Molecular Evidence Shows Low Species Diversity of Coral-Associated Hydroids in Acropora Corals

Silvia Fontana,Shashank Keshavmurthy,Chia-Ming Hsu,Carden C Wallace,Chao-Yang Kuo,Wan-Sen Tsai,Vianney Denis,Hernyi Justin Hsieh,Julia K L Leung,Chaolun Allen Chen,Christopher Fulton

doi:10.1371/journal.pone.0050130

Abstract

A novel symbiosis between scleractinians and hydroids (Zanclea spp.) was recently discovered using taxonomic approaches for hydroid species identification. In this study, we address the question whether this is a species-specific symbiosis or a cosmopolitan association between Zanclea and its coral hosts. Three molecular markers, including mitochondrial 16S and nuclear 28S ribosomal genes, and internal transcribed spacer (ITS), were utilized to examine the existence of Zanclea species from 14 Acropora species and 4 other Acroporidae genera including 142 coral samples collected from reefs in Kenting and the Penghu Islands, Taiwan, Togian Island, Indonesia, and Osprey Reef and Orpheus Island on the Great Barrier Reef, Australia. Molecular phylogenetic analyses of the 16S and 28S genes showed that Acropora-associated Zanclea was monophyletic, but the genus Zanclea was not. Analysis of the ITS, and 16S and 28S genes showed either identical or extremely low genetic diversity (with mean pairwise distances of 0.009 and 0.006 base substitutions per site for the 16S and 28S genes, respectively) among Zanclea spp. collected from diverse Acropora hosts in different geographic locations, suggesting that a cosmopolitan and probably genus-specific association occurs between Zanclea hydroids and their coral hosts.

Highlights

Hydroids (Hydrozoa, Hydroida) establish relationships with a wide range of marine organisms, including anthozoans [1,2], due to their ability to associate with various types of substrates, including substrate generalist species and species that live on the surface of other organisms such as algae, bryozoans, bivalves, and corals [3,4]
Collection of samples in Australia was made possible by permission of the Great Barrier Reef Marine Park Authority for Orpheus Island, and in the case of Osprey Reef (Coral Sea), no permit was required at the time of collecting
Inter-colony variations in hydroid associations Results from the visual survey carried out at Chinwan Inner Bay (CIB), Penghu, Taiwan showed the presence of hydroids in several colonies of A. muricata, A. humilis, and A. valida

Summary

Introduction

Hydroids (Hydrozoa, Hydroida) establish relationships with a wide range of marine organisms, including anthozoans [1,2], due to their ability to associate with various types of substrates, including substrate generalist species and species that live on the surface of other organisms such as algae, bryozoans, bivalves, and corals [3,4]. These relationships range from epibiotic associations to stricter symbioses (mutualism or parasitism) [5,6]. Zanclea margaritae sp. nov. was found in specific association with the reef-building coral, Acropora muricata, on the Great Barrier Reef [10,11], and Zanclea sango sp. nov., described from Okinawa, Japan, was associated with 3 other coral species, Pavona divaricata, P. venosa, and Psammocora contigua [6]

Methods

Results

Discussion

Conclusion