Crab
Crabs are decapod crustaceans, most of which belong to the infraorder Brachyura, often called true crabs.
Crabs are decapod crustaceans, most of which belong to the infraorder Brachyura, known as true crabs. They typically have a broad shell, a short abdomen folded under the body, and a first pair of legs modified into claws or pincers.
What it is
Crabs are crustaceans in the order Decapoda, with five pairs of legs, the front pair modified into pincers. True crabs are classified in the infraorder Brachyura, while crab-like animals such as hermit crabs belong to other groups. They have a hard exoskeleton and a short abdomen tucked beneath the body.
Key details
Crabs live in marine, freshwater, and terrestrial habitats, though most are marine. They are known for sideways walking and use their claws for feeding and defense. Sources estimate 7,000 to 10,000 described species, and many are omnivores or scavengers.
Why it matters
Crabs are ecologically important as scavengers, predators, and herbivores. In Canada, they are familiar through Atlantic and Pacific fisheries, seafood markets, and coastal ecosystems, especially along British Columbia and Atlantic Canada.
In short
- Crabs are decapod crustaceans with five pairs of legs and pincers.
- True crabs belong to the infraorder Brachyura; hermit crabs are not true crabs.
- They live in marine, freshwater, and terrestrial habitats, with 7,000–10,000 species.
- In Canada, crabs are key to fisheries and coastal ecosystems.
Crabs are familiar to Canadian readers through Atlantic and Pacific fisheries, seafood markets, and coastal ecosystems, especially along British Columbia and Atlantic Canada.
Quick questions
What is a crab in biological terms?
How many legs do crabs have?
Are hermit crabs true crabs?
Sources
- Encyclopaedia Britannica — https://www.britannica.com/animal/crabSupports: Definition of crab as a decapod crustacean; habitat range; approximate species count; mention of true crabs and related groups.
- Encyclopaedia Britannica — https://www.britannica.com/summary/crabSupports: Broad overview of crab anatomy, habitat, movement, diet, and examples.
- Wikipedia — https://en.wikipedia.org/wiki/BrachyuraSupports: Brachyura as the infraorder of true crabs; fossil record timing; approximate extant species count.
- Simple English Wikipedia — https://simple.wikipedia.org/wiki/CrabSupports: Basic anatomy, habitat diversity, and approximate number of known species.
- Oxford Learner's Dictionaries — https://www.oxfordlearnersdictionaries.com/us/definition/english/crabSupports: Basic description of crab body form, legs, pincers, and sideways movement.
- Britannica Kids — https://kids.britannica.com/kids/article/crab/353009Supports: Species count, habitats, hard exoskeleton, leg count, and feeding habits.