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This study aimed to elucidate the physiological processes of oogenesis in Acropora tenuis. Genes/proteins related to oogenesis were investigated: Vasa, a germ cell marker, vitellogenin (VG), a major yolk protein precursor, and its receptor (LDLR). Coral branches were collected monthly from coral reefs around Sesoko Island (Okinawa, Japan) for histological observation by in situ hybridisation (ISH) of the Vasa (AtVasa) and Low Density Lipoprotein Receptor (AtLDLR) genes and immunohistochemistry (IHC) of AtVasa and AtVG. AtVasa immunoreactivity was detected in germline cells and ooplasm, whereas AtVG immunoreactivity was detected in ooplasm and putative ovarian tissues. AtVasa was localised in germline cells located in the retractor muscles of the mesentery, whereas AtLDLR was localised in the putative ovarian and mesentery tissues. AtLDLR was detected in coral tissues during the vitellogenic phase, whereas AtVG immunoreactivity was found in primary oocytes. Germline cells expressing AtVasa are present throughout the year. In conclusion, Vasa has physiological and molecular roles throughout the oogenic cycle, as it determines gonadal germline cells and ensures normal oocyte development, whereas the roles of VG and LDLR are limited to the vitellogenic stages because they act in coordination with lipoprotein transport, vitellogenin synthesis, and yolk incorporation into oocytes.

Acropora is a species-rich genus of reef-building corals with highly diverse morphologies. Hybridization among intercrossing species potentially influences species diversity within Acropora. However, the mechanisms that allow hybridization/backcrossing remain unknown. Although we tested a limited number of species, we hypothesized that Acropora gametes in the Indo-Pacific may preferentially fertilize conspecific gametes despite their compatibility with heterospecific gametes, leading to infrequent hybridization between potentially intercrossing species. In this study, F

The discovery of multi-species synchronous spawning of scleractinian corals on the Great Barrier Reef in the 1980s stimulated an extraordinary effort to document spawning times in other parts of the globe. Unfortunately, most of these data remain unpublished which limits our understanding of regional and global reproductive patterns. The Coral Spawning Database (CSD) collates much of these disparate data into a single place. The CSD includes 6178 observations (3085 of which were unpublished) of the time or day of spawning for over 300 scleractinian species in 61 genera from 101 sites in the Indo-Pacific. The goal of the CSD is to provide open access to coral spawning data to accelerate our understanding of coral reproductive biology and to provide a baseline against which to evaluate any future changes in reproductive phenology., info:eu-repo/semantics/published

Most broadcast spawner corals have a vitellogenic phase that lasts at least 6 months. It is established that estrogen regulates vitellogenin synthesis in vertebrates. Although some research have been conducted on the physiological role of sex steroids in corals, little is known about their involvement in oocyte development. This study aimed to detect steroid hormones – progesterone, testosterone, and estradiol-17β (E2) – in Acropora tenuis and study the relationships between vitellogenesis/vitellogenin synthesis and these steroids. This study also investigated the effect of E2 on vitellogenin synthesis in corals and identified steroidogenic enzymes in A. tenuis genome. Branches from tagged coral colonies were collected monthly from March to November. Histological observations showed that oocytes were vitellogenic from March to May (Stage IV and V), but not in June, and that gonads were occupied by immature oocytes in September (Stage I). Real-time qPCR revealed that vitellogenin (vg1 and vg2) transcript levels in coral branches were high in April and May, implying that corals actively underwent vitellogenesis during these months, and spawned before June. Liquid chromatography-mass spectrometry revealed that E2 could be detected in coral branches in March, April, and May, but not in June, whereas testosterone and progesterone did not fluctuate much in the same months. Immersing branches in E2–containing seawater failed to increase vitellogenin transcript levels. The results indicate that E2 is involved in oogenesis but does not positively regulate vitellogenin synthesis. Steroidogenic enzymes (except CYP19A) were identified in A. tenuis, suggesting that corals may endogenously synthesize progestogens and androgens from cholesterol.

Background The coral genus Acropora contains more than 150 species with very high morphological diversity. This high diversity may have been caused by repeated hybridization via mass spawning. However, we have little information whether hybrids are formed in these corals. Identifying morphological differences between hybrids and their parental species would provide an opportunity to find wild hybrids in the field and to understand how colony shapes of Acropora have become highly diversified throughout evolutionary history. In the two morphologically distinctive coral species Acropora florida and A. intermedia in the Indo-Pacific, their gametes show high rates of bi-directional intercrossing in vitro, and thus these two species are ideal species to investigate the morphological traits of the hybrids. Methods We examined morphological characters of F1 hybrids from A. florida to A. intermedia, which were produced from in vitro crossing experiments. To compare morphological differences, we grew juveniles and mature colonies of reciprocal F1 hybrids (FLOint: A. florida eggs × A. intermedia sperm, and INTflo: A. intermedia eggs × A. florida sperm) and of the parental species (purebreds of A. intermedia and A. florida). We analyzed skeletal morphology such as colony size, branch length, and branching number, and compared them with those of a putative F1 hybrid between A. florida and A. intermedia found in the field. We also confirmed the molecular phylogenetic position of F1 hybrids, parental species, and a putative F1 hybrid using the mitochondrial non-coding region. Results Our morphological analysis revealed that branching number of the F1 hybrids was intermediate relative to the parental species. Moreover, the FLOint hybrids were morphologically more closely related to the maternal species A. florida, and the INTflo hybrids were to A. intermedia. Molecular data showed that A. florida and A. intermedia were clearly divided into two clades, and that F1 hybrids grouped in the clade based on their maternal parent. A very similar pattern to the INTflo hybrids was obtained for the putative F1 hybrid in nature. Discussion Our results revealed that F1 hybrids between two Indo-Pacific species A. florida and A. intermedia had intermediate morphology relative to their parent species but reflected the maternal parent more. Similarity to maternal species in hybrids is opposite to the Caribbean Acropora species that had more paternal morphological characters in hybrids. These results further suggest that some genetic factor in eggs is likely to affect determination of colony shape in the Indo-Pacific. At present, we have considered colonies with intermediate morphs between different species to be intra-specific morphological variation, but they may be real F1 hybrids. Indeed, a putative F1 hybrid represented similar morphological and molecular features to the F1 hybrids, and thus it is plausible to be attributed as a “real” F1 hybrid in nature.

沖縄県名護市大浦湾のアオサンゴ群集は，その大きさと特異な形状から保全が求められており，大浦湾のサンゴ礁生態系を代表する存在である。2009年に見られたアオサンゴの白化は，オオギケイソウがサンゴ表面に繁茂することでサンゴにダメージを与え，健康な状態を阻害された結果起きたものと考えられている。今回，アオサンゴ上にオオギケイソウとは異なる藻体が発見された。慶良間諸島で確認されたアミメヒラヤギにからむクダモの状況と類似していたことから，藻体はシアノバクテリアであると考えた。サンゴ礁域では，栄養塩の増加によって大発生したシアノバクテリアがサンゴにからみついてサンゴが死亡した例や，複数属のシアノバクテリアが引き起こす致死性の病気が知られている。そこで本研究では，大浦湾のアオサンゴ群体表面とその周辺の岩盤から採集した藻体の形態を顕微鏡で観察し，また16SrDNA配列を調べて，既知のシアノバクテリアの配列と比較して藻体の正体を明らかにし，さらにシアノバクテリアがアオサンゴへ及ぼす影響について検討することを目的とした。解析の結果，アオサンゴと岩盤から得られた藻体は，レプトリングビア属を始めとした複数属および複数種からなるシアノバクテリアのコンソーシアムであることがわかった。この中には，海水中の栄養塩濃度が高まると大量発生することもあるLyngbya majusculaやHydrocoleum lyngbyaceumが含まれていた。今回確認されたシアノバクテリアがアオサンゴ群体に与えている影響は現段階では小さいと考えられるが，微少な生物ながらその繁茂については警戒が必要である。

The distribution of sea anemones on the rocky intertidal zone at 12 stations in Mutsu Bay and at 7 stations at a 5-km scale was investigated. Seven species of sea anemone were noted at sampling stations: Anthopleura japonica, A. fuscoviridis, A. pacifica, A. atodai, Cnidopus japonicus, Haliplanella lineata, and Actinia equina. In Anthopleura, the appearance frequencies of A. japonica (spawner) were higher than those of other anemones that occurred at each station, while A. atodai (brooder) showed a limited distribution. C. japonicus, C. japonicus, and A. equina were very rare. Sea anemones and sympatric benthic organisms occurred at the same stations, and no significant relationship between the number of sea anemones and the coverages of mussels which might be strong competitors for space was found. We show that the reproductive mode and sympatric organisms of sea anemones may be included among the factors that determine the distribution of sea anemones in Mutsu Bay, Japan. However, we need to further examine the environmental factors in this area, as well as intra- and interspecific relationships among anemones.

We investigated the seasonal prevalence of reproductive activities and of the development of brooded propagules in an intertidal sea anemone, Anthopleura sp., on the rocky shore of Mutsu Bay, in northern Japan. A monthly examination of anemones, by dissection and histological techniques, revealed no sign of gonad development, but did reveal that they produce and internally brood propagules throughout the year. Release of propagules was observed in the field. This anemone population appears to be entirely asexual and agametic, and may persist solely through clonal propagation.

Coral populations are in decline due to environmental changes and biological attacks by predators and infectious diseases. Here, we report a localized bloom of the benthic filamentous cyanobacterium Moorea bouillonii (formerly Lyngbya bouillonii) observed exclusively on the gorgonian (sea fan) coral Annella reticulata at around 20 m depth in Japan. The degree of infection has reached 26% among different sizes of Annella colonies. Thick and continuous growth of Moorea may be sustained partly by symbiotic alpheid shrimp, which affix Moorea filaments to gorgonian corals for use as food and shelter. Most filaments get entangled on the coral colony, some penetrate into the stem of the coral with a swollen end like a root hair, which appears to function as an anchor in Annella. In addition to the cyanobacterium–shrimp interaction, the new trait of anchoring by the cyanobacterium into gorgonian coral may contribute to persistence of this bloom.

This paper describes the underwater data collection utilizing stationary sensor node and movable sensor node. We consider applying the system to investigate the conditions of marine ecosystem around the coral reef at Okinawa, Japan. The framework and fundamental design of our proposed underwater information gathering system under development are introduced. It is also reported the development of the prototypes of the sensory node and movable sensor node. Basic examinations utilizing such prototype at underwater environment are also described. This paper also describes experimental results of image gathering from via wireless local area network communication. Our future trials based on the current developmental situation are also discussed.

Most corals undergo spawning after a particular moon phase, but how moon-related spawning is endogenously regulated in corals remains unknown. The objective of the present study was to evaluate whether dopamine (DA) affects spawning in Acropora tenuis. When pieces of four A. tenuis colonies were reared under a natural photoperiod and water temperature, spawning was observed after the predicted moon phase. After exposure to water containing DA at 0.1 μM, pieces of the same colonies only released 5 to 10 bundles. Co-treatment with DA and pimozide (D1 and D2 receptors antagonist), but not domperidone (D2 receptor antagonist), induced mass release of bundles from the colonies. A cross-experiment revealed high fertilization rates between the control colonies (95%) and between the control and DA-treated colonies (90%), suggesting that gametes developed normally in coral tissue. Therefore, DA appears to have an inhibitory effect on the spawning of A. tenuis.

Multi-specific synchronous spawning risks both sperm limitation, which reduces fertilization success, and hybridization with other species. If available sperm of conspecifics are limited, hybridization with heterospecific sperm could be an alternative. Some species of the reef-building coral Acropora produce hybrid offspring in vitro , and therefore hybridization between such species does sometimes occur in nature. Here, we report that the interbreeding species Acropora florida and A. intermedia preferentially bred with conspecifics at optimal gamete concentrations (10 6 cells ml −1 ), but when sperm concentration was low (10 4 cells ml −1 ), A . florida eggs displayed an increased incidence of fertilization by sperm of A . intermedia . However, A . intermedia eggs never crossed with heterospecific sperm, regardless of gamete concentrations. It appears that A . florida eggs conditionally hybridize with heterospecific sperm; in nature, this would allow A . florida to cross with later-spawning species such as A . intermedia . These results indicate that hybridization between some Acropora species could occur in nature according to the number of available sperm, and the choice of heterospecific sperm for fertilization could be one of the fertilization strategies in the sperm-limited condition.

We have been developing a wireless sensor network system to support coral ecological system survey activities. This paper studies the required functions of a wireless sensor node for gathering information on underwater environmental conditions. For this purpose, a prototype sensor node is developed to clarify necessary functions through a practical experiment. In this paper, the hardware configuration of a latest prototype of wireless sensor node is described. The design of this prototype was based on our previous experiments and the comments of coral reef researchers. We conducted practical field experiments to observe the coral reefs along the Okinawa coast in Japan by using the prototype. Moreover, a browsing system of gathered information by the sensor network is described. Finally, we discuss the experimental results and the required functions of the sensor node for the future research.