Life history ofEuphausia similis (crustacea,euphausiacea) in Sagami Bay,central Japan

The life history ofEuphausia similis G.O. Sars in Sagami Bay, central Japan, has been studied by examining the abundance, size distribution, and occurrence of each growing stage from egg to adult. Three cohorts were laid within the period from July 1979 to July 1980. Individuals of cohort I of 1980 were laid in November and December 1979, and matured and spawned in March and April of the following year. Those of cohort II of 1980 laid in January and February 1980 should mature in November and spawn after December, by analogy with cohort II of 1979. Cohort III of 1980 was laid in April 1980, but decreased in number in July. Cohort II was the dominant cohort in Sagami Bay throughout the period studied. From December 1979 to April 1980 when the mixing layer was present, many eggs ofE. similis were in the epipelagic zone. It is suggested that the spawning season ofE. similis roughly coincided with the season of active feeding, indicated by high fullness of stomachs in individuals. The production of juveniles and adults was about 1.33 mg C m^–2 day^–1, and the production to bio mass (P/B) ratio was estimated to be 4.78 between July 1979 and July 1980.     

Monitoring over‐winter soil water dynamics in a freezing and snow‐covered environment using a thermally insulated tensiometer

Water potential below a frozen soil layer was continuously monitored over an entire winter period (using thermally insulated tensiometers sheltered in a heated chamber) along with other soil, snow and atmospheric variables. In early winter, the freezing front advanced under a thin snow cover, inducing upward soil water flow in the underlying unfrozen soil. The freezing front started to retreat when the snow cover became thick enough to insulate the soil, resulting in the reversal of the flow direction in the unfrozen zone. These data provide a clear illustration of soil water dynamics, which have rarely been monitored with a tensiometer. Copyright © 2005 John Wiley & Sons, Ltd.     

Miocene pinnipeds of the otariid subfamily Allodesminae in the North Pacific Ocean: Systematics and relationships

Abstract Fossil pinnipeds in the extinct otariid subfamily Allodesminae are large, relatively highly evolved marine carnivores that became abundant and diverse in Middle Miocene time and were restricted to the North Pacific Ocean. Their record extends from early Middle Miocene through Late Miocene, with records from California, Oregon, Washington, Baja California and Japan. Allodesmines are characterized by extreme sexual dimorphism, a large orbit, retracted orbital margin of the zygomatic arch, a deeply mortised jugal-squamosal junction, wide palate, bulbous cheek tooth crowns, nearly flat tympanic bulla with wrinkled ventral surface, a large tympanohyal fossa, large ear ossicles and deep mandible. Eleven allodesmine species are known (eight of which are named), in at least four genera, and most belong to the typical genus Allodesmus Kellogg, 1922. The earliest and most generalized allodesmine known is from the early Middle Miocene (ca 16 Ma) Astoria Formation in coastal Oregon. The last known records are from Late Miocene rocks (ca 10 Ma) in California and Washington. New taxa proposed here are: the genus Brachyallodesmus Barnes and Hirota, to contain Allodesmus packardi Barnes, 1972; the genus Megagomphos Hirota and Barnes, to contain Allodesmus sinanoensis (Nagao, 1941); the species Allodesmus sadoensis Hirota, (Middle Miocene, Japan); the species Allodesmus megallos Hirota (Middle Miocene, Japan); and the species Allodesmus gracilis Barnes (Middle Miocene, California). Additionally, the genus Atopotarus Downs, 1956, and the species Allodesmus kelloggi Mitchell, 1966, are resurrected. Allodesmines were apparently a rapidly evolving group, and most appear to have been adapted to roles later filled by otariine, dusignathine and imagotariine otariids, and the Phocidae (true seals). They became extinct in Late Miocene time and left no living descendants. Although some of their characters evolved convergently with various living species of the pinniped family Phocidae, Allodesminae are an otariid group and not part of the evolutionary history of Phocidae.     

Summary of the fossil record of pinnipeds of Japan, and comparisons with that from the eastern North Pacific

Abstract The fossil pinniped record of the North Pacific Ocean includes both Phocidae and Otariidae ( sensu lato ), extends from the Late Oligocene to the Late Pleistocene, is taxonomically diverse, and is constantly becoming more complete owing to additional important discoveries. The earliest and most diverse fossil pinnipeds in the North Pacific are otariids, the phocids not appearing until the latest Pliocene. The theoretical center of otariid pinniped evolutionary history has been considered by some to be in the eastern North Pacific. New materials from the western North Pacific, however, including representatives of the subfamilies Enaliarctinae, Imagotariinae, Odobeninae and Otariinae, indicate that pinniped evolutionary patterns were basin-wide phenomena, and that a more complete record undoubtedly would reveal numerous trans-Pacific distributions. This would be expected considering the distributions of living species. The paucity of fossil Phocidae and their absence from pre-Pliocene deposits are consistent with theories that the family primarily evolved outside the North Pacific.     

The distribution of Fe3+ and Ga3+ between two tetrahedral sites in melilites,Ca2(Mg,Fe3+, Ga,Si)3O7

The distribution of Fe³⁺ and Ga³⁺ between the two tetrahedral sites in three synthetic melilites has been studied by using ⁵⁷Fe Mössbauer spectroscopy. In the melilite, (Ca₂Ga₂SiO₇)₅₀ (Ca₂Fe³⁺GaSiO₇)₅₀ (mol %), the distribution of Fe³⁺ and Ga³⁺ in T1 and T2 sites is apparently random, which can be explained in terms of the electrostatic valence rule. However in the melilites, (Ca₂MgSi₂O₇)₅₂ (Ca₂Fe³⁺GaSiO₇)₄₂ (Ca₂Ga₂SiO₇)₆ and (Ca₂MgSi₂O₇)₆₂ (Ca₂Fe³⁺GaSiO₇)₃₆ (Ca₂Ga₂SiO₇)₂ (mol %), Fe³⁺ shows preference for the more ionic T1 site and Ga³⁺ for the more covalent T2 site. If the electronegativity of Ga³⁺ is assumed to be larger than that of Fe³⁺, the mode of distribution of Fe³⁺ and Ga³⁺ can be explained in terms of our previous hypothesis that a large electronegativity induces a stronger preference for the more covalent T2 site.     

Probabilistic aspects of micropaleontologic assemblage zones

A micropaleontologic assemblage zone is defined by occurrence of some characteristic species among many coeval species. When number of assemblage-defining species and total number of species observed are designated as Aand N,respectively, the ratio, A/N,is strongly dependent on duration of the assemblage. Theoretical consideration on the basis of a micropaleontologic cohort model shows that, when origination rate and extinction rate of species are obtained, the most reasonable ratio (A/N) and duration of the assemblage can be determined. The probabilistic model described in this paper provides a theoretical relation between the ratio and the duration. Inaccuracy in correlating micropaleontologic data to certain assemblage zones established can not be avoided because of many natural sorting and artificial biases. Ambiguity arising when data with a small number of characteristic species are correlated with a certain assemblage is numerically estimated.     

Current Nature of the Kuroshio in the Vicinity of the Kii Peninsula

The Kuroshio flows very close to Cape Shionomisaki when it takes a straight path. The detailed observations of the Kuroshio were made both on board the R/V Seisui-maru of Mie University and on board the R/V Wakayama of the Wakayama Prefectural Fisheries Experimental Station on June 11–14, 1996. It was confirmed that the current zone of the Kuroshio touches the coast and bottom slope just off Cape Shionomiaki, and that the coastal water to the east of the cape was completely separated from that to the west. The relatively high sea level difference between Kushimoto and Uragami could be caused by this separation of the coastal waters when the Kuroshio takes a straight path. This flow is rather curious, as the geostrophic flow, which has a barotropic nature and touches the bottom, would be constrained to follow bottom contours due to the vorticity conservation law. The reason why the Kuroshio leaves the bottom slope to the east of Cape Shionomisaki is attributed to the high curvature of the bottom contours there: if the current were to follow the contours, the centrifugal term in the equation of motion would become large and comparablee to the Coriolis (or pressure gradient) term, and the geostrophic balance would be destroyed. This creates a current-shadow zone just to the east of the cape. As the reason why the current zone of the Kuroshio intrudes into the coastal region to the west of the cape, it is suggested that the Kii Bifurcation Current off the southwest coast of the Kii Peninsula, which is usually found when the Kuroshio takes the straight path, has the effect of drawing the Kuroshio water into the coastal region. The sea level difference between Kushimoto and Uragami is often used to monitor the flow pattern of the Kuroshio near the Kii Peninsula. It should be noted that Uragami is located in the current shadow zone, while Kushimoto lies in the region where the offshore Kuroshio water intrudes into the coastal region. The resulting large sea level difference indicates that the Kuroshio is flowing along the straight path.     

Local records of long-term dynamics of bamboo gregarious flowering in northern Laos and regional synchronicity of <Emphasis Type="Italic">Dendrocalamus membranaceus</Emphasis> in two flowering sites

Bamboos are widely distributed in mainland Southeast Asia and have abundant biomass. They are characterized by prolonged vegetative growth and semelparity. Where bamboos are dominant, their synchronous flowering and death has a major impact on forest vegetation. Although the small-scale dynamics of this process have become clearer in recent years, the history, geographical scale and synchronicity of bamboo flowering over broad areas remains unknown. This study focused on the flowering history of six bamboo species, Bambusa tulda, Cephalostachyum virgatum, Dendrocalamus hamiltonii, Dendrocalamus membranaceus, Indosasa sinica and Oxytenanthera parvifolia, over 40 years across a broad area of northern Laos. We also examined the synchronicity of flowering in D. membranaceus. We visited 49 villages in northern Laos and surveyed knowledgeable inhabitants about bamboo flowering history. The timing, scale and synchronicity of gregarious flowering varied among species. D. hamiltonii and D. membranaceus showed higher flowering synchronicity than other species. All the species except I. sinica had both sporadic and gregarious flowering traits, and showed conspicuous variability in their flowering scale. The flowering bamboo population at two gregarious flowering sites for D. membranaceus was surveyed. While this species had the highest synchronicity in this study, its synchronicity was lower than other species in previous studies worldwide. We found that the gregarious flowering of bamboos in northern Laos over the last 40 years showed lower synchronicity than bamboo flowering reported in other areas of the world. The historical dynamics and scale of bamboo flowering must be further clarified to understand the vegetation composition of this area.     

Intraannual variability of sea level around Tosa Bay

Through analysis of monthly in situ hydrographic, tide gauge, altimetry and Kuroshio axis data for the years 1993–2001, the intraannual variability of sea level around Tosa Bay, Japan, with periods of 2–12 months is examined together with the intraannual variability of the Kuroshio south of the bay. It is shown that the intraannual variation of steric height on the slope in Tosa Bay can account for that of sea level at the coast around the bay as well as on this slope. It is found that the steric height (or sea level) variation on the slope in this bay is mainly controlled by the subsurface thermal variation correlated with the Kuroshio variation off Cape Ashizuri, the western edge of Tosa Bay. That is, when the nearshore Kuroshio velocity south of the cape is intensified [weakened] concurrently with the northward [southward] displacement of the current axis, temperature in an entire water column decreases [increases] simultaneously, mainly due to the upward [downward] displacement of isotherms, coincident with that of the main thermocline. It follows that the steric height (or sea level) decreases [increases].     

Larval development ofEuphausia similis (Crustacea,Euphausiacea) in Sagami Bay,central Japan

The larvae ofEuphausia similis G. O. Sars in Sagami Bay, Central Japan, are described. Nauplius, metanauplius, calyptopis and furcilia stages are included. In the furcilia stage, six forms are identified on the basis of the form of the pleopods and the number of terminal telson spines. Furcilia I: a pair of non-setose pleopods and seven terminal telson spines. Furcilia II: a pair of setose and three pairs of non-setose pleopods and seven terminal spines. Furcilia III: four pairs of setose and a pair of non-setose pleopods and seven terminal spines. Furcilia IV: five pairs of setose pleopods and five terminal telson spines. Furcilia V: five pairs of setose pleopods and three terminal telson spines. Furcilia VI: five pairs of setose pleopods and one terminal telson spine. On the basis of the developmental pathway of the larvae,E. similis is suggested to be related toE. spinifera, E. longirostris, E. hanseni and theE. gibboides group species. The size ofE. similis larvae, expressed as total length, in Sagami Bay varied according to month. The sizes of calyptopis III and furcilia I–V stages were smallest in November and March and largest in May.