Mitochondrial DNA control region diversity and population structure of Pacific herring (Clupea pallasii) in the Yellow Sea and the Sea of Japan

To investigate the genetic variation and population structure of Pacific herring in the Yellow Sea and the genetic differentiation between the Yellow Sea and the Sea of Japan,fragments of 479-bp mitochondrial DNA control region were sequenced for 110 individuals collected from three different periods in the Yellow Sea and one locality in the Sea of Japan.High haplotype diversity and moderate nucleotide diversity were observed in Pacific herring.AMOVA and exact test of population differentiation showed no significant genetic differentiations among the three populations of the Yellow Sea and suggested the populations can be treated as a single panmictic stock in the Yellow Sea.However,a large and significant genetic differentiation(WST50.11;P50.00) was detected between the populations in the Yellow Sea and the Sea of Japan.The high sea water temperature in the Tsushima Strait was thought a barrier to block the gene exchange between populations of the two sea areas.The neutrality tests and mismatch distribution indicated recent population expansion in Pacific herring.     

A new approach for mobile and expandable real-time deep seafloorobservation - adaptable observation system

Although submarine cable in-line seafloor observation systems are very effective tools for real-time/long-term geo-scientific measurements,, there are technological difficulties for deploying as many sensors as on land. To solve this problem, JAM-STEC developed an expandable and replaceable satellite measurement station called the adaptable observation system (AOS). The AOS is a battery operated mobile observatory connected to the backbone cable system by a 10 km long thin fiber cable to ensure real-time data recovery. The system consists of a branching system, a junction box, a fiber cable, and a battery system for a six-month operation. Installation and construction of the AOS will be conducted by a towed vehicle and an ROV. A thin fiber cable-laying system was developed and tested for practical operation. This observation system provides a chance to extend existing seafloor networks from an in-line area to a wider area     

Distinctive erosional and depositional structures formed at a canyon mouth: A lower Pleistocene deep‐water succession in the Kazusa forearc basin on the Boso Peninsula,Japan

The canyon mouth is an important component of submarine‐fan systems and is thought to play a significant role in the transformation of turbidity currents. However, the depositional and erosional structures that characterize canyon mouths have received less attention than other components of submarine‐fan systems. This study investigates the facies organization and geometry of turbidites that are interpreted to have developed at a canyon mouth in the early Pleistocene Kazusa forearc basin on the Boso Peninsula, Japan. The canyon‐mouth deposits have the following distinctive features: (i) The turbidite succession is thinner than both the canyon‐fill and submarine‐fan successions and is represented by amalgamation of sandstones and pebbly sandstones as a result of bypassing of turbidity currents. (ii) Sandstone beds and bedsets show an overall lenticular geometry and are commonly overlain by mud drapes, which are massive and contain fewer bioturbation structures than do the hemipelagic muddy deposits. (iii) The mud drapes have a microstructure characterized by aggregates of clay particles, which show features similar to those of fluid‐mud deposits, and are interpreted to represent deposition from fluid mud developed from turbidity current clouds. (iv) Large‐scale erosional surfaces are infilled with thick‐bedded to very thick‐bedded turbidites, which show lithofacies quite similar to those of the surrounding deposits, and are considered to be equivalent to scours. (v) Concave‐up erosional surfaces, some of which face in the upslope direction, are overlain by backset bedding, which is associated with many mud clasts. (vi) Tractional structures, some of which are equivalent to coarse‐grained sediment waves, were also developed, and were overlain locally by mud drapes, in association with mud drape‐filled scours, cut and fill structures and backset bedding. The combination of these outcrop‐scale erosional and depositional structures, together with the microstructure of the mud drapes, can be used to identify canyon‐mouth deposits in ancient deep‐water successions.     

Effects of heavy oil in the developing spotted halibut, Verasper variegatus

It is well known that heavy oil (HO) on the sea surface causes serious problems in the aquatic environment. In particular, some species of teleosts which develop on the sea surface are thought to be affected by the HO which flows out from tankers or coastal industry. However, the toxicological effects of HO are not fully understood. We performed exposure experiments using the Pleuronectiformean fish, spotted halibut (Verasper variegatus), which is an important fishery resource in Japan. In course of the development, HO-exposed embryos showed remarkable delay in developmental processes including somite formation. We further observed abnormal development of the head morphology. Notably, treated embryos had relatively small eyes and craniofacial structures. These findings strongly suggest that HO seriously affects the cell proliferation and differentiation of the embryo. In addition, HO-exposed embryos showed abnormal neuronal development. We also performed the exposure in the larval stage. Treatment of post-hatching larvae with HO resulted in significantly greater mortality compared with controls. Through these observations, we finally conclude that HO is strongly toxic to halibut in their early life stages.     

Toxicogenomic analysis of immune system-related genes in Japanese flounder (Paralichthys olivaceus) exposed to heavy oil

Heavy oil contamination is one of the most important environmental issues. Toxicities of polycyclic aromatic hydrocarbons (PAHs), including immune toxicities, are well characterized, however, the immune toxic effects of heavy oil, as a complex mixture of PAHs, have not been investigated. In the present study, we selected Japanese flounder (Paralichthys olivaceus) as a model organism, and observed alteration of immune function by the exposure to heavy oil. To analyze the expression profiles of immune system-related genes, we selected 309 cDNAs from our flounder EST library, and spotted them on a glass slide. Using this cDNA array, alteration of gene expression profiles was analyzed in the kidneys of flounders exposed to heavy oil. Six Japanese flounders (mean body weight: 197 g) were acclimated to laboratory conditions at 19-20 degrees C. Three fish were exposed to heavy oil C (bunker C) at a concentration of 3.8 g/L for 3 days, and the others were kept in seawater without heavy oil and used as the control. After the exposure period, the fish were transferred into control seawater and maintained for 4 days, and then they were dissected and their kidneys were removed. Total RNA was extracted from the kidney samples to use in gene expression analyses. The microarray detected alteration of immune system-related genes in the kidneys of heavy oil-exposed flounders, including down-regulation of immunoglobulin light chain, CD45, major histocompatibility complex class II antigens and macrophage colony-stimulating factor precursor, and up-regulation of interleukin-8 and lysozyme. These results suggest that pathogen resistance may be weakened in heavy oil-exposed fish, causing a subsequent bacterial infection, and then proinflammatory genes may be induced as a defensive response against the infection. Additionally, we found candidate genes for use as biomarkers of heavy oil exposure, such as N-myc downstream regulated gene 1 and heat shock cognate 71 kDa proteins.     

Effects of heavy oil in the developing spotted halibut, Verasper variegatus

It is well known that heavy oil (HO) on the sea surface causes serious problems in the aquatic environment. In particular, some species of teleosts which develop on the sea surface are thought to be affected by the HO which flows out from tankers or coastal industry. However, the toxicological effects of HO are not fully understood. We performed exposure experiments using the Pleuronectiformean fish, spotted halibut (Verasper variegatus), which is an important fishery resource in Japan. In course of the development, HO-exposed embryos showed remarkable delay in developmental processes including somite formation. We further observed abnormal development of the head morphology. Notably, treated embryos had relatively small eyes and craniofacial structures. These findings strongly suggest that HO seriously affects the cell proliferation and differentiation of the embryo. In addition, HO-exposed embryos showed abnormal neuronal development. We also performed the exposure in the larval stage. Treatment of post-hatching larvae with HO resulted in significantly greater mortality compared with controls. Through these observations, we finally conclude that HO is strongly toxic to halibut in their early life stages.     

Aluminum in the East China Sea and Okinawa Trough, marginal sea areas of the Western North Pacific

The distribution of aluminum (Al) in seawater has been investigated in the continental slope and the Okinawa Trough areas of the East China Sea, which is one of the marginal seas in the western North Pacific Ocean. Aluminum concentration in waters over the slope and the Trough ranged from 5.6 to 25 nmol/kg in the surface layer (0–100 m), and had a minima of 1.1 nmol/kg between 400 and 500 m depth and ranged from 1.3 to 9.7 nmol/kg in the deep or bottom waters. Aluminum values were higher than in the surface waters of the central North Pacific, while minimum values were similar to levels in the intermediate or deep waters of the central North Pacific, except for the bottom water over the slope. This suggests that the high Al concentration in the surface reflects the large atmospheric input of Asian dust around the western side of the North Pacific region. On the continental slope, Al concentrations in the upper 500 m depth decreased slopeward. This horizontal gradient of Al can be explained from the combination of dilution by upwelling of Al-poor water originated from the North Pacific Intermediate Water (NPIW) which intrudes into the mid-depth of the Okinawa Trough and the scavenging of Al by biogenic particles in the continental slope zone.     

Dietary shift and feeding intensity of <Emphasis Type="Italic">Stenobrachius leucopsarus</Emphasis> in the Bering Sea

The food habits of the dominant myctophid Stenobrachius leucopsarus were examined in the central basin of the Bering Sea in relation to oceanographic conditions, in summer 2002 and 2003 and spring 2006. S. leucopsarus exhibited an ontogenetic and seasonal dietary shift. In spring, small fish (≤40 mm) preyed mainly on Neocalanus flemingeri/plumchrus whereas large fish fed mainly on Neocalanus cristatus. In summer, small fish preyed mainly on Metridia pacifica whereas large fish fed mainly on euphausiids (Thysanoessa spp.). In the summer of 2003, when water temperature in the epipelagic layer (≤100 m) was warmer, reflecting the prevalence of the Alaskan Stream, small-sized S. leucopsarus showed a higher stomach content index, perhaps reflecting the greater abundance of M. pacifica. Thus, the present study shows that the physical variability in the epipelagic layer affects not only diets but also feeding performance of micronekton.     

Nonlinear periodic and algebraic ion-acoustic solitary waves in a relativistic plasma

We derive a mixed modified Korteweg-de Vries (MK-dV) equation from a semi-relativistic ion acoustic wave with hot ions by the fluid approximation. The positive cubic nonlinearity of the mixed MK-dV equation give rise to the periodic progressive waves and the algebraic solitary waves. The periodic wave bears a series of solitary pulses, and the algebraic solitary wave reduces the rarefactive solitary wave in the limit of the particular boundary condition. These nonlinear wave modes explain, respectively, the periodic pulse of the potential and the rarefactive solitary wave of the fine structure observed in space.     

In Search of the Cretaceous-Tertiary Boundary in Heilongjiang River Area of China

Abstract A new geological section recognized in Baishantou of Jiayin, Heilongjiang Province, China, was studied preliminarily in searching for the K/T boundary. An early Paleocene florule characrerized by abundant Tiliaephyllum tsagajanicum leaves and its associated plants, was collected from the Baishantou Member (new member representing the lower part of the Paleocene Wuyun Formation) overlying the possible K/T boundary. A tuff bed was found from the upper part of the Furao Formation (uppermost Cretaceous) in this section. The new findings imply that the K/T boundary is probable lying in the interval between the base of the Baishantou Member and the tuff bed, based on the correlation of the present strata with the stratotype of the Tsagajan Group spanning the K/T boundary in "Belaya Gara" of the Bureya Basin, Russia. The early Paleocene florule from the Baishantou Member and the early-middle Maastrichtian dinosaurs found from the Yuliangzi Formation underlying the Furao Formation suggest that the Baishantou section is more promising for searching for the K/T boundary in this area. Further studies of the section is needed, integrating paleontological, biostratigraphic, geochemical, paleomagnetic, and sedimentary research would benefit our understanding the mass extinction event and biotic recovery in the Heilongjiang River area, China, and even all of northeast Asia during the K/T boundary interval.