ a documentary from 1985 about mantis shrimp. It is narrated by blog-hero David Attenborough, and features stomatopod expert Roy Caldwell. It turns out you can watch the whole thing on Youtube. It’s great fun and very informative. I highly recommend it:

‘The Fastest Claw in the West’: Part 1, Part 2, Part 3

Also, check out Dr. Caldwell’s youtube channel for more great stomatopod videos.

Gonodactylus chiragra (Gonodactyloidea)

In contrast to the pretty and placid G. playtsoma, today I have a photo and video of one of the meanest mantis shrimps I have encountered. Gonodactylus chiragra occurs in the same intertidal reef flats as G. playtsoma, but its temperament is the polar opposite. It hits hard and often.

You lookin' at me?

Its coloration is a mottled brownish-yellow-green on creme; except for bright orange and yellow accents on the antennae, mouthparts, and walking legs.

Here is a quick video of G. chiragra, whalloping the wall of its aquarium; attempting to hammer my finger (off-screen). It plays at regular speed and then at one-tenth speed (the slow-mo is much more impressive and/or comical, in my opinion).

If you want to know more about the astounding stomatopod strike, check out my previous article: Why Stomatopods are Awesome, I: Super Strength.

This was my first attempt at editing together a video, and I will hopefully have more content like this in the future.

I want my own enormous robotic ant

Unleash the awesome!

A robotic engineer has developed a beautifully designed hexapod robot based on the biomechanics of ants. He calls his remote controlled creation A-pod, and cites the photography of Alexander Wild (of Myrmecos) as an influence on his design.

A-pod is capable of a wide range of motions and body contortions. In addition to walking around, A-pod can grasp and carry objects in its metallic mandibles. The motions are incredibly fluid and I can’t imagine the amount of work that had to go into programming the synchronous movements of all six legs. You can watch videos of A-pod in action here and here, and learn more about the construction of the robo-beastie here.

At this point, A-pod just needs to be programmed to find Sarah Connor, and then it can assist in the inevitable robot uprising.

Aeronautic ants

Gliding ant, Cephalotes atratus. Photo by Alex Wild of Myrmecos.

The Neotropical arboreal ant, Cephalotes atratus, is a species of gliding ant. These ants live rain forest canopies where the workers spend a lot of time on exposed branches and leaves. If one these ants accidentally falls, or intentionally leaps from a branch to avoid predation, it is able to glide adeptly back to a target tree trunk or branch. A video of this gliding behavior can be seen, here. As the ant falls, it turns itself over on its back and uses its head and appendages as rudders to steer itself backwards to a tree.

These ants possess obvious evolutionary adaptations to aid their gliding behavior. Namely, the top of their head is flattened in order to generate lift as they fall upside down. In addition, the terminal segment of their hind legs is elongated and flattened (see photo below). In order to determine the importance of these specialized leg structures in generating lift and steering during descent, researchers preformed a series of experiments on the ants. They excised various body parts and then dropped the ants from the forest canopy, recording their success in gliding back to a tree.

Left: Tarsal segment of C. atratus leg viewed from the top and the side showing flattened surface. Right: Percent success of gliding back to a tree from dropped ants with various excised body parts. Adapted from Yanoviak et al., 2010.

The first thing you should note from this experiment is how damn good these ants are at gliding back to a tree when they are dropped. The unmolested control ants on the right make it to a tree over 90% of the time. However, the researchers found that if the hind legs are removed, gliding success drops to 40%, making the hind legs the most crucial appendages for steering while gliding. Also, despite the removal of a single hind leg, the other legs, or the gaster, the ants still did a pretty decent job of getting back to a tree. This success in the face of adversity suggests that steering control is highly flexible and adaptable in these worker ants. Therefore, even if a limb is lost to a predator, they are still able to glide to safety.

This research sheds light onto the complex bio-mechanics of gliding ants. They are required to preform a tightly controlled set of maneuvers as they fall in order to generate directional gliding forces. This research has shown that several structural adaptations cooperatively assist in these maneuvers.

In addition, the study of arboreal ant gliding behavior may provide clued about the origins of insect flight. Though ants are highly derived, previous fossil evidence has shown that early hexapods may have glided before developing wings. Similar gliding phases are also hypothesized in the evolutionary history of winged vertebrates. Therefore, continued research into the aerodynamic forces at work in gliding ants may suggest clues regarding the necessary stepping stones in gradual evolution of animal flight.

More on gliding ants:

References:

  • Yanoviak SP, Munk Y, Kaspari M, & Dudley R (2010). Aerial manoeuvrability in wingless gliding ants (Cephalotes atratus). Proceedings. Biological sciences / The Royal Society PMID: 20236974

Why Stomatopods are Awesome, I: Super Strength

Stomatopods, or mantis shrimp, are an exceptional order of marine crustaceans made up of over 500 species that live in a variety of benthic habitats around the world. They are aggressive predators that actively seek out their prey with an advanced suite visual and chemosensory organs. Stomatopods are immediately distinguished by a pair of enlarged raptorial appendages located ventrally, near their heads. Stomatopods use these appendages as their primary means of predation, as well as for digging in substrate, defense, and intraspecific sparring.

The appearance of the raptorial appendages varies from species to species as they are evolutionarily specialized for capturing or killing distinct prey animals. The raptorial appendages can be deployed at lightning speeds, and with tremendous force relative to the size of the stomatopods; which can range from under 2 cm to 40 cm body length. Depending on the species, these appendages can be employed to smash, spear, or grab their prey.

Here are video examples of “smasher” and “sprearer” stomatopods in action:

Odontodactylus scyllarus smashes the shells of mollusks and crustaceans.

Lysiosquillina maculata ambushes swimming fish and crustaceans, spearing them out of the water column. Click through to Youtube to see this one.

Since the 1960’s, a series of research has unraveled the speed, power, and mechanics of the stomatopod’s astonishing attack.

Continue reading ‘Why Stomatopods are Awesome, I: Super Strength’


I have moved.
Arthropoda can now be found here.

Michael Bok is a graduate student studying the visual system of mantis shrimp.

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