Life on the Leg of a Crab

Spider Crab feasts on the remains of a fish (Depth: 2229 m) Observation : 7282, 2012-06-15 00:07:11UTC, 1564. N47°55.9909′, W129°5.9243′ Credit: NEPTUNE Canada/CSSF

Neptune Canada, the world’s first regional-scale underwater ocean observatory network that plugs directly into the Internet, has an excellent Flickr photostream of deep-sea beasties.

A close up on the legs on the crab above reveals something amazing.

Close-up view of a crab feasting on fish (Depth: 2229 m) Observation : 7282, 2012-06-15 00:07:11UTC, dive 1564. N47°55.9909′ W129°5.9243′ Credit: NEPTUNE Canada/CSSF

Do you see it? Let me help.

What you see attached to the legs of the crab are skeleton or ghosts shrimps (there is actually a three, the third is just left of the upper red box). Ghost shrimps are not actually shrimps (in a group we call the Caridea) but rather in a group called the Caprellidae.  In fact they are not even in the same order (Decapoda vs. Amphipoda).  Caprellids are only found in the oceans and have a special pair of appendages for attaching to things like kelp, seagrass, small children swimming, or crab’s legs.  Although a few species filter feed particles out of the water.  Some are sit and wait predators patiently awaiting for another animal or really small child to get too close.  THEN BAM! A SMALL INVERTEBRATES MEETS ITS MAKER!

From Wikimedia CommonsCaprella mutica Schurin, 1935 Morphology (Male) Japanese skeleton shrimp.


Dr. M (1729 Posts)

Craig McClain is the Assistant Director of Science for the National Evolutionary Synthesis Center, a National Science Foundation supported initiative. He has conducted deep-sea research for 20 years and published over 50 papers in the area. He has participated in and led dozens of oceanographic expeditions taken him to the Antarctic and the most remote regions of the Pacific and Atlantic. Craig’s research focuses on how energy drives the biology of marine invertebrates from individuals to ecosystems, specifically, seeking to uncover how organisms are adapted to different levels of carbon availability, i.e. food, and how this determines the kinds and number of species in different parts of the oceans. Craig’s research has been featured on National Public Radio, Discovery Channel, Fox News, National Geographic and ABC News. In addition to his scientific research, Craig also advocates the need for scientists to connect with the public and is the founder and chief editor of the acclaimed Deep-Sea News (, a popular ocean-themed blog that has won numerous awards. His writing has been featured in Cosmos, Science Illustrated, American Scientist, Wired, Mental Floss, and the Open Lab: The Best Science Writing on the Web. His forthcoming book, Science of the South (, connects cultural icons of South such as pecan pie with the science behind them.

3 comments on “Life on the Leg of a Crab
  1. Wow!! Amazing pictures. Never thought of learning so much from crab legs. What is the age of this crab? The second picture looks broken or is it just men..Was the crab hurt in anyway?

  2. We get hundreds of these little guys on the ropes of our offshore acoustic stations. Sometimes they bite hard enough that you can actually feel them.

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