TLDR: Carcinization: The evolutionary trend of diverse crustaceans repeatedly evolving into crab-like forms due to mobility, habitat versatility, and predator evasion benefits.
This article is a summary of a You Tube video “Why Do Things Keep Evolving Into Crabs?” by PBS Eons
Key Takeaways:
- Ancient Crab Ancestors: The narrative begins with the description of an ancient ancestor of modern king crabs, Paralomis debodeorum, dating back to 10 million years ago.
- Crab Evolution: Multiple species, not originally crabs, have evolved independently into crab-like forms, a phenomenon known as “carcinization.”
- Anomura and Brachyura: The crustacean infraorder Anomura includes species like king crabs, which are not true crabs, whereas Brachyura includes true crabs.
- Evolutionary Flexibility: The crab form is noted for its evolutionary success, attributed to its flexibility and adaptability in various environments.
- Decapods and Diversification: The decapods, a group including shrimps, lobsters, and crabs, have diversified significantly over time, with a shift towards the crab shape.
- Mesozoic Era and Crab Explosion: There was a significant increase in crab-shaped species during the Mesozoic Era, especially in the Cretaceous Period.
- Advantages of Crab Shape: The crab shape offers advantages in mobility, habitat exploitation, and predator evasion.
- Carcinization and Decarcinization: The process of evolving into a crab-like shape is called carcinization, while the reverse is decarcinization, which has also occurred.
- Convergent Evolution: Carcinization is a prime example of convergent evolution, where unrelated species evolve similar traits.
- Versatility of Crabs: Crabs, both true and false, are found in diverse environments, from deep sea to land, showcasing their adaptability and survival skills.
