Published Papers - HARII Saki

Shift of symbiont communities in <i>Acropora tenuis</i> juveniles under heat stress.

Yorifuji M, Harii S, Nakamura R, Fudo M

PeerJ ( PEERJ INC )  5 ( 12 ) e4055   2017 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Ocean warming is a major threat to coral reefs, leading to an increasing frequency and amplitude of coral bleaching events, where the coral and its algal symbiont associations breakdown. Long-term change'and resilience of a symbiont community in coral juveniles is l thought to be one of the most important aspects for determining therma tolerance of the coral holobionts; however, despite its importance, they are not well documented in both under elevated temperature and even under natural condition. Here we investigated changes in symbiont communities in juveniles of the coral Acropora tenuis under controlled heat stress conditions (30 degrees C, 31/32 degrees C) and natural variations in seawater temperatures (19-30 degrees C) for up to four months. Compared with the ambient temperature conditions, coral survival rates were higher when exposed to 30 degrees C, but survival rates decreased when exposed to 31/32 degrees C. Symbiodinium types A3, Cl, sand D1-4 were detected in the juveniles under all thermal conditions; however, in higher water temperatures (31/32 degrees C), both the prevalence of D1-4 Symbiodinium and the number of juveniles harboring only this type of symbiont increased after two to four months later. In contrast, colonies at lower temperatures (30 degrees C and ambient) harbored multiple clades of symbionts over the same experimental period. These results highlight.. the flexibility of the coral Symbiodinium symbiosis for juvenile A. terms under variable thermal conditions. In particular, the benefit of the preferential association with type D1-4 can be considered as a response when under heat-stress conditions, and that could help corals to cope with ocean warming.

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Effect of elevated temperature on fecundity and reproductive timing in the coral Acropora digitifera.

Paxton CW, Baria MV, Weis VM, Harii S

Zygote (Cambridge, England) ( CAMBRIDGE UNIV PRESS )  24 ( 4 ) 511 - 6   2016.08 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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The synchrony of spawning is of paramount importance to successful coral reproduction. The precise timing of spawning is thought to be controlled by a set of interacting environmental factors, including regional wind field patterns, timing of the sunset, and sea surface temperatures (SST). Climate change is resulting in increased SST, which is causing physiological stress in corals and could also be altering spawning synchrony and timing. In this study, we examined the effect of increasing seawater temperature by 2 degrees C for 1 month prior to the predicted spawning time on reproduction in the coral Acropora digitifera. This short period of elevated temperature caused spawning to advance by 1 day. In animals incubated at elevated temperature, egg number per egg bundle did not change, however, egg volume significantly decreased as did sperm number. Our results indicate that temperature is acting both as a proximate cue to accelerate timing and as a stressor on gametogenesis to reduce fecundity. This finding suggests that increasing SSTs could play a dramatic role in altering reproductive timing and the success of corals in an era of climate change.

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The transcriptomic response of the coral Acropora digitifera to a competent Symbiodinium strain: the symbiosome as an arrested early phagosome

A. R. Mohamed, V. Cumbo, S. Harii, C. Shinzato, C. X. Chan, M. A. Ragan, D. G. Bourne, B. L. Willis, E. E. Ball, N. Satoh, D. J. Miller

MOLECULAR ECOLOGY ( WILEY )  25 ( 13 ) 3127 - 3141   2016.07 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Despite the ecological significance of the relationship between reef-building corals and intracellular photosynthetic dinoflagellates of the genus Symbiodinium, very little is known about the molecular mechanisms involved in its establishment. Indeed, microarray-based analyses point to the conclusion that host gene expression is largely or completely unresponsive during the establishment of symbiosis with a competent strain of Symbiodinium. In this study, the use of Illumina RNA-Seq technology allowed detection of a transient period of differential expression involving a small number of genes (1073 transcripts; &lt;3% of the transcriptome) 4 h after the exposure of Acropora digitifera planulae to a competent strain of Symbiodinium (a clade B strain). This phenomenon has not previously been detected as a consequence of both the lower sensitivity of the microarray approaches used and the sampling times used. The results indicate that complex changes occur, including transient suppression of mitochondrial metabolism and protein synthesis, but are also consistent with the hypothesis that the symbiosome is a phagosome that has undergone early arrest, raising the possibility of common mechanisms in the symbiotic interactions of corals and symbiotic sea anemones with their endosymbionts.

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Gametogenesis and fecundity of Acropora tenella (Brook 1892) in a mesophotic coral ecosystem in Okinawa, Japan

Rian Prasetia, Frederic Sinniger, Saki Harii

CORAL REEFS ( SPRINGER )  35 ( 1 ) 53 - 62   2016.03 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Mesophotic coral ecosystems (below 30-40 m depth) host a large diversity of zooxanthellate coral communities and may play an important role in the ecology and conservation of coral reefs. Investigating the reproductive biology of mesophotic corals is important to understand their life history traits. Despite an increase in research on mesophotic corals in the last decade, their reproductive biology is still poorly understood. Here, gametogenesis and fecundity of the Indo-Pacific mesophotic coral, Acropora tenella, were examined in an upper mesophotic reef (40 m depth) in Okinawa, Japan for the first time. Acropora tenella is a hermaphrodite with a single annual gametogenic cycle, and both oogenesis and spermatogenesis occurring for 11-12 and 5-6 months, respectively. Timing of spawning of this species was similar to other shallow Acropora spp. in the region. However, colonies had longer gametogenic cycles and less synchronous gamete maturation compared to shallow acroporids with spawning extended over consecutive months. Both the polyp fecundity (number of eggs per polyp) and gonad index (defined as the number of eggs per square centimeter) of A. tenella were lower than most acroporids. Our findings contribute to understanding of the life history of corals on mesophotic reefs and suggest that the reproductive biology of upper mesophotic corals is similar to that of shallow-water corals.

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Worldwide analysis of sedimentary DNA reveals major gaps in taxonomic knowledge of deep-sea benthos

Frédéric Sinniger, Jan Pawlowski, Saki Harii, Andrew J. Gooday, Hiroyuki Yamamoto, Pierre Chevaldonné, Tomas Cedhagen, Gary Carvalho, Simon Creer

Frontiers in Marine Science ( Frontiers Media S. A )  3 ( 92 ) 1 - 14   2016 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Deep-sea sediments represent the largest but least known ecosystem on earth. With increasing anthropogenic pressure, it is now a matter of urgency to improve our understanding of deep-sea biodiversity. Traditional morpho-taxonomic studies suggest that the ocean floor hosts extraordinarily diverse benthic communities. However, due to both its remoteness and a lack of expert taxonomists, assessing deep-sea diversity is a very challenging task. Environmental DNA (eDNA) metabarcoding offers a powerful tool to complement morpho-taxonomic studies. Here we use eDNA to assess benthic metazoan diversity in 39 deep-sea sediment samples from bathyal and abyssal depths worldwide. The eDNA dataset was dominated by meiobenthic taxa and we identified all animal phyla commonly found in the deep-sea benthos yet, the diversity within these phyla remains largely unknown. The large numbers of taxonomically unassigned molecular operational taxonomic units (OTUs) were not equally distributed among phyla, with nematodes and platyhelminthes being the most poorly characterized from a taxonomic perspective. While the data obtained here reveal pronounced heterogeneity and vast amounts of unknown biodiversity in the deep sea, they also expose the difficulties in exploiting metabarcoding datasets resulting from the lack of taxonomic knowledge and appropriate reference databases. Overall, our study demonstrates the promising potential of eDNA metabarcoding to accelerate the assessment of deep-sea biodiversity for pure and applied deep-sea environmental research but also emphasizes the necessity to integrate such new approaches with traditional morphology-based examination of deep-sea organisms.

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Genetic diversity, paraphyly and incomplete lineage sorting of mtDNA, ITS2 and microsatellite flanking region in closely related Heliopora species (Octocorallia).

Yasuda N, Taquet C, Nagai S, Fortes M, Fan TY, Harii S, Yoshida T, Sito Y, Nadaoka K

Molecular phylogenetics and evolution ( ACADEMIC PRESS INC ELSEVIER SCIENCE )  93   161 - 71   2015.12 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Examining genetic diversity and lineage sorting of different genes in closely related species provide useful information for phylogenetic analyses and ultimately for understanding the origins of biodiversity. In this study, we examined inter- and intraspecific genetic variation in internal transcribed spacer 2 (ITS2), partial mitochondrial gene (mtMutS), and nuclear microsatellite flanking region in two closely related octocoral species (Heliopora coerulea, HC-A and HC-B). These species were recently identified in a population genetic study using microsatellite markers. The two species have different reproductive timing, which ecologically promotes lineage sorting. In this study, we examined whether species boundaries could be detected by the commonly used nuclear ITS2 and mtMutS, as well as by possibly neutral microsatellite flanking sequences. Haplotype network analysis of microsatellite flanking region revealed that a possible ancestral haplotype was still shared between the two species, indicating on-going lineage sorting. Haplotype network analysis of ITS2 and microsatellite flanking region revealed shared haplotypes between the two lineages. The two species shared fewer ITS2 sequences than microsatellite flanking region sequences. The almost fixed point mutation at the tip of helix 3 of ITS2 was not associated with the secondary structure or compensatory base changes (CBCs). The phylogenetic tree of ITS2 showed paraphyly and that of the microsatellite flanking region indicated that lineage sorting for the two species may be incomplete. Much higher intra-and inter-individual variation of ITS2 was observed in HC-B than that in HC-A, highlighting the importance of examining ITS2 from multiple individuals to estimate genetic diversity. The mitochondrial mtMutS gene sequences from 39 individuals, including both species collected from Japan and Taiwan, showed no variation because of slow rates of mitochondrial nucleotide substitution. This study suggests caution is warranted when reciprocal monophyly in a phylogenetic tree is used as the criterion for delimiting closely related octocoral species based on ITS2 or mtMtuS sequences. Detection of boundaries between closely related species requires multi-locus analysis, such as genetic admixture analysis using multiple individuals. (C) 2015 The Authors. Published by Elsevier Inc.

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Tolerance to Elevated Temperature and Ocean Acidification of the Larvae of the Solitary Corals Fungia fungites (Linnaues, 1758) and Lithophyllon repanda (Dana, 1846).

Baria MV, Kurihara H, Harii S

Zoological science ( ZOOLOGICAL SOC JAPAN )  32 ( 5 ) 447 - 54   2015.10 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Increase in atmospheric CO2 is the main driver of global climate change and is projected to elevate sea surface temperature by at least 2 degrees C and to decrease oceanic pH by 0.3 to 0.4 units by the end of the century. These factors seriously threaten coral reef ecosystems worldwide. In Okinawa, solitary corals are an important feature of the coral community structure. While previous studies on the effects of ocean warming (OW), ocean acidification (OA) and its combination on larval survival focused on colonial coral species, the present study assessed the effect of high temperature on larvae from solitary corals. In this study, we examined the influence of OW (control = 28 degrees C; control + 3 = 31 degrees C; control + 6 = 34 degrees C) and OA (control, pCO(2) = 400 to 500 mu atm; medium, pCO(2) = 1000 to 1300 mu atm; high, pCO(2) = 1700 to 2200 mu atm) on the larval survival of two solitary corals, Fungia fungites and Lithophyllon repanda for eight days. Results showed that F. fungites was neither affected by OW, OA, nor its combination. Similarly, survival of L. repanda was not affected by OA however it was significantly affected by temperature. Temperature tolerance varies between species; L. repanda (+3 degrees C above ambient) has lower tolerance than F. fungites (+6 degrees C above ambient). This observation suggests that fungiid larvae had higher tolerance to elevated temperature stress relative to other scleractinian corals. With the projected increase in OW and OA in the future, fungiids may retain good potential to widely disperse and successfully recruit to natal and other neighbouring reefs.

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Cues from the reef: olfactory preferences of a symbiotically luminous cardinalfish

Alison L. Gould, Saki Harii, Paul V. Dunlap

CORAL REEFS ( SPRINGER )  34 ( 2 ) 673 - 677   2015.06 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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The symbiotically luminous, reef-dwelling cardinalfish, Siphamia tubifer (Perciformes: Apogonidae), exhibits daily site fidelity, homing behavior, and a preference for the long-spined urchin, Diadema setosum, as its daytime host. The fish acquires its symbiont during larval development and releases large numbers of the bacteria with its feces daily at a host urchin. To examine the role of olfaction in site fidelity and homing by S. tubifer, juvenile and adult fish were tested in a two-channel choice flume for their olfactory preferences. Neither juveniles nor adults showed a preference for seawater conditioned by D. setosum. Juvenile fish, but not adults, preferred seawater conditioned by conspecific fish versus unconditioned seawater. Both juveniles and adults preferred seawater conditioned by their luminous symbiont and also preferred home site water to foreign reef water. These results suggest that S. tubifer uses chemical cues for homing and possibly settlement and symbiont acquisition, but not for host urchin recognition.

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Possible involvement of Tachylectin-2-like lectin from Acropora tenuis in the process of Symbiodinium acquisition

Nami Kuniya, Mitsuru Jimbo, Fumika Tanimoto, Hiroshi Yamashita, Kazuhiko Koike, Saki Harii, Yoshikatsu Nakano, Kenji Iwao, Ko Yasumoto, Shugo Watabe

FISHERIES SCIENCE ( SPRINGER JAPAN KK )  81 ( 3 ) 473 - 483   2015.05 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Most reef-building corals in tropical and subtropical areas symbiose with microalgae from the genus Symbiodinium (dinoflagellate) and depend on the photosynthate produced by the microalgae. The majority of corals acquire Symbiodinium from the surrounding environment through horizontal transfer, but the molecular mechanisms involved in the acquisition of Symbiodinium remain unknown. It has been hypothesized that carbohydrate-binding proteins, or lectins, of the host coral recognize cell surface carbohydrates of Symbiodinium in the process of acquiring symbionts. Thus, we examined the molecular mechanisms involving lectins and carbohydrates using model organism Acropora tenuis, a common reef-building coral, and Symbiodinium culture strains. Juvenile polyps acquire more cells of Symbiodinium strain NBRC102920 at 72-96 h of metamorphosis induction than in any other period. Glycosidase treatment of Symbiodinium inhibited the acquisition of Symbiodinium by juvenile coral polyps. The presence of carbohydrates D-galactose, N-acetyl-D-galactosamine, and N-acetyl-D-glucosamine at 10 mM also tended to decrease Symbiodinium acquisition. We isolated two N-acetyl-D-galactosamine binding lectins with apparent molecular masses of 14.6 and 29.0 kDa from A. tenuis, and de novo sequencing and cDNA cloning showed that the 29.0 kDa protein is Tachylectin-2-like lectin (AtTL-2). The anti-Tachylectin-2 antibody is suggested to bind specifically to AtTL-2. The antibody also inhibited binding of AtTL-2 to N-acetyl-D-galactosamine-resin and the acquisition of Symbiodinium by juvenile A. tenuis polyps. Based on these results, AtTL-2 is likely involved in the process of Symbiodinium acquisition.

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Geographic variation in long-term trajectories of change in coral recruitment: a global-to-local perspective

P. J. Edmunds, R. Steneck, R. Albright, R. C. Carpenter, A. P. Y. Chui, T. -Y. Fan, S. Harii, H. Kitano, H. Kurihara, L. Legendre, S. Mitarai, S. Muko, Y. Nozawa, J. Padilla-Gamino, N. N. Price, K. Sakai, G. Suzuki, M. J. H. van Oppen, A. Yarid, R. D. Gates

MARINE AND FRESHWATER RESEARCH ( CSIRO PUBLISHING )  66 ( 7 ) 609 - 622   2015 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Compiled abundances of juvenile corals revealed no change over time in the Pacific, but a decline in the Caribbean. Using these analyses as a rationale, we explored recruitment and post-settlement success in determining coral cover using studies in the Caribbean (St John, Bonaire) and Pacific (Moorea, Okinawa). Juvenile corals, coral recruits, and coral cover have been censused in these locations for years, and the ratio of juvenile (J) to recruiting (R) corals was used to measure post-settlement success. In St John and Bonaire, coral cover was stable but different between studies, with the ratio of the density of juveniles to density of recruits (J:R) 0.10; in Moorea, declines in coral cover were followed by recovery that was related to the density of juvenile corals 3 years before, with J:R 0.40; and in Okinawa, a decline in coral cover in 1998 was followed by a slow recovery with J/R 0.01. Coral cover was associated positively with juvenile corals in St John, and in Okinawa, the density of juvenile corals was associated positively with recruits the year before. J:R varied among studies, and standardised densities of juvenile corals declined in the Caribbean, but increased in the Pacific. These results suggest that differences in the post-settlement success may drive variation in coral community structure.

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High tolerance of symbiotic larvae of <i>Pocillopora damicornis</i> to thermal stress.

Haryanti D, Yasuda N, Harii S, Hidaka M

Zoological studies ( SPRINGER HEIDELBERG )  54 ( JULY ) e52   2015 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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Background: When coral planulae, which use a horizontal mode of symbiont transmission, are inoculated with Symbiodinium, they suffer greater oxidative stress under strong light or high-temperature stress than non-symbiotic counterparts. Thus, dinoflagellate symbionts may become a source of reactive oxygen species (ROS) under stress. However, it remains unknown whether vertically transmitted symbionts negatively affect coral larvae under stress. We investigated the thermal tolerance of symbiotic planulae of a vertical transmitter coral, Pocillopora damicornis. Results: P. damicornis larvae, which have a large number of symbionts, survived the high-temperature treatment (32 degrees C) for 2 weeks. Significant reductions in Symbiodinium cell density were observed, but these did not lead to increased mortality of planulae during the 2-week experimental period. Although no significant difference was detected in the percentage of apoptotic cells between temperature treatment groups, pre-bleaching larvae exposed to 31 degrees C tended to exhibit higher percentages of apoptotic (TUNEL-positive) cells in the gastrodermis than 32 degrees C-treated larvae, which contained reduced numbers of Symbiodinium cells. Conclusions: Symbiotic larvae of P. damicornis survived well under high-temperature conditions, although their Symbiodinium cell density decreased. This suggests that P. damicornis larvae have the capacity to reduce the symbiont cell density without a harmful effect on their survivorship under thermal stress. Further studies on antioxidant systems and possible suppression of apoptotic pathways are necessary to elucidate the mechanism underlying the high thermal tolerance of symbiotic larvae of P. damicornis.

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Spectral Diversity and Regulation of Coral Fluorescence in a Mesophotic Reef Habitat in the Red Sea.

Eyal G, Wiedenmann J, Grinblat M, D'Angelo C, Kramarsky-Winter E, Treibitz T, Ben-Zvi O, Shaked Y, Smith TB, Harii S, Denis V, Noyes T, Tamir R, Loya Y

PloS one ( PUBLIC LIBRARY SCIENCE )  10 ( 6 ) e0128697   2015 [ Peer Review Accepted ]

Type of publication: Research paper (scientific journal)

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The phenomenon of coral fluorescence in mesophotic reefs, although well described for shallow waters, remains largely unstudied. We found that representatives of many scleractinian species are brightly fluorescent at depths of 50-60 m at the Interuniversity Institute for Marine Sciences (IUI) reef in Eilat, Israel. Some of these fluorescent species have distribution maxima at mesophotic depths (40-100 m). Several individuals from these depths displayed yellow or orange-red fluorescence, the latter being essentially absent in corals from the shallowest parts of this reef. We demonstrate experimentally that in some cases the production of fluorescent pigments is independent of the exposure to light; while in others, the fluorescence signature is altered or lost when the animals are kept in darkness. Furthermore, we show that green-to-red photoconversion of fluorescent pigments mediated by short-wavelength light can occur also at depths where ultraviolet wavelengths are absent from the underwater light field. Intraspecific colour polymorphisms regarding the colour of the tissue fluorescence, common among shallow water corals, were also observed for mesophotic species. Our results suggest that fluorescent pigments in mesophotic reefs fulfil a distinct biological function and offer promising application potential for coral-reef monitoring and biomedical imaging.

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Onset and flexibility of symbiosis and effect of symbiotic dinoflagellate on energy source in scleractinian coral larvae

Yasuda　Naoko,Rodriguez-Lanetty　Mauricio,Hidaka　Michio,

COE報告書（平成19年度） ( 琉球大学21世紀COEプログラム )    2008.03

Type of publication: Research paper (other science council materials etc.)

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琉球大学21世紀COEプログラム「サンゴ礁島嶼系の生物多様性の総合解析」平成19年度成果発表会（平成20年3月1日開催）　招待講演会会場：理系複号棟102号室，ポスター発表会場：琉球大学50周年記念館1F （管理者追加）リポジトリ登録情報を移行しました。確認のうえ、加除修正をしてください。

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