Interspecific coral competition does not affect the symbiosis of gall crabs (Decapoda: Cryptochiridae) and their scleractinian hosts

Susanne Bähr*, Sancia E.T. van der Meij, Tullia I. Terraneo, Tao Xu, Francesca Benzoni

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Scopus citations


Coral reefs accommodate a myriad of species, many of which live in association with a host organism. Decapod crustaceans make up a large part of this associated fauna on coral reefs. Among these, cryptochirid crabs are obligately associated with scleractinian corals, in which they create dwellings where they permanently reside. These gall crabs show various levels of host specificity, with the majority of cryptochirids inhabiting a specific coral genus or species. Here, we report the first records of gall crabs living in association with two different Porites species in the Red Sea. Crescent-shaped dwellings were observed in Porites rus and a Porites sp. in situ, and colonies with crabs were collected for further study in the laboratory. Using a combination of morphology and DNA barcoding, the crabs were identified as belonging to Opecarcinus, a genus only known to inhabit Agariciidae corals. The coral skeleton was bleached and studied under a stereo microscope, which revealed that the Porites corals overgrew adjoining agariciid Pavona colonies. We hypothesize that the gall crab originally settled on Pavona, its primary host of choice. Due to coral interspecific competition the Porites colony overgrew the adjacent Pavona colonies, resulting in a secondary and never before reported association of Opecarcinus with Porites. These findings suggest that cryptochirid crabs can adapt to the new microenvironment provided by a different coral host and survive competition for space on coral reefs.

Original languageEnglish (US)
Article numbere10051
JournalEcology and Evolution
Issue number5
StatePublished - May 2023

Bibliographical note

Funding Information:
This project was supported by funding from KAUST baseline research funds of F. Benzoni.

Publisher Copyright:
© 2023 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.


  • associated fauna
  • coral reefs
  • host-specificity
  • Pavona
  • Porites

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Ecology
  • Nature and Landscape Conservation


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