Explore the vast range of titles available.

Coral reef ecosystems are based on coral-zooxanthellae symbiosis. During the initiation of symbiosis, majority of corals acquire their own zooxanthellae (specifically from the dinoflagellate genus Symbiodinium) from surrounding environments. The mechanisms underlying the initial establishment of symbiosis have attracted much interest, and numerous field and laboratory experiments have been conducted to elucidate this establishment. However, it is still unclear whether the host corals selectively or randomly acquire their symbionts from surrounding environments. To address this issue, we initially compared genetic compositions of Symbiodinium within naturally settled about 2-week-old Acropora coral juveniles (recruits) and those in the adjacent seawater as the potential symbiont source. We then performed infection tests using several types of Symbiodinium culture strains and apo-symbiotic (does not have Symbiodinium cells yet) Acropora coral larvae. Our field observations indicated apparent preference toward specific Symbiodinium genotypes (A1 and D1-4) within the recruits, despite a rich abundance of other Symbiodinium in the environmental population pool. Laboratory experiments were in accordance with this field observation: Symbiodinium strains of type A1 and D1-4 showed higher infection rates for Acropora larvae than other genotype strains, even when supplied at lower cell densities. Subsequent attraction tests revealed that three Symbiodinium strains were attracted toward Acropora larvae, and within them, only A1 and D1-4 strains were acquired by the larvae. Another three strains did not intrinsically approach to the larvae. These findings suggest the initial establishment of corals-Symbiodinium symbiosis is not random, and the infection mechanism appeared to comprise two steps: initial attraction step and subsequent selective uptake by the coral.

Precious corals from the Corallidae family (Corallium, Hemicorallium, and Pleurocorallium genera) are well known in the high-end jewelry industry due to their colorful and durable axial skeleton. They exist in various colors from white to pink to dark red. One highly appreciated shade is the light pink color, the so-called ‘angel skin’. This color is most often associated with Pleurocorallium elatius and Pleurocorallium secundum, species listed in CITES Appendix III. However, this has been based on an assumption of their visual similarity and has never been underpinned by detailed morphologic or genetic data. In this study, we present the analysis of an ‘angel skin’ coral necklace of exceptional size and homogeneous color and quality. Visual observation and Raman spectroscopy confirmed that the necklace consists of genuine, untreated precious coral material. Following minimally destructive sampling, respectively, drilling 2.2, 2.4, and 2.4 milligrams of material from the existing drill-holes, three randomly selected beads from the necklace were subject to a routine genetic identification assay, which is based on sequencing a short, taxonomically informative mitochondrial region. This genetic analysis identified the coral material as not from P. elatius or P. secundum but from another Pleurocorallium species. We subsequently sequenced additional mitochondrial DNA fragments from one ‘angel skin’ coral bead and compared them against a well-represented, curated reference data set of Pleurocorallium, including the first-ever sequencing of Pleurocorallium gotoense, Pleurocorallium johnsoni, Pleurocorallium cf. pusillum, and Pleurocorallium uchidai. We concluded that the analyzed material of the ‘angel skin’ coral necklace belongs to the Pleurocorallium norfolkicum species complex but is not identical to any hitherto analyzed and published Pleurocorallium specimens. A comparison with further taxonomically unidentified precious coral colony fragments identified a single sample fished in Vietnam to be completely identical to the ‘angel skin’ coral bead in the studied DNA regions. Thus, by the analysis of a high-end jewel, we discovered a species new to the jewelry trade and potentially also unknown to science. This implies that the currently considered list of species present in the precious coral trade is incomplete.

Zooxanthellate corals are found throughout the tropics, but also extend into subtropical and marginal locations due to the presence of warm ocean currents. The population history of corals in marginal locations is of great interest in relation to changing global climatic conditions, as species edge zones might play an important role in evolutionary innovation. Here, we examine the genetic structure of a widely distributed coral species complex, Acropora hyacinthus , from tropical to high subtropical regions along the Kuroshio Current in Taiwan and Japan. Population genetic analysis of 307 specimens from 18 locations (7 reefal and 11 marginal) identified at least four genetic lineages within the A. hyacinthus complex: HyaA, HyaB, HyaC (dominating reefal locations) and HyaD dominating marginal locations in mainland Japan and Taiwan, except the upper Penghu Islands, which were dominated by HyaC. Crossing experiments suggested semi-incompatibility and hybridization between HyaC and D from reefal locations, implying that the existence of hybridization partners enhances diversification and genetic diversity. An incomplete barrier between the HyaC and HyaD dominations was found along the two straits in the Ryukyu Islands, where Kuroshio Current flows constantly. Despite geographical distance, the genetic composition of populations in mainland Japan was comparable to that in mainland Taiwan, which may reflect a region-specific connectivity around the northern limit of A. hyacinthus in the Pacific. In contrast, populations in the Ryukyu Islands were not significantly different from those of Palau and the Great Barrier Reef. While the precise taxonomic nature of the lineages found around the Kuroshio Current remains to be elucidated, these results indicate that, despite the presence of four lineages in the Kuroshio triangle, low genetic diversity populations of the two main lines might be isolating and differentiating in the marginal region.

Little is known about the behavior and migration of deep-sea snappers, as observation of their deep-sea habitats is difficult. Manual acoustic tracking of deepwater longtail red snappers Etelis coruscans was conducted at the Ojika Se Bank, in the waters around the Satsunan Islands, Japan, to investigate their post-release horizontal and vertical behavior. Eight individuals were tagged with transmitters equipped with depth sensors for tracking. At least six of these eight fish survived after release. The fish gradually dispersed from the Ojika Se Bank, and only one-third remained there 33–34 days after release. The fish that remained at the Ojika Se Bank moved horizontally by 2.2 ± 2.0 km daily, but remained near the top of the bank. The fish were distributed in the 168.8- to 288.8-m depth range, and moved vertically by up to 50.0 m between consecutive days. To the best of our knowledge, this is the first report on the daily fine-scale horizontal and vertical movements of any species of deep-sea snapper.

Loss of zooxanthellae (dinoflagellate Symbiodinium) from corals will sometimes lead to mass mortality of corals. To detect and quantify Symbiodinium released from corals, we developed a zooxanthellae “trap” and a quantitative PCR (qPCR) system with Symbiodinium clades A-F-specific primer sets. The trap was attached to a branch or the surface of several wild stony corals, and the water samples within the traps, including released Symbiodinium, were subjected to qPCR. All tested corals released clade C Symbiodinium at estimates of ~5,900 cells h⁻¹ cm⁻² of coral surface. Although all tested Pocillopora eydouxi harboured both clades C and D, some of these colonies released only clade C or released a lesser amount of clade D than that in the tissues. Our Symbiodinium quantification system revealed that wild hermatypic corals constantly release Symbiodinium to the environment. Our result suggests that some corals may discharge certain clades of Symbiodinium alternatively.

Effects of moderate nutrient enrichment ($NO_3^-: <5 \\mumol L^{-1}$, $PO_4^{3-}: <0.3 \\mumol L^{-1}$) on two carbon (C) fixation rates (photosynthesis and calcification) of the zooxanthellate coral Acropora pulchra were investigated under laboratory conditions. The coral branches were incubated in the nutrient condition for three different periods (0, 5, 10 d) to observe changes in tissue biomass and zooxanthellate chlorophyll a (Chl a) concentration. Next, the incubated corals were simultaneously transferred to nutrient-depleted seawater containing $^{13}C-labeled$ dissolved inorganic carbon to assay net photosynthesis and calcification rates. Chl a concentration per unit surface area increased 2.6-fold for the 10-d enrichment, and net photosynthetic rates were also stimulated up to a similar level (2.8-fold). Tissue biomass of the host coral and zooxanthellae was approximately doubled during the period. On the other hand, calcification rates only increased 1.3-fold, suggesting that even moderate nutrient loading resulted in one-sided enhancement of the algal photosynthetic activity. The measured C fixation ratios of organic C:skeletal C were higher than the structural ratios, and the inconsistency became greater as Chl a concentration increased. The increased photosynthetic products could be excessively stored in the organic tissue and/or released into the ambient seawater.

Extremely low post-settlement survival is one of the largest barriers for artificial rehabilitation of Acropora corals. However, little data have been found for interspecific difference of the post-settlement survival probably because the observation of coral juvenile is difficult in the field. Here, we analyzed the survival of three dominant species of Acropora corals (A. digitifera, A. tenuis, A. yongei), with different colony morphologies and habitat preferences, for 2 years after settlement under the same environmental conditions. The post-settlement survival was significantly higher for A. tenuis than for A. digitifera 3 months after settlement. Two years later, the survival rate of A. tenuis was approximately 15 times higher than A. digitifera. In a separate analysis of three bottle-brush species (A. awi, A. echinata, A. subglabra) and A. tenuis, post-settlement survival was always higher for A. awi than for other two bottle-brush species, suggesting that the initial survival was different among morphologically sister species. Low survival was possibly associated with slow growth rates during the first 7 months. Thus, species selection is important for successful artificial coral rehabilitation, with A. tenuis being the most viable option. Alternatively, new techniques are required to improve post-settlement survival of slow growing coral species.

In situ larval seeding is a low-cost technique that is currently under development for the large-scale restoration of coral populations. One problem that still needs to be solved is the preparation of coral larvae for seeding, i.e., how many larvae are required to restore a certain area? In this study, we focused on the relationship between the numbers of larvae, settlers, and survivors for three months post-settlement to determine the optimal larval seeding density. A comparison of three different larval densities (low, middle, and high) indicated that the number of settlers was proportional to the larval density, suggesting that settler density is determined by the number of larvae supplied. However, the survival rate of settlers on high-density plates was much lower than the corresponding rates on low- or middle-density plates during the first month after settlement. Moreover, most of the seeded corals had not survived on the low-density plates at three months after settlement. Therefore, the middle larval density (i.e., 5000 larvae m −2 ) appears to be optimal for seeding on grid plates.

The genus Acropora is the most abundant and diversified genus on coral reefs in the Indo-Pacific. As such, these corals have been the focus of many different types of studies, such as reproductive biology and phylogenetic studies. They have been chosen for genetic studies and have been found to be a good model for the theory of reticulate evolution; the large number of species within this genus has been used in cross-hybridization experiments among species. Members of this genus also seem to be particularly amenable to genetic analysis as evidenced by the number of studies using coral genes isolated from gametes released at the time of mass-spawning, the reproductive strategy adopted by members of this genus. Many species of staghorn corals participate in mass spawning events that occur annually either in early summer or early fall. It is, however, difficult to predict the exact date of spawning. For example, synchronous spawning of Acropora spp. has been recorded at Okinawa, Japan, over a wide time frame, -3 days to +7 days relative to the full moon. Opportunities for studying reproductive biology and cross-fertilization experiments are quite limited, often only once a year. The ability to control the induction of spawning of acroporid species is a very desirable tool not only for reproductive and phylogenetic studies, but also for reef restoration. During recent worldwide bleaching events, staghorn corals were subject to severe damage and death. Additionally, the corals in the genus Acropora are particularly susceptible to predation. At the same time, their recovery is helped by the fact that these corals grow more rapidly than most others. This latter property has made them target species for reef restoration projects that are dependent on a supply of reproductive products (gametes) to provide seed for restoration and remediation. Control of reproduction has been achieved with other invertebrates, particularly molluscs. Morse et al. (1997) successfully induced spawning of the red abalone with the use of hydrogen peroxide (H sub(2)O sub(2)). They found that H sub(2)O sub(2) activated the prostaglandin-dependent spawning reaction in abalone and other molluscs (Morse et al. 1977; Morse 1984). A number of prostaglandins have been found in some soft coral species, and one of them (15-epiacetoxy-PGA sub(2) was surmised to play a role in egg release (Coll et al. 1989). It is believed, however, that there has been no attempt to induce spawning with H sub(2)O sub(2) in cnidarians. Therefore the authors were prompted to try to induce spawning (gamete release) of corals with the same chemical.

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.