c0nc0rdance: Iwasaki's snail-eater (Pareas iwasakii) is a snake native to the Ryukyu Islands of Japan. As the name suggests, they're specially adapted to eating snails. Rather than crushing, it strikes into the shell and pulls the prey out with a weirdly asymmetrical jaw (25 vs. 15 teeth). (📷: orthoptera-jp)

Iwasaki's snail-eater (Pareas iwasakii) is a snake native to the Ryukyu Islands of Japan. As the name suggests, they're specially adapted to eating snails. Rather than crushing, it strikes into the shell and pulls the prey out with a weirdly asymmetrical jaw (25 vs. 15 teeth). (📷: orthoptera-jp)

Note the difference in teeth in the figure below. The snail-eater has adapted to be especially good at attacking right-handed coiling snail, but has difficulty attacking rare left-handed coiling snails. As a result, the percentage of rare 'lefties' on Ryukyu may be the highest in the world.

It's an interesting example of the Red Queen Race, where adaptations between snail and snail-eater are constantly seeking maxima for each species. You can read more about the right handed snake that eats right handed snails here: www.ncbi.nlm.nih.gov/pmc/articles...

Right-handed snakes: convergent evolution of asymmetry for functional specializationwww.ncbi.nlm.nih.gov External asymmetry found in diverse animals bears critical functions to fulfil ecological requirements. Some snail-eating arthropods exhibit directional asymmetry in their feeding apparatus for foragi...

I love evolved asymmetry!! It’s so weird to think that symmetry in most bilaterians is evolutionarily maintained. Like symmetry has a selective advantage in most cases.

I have a thread for that!

The ears of the Superb Owl🦉are exceptional: they're INTENTIONALLY ASYMMETRICAL to allow for not only left-right discrimination, but also "up-down" sound orientation. This ability lets them accurately & quickly find the scurrying mouse under the leaf mold.

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