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Species delimitation of corals is one of the most challenging issues in coral reef ecology and conservation. Morphology can obscure evolutionary relationships, and molecular datasets are consistently revealing greater within-species diversity than currently understood. Most phylogenetic studies, however, have examined narrow geographic areas and phylogeographic expansion is required to obtain more robust interpretations of within- and among- species relationships. In the case of the blue coral Heliopora, there are currently two valid species (H. coerulea and H. hiberniana) as evidenced by integrated genetic and morphological analyses in northwestern Australia. There are also two distinct genetic lineages of H. coerulea in the Kuroshio Current region that are morphologically and reproductively different from each other. Sampling from all Heliopora spp. across the Indo-Pacific is essential to obtain a more complete picture of phylogeographic patterns. To examine phylogenetic relationships within the genus Heliopora, we applied Multiplexed inter simple sequence repeat (ISSR) Genotyping by sequencing (MIG-seq) on > 1287 colonies across the Indo-West Pacific. Maximum likelihood phylogenetic trees indicated the examined Heliopora samples comprise three genetically distinct groups: H. coerulea group, H. hiberniana group, and a new undescribed Heliopora sp. group with further subdivisions within each group. Geographic structuring is evident among the three species with H. hiberniana group found in the Indo-Malay Archipelago and biased toward the Indian Ocean whilst Heliopora sp. was only found in the Kuroshio Current region and Singapore, indicating that this taxon is distributed in the western Pacific and the Indo-Malay Archipelago. Heliopora coerulea has a wider distribution, being across the Indian Ocean and western Pacific. This study highlights the effectiveness of phylogenetic analysis using genome-wide markers and the importance of examining populations across their distribution range to understand localized genetic structure and speciation patterns of corals.

Nanipora Miyazaki & Reimer, 2015 is a recently discovered genus of aragonite-skeleton producing octocorals closely related to the blue coral genus Heliopora de Blainville, 1830. Since its discovery, Nanipora has been reported from coral reefs in Okinawa, Japan, and Thailand, and from seagrass beds in the northern South China Sea. However, it remains little known and studied. Here, we report on the unexpected discovery of an abundance of Nanipora colonies in shallow waters less than 2-m deep around a CO2 vent from the uninhabited volcanic island of Iwotorishima, Okinawa, in southern Japan. Nanipora colonies were found covering both coral rubble and hard substrates, alongside a few soft coral and zoantharian species. Polyps were pale white in color with none brown or darker in coloration as in some recent reports. As the original description of N. kamurai from Zamami Island in Okinawa describes the species as azooxanthellate, as the current Iwotorishima specimens also appear to be, and recently reported specimens from Thailand, Dongsha Atoll, and Yaeyama are zooxanthellate, it may be that there are more than one Nanipora species; the type species N. kamurai that is also likely at Iwotorishima, and a zooxanthellate species that constitutes the other records. Although Nanipora is not well studied, its presence at this volcanic CO2 seep suggests it has the ability to survive under unique and extreme environmental conditions, rendering it as a potentially important subject of study in the face of increasing ocean acidification.

Towards the sustainable development, optoelectronic devices with biodegradability and biocompatibility have been a desirable but challenging issue for years. In this study, an all-biomaterial random laser device based on all-marine elements has been demonstrated. Chlorophyll and blue coral skeletons serve as gain medium and scattering centers, respectively. The chlorophyll is derived from marine diatoms, which are ubiquitous in the ocean and set up an abundant source for the device. On the other hand, the coral skeletons with intrinsic nanorod structures can provide a strong optical confinement and feedback for laser action. The proposed design signifies the novel application of marine materials and represents a significant step for the development of bio-inspired photonics modules.

Maintaining the accretion potential and three dimensional structure of coral reefs is a priority but reef-building scleractinian corals are highly threatened and retreating. Hence future reefs are predicted to be dominated by non-constructional taxa. Since the Late Triassic however, other non-scleractinian anthozoans such as Heliopora have contributed to tropical and subtropical reef-building. Heliopora is an ancient and highly conserved reef building octocoral genus within the monospecific Family Helioporidae, represented by a single extant species – H. coerulea, Pallas, 1766. Here we show integrated morphological, genomic and reproductive evidence to substantiate the existence of a second species within the genus Heliopora. Importantly, some individuals of the new species herein described as Heliopora hiberniana sp. nov. feature a white skeleton indicating that the most diagnostic and conserved Heliopora character (the blue skeleton) can be displaced. The new species is currently known only from offshore areas in north Western Australia, which is a part of the world where coral bleaching events have severely impacted the scleractinian community over the last two decades. Field observations indicate individuals of both H. coerulea and H. hiberniana sp. nov. were intact after the 2016 Scott Reef thermal stress event, and we discuss the possibility that bleaching resistant non-scleractinian reef builders such as Heliopora could provide new ecological opportunities for the reconfiguration of future reefs by filling empty niches and functional roles left open by the regression of scleractinian corals.

Corals are ecosystem engineers of the coral reefs, one of the most biodiverse but severely threatened marine ecosystems. The ability of corals to form the three dimensional structure of reefs depends on the precipitation of calcium carbonate under biologically control. However, the exact mechanisms underlying this biologically controlled biomineralization remain to be fully unelucidated, for example whether corals employ a different molecular machinery for the deposition of different calcium carbonate (CaCO3) polymorphs (i.e., aragonite or calcite). Here we used tandem mass spectrometry (MS/MS) to compare skeletogenic proteins, i.e., the proteins occluded in the skeleton of three octocoral and one scleractinian species: Tubipora musica and Sinularia cf. cruciata, both forming calcite sclerites, the blue coral Heliopora coerulea with an aragonitic rigid skeleton, and the scleractinian aragonitic Montipora digitata. We observed extremely low overlap between aragonitic and calcitic species, while a core set of proteins is shared between octocorals producing calcite sclerites. However, the same carbonic anhydrase (CruCA4) is employed for the formation of skeletons of both polymorphs. Similarities could also be observed between octocorals and scleractinians, including the presence of a galaxin-like protein. Additionally, as in scleractinians, some octocoral skeletogenic proteins, such as acidic proteins and scleritin, appear to have been secondarily co-opted for calcification and likely derive from proteins playing different extracellular functions. In H. coerulea, co-option was characterized by aspartic acid-enrichment of proteins. This work represents the first attempt to identify the molecular basis underlying coral skeleton polymorph diversity, providing several new research targets and enabling both future functional and evolutionary studies aimed at elucidating the origin and evolution of biomineralization in corals.

Coral reefs are declining worldwide due to regional and global anthropogenic stress. Sekisei Lagoon and areas in its vicinity are impacted by the same stresses. Sekisei Lagoon is the largest coral reef area in Japan covering an area of almost 15 km × 20 km. Being situated upstream of Kuroshio Current, coral reefs in this area could supply larvae to downstream such as the Ryukyu Archipelago, facilitating high biodiversity. To conserve corals in such an area, estimation of larval dispersal among populations is essential because connectivity via larval dispersal is associated with the time for replenishment after disturbance. Isolated coral populations have a higher risk of local extinction. The purpose of this study is to reveal genetically isolated populations of brooding corals with short larval durations in and around Sekisei Lagoon. For this purpose, we utilized both population genetic analysis and larval dispersal simulations. Based on genotyping of 929 colonies of blue coral, Heliopora spp., collected from 22 sites around Sekisei Lagoon, genetic analysis suggested self-recruitment with connectivity in the southeastern sites and northwestern sites. Particle-tracking larval dispersal simulations also revealed similar patterns, corroborating the genetic results. These results suggest that lagoonal scale connectivity among populations of Heliopora spp. in Sekisei Lagoon is limited, as expected based on its short larval duration. Our results highlight the fact that most of the Heliopora spp. populations are genetically isolated, even inside Sekisei Lagoon, implying that the likelihood of being replenished by larval supply from surrounding populations after a disturbance is low and have a higher risk of local extinction than other coral species with high larval dispersal potential.

Background Heliopora coerulea, the blue coral, is a reef building octocoral that is reported to have a higher optimum temperature for growth compared to most scleractinian corals. This octocoral has been observed to grow over both live and dead scleractinians and to dominate certain reefs in the Indo-Pacific region. The molecular mechanisms underlying the ability of H. coerulea to tolerate warmer seawater temperatures and to effectively compete for space on the substrate remain to be elucidated. Methods In this study, we subjected H. coerulea colonies to various temperatures for up to 3 weeks. The growth and photosynthetic efficiency rates of the coral colonies were measured. We then conducted pairwise comparisons of gene expression among the different coral tissue regions to identify genes and pathways that are expressed under different temperature conditions. Results A horizontal growth rate of 1.13 ± 0.25 mm per week was observed for corals subjected to 28 or 31 °C. This growth rate was significantly higher compared to corals exposed at 26 °C. This new growth was characterized by the extension of whitish tissue at the edges of the colony and was enriched for a matrix metallopeptidase, a calcium and integrin binding protein, and other transcripts with unknown function. Tissues at the growth margin and the adjacent calcified encrusting region were enriched for transcripts related to proline and riboflavin metabolism, nitrogen utilization, and organic cation transport. The calcified digitate regions, on the other hand, were enriched for transcripts encoding proteins involved in cell-matrix adhesion, translation, receptor-mediated endocytosis, photosynthesis, and ion transport. Functions related to lipid biosynthesis, extracellular matrix formation, cell migration, and oxidation-reduction processes were enriched at the growth margin in corals subjected for 3 weeks to 28 or 31 °C relative to corals at 26 °C. In the digitate region of the coral, transcripts encoding proteins that protect against oxidative stress, modify cell membrane composition, and mediate intercellular signaling pathways were enriched after just 24 h of exposure to 31 °C compared to corals at 28 °C. The overall downregulation of gene expression observed after 3 weeks of sustained exposure to 31 °C is likely compensated by symbiont metabolism. Discussion These findings reveal that the different regions of H. coerulea have variable gene expression profiles and responses to temperature variation. Under warmer conditions, the blue coral invests cellular resources toward extracellular matrix formation and cellular migration at the colony margins, which may promote rapid tissue growth and extension. This mechanism enables the coral to colonize adjacent reef substrates and successfully overgrow slower growing scleractinian corals that may already be more vulnerable to warming ocean waters.

The octocoral Heliopora coerulea has emerged as one of the most dominant reef-building corals in the Bolinao Reef Complex, northern Philippines. One of the possible mechanisms that may contribute to the success of H. coerulea over scleractinian corals is its ability to compete effectively for space on the reef by inhibiting the settlement of coral larvae in its immediate vicinity. To determine whether H. coerulea can indeed inhibit larval recruitment, settlement tiles were deployed inside H. coerulea aggregations or on hard substrate at a distance of about 2 to 3 meters away. After three months of deployment, only a single H. coerulea recruit was observed on tiles placed within aggregations whereas many different coral recruits were observed on tiles placed on substrate away from the blue coral. These results suggest that adult H. coerulea can inhibit the settlement of scleractinian larvae. This effect may be mediated by various mechanisms, such as the production of allelopathic compounds, deployment of mesenterial filaments, and sweeper tentacles. However, further studies are needed to determine the modes of competition that are used by the coral.

The Asiatic coral snakes are basal in the phylogeny of coral snakes. Although envenoming by the Asiatic coral snakes is rarely fatal, little is known about their venom properties and variability from the American coral snakes. Integrating reverse-phase high performance liquid chromatography and nano-liquid chromatography-tandem mass spectrometry, we showed that the venom proteome of the Malaysian banded or striped coral snake (Calliophis intestinalis) was composed of mainly phospholipases A2 (PLA2, 43.4%) and three-finger toxins (3FTx, 20.1%). Within 3FTx, the cytotoxins or cardiotoxins (CTX) dominated while the neurotoxins' content was much lower. Its subproteomic details contrasted with the 3FTx profile of most Micrurus sp., illustrating a unique dichotomy of venom phenotype between the Old and the New World coral snakes. Calliophis intestinalis venom proteome was correlated with measured enzymatic activities, and in vivo it was myotoxic but non-lethal to mice, frogs and geckos at high doses (5–10 μg/g). The venom contains species-specific toxins with distinct sequences and antigenicity, and the antibodies raised against PLA2 and CTX of other elapids showed poor binding toward its venom antigens. The unique venom proteome of C. intestinalis unveiled a repertoire of novel toxins, and the toxicity test supported the need for post-bite monitoring of myotoxic complication. Significance Malaysian banded or striped coral snake (Calliophis intestinalis) has a cytotoxin (CTX)-predominating venom proteome, a characteristic shared by its congener, the Malayan blue coral snake (Calliophis bivirgata). With little neurotoxins (NTX), it illustrates a CTX/NTX dichotomy of venom phenotype between the Old World and the New World coral snakes. The low toxicity of the venom imply that C. intestinalis bite envenoming can be managed via symptomatic relief of the mild to moderate pain with appropriate analgesia. Systemically, the serum creatine kinase level of patients should be monitored serially for potential complication of myotoxicity. The distinct antigenicity of the venom proteins implies that the empirical use of heterologous antivenom is mostly inappropriate and not recommended.

A new genus and species of octocoral with a calcium-carbonate skeleton, Nanipora kamurai sp. n., is described from a shallow coral reef in Okinawa, Japan. Contrary to most octocorals, the skeleton is composed of crystalline aragonite as in blue coral Heliopora. The results of molecular phylogenetic analyses of sequences of mtMutS, COI, and ITS1-5.8s-ITS2-28S region suggest Nanipora gen. n. specimens should be included in order Helioporacea. Based on morphological results compared with other Helioporacea including the genus Epiphaxum (family Lithotelestidae), we establish the new genus Nanipora within Lithotelestidae. This is the first time that a close molecular phylogenetic relationship between Heliopora and a related genus within Helioporacea has been revealed.

Heliopora coerulea is the only species in the subclass Octocorallia that has a crystalline aragonite skeleton. The skeleton has been reported to contain the blue pigment, biliverdin IXα, which is formed by heme oxygenase (HO) during heme decomposition. There is little information regarding gene expression in H. coerulea; therefore, the biosynthesis pathway for biliverdin IXα is poorly understood. To identify the genes related to heme synthesis and degradation, metatranscripts of H. coerulea and its symbiont Symbiodinium spp. were sequenced and separated from the host- and symbiont-derived sequences. From the metatranscriptome analyses, all genes for heme synthesis and three HOs were isolated from the host and symbiont. From our phylogenetic and amino acid analysis, we noted that one of the HO isoforms in the host coral was predicted to possess HO activity. However, biliverdin reductase, which reduces biliverdin to bilirubin, was not identified in the present study. Similarly, biliverdin reductase was not identified in the transcripts of the red coral Corallium rubrum, a species that also belongs to Octocorallia. However, genes related to heme synthesis and HO were found in C. rubrum. We speculate that Heliopora coerulea can produce biliverdin and accumulate it in the skeleton, while red corals and other Octocorallia species cannot. Further information from molecular studies of H. coerulea will provide insights into the synthesis of biliverdin IXα, the blue pigment in the hard crystalline aragonite skeleton, and will be fundamental to future ecological and physiological studies.

Recurrent thermal stress events and intensified precipitation alter the ocean environment resulting in the decline of coral populations. However, the influence of these changes on larval survival and settlement is not well understood. We examined the effect of salinity (15, 20, 25, 30, 35, and 40 ppt) and temperature (27 °C, 30 °C, and 33 °C) on settlement and survival of larvae of the octocoral, Heliopora coerulea. Larvae settled successfully at salinities from 25 to 30 ppt. On the other hand, larval survival and settlement decreased with increasing temperature. A combination of 25–35 ppt and 27–30 °C resulted in highest survival and settlement. These results indicate that early life stages of H. coerulea are negatively impacted by thermal stress but may be able to survive at reduced salinity. The wider tolerance range of H. coerulea larvae compared to most scleractinian larvae may thus contribute to the success of this coral on disturbed reef ecosystems.

The blue coral Heliopora coerulea (Pallas, 1766), a reef-building coral, is the sole member of the alcyonarian order Coenothecalia. Recently, local and global anthropogenic stresses on its habitat have led to this species being listed as threatened. Strong genetic differentiation has been observed between populations of H. coerulea that have been found only 500 m apart. Despite the wide geographical distribution of H. coerulea in the Indo-Pacific oceans, such localized genetic structuring has led to speculation about whether H. coerulea populations are completely isolated over different geographic scales (including speciation). To investigate gene flow in H. coerulea, we genotyped seven microsatellite loci in 611 H. coerulea colonies collected from along the Kuroshio Current. Genetic admixture analysis and principal coordinate analysis suggested the existence of two cryptic species in the studied area. In addition, distinct typical gross morphologies were shown by both these cryptic species. Patterns of isolation by distance were more obvious and significant when each genetic clade was analyzed separately than when the populations were analyzed together. In addition, we found that some populations had extremely low genotypic diversity. These findings indicate that these populations may be more threatened than previously believed and emphasize the threatened status of H. coerulea.

This is the first study of Helioporacea Bock, 1938 for symbiotic copepods. A new species of copepod, Indoclausia helioporae sp. nov., was obtained by washing segments of blue coral, Heliopora coerulea (Pallas, 1766), collected from shallow water reefs in southern Taiwan. A full description of the new species is provided. The new species can be easily distinguished from its only congener, Indoclausia bacescui Sebastian & Pillai, 1974, by having (1) a small body of 1.32 × 0.20 mm; (2) a small caudal ramus, 33 × 15 μm; (3) a short antennule with formula: 4, 10, 11, 4, 2 + 1 aesthetasc and 7 + 1 aesthetasc (very short); (4) a 2-segmented maxilliped; (5) the exopod of leg 1 with formula: I-0; III-0; (6) the exopod of leg 2 with formula: I-0; I, III; (7) no seta on the endopod of legs 1 and 2; (8) a uniseriate egg-sac with 6 eggs.

The blue coral, Heliopora coerulea, is a reef-building octocoral that prefers shallow water and exhibits optimal growth at a temperature close to that which causes bleaching in scleractinian corals. To better understand the molecular mechanisms underlying its biology and ecology, we generated a reference transcriptome for H. coerulea using next-generation sequencing. Metatranscriptome assembly yielded 90,817 sequences of which 71% (64,610) could be annotated by comparison to public databases. The assembly included transcript sequences from both the coral host and its symbionts, which are related to the thermotolerant C3-Gulf ITS2 type Symbiodinium. Analysis of the blue coral transcriptome revealed enrichment of genes involved in stress response, including heat-shock proteins and antioxidants, as well as genes participating in signal transduction and stimulus response. Furthermore, the blue coral possesses homologs of biomineralization genes found in other corals and may use a biomineralization strategy similar to that of scleractinians to build its massive aragonite skeleton. These findings thus offer insights into the ecology of H. coerulea and suggest gene networks that may govern its interactions with its environment.

New data on the species composition and distribution of reef-building corals on some reefs of the Seychelles Islands are presented. The study revealed 236 species belonging to 68 genera, which exceeds the well-known values of scleractinian species composition in this region by almost two times. Representatives of the families Acroporidae, Poritidae, and Faviidae dominated. Settlements of the blue coral Heliopora coerulea and the hydroid Millepora dichotoma were fairly numerous and in aggregate covered up to 40% of the substratum. In its species composition, the coral fauna of the Seychelles reefs makes a single unit with the Indo-Pacific tropical fauna.

We examined the genotypic diversity of the large population of Heliopora coerulea, discovered recently in Ooura Bay, northern Okinawa Main Island Japan, together with another large population in Shiraho Reef, also in southwest Japan, using 9 polymorphic microsatellite markers. From each population, 40 samples were systematically collected along 2 transect lines with 4-m intervals. Surprisingly, all 40 samples from Ooura Bay were mono-genotypic, implying that the huge coral structure (30 m × 80 m) originated from a single larva. Conversely, the 40 samples collected from the Shiraho Reef site all had different genotypes; measurements of genetic diversity, HE and HO, were 0.075–0.975 and 0.064–0.655, respectively. At least four factors are considered to make such a huge H. coerulea population with a single genotype in Ooura Bay, (1) origin of single larva or fragment (2) a genetic bottleneck, (3) post settlement selection, and (4) frequent asexual propagation.

We isolated 11 polymorphic microsatellites from blue coral (Heliopora coerulea), whose conservation and management are of great concern. The number of alleles ranged from 3 to 20 with an average of 5.5, and the observed and expected heterozygosities ranged from 0.115 to 0.833 and from 0.371 to 0.915, respectively. These loci are useful for conservation genetics in H. coerulea populations.

Approximately 3,000 species of Octocorallia are distributed worldwide (Williams and Cairns 2005; Daly et al. 2007). New species, even genera and families, continue to be described especially from the deep-sea environment and the Indo-Pacific. A total number of 46 octocoral families (van Ofwegen and McFadden 2010) are described of which 29 (excluding sea pens) are in the order Alcyonacea; 23 are found in the warm, shallow waters of the Red Sea, Indian, and Pacific Ocean. The subclass octocorallia (Alcyonaria) has three major orders: Helioporacea (blue coral), Alcyonacea (soft corals and gorgonians) and Pennatulacea (sea pens), only the two latter have been recorded in the Persian Gulf (Samimi-Namin and van Ofwegen 2009a, b).

The presence and localization of organic matrix associated with the aragonite phase in the fibers of blue coral Heliopora coerulea skeletons were studied by in situ microRaman mapping spectra, with a spatial resolution of ~0.3 μm. Spatial variations in the amounts and chemical compositions of the fibers were imaged. The results showed that the amide I and the α-helix of amide III were perpendicular to the c-axis of fibers' growth, whereas the β-turns/sheet of amide III was in the parallel conformation. Visible S-S and C-S bonds were consistent with the XANES results, which indicated the existence of organic sulfur in coral skeletons. Regular cyclic changes between aragonite and organic matrix refined a stepping growth mode of the fibers' biomineralization. An inorganic PO(4) bond was detected and exhibited the same concentration variation trends as the v(4) aragonite bands. Instead of providing an ocean P proxy on the subseasonal to centennial scale by LA-ICPMS, the possibility was raised of producing high resolution surface ocean phosphorus records on daily environmental variation via P/Ca variation cycles determined from Raman mapping data.

Seven new diterpenes, helioporins A-G (1–7), have been isolated from the blue coral Heliopora coerulea . The structures determined by spectroscopic data and chemical conversions are related to the aglycons of pseudopterosins and seco-pseudopterosins, which are antiinflammatory glycosides from Caribbean gorgonians. Treatment of helioporin A ( a ) with TMSI/NaI followed by Na 2 S 2 O 3 gave helioporin E ( 5 ) and an unusual product ( 11 ) resulting from CC bond cleavage. Reaction of helioporin B ( 2 ) with Tf 2 O/C 5 H 2 NMe t -Bu 2 followed by catalytic reduction gave a cyclization product ( 14 ) which was identical with a compound derived from 5 . All helioporins were chemically correlated and their relative stereochemistry was related to that of the aglycon of pseudopterosin G ( 10 ). Helioporins A and B showed antiviral activity against HSV1 and C-G cytotoxicity against P388.

Seven new diterpenes, helioporins A-G (1–7), have been isolated from the blue coral Heliopora coerulea . The structures determined by spectroscopic data and chemical conversions are related to the aglycons of pseudopterosins and seco-pseudopterosins, which are antiinflammatory glycosides from Caribbean gorgonians. Treatment of helioporin A ( a ) with TMSI/NaI followed by Na 2 S 2 O 3 gave helioporin E ( 5 ) and an unusual product ( 11 ) resulting from CC bond cleavage. Reaction of helioporin B ( 2 ) with Tf 2 O/C 5 H 2 NMe t -Bu 2 followed by catalytic reduction gave a cyclization product ( 14 ) which was identical with a compound derived from 5 . All helioporins were chemically correlated and their relative stereochemistry was related to that of the aglycon of pseudopterosin G ( 10 ). Helioporins A and B showed antiviral activity against HSV1 and C-G cytotoxicity against P388.

A mass mortality of coral communities dominated by Porites spp. was observed in the reef flats off the east coast of Ishigaki Island, Okinawa, Japan. Mortality was concentrated around the mouth of the Todoroki River, from which a large amount of terrigenous fine particles had been discharged during a heavy rain. Mortality was observed over an area of ca. 30 ha in early June 2001. Damaged corals included massive Porites and Favia, branching Montipora, and the blue coral Heliopora coerulea. The most conspicuous damage was evident in large colonies of Porites because of the abundance of this species in the area. Fine particles 0.5%) just after the mass-mortality event and decreased over time. This mass mortality was apparently caused by several simultaneously occurring factors, including low tide, unusually strong north winds, and heavy precipitation that caused extensive sediment runoff.

Up to the present time, the reproductive cycle and larval development ofHeliopora coerulea, living fossil and sole member of the alcyonarian order Coenothecalia, have been undescribed. Populations ofH. coerulea studied on the Great Barrier Reef between 1984 and 1989 were found to have separate sexes and an annual gametogenic cycle. Mature eggs were large (>800µm diam), and their development was initiated internally. There appeared to be a lunar or semi-lunar periodicity in reproductive behaviour, with brooding of larvae commencing around either full or new moon. Development proceeded via superficial cleavage and a solid stereoblastula. Subsequent development took place on the surface of the colony, within a temporary brood-space created by protracted distension of the polyps. Larvae lacked zooxanthellae and were brooded for between 6 and 14 d prior to leaving the colony. Reproduction and development reflected the taxonomic affinities ofH. coerulea, but brooding and embryological development also appeared to be constrained by its morphology. Reproductive and larval characteristics ofH. coerulea may offer a partial explanation of the current biogeographic range ofH. coerulea.

Zeatin, zeatin riboside, dihydrozeatin and isopentenyladenine have been isolated from green algae and blue coral along with two new cytokinins, characterized as 2-hydroxy-6-methylaminopurine and 2-hydroxy-1′methylzeatin.

Three new diterpenes, helioxenicins A-C (2–4), have been isolated from the blue coral Heliopora coerulea. The structures were initially determined from NMR spectroscopic data and confirmed by an X-ray analysis of helioxenicin B.

Light and transmission electron microscopic observations of the venom gland of the blue coral snake revealed a main venom gland and a long duct. The main secretory cell showed characteristic features of a protein secreting cell, with small microvilli, and a cytoplasm containing vacuoles and vesicles. Another type of "dark cell" and a third type of "basal cell" were also seen. "Nerve terminals" supplying the gland showed pleomorphic vesicles. The compressor muscle surrounding the venom gland showed the A band, Z disc, and H zone. Satellite cells were seen among muscle fibres. The neuromuscular junctions supplying the muscle showed clear vesicles. Scanning electron microscopy of the fangs showed the entrance lumen, discharge orifice, suture and the dental ridge. These findings are compared with relevant structures in other snake species.

The occurrence of symbiotic zooxanthellae in further aeolid and arminacean nudibranch molluscs is described for the first time. The aeolid Aeolidiopsis ransoni Pruvot-Fol is redescribed, and a new species of Aeolidiopsis, also feeding on the colonial zoantharian Palythoa, is described. Both have symbiotic zooxanthellae. The taxonomy of the family Aeolidiidae is discussed and the genus Berghia Trinchese, 1877 is considered a synonym of Spurilla Bergh, 1864. Spurilla major (Eliot, 1903) and a new species of Spurilla are reported to have zooxanthellae while another new species of Spurilla is without zooxanthellae. The glaucid aeolid Pteraeolidia ianthina (Angas) is shown to have symbiotic zooxanthellae, as is the arminacean Doridomorpha gardineri Eliot, which is reported to feed on the alcyonarian blue coral, Heliopora. In all cases, the morphological adaptations developed for this symbiosis are described. Further notes on the Porites-fetding arminacean Pinufius rebus Marcus & Marcus and the aeolid Phestilla lugubris (Bergh) are included and a facultative symbiosis with zooxanthellae is suggested for the latter. The tion of symbiosis with zooxanthellae within nudibranchs is discussed and it is suggested that the relationship has evolved independently on several occasions.

Heliopora coerulea (Alcyonaria, Coenothecalia), widespread since the Cretaceous, is today found in the Indo-Western Pacific between 25° N and 25° S but is uncommon throughout most of its range. Studies around its reported southern and eastern limits of distribution (Great Barrier Reef, Vanuatu, Fiji, Tonga, Western Samoa, Tuvalu, Gilbert Group) suggest that ocean temperature (a lower marginal isotherm of 22°C), duration of larval life-span, prevailing currents, and the geological and climatic history of isolated archipelagoes determine distribution. Heliopora was found to be far more abundant in the equatorial Central Pacific sites (Tuvalu and Gilbert growps) than in the Western Pacific (Great Barrier Reef, New Guinea, Solomon Islands, Ponape, Palau). Heliopora comprised up to 16% of beach sediments in Tuvalu atolls, and was the dominant coral (averaging 40% of substrate between 6 m and 10 m on reef slopes) in coral assemblages on Tarawa Atoll. From ecological studies in Tarawa it is suggested that competition from the more specialized and “aggressive” Scleractinia (particularly Acroporidae and Faviidae) is the major factor limiting abundance in the equatorial Western Pacific.

The fossil record of the genus Heliopora begins in the Early Cretaceous Period with its oldest representative Heliopora japonica, and “notwithstanding its great antiquity, it differs very little from the living Heliopora coerulea” (Eguchi 1948). Heliopora coerulea, the blue coral, is a common reef former of modern Indo-Pacific reefs and the sole surviving species of the Helioporidae, the only family of the order Coenothecalia. Coenothecalia, one of six orders of the subclass Octocorallia, is unique among the Octocorallia because Heliopora has a trabecular skeleton of fibrous aragonite (Hill 1960). Scattered throughout the corallum are autopores (0.5 mm to 2.0 mm) surrounded by a coenenchyma of numerous smaller siphonopores (Fig. 1).

THE remarkable blue coral, Heliopera cerulea, of Blainville, represents, I believe, one of those species that, in common with Stylaster, Millepora, and other allied genera, have been recently relegated to the Hydrozoic subdivision of the Cœlenterata. So far as I remember, however, and without having present access to the most recent literature of this subject, Heliopora was thus transferred with reference to the structure of its corallum only, the living animal having been but imperfectly if at all observed.