Invertebrate · GBIF taxon 5790281
Japanese Freshwater Crab
Geothelphusa dehaaniAlso known as Sawagani, Sawa Crab, Japanese Mountain Crab
Sawagani spend their lives entirely in cold, oxygen-rich mountain streams, bypassing the free-swimming marine larval stage typical of most crabs. Females carry relatively large, nutrient-rich eggs under their abdomens until miniature juveniles hatch fully formed. Coloration ranges strikingly across regional populations, presenting shades of porcelain blue, rusty red, or mottled olive brown.
NocturnalFreshwaterEndemic
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—observations
—countries
—peak records
Not EvaluatedConservation statusIUCN Red List categoriesLCNTVUENCREWEXNot Evaluated — not placed on the risk ladderRed List categories, explained →
Diet & prey
- Aquatic larvae
- Fallen leaves
- Freshwater snails
Predators
- Herons
- Raccoon dogs
- Giant salamanders
ThreatsWater pollution, stream channelization, deforestation, localized overcollecting
HabitatsClean mountain streams, cold headwater brooks, damp forest floors
Life span3–5 years
Size / weightNot available
Classification
- FamilyPotamidae
- SpeciesGeothelphusa dehaani
Range data is not available yet.
Interaction riskLow
- Low
- Moderate
- High
- Very high
- Why interaction risk is low
- Safe to observe at a normal distance along shaded stream banks.
Responsible observation
- Stream Scouting: Look beneath submerged rocks and along mossy banks during humid nights when crabs emerge to forage.
- Habitat Ethics: Carefully return turned stones to their original positions to protect delicate aquatic microhabitats.
Sympatric Crustacean Related Crustacean
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