The intimate relationship between boxer crabs and sea anemones: What is known and what is not

Yisrael Schnytzer, Yair Achituv, G. Curt Fiedler, Ilan Karplus

Research output: Chapter in Book/Report/Conference proceedingChapterpeer-review

3 Scopus citations


Crabs of the xanthid subfamily Polydectinae (boxer crabs) have the remarkable habit of holding another animal, usually a sea anemone, in each of their claws. Some boxer crab species hold nudibranchs and holothurians. Boxer crabs are the only known crab species to have effectively lost all ability to use their claws in typical fashion, having formed what appears to be an obligate dependence on the animal held in its claws. Several, although not all, of the associated anemone species are known to occur free-living. Due to the anemones being held in the 'hands' of the crab, it is easy to envision how the stinging anemones are used for defence and food gathering. Boxer crabs have been mentioned often in this regard in popular culture and are commonly kept by marine aquarists. However, since their first appearance in the literature over 200 years ago, very few systematic studies have been conducted into the particulars of this symbiosis. Recent laboratory studies have expanded on various aspects of the natural history of boxer crabs, as well as the discovery of additional species in this subfamily. This review covers the literature on the boxer crab-anemone association, using the more extensively studied hermit crab-anemone association as a point of comparison. The review covers many aspects of the symbiosis, including the cost and benefits to each of the partners, the defensive value of the anemones to the crab, how the crabs locate their anemones, their respective morphological adaptations, anemone splitting and theft, as well as distribution and phytogeny. Due to their small size, most of the experimental work conducted to date has been limited to the laboratory. Recent advances in video recording as well as other tracking methods may allow for a closer look at this association in the wild, laying out the path to answering the many questions in this fascinating partnership.

Original languageEnglish
Title of host publicationOceanography and Marine Biology
Subtitle of host publicationAn Annual Review, Volume 60
PublisherCRC Press
Number of pages37
ISBN (Electronic)9781000781113
ISBN (Print)9781032265056
StatePublished - 8 Dec 2022

Bibliographical note

Publisher Copyright:
© 2022 S. J. Hawkins, A. J. Lemasson, A. L. Allcock, A. E. Bates, M. Byrne, A. J. Evans, L. B. Firth, C. H. Lucas, E. M. Marzinelli, P. J. Mumby, B. D. Russell, J. Sharples, I. P. Smith, S. E. Swearer, P. A. Todd.


  • Alicia
  • Asexual reproduction
  • Boxer crab
  • Defense
  • Lybia
  • Sea anemone
  • Symbiosis
  • Tool use


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