Pacific Coast Of Central Japan Research Articles

Three new species of sea star parasite Dendrogaster (Crustacea: Thecostraca) from Japan.

Three new species of ascothoracidan crustaceans, Dendrogaster danni sp. nov., Dendrogaster tanabensis sp. nov., and Dendrogaster jinshomaruae sp. nov. are described from the sea around the Kii Peninsula on the Pacific coast of central Japan. They are found in the coelomic cavities of the sea stars, Neoferdina japonica Oguro & Misaki, 1986., Henricia sp., and Coronaster volsellatus (Sladen, 1889), respectively. Morphological examinations and DNA barcoding analyses of these new species are reported in this study. The emergence of Dendrogaster from their host sea stars is also noted. These findings represent the 11th to 13th species of Dendrogaster that infest Japanese sea stars.

Three new interstitial species of the genus Neonesidea (Bairdioidea: Podocopida: Ostracoda) from the infralittoral zone in Japan.

This study is the first to report on interstitial species of the genus Neonesidea: Neonesidea arenalocus sp. nov. from the Pacific coast of central Japan, Neonesidea alyamanai sp. nov. from the Pacific coast of south-western Japan, and Neonesidea alwakasaensis sp. nov. from the Sea of Japan coast of western Japan. All three species share a smaller carapace size than that of the epiphytic Neonesidea species; in particular, the carapace width and valve thickness are significantly less. Furthermore, the terminal claws on the walking legs are more linear than those of the epiphytic Neonesidea species. However, these three new species share a feature in the apical portion of the terminal claw on the males second antennae and asymmetric brush-shaped organs, which are common to this genus. In addition, the results of our field survey indicate that all three new species occur in coarse-grained sediments (coarse sand to pebbles) in the upper infralittoral zone, particularly on Miho-Masaki Beach, which contains an optimum zone for N. arenalocus sp. nov.

Marine inundation history during the last 3000 years at Lake Kogare-ike, a coastal lake on the Pacific coast of central Japan

Sediment cores collected at Lake Kogare-ike, a coastal lake on the Pacific coast of central Japan, record the marine inundation history during the last 3000 years. The sediments consist mainly of organic mud, sand, gravel, inorganic mud, and volcanic ash, and inundation events were recognized as 19 event deposits (E1–E19, from top to bottom) interbedded with the organic mud. Visual observation by naked eyes and X-ray computed tomography (CT) images identified 16 event deposits based on quantitative and qualitative changes in sand contents and changes in the textures and colors of the sediment samples (E1–E3, E5, E6, E8, E9, and E11–E19). The other three event deposits (E4, E7, and E10) were identified only on the CT images as layers with higher radiodensity than the underlying and overlying organic mud layers. The sedimentary features, the spatial bias of the event deposits toward seaward areas, the diatom assemblages, and the frequency of inundation events suggest that 13 (E1–E10 and E12–E14) of the 19 event deposits were formed by tsunamis or extraordinary storms. To constrain the depositional ages of the event deposits, Bayesian age–depth models were constructed based on radiocarbon dating of plant macrofossils and concentrated fossil pollen and the 137Cs profile. The depositional ages of the event deposits indicate that five or possibly six event deposits can be correlated with historical tsunamis along the Nankai Trough: E2, either of E3 or E4, E5, E7, and E9 correspond to the 1707 CE Hoei, the 1605 CE Keicho, the 1498 CE Meio, the 1096 CE Eicho, and the 684 CE Hakuho tsunamis, respectively. E1 was possibly formed by the 1944 CE Showa-Tonankai tsunami, the 1854 Ansei–Tokai tsunami, the 1959 Isewan typhoon, or a combination of two or all three events.

Development of two new sets of PCR primers for eDNA metabarcoding of brittle stars (Echinodermata, Ophiuroidea)

Brittle stars (class Ophiuroidea) are marine invertebrates comprising approximately 2,100 extant species, and are considered to constitute the most diverse taxon of the phylum Echinodermata. As a non-invasive method for monitoring biodiversity, we developed two new sets of PCR primers for metabarcoding environmental DNA (eDNA) from brittle stars. The new primer sets were designed to amplify 2 short regions of the mitochondrial 16S rRNA gene, comprising a conserved region (111–115 bp, 112 bp on average; named “16SOph1”) and a hyper-variable region (180–195 bp, 185 bp on average; named “16SOph2”) displaying interspecific variation. The performance of the primers was tested using eDNA obtained from two sources: a) rearing water of an 2.5 or 170 L aquarium tanks containing 15 brittle star species and b) from natural seawater collected around Misaki, the Pacific coast of central Japan, at depths ranging from shallow (2 m) to deep (> 200 m) sea. To build a reference library, we obtained 16S rRNA sequences of brittle star specimens collected from around Misaki and from similar depths in Japan, and sequences registered in International Nucleotide Sequence Database Collaboration. As a result of comparison of the obtained eDNA sequences with the reference library 37 (including cryptic species) and 26 brittle star species were detected with certain identities by 16SOph1 and 16SOph2 analyses, respectively. In shallow water, the number of species and reads other than the brittle stars detected with 16SOph1 was less than 10% of the total number. On the other hand, the number of brittle star species and reads detected with 16SOph2 was less than half of the total number, and the number of detected non-brittle star metazoan species ranged from 20 to 46 species across 6 to 8 phyla (only the reads at the “Tank” were less than 0.001%). The number of non-brittle star species and reads at 80 m was less than 10% with both of the primer sets. These findings suggest that 16SOph1 is specific to the brittle star and 16SOph2 is suitable for a variety of marine metazoans. It appears, however, that further optimization of primer sequences would still be necessary to avoid possible PCR dropouts from eDNA extracts. Moreover, a detailed elucidation of the brittle star fauna in the examined area, and the accurate identification of brittle star species in the current DNA databank is required.

Relationship between iodine and carbohydrate contents in the seagrass Zostera marina on the northwestern Pacific coast of central Japan

AbstractPreviously, we reported seasonal variation in iodine contents in the seagrass Zostera marina. Herein, we sought the factors controlling this variation, and investigated relationships between iodine and carbohydrate contents, using extracts and residues of seagrass samples extracted with 0.1 N HCl. In plants, carbohydrates in HCl-extracted and residual fractions are considered to represent storage and structural carbohydrates, respectively. On average, 44% and 56% of total iodine in samples was contained in the HCl-extracted and residual fractions, respectively. Both HCl-extracted and residual iodine contents showed seasonal trends similar to that of total iodine, being high in winter–spring and low in summer. Total and HCl-extracted carbohydrate contents showed reverse seasonal trends from those of iodine, whereas residual carbohydrate contents had comparable values throughout the sampling period. In the total and HCl-extracted fractions, negative correlations between iodine and carbohydrate contents were confirmed, suggesting that carbohydrates do not play important roles in iodine accumulation. Although most monosaccharide contents were not correlated with iodine contents in these two fractions, residual galactose content was positively correlated with residual iodine. We accordingly suggest that one or more specific structural carbohydrate constituents may potentially function as an iodine store in Z. marina.

Using organic compounds to assess the dominant controls on seasonal iodine variability in the brown alga Ecklonia cava in the northwestern Pacific coast of central Japan

Brown algal species are among the most efficient iodine accumulators and thus heavily influence the biogeochemical cycling of iodine in coastal environments. Previously, we reported seasonal variability in iodine concentrations in the brown alga Ecklonia cava collected from the Japanese coast over a 2-year period. In this study, we sought to identify the factors controlling this observed variability by investigating the relationships between the concentrations of iodine and major organic compounds (carbohydrates and fatty acids). The concentrations of total carbohydrates and individual constituent monosaccharides showed no significant correlations with iodine concentration, implying that carbohydrate concentration and composition are not the dominant controls on iodine concentration in E. cava. However, fucose concentrations were significantly correlated when data points of highest iodine concentrations were removed, potentially suggesting some influence of structural carbohydrate on iodine variability. Significant positive correlations with iodine concentration were only observed in odd-chain fatty acids, which are known to be bacterial biomarkers; in particular, the C17:1 fatty acid showed the highest correlation (r = 0.83). The concentrations of the remaining fatty acids, as well as total concentration of fatty acids, did not correlate significantly with iodine concentrations. Our results suggest that, in general, the concentration and composition of fatty acids do not directly influence iodine variability and that iodine concentrations in E. cava are predominantly controlled by bacteria living on its surface.

Vertical and seasonal variations of dissolved iodine concentration in coastal seawater on the northwestern Pacific coast of central Japan

Vertical and seasonal variations in the concentrations of total dissolved iodine (TDI), iodide (I−), iodate (IO3−), and dissolved organic iodine (DOI) were examined for seawaters from the northwestern Pacific coast of central Japan (48 m water depth, ca. 1 km offshore) from 2012 to 2016. The annual averages of TDI and iodate concentrations in the upper layer (water depth < 10 m) were below those from deeper levels. Additionally, the concentrations decreased significantly during summer to autumn. The vertical and seasonal trends in TDI and iodate concentrations were suggested to be originated from the uptake of iodate by settling particles within the water column and partially from the input of river waters. The annual average of iodide concentration in the upper layer was higher than that in deeper levels, and the concentration tended to increase during summer to autumn. Further, the iodide concentration showed a significant positive correlation with the water temperature. The results suggest that the iodide concentration was mainly controlled by the efficiency of vertical mixing in the water column, as deeper seawater generally contains low iodide concentration. The vertical and seasonal variations in DOI concentration were erratic and thus obscured its controlling factors.

Development of a new set of PCR primers for eDNA metabarcoding decapod crustaceans

The Decapoda is one of the largest orders within the class Malacostraca, comprising approximately 14,000 extant species and including many commercially important species. For biodiversity monitoring in a non-invasive manner, a new set of PCR primers was developed for metabarcoding environmental DNA (eDNA) from decapod crustaceans. The new primers (herein named “MiDeca”) were designed for two conservative regions of the mitochondrial 16S rRNA gene, which amplify a short, hyper-variable region (153–184 bp, 164 bp on average) with sufficient interspecific variations. With the use of MiDeca primers and tissue-derived DNA extracts, we successfully determined those sequences (154–189 bp) from 250 species, placed in 186 genera and 65 families across the suborder Dendrobranchiata and 10 of the 11 infraorders of the suborder Pleocyemata. We also preliminarily attempted eDNA metabarcoding from natural seawater collected at Banda, Tateyama, the Pacific coast of central Japan and detected 42 decapod species including 34 and 8 species with sequence identities of &amp;gt; 98% and 80–98%, respectively. The results suggest the usefulness of eDNA metabarcoding with MiDeca primers for biodiversity monitoring of the decapod species. It appears, however, that further optimisation of primer sequences would still be necessary to avoid possible PCR dropouts from eDNA extracts.

Plectranthias maekawa, a new species of perchlet from the Tokara Islands, Kagoshima, Japan, with a review of Japanese records of P. wheeleri (Serranidae: Anthiadinae)

A new species of perchlet, Plectranthias maekawa, is described on the basis of three specimens (58.2–65.1 mm standard length: SL) from the Tokara Islands, Kagoshima, Japan. The new species can be distinguished from all congeners by the following combination of characters: X, 15 or 16 dorsal-fin rays; 14 pectoral-fin rays; lateral line complete with 30 pored scales; 3 scale rows above lateral line; 6 diagonal rows of large scales on cheek between eye and corner of preopercle; two antrorse spines on ventral margin of preopercle; margins of subopercle and interopercle smooth; body depth 33.5–34.7% of SL; body width 17.2–17.4% of SL; third dorsal-fin spine longest, its length 46.2–47.2% of HL; caudal-peduncle depth 58.0–63.2% of caudal-peduncle length; body pinkish-white with five orange-red bands on lateral surface when fresh, first band broadest, first, fourth and fifth bands vertical to body longitudinal axis, second and third bands slightly backwardly oblique; small poorly defined yellow blotches scattered below lateral line when fresh, especially along red bands; scales above lateral line white, with distinct red margins when fresh; most cheek scales white or yellowish-white, without distinct red or yellow margins; body uniformly pale, with reduced nape pigmentation in preserved specimens. Japanese records of Plectranthias wheeleri Randall 1980, closely related to P. maekawa, is reviewed, with additional specimens of P. wheeleri from the Ryukyu Islands and Sagami Bay, Pacific coast of central Japan, the latter representing the northernmost record for the species. An unidentified specimen of Plectranthias from Okinawa, Japan, is briefly described.

Stratigraphic evidence of historical and prehistoric tsunamis on the Pacific coast of central Japan: Implications for the variable recurrence of tsunamis in the Nankai Trough

To complement historical written records of tsunamis in the Nankai Trough and reconstruct prehistoric tsunami records, we conducted a coring survey at a coastal lowland in Mie Prefecture, central Japan. We found 10 sand layers deposited from about 4500 to 500 years ago. The layers are interpreted as tsunami deposits because of the presence of abundant bioclasts of marine organisms and sedimentary structures such as alternating sub-layers of sand and silt, rip-up clasts, and upward-fining structures, all of which are common in modern tsunami deposits. At the study site, no substantial seawater inundations and sand depositions have been recorded even for the largest typhoons to ever hit the region. There are historical accounts of earthquake and tsunami damage along the Nankai Trough in 1498, 1361, 1096, 887, and 684 CE. Estimated ages of the youngest three sand layers overlap well with tsunamis in 1498, 1096, and 684 CE. Our results support the hypothesis suggested by archaeological studies that the 684 CE rupture extended farther eastward than the historical record indicates or that another tsunami occurred at some time close to 684 CE. We did not find any sand layers that were definitely correlated with the tsunamis of 1361 and 887 CE, which are thought to have occurred by multi-segment ruptures of the Nankai Trough that includes the segment directly offshore from the study site. If the sand layers found at the study site were deposited by the tsunamis of 1498, 1096, and 684 CE, and if the tsunamis of 1361 and 887 CE did not inundate the study site, the tsunami recurrence interval during the relevant time period was about 400 years. This finding does not support the widely believed hypothesis that earthquakes and tsunamis occur at regular intervals of approximately 100 years in this area. In addition, similar to the historical tsunamis, intervals of geologically recorded prehistoric tsunamis at the study site vary from about 100 to 600 years. The hypothesis of variable recurrence of earthquakes and tsunamis along the Nankai Trough should be tested by future geological and historical studies in unbiased way.

Seasonal variations in iodine concentrations in a brown alga (Ecklonia cava Kjellman) and a seagrass (Zostera marina L.) in the northwestern Pacific coast of central Japan

Seasonal variations in iodine concentrations were investigated for two years in a brown alga (Ecklonia cava Kjellman) and a seagrass (Zostera marina L.) occurring in the northwestern Pacific coast of central Japan. The iodine concentration in E. cava was 0.92–5.6 mg per gram dry weight (g‒ 1 DW) (mean ± SD:2.3 ± 1.1 mg g‒1 DW), and its variation was similar to that of other brown algae. In Z. marina, the iodine concentration was 17–110 μg g‒1 DW (61 ± 28 μg g‒ 1 DW) and displayed seasonal variation, as it was high in winter and spring and low in autumn.

Single-grain feldspar luminescence chronology of historical extreme wave event deposits recorded in a coastal lowland, Pacific coast of central Japan

Abstract The Shirasuka lowlands, located on the Enshu-nada coast of central Japan, record evidence for numerous extreme wave events. Here we test the applicability of using the luminescence signal from feldspars to date these young (

富士山の地質と地下水流動

Mt. Fuji, at 3,776m, is a stratovolcano located on the Pacific coast of central Japan. It started to form at ca. 100,000 yr. B.P. and continued eruptions ejected huge quantities of basaltic lavas and volcanic ashes. Its activities are divided into two stages: before and after ca. 11,000 yr. B.P. The old stage, or the Ko-Fuji stage, is characterized by frequent volcanic mudflows and ashes, and the new stage, or the Shin-Fuji stage, is characterized by continuous effusions of enormous basaltic lava flows at its initial phase. Basaltic lava flows ejected at the initial phase of the Shin-Fuji stage flew extended to cover most of the foot of the volcano. There are many springs at the foot of Mt. Fuji. Among these, large springs such as the Kakidagawa and Wakuike are located at the termini of the lava flows of the Shin-Fuji stage. Groundwater recharged at the upper parts of Mt. Fuji flows down the flanks under confined conditions through clincker zones formed above and below the massive central cores of basaltic lava flows. At the termini of the lava flows, confined groundwater gushes out of the clinker zones under pressure, forming many large springs. Hydrologic studies indicate that the total recharge to these confined aquifers in Mt. Fuji is ca. 4,700,000 m3/day.

Molecular identification of Anisakis and Hysterothylacium larvae in marine fishes from the East China Sea and the Pacific coast of central Japan

Anisakiasis is a human disease caused by the accidental ingestion of larvae belonging to the family Anisakidae. Three fish species, the small yellow croaker Pseudosciaena polyactis, the mackerel Pneumatophorus japonicus and the hairtail Trichiurus haumela are important source for food products in the East China Sea. The prevalence and the identification of Anisakidae larvae in these fishes will benefit the prevention and control of anisakiasis. In this study, fish samples were obtained from fish markers in the East China Sea and the Pacific coast of central Japan during April 2011 and July 2013. For species identification, the PCR-based restriction fragment length polymorphism (PCR–RFLP) analysis of the entire ITS region (ITS1, 5.8 S and ITS2) of nuclear ribosomal DNA (rDNA) was performed. In total, 2004 larvae were collected from 80 hairtail fish, 20 small yellow croaker, and 27 mackerel from the East China Sea and the Pacific coast of central Japan. High prevalence of Anisakidae larvae infection (116/122, 95.1%) was detected in the East China Sea. Seven species were identified belonging to the genera Anisakis (Nematoda: Anisakidae) and Hysterothylacium (Nematoda: Anisakidae). Anisakis pegreffii was the predominant species accounting for 84.8% of all larvae examined in East China Sea, while all Anisakidae larvae isolated from Japan were identified as Anisakis simplex sensu stricto (s.s.). In the East China Sea, A. simplex s.s. and Anisakis typica were 0.6% (4/619) and 1.5% (9/619) of the identified nematodes, respectively. Interestingly, one larva was identified as a recombinant genotype of A. simplex s.s. and A. pegreffii. In addition, four species of the genus Hysterothylacium, namely, Hysterothylacium amoyense (31/619, 5.0%), Hysterothylacium aduncum (10/619, 1.6%), Hysterothylacium fabri (21/619, 3.4%) and Hysterothylacium spp. (18/619, 2.9%) were also identified in the present study. This is a comprehensive epidemiological dataset for the family Anisakidae in the East China Sea. The identification of A. typica, recombinant genotype of A. simplex s.s. and A. pegreffii, H. amoyense and H. fabri is first reported in this area. The wide diversity and substantial geographical distributions of these nematodes will provide a foundation for future studies of Anisakidae family. The high prevalence of these nematodes in marine fishes off the East China Sea may pose considerable food safety problems, which is a potential cause of human anisakiasis.

A new hemiarthrine bopyrid, &lt;i&gt;Izuohshimaphryxus hoshinoi&lt;/i&gt; (Crustacea: Isopoda) from Izu-Ohshima Island, Sagami Sea, Pacific coast of central Japan

Izuohshimaphryxus hoshinoi, a new genus and species of hemiarthrine bopyrid, is described on the basis of a single female specimen from the coastal waters of Izu-Ohshima Island, Sagami Sea, Pacific coast of central Japan. This bopyrid infests an anthozoan-associated shrimp, Ancylomenes speciosus (Okuno, 2004), attaching to the dorsal surface of the pleon. This new genus is most similar to Filophryxus Bruce, 1972 but is distinguished by a) the presence of pereopods on the concave side, b) number of lateral plates of the pleon, and c) absence of a pleotelson. This is the third identified species known to attach to the dorsal surface of the pleon of a caridean shrimp host.

A latitudinal gradient in the biogeographic compositions of rock pool fish assemblages on the Pacific coast of central Japan: an examination of the influence of the Kuroshio Current

A latitudinal gradient in the biogeographic compositions of rock pool fish assemblages on the Pacific coast of central Japan: an examination of the influence of the Kuroshio Current

静岡県西部の太田川低地で見られる弥生時代中・後期の相対的海水準上昇

静岡県西部の太田川低地で見られる弥生時代中・後期の相対的海水準上昇

Archaeal polar lipids in subseafloor sediments from the Nankai Trough: Implications for the distribution of methanogens in the deep marine subsurface

Although the methane in marine methane hydrates is mainly of microbial origin, information about the distribution of methanogens in subseafloor sediments is limited. To address this issue, we analyzed sediment core samples from two sites in the Nankai Trough, off the Pacific coast of central Japan, including those bearing methane hydrates from depths >100m below the seafloor (mbsf), for isopranyl ether-linked polar lipids (i.e. with polar head groups of phosphate, sugar, or both) as biomarkers of archaea, including methanogens. In most samples, including the deepest (381mbsf), archaeol, and sn-2- and sn-3-hydroxyarchaeols were detected as their hydrolyzed derivatives. Concentrations of these three archaeal lipids correlated strongly with each other, suggesting a common biological source. The δ13C values of phytane derived from the phytanyl groups in the archaeal lipids were distinctly higher than those of methane, indicating that methanogens rather than anaerobic methanotrophic archaea were the major biological source. Depth profiles of polar sn-2-hydroxyarchaeol concentration were consistent with those of the potential methane production activity previously estimated from incubation of core sediments from the same sites. This observation, together with results of previous studies showing the presence of sn-2-hydroxyarchaeol mainly in shallow young sediments, strongly suggests that this polar lipid is a valid biomarker for in situ methanogens in sediments. There was a strong correlation between the concentration of polar sn-2-hydroxyarchaeol and that of total organic carbon, suggesting that bulk organic matter concentration is a primary control on the distribution of methanogens in sediments.

Traces of paleo-earthquakes and tsunamis along the eastern Nankai Trough and Sagami Trough, Pacific coast of central Japan

Traces of paleo-earthquakes and tsunamis along the eastern Nankai Trough and Sagami Trough, Pacific coast of central Japan

Physical Factors Involved in the Isoyake (Seaweed Forest Depletion) at Mio, Pacific Coast of Central Japan

Physical Factors Involved in the Isoyake (Seaweed Forest Depletion) at Mio, Pacific Coast of Central Japan In Japan, seaweed forest depletion is known as isoyake. We conducted a study on the marine environment to clarify the cause and the persistence of the isoyake in the sea area at Mio, on the west coast of the Kii Peninsula, central Japan. In the sea area at Mio, a layer of high-turbidity seawater formed on the sea surface (lowest Secchi disc depth: 1m) during and after precipitation. The average accumulation of sediment on the bedrock was 6.7 mg/ cm2. This value was approximately four times that recorded in the sea area at Noshima, where seaweed communities were present. These results imply that the large amounts of suspended particles in the seawater and sediment particles that settled on the bedrock were the major factors contributing to the continuation of the isoyake at Mio.