Microboring organisms in living stylasterid corals (Cnidaria, Hydrozoa)

ABSTRACT

Microboring or euendolithic microorganisms, which colonize and penetrate various carbonate substrates, are abundant in coral reef ecosystems and play a major role in reef carbonate dissolution. A few studies reported the presence of euendoliths in stylasterid coral skeletons but the biological identity, distribution and abundance of these microorganisms remain largely unknown. Observations of over 100 stylasterid colonies, collected in the Indo-Pacific area, revealed for the first time that the association between these corals and euendolith organisms appears to be quite common in shallow tropical waters. The most abundant euendolith was identified as a cryptic stage in the development of the rhodophyte Porphyra (Conchocelis stage). The euendoliths were observed in the skeletons of seven species of three genera (four Stylaster, two Distichopora and one Lepidotheca). The presence of euendoliths inside skeletons conferred a particular colour to the studied stylasterid corals. Distribution and abundance of microborings varied significantly among stylasterid species and among branches of a single colony and so did the colour of their skeletons. Colonization of skeletons and the associated colour distribution were almost uniform in some stylasterids, forming an upward gradually diminishing or sharply limited gradient. This study shows that patterns of euendolith colonization and growth in stylasterid skeletons may depend on the stage of the euendolith development as well as on their environmental requirements such as light exposure.

RESPONSIBLE EDITOR:

• Tina Molodtsova

KEYWORDS:

• Conchocelis
• coral reefs
• euendoliths
• hydroid
• microborers
• stylasterid corals

Acknowledgements

The specimens collected in Indonesia (Ambon, Bali and Sulawesi areas) were imported by CITES permit code 04291/IV/SATS-LN/2011. Thanks to the Museums BMNH (London) and NBC (Leiden) for allowing us to work on museum specimens. The authors are indebted to the staff of the Coral Eye Research Centre in Indonesia for their logistical support. Finally, we thank the Centre IRD (Institut de Recherche pour le Développement) for supporting some of the microscopy analyses.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Daniela Pica http://orcid.org/0000-0001-7823-0488

Additional information

Funding

This research was supported by the European ‘SYNTHESYS’ Project financed by the European Community Research Infrastructure Action under the FP7 Integrating Activities Programme, and a Smithsonian Short Term Visitor Grant.