Japanese Skeleton Shrimp


Common names
Japanese skeleton shrimp
Scientific name
Caprella mutica

Now in Cape Breton


  • Caprella mutica are caprellid amphipods (a group of crustaceans collectively referred to as skeleton shrimp)
  • They superficially resemble preying mantises or walking stick insects
  • C. mutica may be pale green, beige, orange or red in colour
  • Males can achieve a size of 35 to 40mm
  • Females only grow to about 15mm body length
  • Males have large gnathopods with 3 points on the largest joint
  • Males also have many setae and spines on their main body segments
  • Females have a brood pouch that is covered with dark spots
  • Females give birth to live babies that crawl out of the brood pouch as they hatch


Caprella mutica feeds by trapping small food particles on its antennae and between its gnathopods (feeding appendages). It cleans the food particles off its antennae by curling them down around its mouthparts and mouth.
Caprella mutica is considered to be a commanding and thriving invader. They occur in high numbers on artificial structures such as mooring ropes and nets at aquaculture sites, and on floating docks and boat hulls in marinas. Caprella mutica can also be found on various natural substrata such as mussels and tubeworms. It is often found in association with fouling organisms like sea lettuce (Ulva spp.) and hydroids (Turbellaria spp.). The impact of C.mutica on these organisms and our local ecosystems is yet to be determined. Caprella mutica is considered a temperate water species, found in waters with a temperature range of -2 to 25 °C. In the native habitat, salinities of 11 to 35 parts per thousand (ppt) have been recorded. While C. mutica can withstand fluctuations in salinity, 48-hour lethal salinity estimates indicate that it would not withstand long periods at salinities below 20 ppt.
Geographic Range
The Japanese skeleton shrimp has spread from its Pacific origin in the waters off northeastern Japan to twenty-nine non-native locations around the globe, spanning both hemispheres. Caprella mutica has been found in the British Isles, Ireland, Norway, Germany, Belgium, the Netherlands, North America and New Zealand.

 Websites for Additional Information:

Information about the Japanese Skeleton Shrimp from the Marine Life Information Network (MarLIN): http://www.marlin.ac.uk/marine_aliens/species.asp?SpID=20