Northwestern Pacific Waters Research Articles

Three new species in Tetrastemma Ehrenberg, 1828 (Nemertea, Monostilifera) from sublittoral to upper bathyal zones of the northwestern Pacific.

Monostiliferous nemerteans in the genus Tetrastemma Ehrenberg, 1828 are generally characterized as having four eyes, and they occur worldwide, from the intertidal zone to the deep-sea bottom. Recent extensive sampling of Tetrastemma has explored the high species diversity, including many undescribed forms, but phylogenic analysis has revealed non-monophyly of the genus. We herein describe three new species of the genus (T.albumsp. nov., T.personasp. nov., and T.shohoensesp. nov.) from northwestern Pacific waters based on specimens collected by dredging or by use of a remotely operated vehicle at depths of 116-455 m. Since anatomical and histological characters traditionally used in systematics of the genus are sometimes interspecifically uniform, a histology-free approach is applied for the species descriptions in this study. To confirm the generic affiliation of the new species, a molecular phylogenetic analysis based on partial sequences of cytochrome c oxidase subunit I, 16S rRNA, 18S rRNA, 28S rRNA, and histone H3 genes was performed. Our result shows that all three new species are nested in a subclade formed by species from the North Pacific and American Atlantic, inferring that geographic distribution does not reflect the cladogenesis of Tetrastemma. Furthermore, two Tetrastemma species with a cylindrical stylet basis, T.freyaeChernyshev et al., 2020 from off the coast of India and Hawaii and T.shohoensesp. nov. from Shoho Seamount, Japan, constitute a clade in the resulting tree.

Deep and intermediate exchange patterns through the Luzon Strait as revealed by synoptic hydrographic observation

Based on full-depth hydrographic observations conducted synoptically, water properties across the Luzon Strait (LS) ridges were compared to investigate the deep and intermediate exchange patterns through the LS. The analysis indicates that, in the sense of vertical distribution of water properties below 1800 m, the Lanyu/Luzon Ridge system rather than the Heng-Chun Ridge is the key barrier that separates the South China Sea (SCS) from the northwestern Pacific (NWP). Below 1800 m, the overflow is subjected to strong mixing in the Luzon Trough (LT). The analysis provides the synoptic snapshot of the LS overflow, which confirms its previously suggested pathway. It is also evident that the intermediate outflow through the LS may occur in 850–1800 m, a much wider depth range than that previous realized. In the 1400–1800 m range, the outflowing SCS water shows little property changes, and hence appears to be advection dominated with little influence of mixing. In the 850–1150 m range, the outflow water appears to be interleaved and mixed with the NWP water. Therefore, the LS intermediate outflow is more complex in both space and time than was believed previously.

Simulated Pathways of the Northwestern Pacific Water in the Okhotsk Sea

Simulated Pathways of the Northwestern Pacific Water in the Okhotsk Sea

Urupocidin C: a new marine guanidine alkaloid which selectively kills prostate cancer cells via mitochondria targeting

New bicyclic guanidine alkaloid, urupocidin C (Ur-C) along with the previously known urupocidin A (Ur-A) were isolated from the rare deep-sea marine sponge Monanchora pulchra, harvested in Northwestern Pacific waters. The unique structure of Ur-C was elucidated using 1D and 2D NMR spectroscopy as well as mass spectra. We discovered a promising selectivity of both alkaloids for human prostate cancer (PCa) cells, including highly drug-resistant lines, compared to non-malignant cells. In cancer cells, marine derived compounds were able to induce G1- and S-cell cycle arrest as well as caspase-mediated cell death. For the first time we have identified mitochondrial targeting as a central mechanism of anticancer action for these and similar molecules. Thus, treatment with the isolated alkaloids resulted in mitochondrial membrane permeabilization consequently leading to the release of cytotoxic mitochondrial proteins to cellular cytoplasm, ROS upregulation, consequent activation of caspase-9 and -3, followed by PARP cleavage, DNA fragmentation, and apoptosis. Moreover, synergistic effects were observed when Ur-A and Ur-C were combined with clinically approved PARP inhibitor olaparib. Finally, these alkaloids exhibited additive effects in combination with docetaxel and androgen receptor inhibitor enzalutamide, both applied in PCa therapy. In conclusion, urupocidin-like compounds are promising lead molecules for the development of new drugs for the treatment of advanced PCa.

Southern limits of distribution of the intertidal gobies Chaenogobius annularis and C. gulosus support the existence of a biogeographic boundary in southern Japan (Teleostei, Perciformes, Gobiidae).

Understanding the distributional patterns of individual animal groups with respect to coastal topology and the local physical environment provides essential foundational frameworks for marine zoogeography. In the northwestern Pacific waters of Japan, the distributional pattern of some cool-temperate species of marine fishes suggests the existence of a biogeographic boundary corresponding to a long sandy shore on the eastern coast of Kyushu, southern Japan. The existence of this hypothetical biogeographic boundary was tested by mapping the southern distributional limit of two species of cool-temperate intertidal gobies, Chaenogobius annularis and C. gulosus, which are endemic to East Asia and common in rock pools within their range in the Japanese Archipelago. Distribution and abundance were assessed by survey of museum collections from south-east Kyushu (i.e., the entire coasts of Kagoshima and Miyazaki prefectures); and a quantitative survey of the abundance of these gobies in rock pools at various sites around the hypothesized boundary on the eastern coast of Kyushu, including the subtropical Tanega-shima Island. The museum collection survey showed different distribution patterns between the two species: C. annularis was distributed along the entire coasts of south-east Kyushu including subtropical islands, whereas C. gulosus was distributed along these coasts, including one site on a subtropical island, except for an area south of the hypothesized boundary on the eastern coast of Kyushu. The density and occurrence rates of C. annularis in rock pools decreased with latitude, it being absent from a subtropical island, and C. gulosus was not detected from sites south of the hypothesized boundary. The qualitative survey showed that the southernmost records of C. annularis and C. gulosus were the adjacent subtropical islands (Yaku-shima and Tanega-shima islands respectively), although the quantitative survey suggested that their normal range of distribution was limited to the southern part of the Kyushu mainland. A combination of qualitative and quantitative survey methods in the present study highlighted that the southernmost record of a certain species may not necessarily indicate the true limit of its distribution. The distribution of C. gulosus supports the existence of the hypothetical biogeographic boundary, and the different distribution patterns of the two species may be caused by differences in their early life histories.

Three‐dimensional pathways of water masses in the South China Sea: A modeling study

AbstractWe conduct a numerical Eulerian analysis on the Lagrangian characteristics of South China Sea (SCS) water masses. This is the first study to investigate the water pathway and residence time in response to time‐dependent, three‐dimensional basin circulation in the SCS. The circulation of the SCS is largely determined by westward intrusions of the northwestern Pacific waters in the upper layer (0–750 m) and deep layer (>1500 m), and by an eastward extrusion in the intermediate layer (750–1500 m) through Luzon Strait (LS). The waters in these three layers are interlinked to sustain the three‐dimensional circulation in the SCS. The upper intrusive waters flow cyclonically and have a residence time of ∼3 years before they subduct into a deeper layer or exit the SCS through surrounding straits. The intrusive denser waters in the deep layer flow along the northern slope and reside for ∼25 years in the northern basin (north of 13°N), where a strong subduction occurs. A cyclonic circulation exists in the deep layer in the southern basin (south of 13°N), where a subduction of intermediate waters occurs over its eastern side and a deep upwelling exists over its western side. The water in the deep southern basin has a residence time of ∼40 years. The upwelled deep waters and the subducted waters from the upper layer form the intermediate water, where waters circulate anti‐cyclonically toward LS and have a longest residence time (∼42 years). These findings are supported by the spatial variation in the observed potential density variance.

Dynamic deep-water circulation in the northwestern Pacific during the Eocene: Evidence from Ocean Drilling Program Site 884 benthic foraminiferal stable isotopes (δ18O and δ13C)

New benthic foraminiferal δ 18 O and δ 13 C data from Ocean Drilling Program (ODP) Site 884 (northwestern Pacific) add significant structure to a previous lower resolution record; our higher resolution detail and comparisons with published isotopic records provide new insights into paleoceanographic changes in the northwestern Pacific from the middle Eocene to the early Oligocene. From the early-middle until the mid-middle Eocene (ca. 49–43 Ma), a comparison of the Site 884 δ 18 O values with published ODP δ 18 O records from the Pacific (Site 1218), Atlantic (Site 1260), and Southern Ocean (Site 689) reveals that these basins were bathed by a common water mass, probably originating from the Southern Ocean, or by different water masses having a similar δ 18 O signature. From the mid-middle until the early-late Eocene (ca. 42–37 Ma), the Site 884 record reveals increasing complexity in deep-water circulation. The relatively low Site 884 δ 18 O values suggest that the northwestern Pacific was bathed by a water mass that was warmer than at the other Pacific, Atlantic, and Southern Ocean sites used in this study. Based on the relatively low δ 13 C values at Site 884, there are two possible scenarios for the origin of this northwestern Pacific water mass: (1) nutrient-rich surface waters downwelling at the higher latitudes of the North Pacific (Bering Sea); or (2) warm saline deep waters originating at low latitudes (possibly from the Tethys). In the late Eocene (ca. 36.5 Ma), the Site 884 δ 18 O and δ 13 C values increased, becoming more similar to Sites 1218 (Pacific), 1053 (Atlantic), and 689 (Southern Ocean), indicating an additional change in deep-water circulation, with a deep-water mass originating from the Southern Ocean bathing the northwestern Pacific.

Review of the ecology of Crangon hakodatei Rathbun, 1902 in the Yellow Sea and Bohai Gulf

The brown shrimp,Crangon hakodateiRathbun, 1902, is a common species in northwestern Pacific waters. Based on an investigation of references since the 1950s, we studied the ecological features of this commercially important shrimp. The results show, that the species has a long reproductive period with ovigerous females throughout the year and two discrete peaks in the spawning season, i.e., in spring and in autumn. Its sex ratio also shows significant seasonal variation. This shrimp is a keystone species in the demersal trophic pathways in the northern Chinese seas. It occupies an intermediate position in the food web, acting both as an important food resource for flatfishes on a higher trophic level, and as a predator upon the early life stages of those flatfishes.

North West Pacific deep-sea barnacles (Cirripedia, Thoracica) collected by the TAIWAN expeditions, with descriptions of two new species

Taiwan is a large island in north western Pacific waters with the sea floor connecting to two major deep-sea basins, the eastern waters facing the Pacific Ocean (to 4000 m depth) and linking to the Philippine Basin, whilst south western waters are associated with the South China Sea Basin (up to 1000 m). Previously, the biodiversity of Taiwanese deep-sea barnacles had not been studied extensively, due to a lack of deep-sea expeditions and sampling. Recently, several TAIWAN deep-sea cruises investigated the biodiversity of the deep-sea fauna of Taiwan and sampling was conducted to depths of 4000 m. The present study reports on the biodiversity of the deep-sea barnacles of Taiwan, a total of 18 species. One species was previously recorded from Taiwanese waters and 17 are new records, including two new species belong to the genera Litoscalpellum and Altiverruca.

Geographical variations in the trophic ecology of Japanese anchovy, Engraulis japonicus, inferred from carbon and nitrogen stable isotope ratios

Carbon and nitrogen stable isotope ratios of Japanese anchovy (Engraulis japonicus) and their stomach contents were examined and compared among various regions around Japan. Geographical variations in the isotope ratios were found between inshore and Pacific offshore regions. While most of the anchovy samples had isotope ratios around −17.6‰ for δ13C and 10.0‰ for δ15N as median values, higher (more enriched) isotope values were found in the anchovy sampled from inshore regions. On the contrary, lower (more depleted) values were found mostly in the anchovy from the Pacific offshore region including the Kuroshio Extension and Kuroshio-Oyashio transition zones. Higher carbon isotope ratios in the inshore regions may reflect a carbon source from benthic primary producers in addition to phytoplankton possibly through the consumption of the larvae of benthic organisms such as bivalves or decapods, which were found in the stomach contents of the inshore anchovy. Variations in the nitrogen isotope ratio may reflect not only differences in the trophic level of prey species, but also variations in the baseline level of food webs. Stable isotope ratios are potentially a useful tool for understanding the stock/population structure and migration of anchovy. The present findings indicate the potential importance of the “inshore–offshore” variations in the biology of Japanese anchovy populations in the northwestern Pacific waters.

Seasonal cycle and inter-annual variability of the Kuroshio/Oyashio current system using multi-channel sea surface temperature and altimetry sea level data

Altimeter data from ERS-2 and TOPEX/POSEIDON are analyzed in conjunction with infrared radiometer data from LANDSAT to study the seasonal cycle and inter-annual variability of the sea surface height and temperature in the northwestern pacific waters, more specific the Kuroshio/Oyashio current system. This entails direct comparisons, frequency and trend analyses, and empirical orthogonal functions analyses. The latter we use for extracting the dominant patterns. Most of the variability propagates westward in correspondence with Rossby wave theory. Deviations are caused by eddies shed from the Kuroshio, and the interaction of current variability with bottom topography.

Serum components of small cetaceans in North-Western Pacific waters.

The serum levels of 18 constituents of 153 small cetaceans of both sexes from North-Western Pacific waters were measured. No sex differences were observed in any biochemical parameters in mature animals, but the serum levels of alkaline phosphatase (Alp), P, Na, and Cl were found to be age-related. The increase in serum Alp activity in younger animals seemed to originate from bone. Comparing the levels with those in humans there was (1) no difference in the levels of total protein, albumin, creatinine, total cholesterol, and γ-glutamyltranspeptidase, (2) a lower level of uric acid, and (3) higher levels of serum urea nitrogen, aspartate aminotransferase, alanine aminotransferase, lactic dehydrogenase, Alp, creatine kinase, Na, K, Cl, Ca, and P.

Serum Components of Small Cetaceans in North-Western Pacific Waters

Serum Components of Small Cetaceans in North-Western Pacific Waters