This paper describes in detail the deep-sea sediments along the Sagami Trough, which is an active subduction margin, mostly from the base of cliffs or knolls in the northern Sagami Bay area. Using Japan Agency for Marine Science and Technology (JAMSTEC) research vessels, we recovered 16 piston- and gravity-core samples of < 4 m in length. Six samples were collected from the knolls, four from the trough floor, and six from the landward trench slope. We determined the geologic ages using 14C and tephra analyses, and the magnetic fabrics using paleomagnetism and anisotropy of magnetic susceptibility (AMS). The average sedimentation rates are ～1 cm/kyr on the upper terrace of the Sagami Knoll, 4-61 cm/kyr on the trough floor, and 40-79 cm/kyr on the landward trench slope. The main direction of magnetic particle arrangement (Kmax) is largely constant in the upslope direction at the foot of Sagami Knoll, the Sagami Trough floor, and the landward trench slopes; in contrast, Kmaxis in the downslope direction in the upper terrace of Sagami Knoll.
The deep-sea mytilid mussel, Bathymodiolus japonicus, harbors methane-oxidizing bacteria in the gill epithelial cells that are transmitted horizontally or environmentally to the next generation of the mussel. It remains to be elucidated how the symbiotic bacteria are maintained under the immune defense system of the host mussels. As hemocytes generally play a major role in the immune system, their characterization is important in understanding the immune defense system of the symbiotic mussel. In hemocytes of B. japonicus, two types of granulocytes and one type of agranulocyte have been reported. To develop biomarkers to identify these hemocyte subpopulations, we generated a monoclonal antibody (mAb) library against mussel hemocytes. We obtained 16 hybridoma clones producing mAbs against the hemocytes. These were divided into six categories based on reactivity to the hemocyte subpopulations. Ten out of 16 mAbs reacted to all of the hemocytes. Four of the remaining six mAbs respectively and exclusively reacted to granulocytes, agranulocytes, a subset of granulocytes, and a subset of agranulocytes. Two of them recognized both granulocytes and agranulocytes but only their subsets. These suggested that granulocytes and agranulocytes are respectively composed of hetetogeneous subsets. The present mAb library may be useful not only for the classification of the hemocytes, but also for investigating their functions, differentiation and localizations in the body. The information obtained from the mAbs will be a baseline for understanding the relationship between the immunological defense system and stable maintenance of symbiotic bacteria in the deep-sea symbiotic bivalves.
In order to determine magnetic mineral distributions in nearshore marine sediments off southwestern Chile, chemical analysis of bottom waters and rock magnetic characterization of surface sediments were performed. The samples analyzed are terrigenous and calcareous sediments recovered with a multiple corer at five stations. Calcareous sediments occur at stations with highly dissolved oxygen catchment in the bottom waters. Concentration-dependent magnetic parameters of calcareous sediment samples show relatively low values, and their magnetic grain sizes are coarse. Higher values of concentration-dependent magnetic parameters are recognized, and fine grain magnetic minerals are distributed in silty and sandy clay sediments. Magnetic mineralogy of the sediment samples reflects not only lithology but also redox conditions in the overlying bottom waters. Thermo-magnetometry results suggest that magnetite (Fe3O4), hematite (αFe2O3), (titano)maghemite (γFe2O3), and goethite (αFeOOH) are common in sediment samples at all stations. Higher coercivities and total organic carbon (TOC) values are also observed at oxic stations, suggesting the presence of goethite and (titano)maghemite. In general, higher TOC contents in sediments lead anoxic conditions due to organic matter decomposition, therefore goethite and (titano)maghemite are unstable. Despite higher TOC contents in this sediment sample, such magnetic minerals can present. This implies that the magnetic minerals are kept in oxic conditions.
Meiofauna are small animals that are frequently used as indicators of environmental impacts. Among the meiofauna, Copepoda (Crustacea: Maxillopoda) is one of the most sensitive taxa to environmental changes. It is necessary to extract DNA sequences of copepods to obtain precise estimations of their biodiversity. However, the data presently registered are insufficient not only because of the inefficiencies in DNA extraction and PCR amplification, but also because there is a need for morphological reexamination after sequencing them. In the present study, we compared the efficiencies of the following three methods of DNA extraction for copepods―the Squish Buffer, GeneReleaser®, and InstaGene methods―with respect to extracted DNA concentrations, morphological characteristics following DNA extraction, in addition to the effect of Rose Bengal staining to PCR amplification. The Squish Buffer method yielded more quantity of DNA than the other methods; however, the morphology of their exoskeleton was better preserved with the InstaGene method. Nested PCR using both the universal and specific primer sets amplified a sufficient amount of DNA for sequencing, even when the extracted DNA concentration was < 10 ng/μL. Thus, DNA extraction by the InstaGene method followed by nested PCR is currently best way to obtain both morphological and genetic information from a single copepod specimen. A comparison of PCR amplification rates indicated that Rose Bengal inhibited amplification, which is consistent with reports in other taxa. The present results should facilitate both morphological and genetic analyses of deep-sea copepods.