How to Identify and Classify Crabs
  • 1. Which feature is MOST important for initial crab classification?
A) Eye color
B) Leg length
C) Claw size
D) Body shape
  • 2. What is the difference between true crabs and false crabs?
A) False crabs are larger
B) True crabs have a reduced abdomen tucked under the cephalothorax
C) True crabs have more legs
D) False crabs live only in freshwater
  • 3. Which crab shape is characteristic of Brachyura (true crabs)?
A) Round and bulbous
B) Broad and flattened
C) Star-shaped
D) Long and narrow
  • 4. What term describes the fused head and thorax of a crab?
A) Carapace
B) Prosoma
C) Abdomen
D) Cephalothorax
  • 5. Which appendage is typically modified into large claws in crabs?
A) Uropods
B) Pleopods
C) Chelipeds
D) Pereiopods
  • 6. How many pairs of walking legs do most true crabs have?
A) Three
B) Six
C) Four
D) Five
  • 7. The small abdominal flap on the underside of a crab is used for what?
A) Digging
B) Reproduction
C) Camouflage
D) Swimming
  • 8. How can you typically determine the sex of a crab?
A) By the length of the legs
B) By the shape of the abdominal flap
C) By the color of the carapace
D) By the size of the claws
  • 9. A wide, U-shaped abdominal flap generally indicates a:
A) Female crab
B) Hermaphrodite crab
C) Male crab
D) Juvenile crab
  • 10. A narrow, V-shaped abdominal flap generally indicates a:
A) Female crab
B) Immature crab
C) Hybrid crab
D) Male crab
  • 11. What is the function of gills in crabs?
A) Sensory perception
B) Waste removal
C) Oxygen extraction
D) Food digestion
  • 12. Where are crab gills typically located?
A) Externally, attached to the body
B) Within the gill chambers beneath the carapace
C) On the legs
D) On the abdomen
  • 13. What is the function of the crab's carapace?
A) Protection
B) Digestion
C) Respiration
D) Locomotion
  • 14. Which of these is a key feature to identify spider crabs?
A) Long legs relative to their body size
B) Large, symmetrical claws
C) Brightly colored carapace
D) Paddle-like swimming legs
  • 15. Which crabs are known for their ability to run sideways quickly?
A) Hermit crabs
B) King crabs
C) Stone crabs
D) Ghost crabs
  • 16. What type of crab is known for carrying a shell for protection?
A) Hermit crab
B) Fiddler crab
C) Box crab
D) Snow crab
  • 17. What distinguishes fiddler crabs?
A) Brightly colored walking legs
B) A flattened, shovel-like carapace
C) One greatly enlarged claw in males
D) The ability to climb trees
  • 18. Which crab is commonly found in saltwater marshes and mudflats?
A) Pea crab
B) Mud crab
C) Decorator crab
D) Coconut crab
  • 19. What is the scientific term for molting in crabs?
A) Osmoregulation
B) Metamorphosis
C) Ecdysis
D) Regeneration
  • 20. Why do crabs molt?
A) To change color
B) To reproduce
C) To grow larger
D) To shed parasites
  • 21. What is the 'crab' in 'horseshoe crab'?
A) A regional term for a certain type of true crab
B) They were once classified as crabs but have since been reclassified.
C) A misnomer, they are more closely related to spiders and scorpions.
D) An accurate descriptor, it's a type of crab.
  • 22. Which of these is NOT a feature typically used for crab identification?
A) Claw shape
B) Leg structure
C) Carapace ornamentation
D) Internal organ structure
  • 23. The teeth-like projections along the front edge of a crab's carapace are called:
A) Branchial ridges
B) Epipods
C) Rostral spines
D) Marginal setae
  • 24. What is the primary diet of most crabs?
A) Detritivorous
B) Omnivorous
C) Carnivorous
D) Herbivorous
  • 25. Which adaptation allows some crabs to survive out of water for extended periods?
A) Specialized lungs
B) Modified gill chambers
C) Ability to absorb oxygen through their skin
D) Waterproof carapace
  • 26. What is the function of the uropods in some crab species?
A) Sensing vibrations
B) Defense
C) Swimming
D) Feeding
  • 27. Which group are considered 'false crabs' because of their flattened shape, despite not being true crabs?
A) Hermit crabs
B) King crabs
C) Shore crabs
D) Spider crabs
  • 28. What is the name of the larval stage of a crab?
A) Zoea
B) Cyprid
C) Megalopa
D) Nauplius
  • 29. Which crab is known for its bright red color and is often harvested for food?
A) Snow crab
B) Dungeness crab
C) Red king crab
D) Blue crab
  • 30. How do crabs communicate?
A) Only through tactile signals
B) Primarily through vocalizations
C) They don't communicate
D) Through visual and chemical signals
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