Terufumi Ohno

Chlorophyll b and phycobilins in the common ancestor of cyanobacteria and chloroplasts

Photosynthetic organisms have a variety of accessory pigments, on which their classification has been based. Despite this variation, it is generally accepted that all chloroplasts are derived fromasingle cyanobacterial ancestor. How the pigment diversity has arisen is the key to revealing their evolutionary history. Prochlorophytes are prokaryotes which perform oxygenic photosynthesis using chlorophyll b, like land plants and green algae (Chlorophyta), and were proposed to be the ancestors of chlorophyte chloroplasts,. However, three known prochlorophytes (Prochloron didemni, Prochlorothrix hollandica and Prochlorococcus marinus) have been shown to be not the specific ancestors of chloroplasts, but only diverged members of the cyanobacteria, which contain phycobilins but lack chlorophyll b,. Consequently it has been proposed that the ability to synthesize chlorophyll b developed independently several times in prochlorophytes and in the ancestor of chlorophytes. Here we have isolated the chlorophyll b synthesis genes (chlorophyll a oxygenase) from two prochlorophytes and from major groups of chlorophytes. Phylogenetic analyses show that these genes share a common evolutionary origin. This indicates that the progenitors of oxygenic photosynthetic bacteria, including the ancestor of chloroplasts, had both chlorophyll b and phycobilins.

Pre-bomb marine reservoir ages in the western north Pacific: Preliminary result on Kyoto University collection

The calibration of radiocarbon dates on marine materials involves a global marine calibration with regional corrections. The marine reservoir ages in the Western North Pacific have not been discussed, while it is quite important to determine the timing of palaeo-environmental changes as well as archaeological interpretation around this region. The lack of adequate collection of the pre-bomb shell from western north Pacific was the biggest problem. Recently we had a chance to examine specimens from an old shell collection stored in Kyoto University, including shell specimens from Japan, Korea, Taiwan and the Micronesia of 1920s and 1930s. We explored the possibility for usage of specimen without clear evidence of live collection by measuring 30 apparent radiocarbon ages of pre-bomb mollusk shells from 18 sites in Western North Pacific. The preliminary results showed several discrepancies with previously reported results and with each other. We have to carefully select the shell specimen that has biological signs such as articulating fulcrum. In order to exploit this big resource of pre-bomb shell collection, the new technique to distinguish fossils from live collected samples should be developed by using chemical and physical methods. ” 2000 Elsevier Science B.V. All rights reserved.

Cambrian Orsten Lagerstätte from the Alum Shale Formation: Fecal pellets as a probable source of phosphorus preservation

Abstract The Furongian Orsten-type fossil Lagerstätte in the Alum Shale Formation of Sweden is an extraordinary deposit known for its detailed, three-dimensional preservation of the soft parts of small animal carcasses which have been replaced by calcium phosphate and occur in organic-rich nodular limestone. The exact cause and mechanism of this unusual fossil preservation, however, particularly the source of phosphorus, which plays a key role, remains unknown. Detailed observation in the Agnostus pisiformis Zone in the Backeborg section (Kinnekulle district) reveals that the phosphatocopine crustaceans showing soft-part preservation occur only in a few thin (<3 cm) layers containing abundant fecal pellets (pellet beds). Development of cross lamination suggests that the pellet beds were formed by low density sediment-gravity flow. Orsten-type preservation has been attributed to high phosphate levels in global marine waters during the Cambrian period; however, wavelength-dispersive X-ray and X-ray diffractometry analyses reveal that the Orsten limestones and surrounding shale were generally poor in phosphorus, which was mostly concentrated in the fecal pellets. The small animal carcasses preserved in such deposits were phosphatized during early diagenesis owing to the high local phosphorus levels of the accumulated fecal pellets. Searches for such cesspool-type preservation may yield further discoveries of Orsten-type fossil Lagerstätten in other strata of various ages.

Continuous growth-line sequences in gastropod shells

Abstract Studies of gastropod shell growth at the level of fine growth layers are scarce, because coiling of gastropod shells hinders the observation of continuous growth series spanning across whorls. We propose here a new method to obtain continuous growth patterns of gastropod shells over whorls with Terebralia palustris (L.) as an example. Comparison of vertical and horizontal sections of the shell of this species reveals that growth patterns can be observed continuously for several whorls on the vertical section of the columella. In addition, an obvious tidal growth pattern preserved in this species enables us to trace its growth with a precision of 12.4 h and indicates that it takes about two years for a shell to grow from 3 cm to 9.5 cm in height and add 5 complete whorls.

Calcite–dolomite cycles in the Neoproterozoic Cap carbonates, Otavi Group, Namibia

Abstract The lower cap carbonate (Rasthof Formation) overlies Neoproterozoic glacial deposits (Chuos Formation) and is exposed in the Khowarib-Warmquelle area in Northern Namibia. The basal 14.2 m part of the Rasthof Formation (total about 220 m) consists of the carbonate rhythmite. The rhythmite part of the Rasthof Formation contains 1 m cycles of dark- and light-coloured rhythmites. Alizarin-red staining of thin sections and elemental mapping of polished samples indicate that the dark-coloured parts are rich in calcite, whereas the light-coloured parts are dolomite-rich. On a 1 cm scale, a reddish clay layer is intercalated in each calcite rich dark-coloured rhythmite part. These cycles of reddish clays as well as some associated major turbidites can be well correlated between columns up to about 20 km distance. Furthermore, at one locality (K4), rip-up clasts occur in a turbidite bed. Their lithology consists of dark- and light-coloured rhythmite and a reddish clay layer and can be judged to have been derived from underlying horizons. Because the clasts are elastically deformed, it is strongly suggested that the difference in lithology observed within the basal part of the Rasthof Formation existed when clasts were ripped-up shortly after sedimentation. This suggests that the cycle involving dolomite is synsedimentary, and not a diagenetic feature. Direct precipitation of dolomite does not occur in present day open marine seawater. Hurtgen et al. (2002) suggest that seawater was depleted in sulphate after Neoproterozoic glaciation. It is proposed here that some possible depositional models of cycles that consist of calcite-rich and dolomite-rich parts as well as reddish clay beds in rhythmites of the Rasthof cap carbonate.

Development of a Multiple User Quiz System on a Shared Display

Collaborative Learning attracts attention as a new teaching method for its effectiveness of acquiring various skills. Recognizing the limit of current design of personal computer (PC) for collaborative learning in face-to-face environment, the authors have proposed a computer system called Socialized Computer (SC) that allows multiple users access to the computer with multiple mice and keyboards, and share information on a single large display. The authors take quiz as learning material, and are developing multiple user quiz system named MultiMouseQuiz (MMQ) for collaborative learning along the concept of SC. This paper reports a prototype system of MMQ and preliminary experiment carried out at Kyoto University Museum using the prototype. Design issues of MMQ is addressed based on the findings obtained in the experiment.

Late Pleistocene changes of tidal amplitude and phase in Osaka Bay, Japan, reconstructed from fossil records and numerical model calculations

Abstract Calculations with a numerical model of the Seto Inland Sea tides show that sea level changes cause strong changes in the tidal range and pattern of diurnal inequality in Osaka Bay. A higher sea level produces a stronger diurnal inequality and a smaller tidal range; a lower sea level produces a weaker diurnal inequality and a larger tidal range. The best fit between the calculated tidal patterns and the tidal pattern that is reconstructed from the growth structures of fossils from the last interglacial is achieved with a sea level approximately 15–20 m lower than present. For a such sea level and tidal pattern, the numerical calculation gives a tidal range of about 2.65–2.8 m in Osaka Bay.

Theoretical morphology of quilt structures in Ediacaran fossils

Abstract Vendobiont type fossils are characterized by possessing ‘gliding symmetry’, in which quilts of the different vanes consisting the body of the Vendobionta meet along the seam with small offset. Because two, three or more vanes are joined along this seam and the quilts of different vanes can be variously offset along the seam, a variety of gliding symmetry exists among Vendobionta. Our theoretical consideration here predicts that the number of possible gliding symmetry is one, two and three for organisms having two, three and four vanes, respectively. We also predict that a special combination of morphological types appear alternatively during the growth of the Vendobionta with two vanes. Further, we were able to identify the existence of two types in gliding symmetry predicted by us for Pteridinium specimens with three vanes. Detailed examination of the gliding symmetry of other Vendobionta, therefore, may give important clues in solving riddles veiling the vendobiont relationships.

Non-destructive method to detect the cycle of lamination in sedimentary rocks: rhythmite sequence in Neoproterozoic Cap carbonates

Abstract Environmental changes were flagged by lamination within Precambrian sedimentary rocks sequences using a high-resolution method. A continuous sample was collected and embedded in epoxy resin to form sample plates in order to investigate 2D laminations on sample surfaces. Elemental distributions in laminated samples were determined and recorded as XRF profiles, using the scanning X-ray analytical microscope (SXAM) and an image processing lamination tracer. These methods were used to study a rhythmite sequence at the base of a Neoproterozoic cap carbonates, which immediately overlies glacial deposits in Namibia, to determine profiles of Si, Ca, Mn, Ti, Fe, and Sr. At the base and top of each interval, the concentrations of six elements were relatively constant. In the middle of the interval, Ca–Sr and Mn, which reflect presence of calcite and dolomite respectively, fluctuated. This reflects seventeen cycles. The cyclic fluctuations of Ca–Sr and Mn were interpreted as calcite–dolomite cycles. Strontium also recorded two cycles. Furthermore, the fluctuations of Ca–Sr and Mn in calcite–dolomite cycles were laterally traceable. Possibly, these calcite–dolomite cycles were deposited synchronously and regionally. New methods allow the extraction of data that record cyclic- and event-phenomena from long sequences of laminated sedimentary rocks; this is not isolated to the Neoproterozoic but also throughout Earths history.

Taxonomic Evaluation of Various Morphological Characters in the Late Cretaceous Desmoceratine Polyphyletic Genus “Damesites” from the Yezo Group in Hokkaido and Sakhalin

Abstract. Intra- and interspecific variation and ontogenetic changes in various shell characters of the Late Cretaceous desmoceratine ammonoid “Damesites” are described, and their taxonomic implications are discussed based on specimens from the Cretaceous Yezo Group in Hokkaido and Sakhalin. Our study reveals that many “diagnostic” features (e. g., appearance of longitudinal striations, height of ribbing, regularity of ribbing as well as constriction curvature) and early internal shell structures, are in fact inappropriate as diagnostic features of “Damesites” morphotypes. In contrast, ontogenetic changes in shell ornament, curvature of growth lines and whorl expansion ratio are herein demonstrated to be key characters for species recognition and reconstructing the phylogenetic relationships of the taxa of the subfamily Desmoceratinae. Based on these results, previously described “Damesites” species from the uppermost Turonian-lower Campanian interval should be reclassified into three groups. “Damesites damesi,” “D. damesi intermedius,” “D. semicostatus,” and “D. laticarinatus” are assigned to the first group. “D. ainuanus” and “Damesites sp.” are assigned to the second group. “D. sugata” from the Yezo Group represents the third group. Furthermore, analysis of ontogenetic changes in shell ornament, curvature of growth lines, and whorl expansion ratio suggests that the second and third groups together belong to a different evolutionary lineage from the first group.