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.

Three species of fire corals are present on the fringing coral reefs of Reunion Island (SW Indian Ocean): Millepora exaesa, Millepora platyphylla and Millepora tenera. Compared with scleractinian corals, reproduction studies on milleporids are scarce and this is the first study to be conducted in the Indian Ocean and on M. exaesa. We used a combination of weekly in situ observations and laboratory studies to document reproductive stages and phenology. The sexual reproductive period was the austral summer (Nov–Jan), the maturation of the colonies being correlated to the seasonal increasing water temperature. We describe both ampullae and short‐lived medusae (medusoids), and report differences in the size and density of ampullae and the distribution of nematocysts in the medusoids of the three species. The absence of radial and circular canals in all medusoids agrees with the original description but not with the current diagnosis of the family Milleporidae. We observed the first mass spawning event in M. exaesa and M. platyphylla, and provide the first description of a zooxanthellate Millepora larva. Spawning always began before dark but was not correlated with the lunar or tidal cycles. Millepora tenera colonies released several batches of medusoids during the reproductive period, suggesting that this species may be a serial spawner.

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The zebra coral, Oulastrea crispata, Lamarck 1816 is a scleractinian (family: Faviidae) commonly occurring in shallow reef de pressions and turbid waters throughout the Indo-Pacific. In Taiwan, preferential association with clade D-Symbiodinium has been proposed as an explanation of how this species can inhabit harsh environments where seawater temperature may present substantial fluctuation (Chen et al. 2003). In July 2011, a colony of O. crispata was placed in dark conditions in large outdoor tank with running seawater at Penghu Marine Biology Research Centre, Penghu Archipelago, Taiwan. On July 26 th 2012, after more than one year in total darkness and being exposed to temperature from 10.7 to 31.3ºC, this colony was still alive and visually seemed unaf fected by such conditions (Fig. 1a). Moreover, extra-tentacular buddings suggested that this colony continues to grow over this period. Lack of chlorophyll fluorescence (Fv /Fm＝0) suggested absence of Symbiodinium within the animal tissue which was further confirmed by microscopic observation (Fig. 1b). In contrast, field collected colony obviously hosts abundant Symbiodinium particularly localized around the mouth and at the base of the tentacles (Fig. 1c). While previous studies reported dark survival of Psammocora gonagra up to 228 days (Yonge and Nicholls 1931) and colonies of O. crispata have been reared under dim light for 215 days (Yamashiro 2000), the observation here, to our knowledge,