• Eriocheir hepuensis Dai, 1991
• Eriocheir japonica (de Haan, 1835)
• Eriocheir ogasawaraensis Komai, 2006

• Setal mats on the chelae
• Quadrate (squarish) carapace
• Frontal margin with deep central cleft and 4 spines
• 4 teeth on the carapace anterolateral margin

Chinese mitten crabs are found on coasts from Japan to the mainland of China, Korean Peninsula, and along the Yellow Sea; they are also found on the coasts of northern and eastern Europe and the United States.

Biogeographic Regions: nearctic (Introduced ); palearctic (Introduced , Native )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Exotic

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Exotic

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

• Medway
• Ouse
• Humber
• Tyne

• the River Teign near Exmouth
• Dungeness in Kent
• the Duddon Estuary near Morcambe Bay

Chinese mitten crabs are light brown and have hairy claws that are typically white-tipped, giving the appearance of mittens. They have a notch between the eyes and 4 lateral carapace spines. Their legs are generally twice as long as the width of the carapace, which has an average maximum width of 80 mm. Males and females are dimorphic: males have a V-shaped abdomen whereas the females have a U-shaped abdomen.

Other Physical Features: ectothermic ; bilateral symmetry

Sexual Dimorphism: sexes shaped differently

Chinese mitten crabs spend most of their lives in brackish water and freshwater rivers and estuaries. Eriocheir sinensis migrates downstream to saltwater environments to reproduce. During migration they are known to cross terrestrial boundaries, but they do not spend much time on land.

Habitat Regions: temperate ; saltwater or marine ; freshwater

Aquatic Biomes: rivers and streams; coastal ; brackish water

Mitten Crabs are omnivores, which means that they eat both plants and animals as its primary food source. As juveniles they mostly eat vegetation but also prey on small invertebrates

Animal Foods: other marine invertebrates

Plant Foods: algae

Other Foods: detritus

Primary Diet: omnivore

Mitten crabs are prey for many animals. They are also a secondary intermediate host of the Oriental lung fluke -- Paragonimus ringeri. Mammals including humans are the final host of this parasite. Mitten crabs can tolerate a wide range of environmental conditions. This is evident as this species has been spread via shipping to North America as well as Europe. When they are introduced to a new environment, their population becomes very large very fast and they change the structure of the local environment. For instance during migration, mitten crabs burrow into sediment and this increases erosion that can lead to collapse of river banks. They may also have a profound effect on biological communities through predation and competition.

Ecosystem Impact: creates habitat; soil aeration

Species Used as Host:

• Paragonimus ringeri

Mitten Crabs are subject to predation by many carnivorous organisms in the water and on land, including fish, frogs, and birds.

Known Predators:

• sunfish
• river otter
• raccoon

A study on mating communication shows that mate recognition occurs only after physical contact. The study indicates that once physical contact is established, a contact pheromone is involved.

Communication Channels: tactile ; chemical

Other Communication Modes: pheromones

Perception Channels: visual ; tactile ; chemical

After the fertilized eggs hatch, they are called zoea and do not look like adults. Zoea have a long dorsal spine, a rostral spine, and 2 lateral spines. They develop appendages on their side that will eventually be involved in feeding. In this stage, they spend 1 to 2 months in brackish water before migrating upstream for further development. After 5 zoeal stages, the crab undergoes metamorphosis from the zoeal stage to a megalopal stage. At this stage, the larvae begin to look like adults but are still distinguishable from them because of the presence of a protruding abdomen. After about 7 days in this stage, molting occurs and juvenile crabs emerge; they then migrate upstream and go on to develop into adults, where sexual maturity is reached between their fourth and fifth years of life.

Development - Life Cycle: metamorphosis

• Juveniles and subadults
• Lasts between 1 to 5 years
• Spent in freshwater (<0.5% salinity)

• Mating, spawning and hatching of larvae
• Occurs in higher salinities (2.6% or above)
• Crabs spend 8-10 months as sexually mature adults

• Normally involves a prezoea stage, 5 zoeal stages and a megalopa stage
• Mitten crabs sometimes pass through an additional zoeal stage, possibly related to unfavourable environmental conditions
• Salinities between 1 and over 3% tolerated, although extremes cause increases in mortality

There are varied reports as to the lifespan of this species. Factors influencing the lifespan include temperature of the water, salinity, and others. Reports vary from lifespan as little as 1-2 years to as much as 3-5 years, depending on the region in which the crabs are located.

Range lifespan

Status: wild: 1 to 5 years.

During the summer months mature Chinese mitten crabs begin their migration to the sea, with males arriving first and females arriving afterwards. Soon after reproduction, however, both sexes die and the progeny are left to fend for themselves.

Mating System: monogamous

Males and females come in contact and after initially fighting, mating behavior begins. During physical contact, males are able to recognize reproductively active females because the females release contact pheromones; they are only released after physical contact has been made.

Breeding season: Summer

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous

Females aerate their eggs after they are fertilized so that nutrients can be passed from mother to baby. Females can produce anywhere between 250,000 to 1 million eggs, depending on the size of the female. After eggs have been fertilized, they are released about 1 day after mating and females then produce a substance that allow her eggs to adhere to part of her abdomen. Over the winter season, the females stay under deep water while the eggs develop.

Parental Investment: pre-hatching/birth (Provisioning: Female)

Eriocheir sinensis is not vulnerable, threatened, or endangered on any part of its native or introduced range.

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

Canada

Rounded National Status Rank: NNA - Not Applicable

United States

Rounded National Status Rank: NNA - Not Applicable

Rounded Global Status Rank: G5 - Secure

When the mitten crabs invade, they can damage the riverbanks because of their burrowing behavior as mentioned in the Ecosystem Roles section. This could be a financial problem if development along the riverbank is threatened. Mitten crabs cause damages to commercial fishing nets. They could also eat the trapped fish in commercial ponds. Crabs damage crops in China by consuming rice shoots. Humans can become infected with Paragonimus ringeri by eating poorly cooked or raw mitten crabs.

Negative Impacts: injures humans (causes disease in humans ); crop pest

Mitten crabs are a delicacy in Asia and other places. They can be used as bait for eel fishing, in the production of cosmetic products, and as fertilizer in agriculture.

Positive Impacts: food

Native To: Pacific coast of China and Korea (NAS Database 2011)