Marine Biodiversity

, Volume 43, Issue 4, pp 429–444

Bryoliths constructed by bryozoans in symbiotic associations with hermit crabs in a tropical heterozoan carbonate system, Golfe d’Arguin, Mauritania

Original Research

DOI: 10.1007/s12526-013-0173-4

Cite this article as:
Klicpera, A., Taylor, P.D. & Westphal, H. Mar Biodiv (2013) 43: 429. doi:10.1007/s12526-013-0173-4


The Golfe d’Arguin offshore of northern Mauritania hosts a rare modern analogue for heterozoan carbonate production in a tropical marine setting. Dominated by ocean upwelling and with additional fertilisation by iron-rich aeolian dust, this naturally eutrophic marine environment lacks typical photozoan communities. A highly productive, tropical cosmopolitan biota dominated by molluscs and suspension-feeders such as bryozoans and balanids characterises the carbonate-rich surface sediments. Overall biodiversity is relatively low and the species present are tolerant against the eutrophic and low-light conditions, the strong hydrodynamic regime governed by ocean upwelling, and the unstable, soft-bottom seafloor with few hard substrata. Here, we describe an ectosymbiosis between the hermit crab Pseudopagurus granulimanus (Miers, 1881) and monospecific assemblages of the encrusting cheilostome bryozoan Acanthodesia commensale (Kirkpatrick and Metzelaar, 1922) that cohabits vacant gastropod shells. Nucleating on an empty gastropod shell, the bryozoan colonies form multilamellar skeletal crusts that produce spherical encrustations and extend the living chamber of the hermit crab through helicospiral tubular growth. This non-obligate mutualistic symbiosis illustrates the adaptive capabilities and benefits from a close partnership in a complex marine environment, driven by trophic conditions, high water energies and instable substratum. Sectioned bryoliths show that between 49 and 97 % of the solid volume of the specimens consists of bryozoan skeleton.


Acanthodesia Pseudopagurus Trophic conditions Banc d’Arguin Northwest Africa 

Supplementary material

12526_2013_173_Fig4_ESM.jpg (1.2 mb)
Suppl. 1

Bivalve shells and bryoliths collected by dredging during the cruise of the R/V Al Awam (IMROP) in late 2012. (JPEG 1224 kb)

Copyright information

© Senckenberg Gesellschaft für Naturforschung and Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  1. 1.ZMT—Leibniz-Center for Tropical Marine EcologyBremenGermany
  2. 2.MARUM—Center for Marine Environmental SciencesUniversity of BremenBremenGermany
  3. 3.Department of Earth SciencesNatural History MuseumLondonUK

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