Identification of mitten crabs

Mitten crabs are large crustaceans. River Thames specimens often have a carapace width over 84mm.

Diagnostic characteristics

The features that facilitate Eriocheir sinensis identification include:

  • setal mats on the chelae
  • quadrate (squarish) carapace
  • frontal margin with deep central cleft and 4 spines
  • 4 teeth on the carapace anterolateral margin

Distinguishing between the sexes

Male

  • narrow abdomen
  • dense setal mats completely surround the claw

Female

  • broad abdomen to protect eggs
  • setal mats do not completely surround the claw

Images of key features

The squarish carapace of a mitten crab

The carapace of Eriocheir sinensis is quadrate (squarish).

Frontal margin between the eyes of a mitten crab, showing the central cleft and four spines

The frontal margin between the eyes has a central cleft and four spines.

Antrolateral lateral carapace margin of a mittten crab, Eriocheir sinensis

The antrolateral lateral carapace margin has four teeth.

Claw of a male mitten crab, Eriocheir sinensis

Left chela of a male mitten crab. Dense setal mats (mittens) completely surround the claw.

Narrow, V-shaped abdomen of an adult male mitten crab, Eriocheir sinensis

Adult males have a narrow, V-shaped abdomen.

Broad, U-shaped abdomen of an adult female mitten crab, Eriocheir sinensis

Adult females have a broad, U-shaped abdomen to protect their eggs.

Video of male and female mitten crabs

Watch the Museum's crustacean expert, Paul Clark, demonstrate the features that distinguish mitten crabs and see how crabs can be identified as male or female.

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