From the Vault: The Glorious Hermit Crab, Part 2
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Deep Dive
Why are hermit crabs not considered true crabs?
Hermit crabs belong to the infraorder Anomura, while true crabs are part of the infraorder Brachyura. Although both are decapod crustaceans with 10 legs, hermit crabs have anatomical differences, such as a diminished or hidden last pair of legs, and they rely on external shelters like shells.
What is unique about the hermit crab species Diogenes heteropsamicola?
Diogenes heteropsamicola is a marine hermit crab species that uses living solitary corals as mobile shelters. The coral grows with the crab, providing a dynamic and protective home, unlike fixed gastropod shells. This symbiotic relationship is mutualistic, as the coral benefits from the crab's mobility, preventing it from being buried or overturned.
How do deep-sea hermit crabs protect themselves without traditional shells?
Deep-sea hermit crabs, such as those in the family Pirapepguridae, often use living sea anemones as shelter. The anemones grow over and dissolve the crab's original shell, providing a living, expanding home that offers chemical protection against predators like octopods.
What is the hermit-to-king hypothesis in crab evolution?
The hermit-to-king hypothesis suggests that king crabs evolved from hermit crab ancestors. This theory is based on morphological similarities, such as asymmetrical abdomens and claw structures, and phylogenetic evidence. It proposes that king crabs abandoned their reliance on external shells and evolved into fully hardened, crab-like forms.
What is a vacancy chain in hermit crab behavior?
A vacancy chain is a process where hermit crabs exchange shells in an organized manner, with each crab upgrading to a better shell left by another. This behavior benefits multiple crabs in a sequence, as each one moves into a more desirable shell. This concept has been compared to human housing markets and job openings.
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