Monday, 13. July 2009, 22:59
Text: Oliver Mengedoht, Monika Rademacher
Photos: Oliver Mengedoht
Translation: Ulli Bauer
Scientific name: Hemigrapsus takanoi
Trivial names: Asian Shore Crab, Brush-Clawed Shore Crab, Pencil Crab, Peenselkrab
Systematics: Domain: Eucaryota, kingdom: Animalia, subkingdom: Metazoa (multiple-celled animals), Eumetazoa (true tissue), grade: Bilateria, branch: Protostomia, infrakingdom: Ecdysozoa (molting animals), phylum: Arthropoda (jointed-leg invertebrates), subphylum: Crustacea, class: Malacostraca (higher crustaceans), superorder: Eucarida, order: Decapoda (ten-legged crayfish), suborder: Pleocyemata, infraorder: Reptantia, section: Brachyura (true crabs), superfamily: Grapsoidea, family: Varunidae, genus: Hemigrapsus, species: Hemigrapsus takanoi
Origin/distribution: Originating in the cold to subtropical parts of the North-West Pacific (Northern Japan To China). In the 1990s they were accidentally introduced to the Bay of Biscay - since then, three populations have established (data from 2002): in the south of the Netherlands, in the port of Le Havre and a large population in the Bay of Biscay off Jard-sur-Mer (France) to the Bay of Santander (Spain).
Recently, the population in the Netherlands has dramatically spread and widened its range to Belgium (where our specimens came from). The species has also surfaced in Germany (reported from the isle of Norderney and from Lower Saxony) and will probably also invade the American Atlantic coast.
[attachment=8314]
Further pics: www.panzerwelten.de/v/Hemigrapsus/Hemigrapsus_Tanakoi/
Description: Grey to brown, also orange-brown or green, light and dark striped legs, small dark spots on the claws, light-colored brush-like growth on the basis of the male's fingers. Three well-visible spikes on the side towards the front (behind the eyes). Females often have two symmetrical spots on the carapace.
Sex differences: Typical for crabs, the males have a narrow abdominal apron, the female's apron is wide and covers almost the entire abdomen. Males have bulkier claws.
Size: The carapace is up to at least 3.25 cm wide.
Life span: few years
[attachment=8315]
Temperature: 15 to 28 °C
Tank size/stock: In nature, there are up to 20 specimens to the square meter - however, these numbers are not recommendable in a tank.
Tank set-up: North Sea, marine or brackish water aquaterrarium (sandy shore, rocks)
[attachment=8316]
Food: typical for crabs, they're omnivores. In nature, they eat algae, small invertebrates, fish fry and juvenile fish - all they can find between the rocks in the tidal zone.
• Dry food: Catfish tabs, fish (flake) food, food pellets, Spirulina tabs, crayfish tabs, Gammarus
• Frozen food: Black, glass and blood worms, Cyclops, brine shrimp, clam meat
• Fish: deep-frozen smelts et.al., tuna fish, sardines, herring etc. fresh or from a can (in their own juice, not in oil)
Behavior: aggressive (also intraspecific), not shy, diurnal as well as nocturnal, like to re-decorate their surroundings. Omnivorous predators.
Reproduction: unspecialized with several larval stages, pelagic (free-swimming) in the sea. H. takanoi as well as H. sanguineus can produce up to 50,000 eggs, three to four times a year (in contrast to local crabs, which only reproduce twice as season as a maximum). The larvae are not as tolerant as the adults regarding salinity and temperature. Larvae need a salinity of 25 to 35 per mil and 23.83 °C +/- 0.91 °C for successfully developing into a megalopa.
Socialization: Only with animals you can accept eventual losses of. They seem to ignore anemones. In general, they are trying to eat anything smaller or of the same size as themselves.
[attachment=8317]
Three H. takanoi and one H. sanguineus (right below).
Additional information:
• Live between rocks and oysters in estuaries, lagoons, ports and sheltered bays. Generally a crab of the tidal zone, they were spotted at depths of up to 20 meters in harbors.
• Was long mistaken for H. penicillatus, they are two different species after all, though.
• Named after Masatsugu Takano, the first to recognize H. penicillatus and H. takanoi have to be two different species.
[attachment=8318]
Typical: The brush-like growth on the males' claws.
• Another Asian shore crab, H. sanguineus, has also settled on a large part of the US Atlantic coast - and has also formed populations in the port of Le Havre in Normandy as well as in the Netherlands. H. sanguineus differs from H. takanoi by larger reddish dots on the claws, shorter but bristlier setae on the legs and, most prominently, by fleshy tubercles instead of the brush-like growth.
• Jan Bossel reported in 2005 (www.dochterland.org/hemigrapsus.htm), that he had found exclusively 2 to 4 cm large crabs of this species in the upper tidal zone, and the familiar local shore crab (Carcinus maenas) just in the lower tidal zone.
[attachment=8319]
Female
[attachment=8320]
Male (Exuvia): narrow apron.
Photos: Oliver Mengedoht
Translation: Ulli Bauer
Scientific name: Hemigrapsus takanoi
Trivial names: Asian Shore Crab, Brush-Clawed Shore Crab, Pencil Crab, Peenselkrab
Systematics: Domain: Eucaryota, kingdom: Animalia, subkingdom: Metazoa (multiple-celled animals), Eumetazoa (true tissue), grade: Bilateria, branch: Protostomia, infrakingdom: Ecdysozoa (molting animals), phylum: Arthropoda (jointed-leg invertebrates), subphylum: Crustacea, class: Malacostraca (higher crustaceans), superorder: Eucarida, order: Decapoda (ten-legged crayfish), suborder: Pleocyemata, infraorder: Reptantia, section: Brachyura (true crabs), superfamily: Grapsoidea, family: Varunidae, genus: Hemigrapsus, species: Hemigrapsus takanoi
Origin/distribution: Originating in the cold to subtropical parts of the North-West Pacific (Northern Japan To China). In the 1990s they were accidentally introduced to the Bay of Biscay - since then, three populations have established (data from 2002): in the south of the Netherlands, in the port of Le Havre and a large population in the Bay of Biscay off Jard-sur-Mer (France) to the Bay of Santander (Spain).
Recently, the population in the Netherlands has dramatically spread and widened its range to Belgium (where our specimens came from). The species has also surfaced in Germany (reported from the isle of Norderney and from Lower Saxony) and will probably also invade the American Atlantic coast.
[attachment=8314]
Further pics: www.panzerwelten.de/v/Hemigrapsus/Hemigrapsus_Tanakoi/
Description: Grey to brown, also orange-brown or green, light and dark striped legs, small dark spots on the claws, light-colored brush-like growth on the basis of the male's fingers. Three well-visible spikes on the side towards the front (behind the eyes). Females often have two symmetrical spots on the carapace.
Sex differences: Typical for crabs, the males have a narrow abdominal apron, the female's apron is wide and covers almost the entire abdomen. Males have bulkier claws.
Size: The carapace is up to at least 3.25 cm wide.
Life span: few years
[attachment=8315]
Temperature: 15 to 28 °C
Tank size/stock: In nature, there are up to 20 specimens to the square meter - however, these numbers are not recommendable in a tank.
Tank set-up: North Sea, marine or brackish water aquaterrarium (sandy shore, rocks)
[attachment=8316]
Food: typical for crabs, they're omnivores. In nature, they eat algae, small invertebrates, fish fry and juvenile fish - all they can find between the rocks in the tidal zone.
• Dry food: Catfish tabs, fish (flake) food, food pellets, Spirulina tabs, crayfish tabs, Gammarus
• Frozen food: Black, glass and blood worms, Cyclops, brine shrimp, clam meat
• Fish: deep-frozen smelts et.al., tuna fish, sardines, herring etc. fresh or from a can (in their own juice, not in oil)
Behavior: aggressive (also intraspecific), not shy, diurnal as well as nocturnal, like to re-decorate their surroundings. Omnivorous predators.
Reproduction: unspecialized with several larval stages, pelagic (free-swimming) in the sea. H. takanoi as well as H. sanguineus can produce up to 50,000 eggs, three to four times a year (in contrast to local crabs, which only reproduce twice as season as a maximum). The larvae are not as tolerant as the adults regarding salinity and temperature. Larvae need a salinity of 25 to 35 per mil and 23.83 °C +/- 0.91 °C for successfully developing into a megalopa.
Socialization: Only with animals you can accept eventual losses of. They seem to ignore anemones. In general, they are trying to eat anything smaller or of the same size as themselves.
[attachment=8317]
Three H. takanoi and one H. sanguineus (right below).
Additional information:
• Live between rocks and oysters in estuaries, lagoons, ports and sheltered bays. Generally a crab of the tidal zone, they were spotted at depths of up to 20 meters in harbors.
• Was long mistaken for H. penicillatus, they are two different species after all, though.
• Named after Masatsugu Takano, the first to recognize H. penicillatus and H. takanoi have to be two different species.
[attachment=8318]
Typical: The brush-like growth on the males' claws.
• Another Asian shore crab, H. sanguineus, has also settled on a large part of the US Atlantic coast - and has also formed populations in the port of Le Havre in Normandy as well as in the Netherlands. H. sanguineus differs from H. takanoi by larger reddish dots on the claws, shorter but bristlier setae on the legs and, most prominently, by fleshy tubercles instead of the brush-like growth.
• Jan Bossel reported in 2005 (www.dochterland.org/hemigrapsus.htm), that he had found exclusively 2 to 4 cm large crabs of this species in the upper tidal zone, and the familiar local shore crab (Carcinus maenas) just in the lower tidal zone.
[attachment=8319]
Female
[attachment=8320]
Male (Exuvia): narrow apron.