The 27 Best Deep-Sea Species: #22 Xenophyophores

Image courtesy of MBARI 2008

#22 Xenophyophore (Domain: Eukaryota, Kingdom Rhizaria, Phylum Foraminifera, Class Xenophyophorea)

Xenophyophores come in at 22 for several reasons.  First, they represent the largest single-celled organism on Earth. The largest of them is Syringammina fragillissima at a maximum of 20cm in diameter.  Second, in some areas of the deep, they are the dominant species with over 2,000 individuals per 100 square meters. Then there is the fact that, like ameobas, they use a pseudopodium to engulf food from the mud around them. While doing this they secrete a mucus that can cover a sizeable area on the seafloor.

Fourth and last, you know this is going to be a cool species when its scientific name means "bearer of foreign bodies".  The over 40 species of Xenophyophores all build tests from the dead parts of other things, be it diatom skeletons, sponge spicules, or broken shells.  To this they may add in sediment grains and a fecal pellet or two for fun.

So to recap, big single-celled animal that secretes a slimy goo all over and attaches the parts of dead things to itself.


Image from Bedford Institute of Oceanography


Image from NOAA Ocean Explorer

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 “The 27 Best Deep-Sea Species: #22 Xenophyophores
  1. To this they may add in sediment grains and a fecal pellet or two for fun.

    Different species use different amounts of different particles. There’s at least one species that constructs its test entirely from faecal pellets, and spends its life happily wrapped up in its own shit.

  2. 20cm !! Wow.

    So each species uses different mix that’s cool, I was thinking before the comments how using “found” objects like that must make it harder to identify them to genus or species visually. Giant-single-celled-snot-net-casting-fecal-palace-building… what more is there to life?

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