Dietary value of benthic diatoms for post-larval abalone <Emphasis Type="Italic">Haliotis diversicolor</Emphasis> associated with feeding transitions

ABSTRACT:   The feeding behavior and growth of post-larval Haliotis diversicolor with initial shell lengths (SL) of approximately 500 μm (Exp. 1-1 and 1-2), 800 μm (Exp. 2), and 1200 μm (Exp. 3) were studied in a laboratory setting while they fed on four species of benthic diatom Achnanthes longipes , Cocconeis sublittoralis , Cylindrotheca closterium , and Navicula ramosissima . Exp. 1-1 and 1-2 revealed no marked differences in post-larval growth rates (mean 24–39 μm SL/day) among the diatom species. However, marked differences in growth rates among the species were revealed in Exp. 2 and 3. Three species, A. longipes , Co. sublittoralis, and Cy. closterium , produced faster growth (Exp. 2 mean 29–51 μm/day, Exp. 3 mean 36–44 μm/day) than N. ramosissima (Exp. 2 mean 18 μm/day, Exp. 3 mean 23 μm/day). Post-larvae fed N. ramosissima had lower digestion efficiency (42.8%) than those fed other diatom species (90.7–100%). Diatom extracellular substances appeared to be principally used from post-settlement to 800 μm SL, and diatom cell contents were required to produce rapid growth of larger post-larvae (>800 μm SL). It is likely that the availability of each diatom for post-larvae was affected by diatom morphology, attachment strength, frustule strength, and post-larval size.     

Distribution of free oxides along soil profiles in time series of dry rice fields in polder lands of Kojima-basin

The distributions of free oxides along profiles of some dry rice fields were set forth in the previous reports²,³,⁴,⁶⁾, In this paper, the distribution of free oxides in dry rice field⁵⁾ in polder lands of Kojima-Basin, Okayama pref. is reported. Localities, years elapsed since the planting of rice began in each field and the characteristic of soil profiles are given in Table 1. All the fields are dry rice fields except Soil A, and carry barley or wheat in winter season. Parent materials are similar in all horizons of all soils and rich in fine particles. Fine sands (0.2-0.02 mm) are mainly composed of quartz somewhat accompanied with feldspars, mica, augite and amphibolite. Clays (< 0.002 mm) are mainly composed of halloysite accompanied with a small proportion of montmorillonite. The structure develops well in all the soils.     

Cold tolerance at the early growth stage in wild and cultivated rice

The present study was conducted to understand the pattern of variation and the genetic bases for cold tolerance at the early growth stage in Asian rice. The genetic variation was investigated at the germination, plumule and seedling stages among 57 strains including cultivated rice (Oryza sativa ssp. indica and ssp. japonica) and its wild progenitor (Oryza rufipogon). The significant differentiation of cold tolerance was observed among the taxonomically divided groups. At the germination stage, both indica and japonica subspecies tended to be more tolerant than O. rufipogon, whereas at the plumule and seedling stages, ssp. japonica tended to be more tolerant than ssp. indica and O. rufipogon. Furthermore, in cold tolerance at the plumule stage, the clinal variation across the latitude of origins was observed within O. rufipogon and ssp. japonica, suggesting that the current pattern of variation seems to have been shaped by both their phylogenetic histories and on-going adaptation to the local environments. QTL analysis between O. sativa ssp. japonica (tolerant) and O. rufipogon (susceptible) revealed five putative QTLs for cold tolerance at the plumule and seedling stages but not at the germination stage. Substitution mapping was also carried out to precisely locate the two major QTLs for cold tolerance at the plumule stage, which could be used for improvement of tolerance to cold stress in ssp. indica.     

Mineralogical study of weathering products of granodiorite at Shinshiro City (I)

Rock weathering has long been a subject of study for geologists, mineralogists, chemists and soil scientists since the dawn of this century. In methods for investigating rock weathering, three aspects seem to be present. The one is a chemical aspect in which weathering process is considered by comparing chemical composition of fresh parent rock with that of the weathered rock, the difference being attributed to gains or losses of chemica,l elements with respect to a supposed immobile element, usually aluminum. This aspect can elucidate the chemical behaviour of rock, that is, of material as an assemblage of constituent minerals in the environment of weathering. Among many such studies mentioned. PoLYNov's “Cycle of Weathering” (6) is one of the most comprehensive and fruitful acheivements. The second aspect is a mineralogical one, in which interests are directed toward skeletal minerals surviving against severe attacks of weathering. It is commonly observed that some of the original constituent minerals still remain in weathered material after others have been extinguished. The former minerals are more stable than the latter. On the basis of these observations, the sequence of resistantiability or stability to weathering can be determined for many rock forming minerals. GOLDICH's study of rock-weathering (3) is a representative one in this aspect. The third aspect is concerned with clay mineralogy. Primary rock-forming minerals are weathered into very finegrained materials most of which had been believed amorphous until techniques now used in clay mineralogical reserch proved their crystalline state. Besides primary skeletal minerals, weathered materials are now known to consist mainly of both amorphous and crystalline secondary minerals, mostly appearing in minus two micron fraction and being objects of interest in clay mineralogy. Any study of rock weathering hitherto performed stood more or less on the three aspects above mentioned but, all the abovementioned seem to fall into the common tendency of dealing with materials as bulk mass. That is, they were concerned much more with fresh rock versus its weathered end products as a whole rather than with the process or mechanism by which fresh rock changed into weathered material. Thus, in the temperate to subtropical humid region, it is known that, for example, kaolinite minerals, gibbsite, and some of 2: 1 type clay minerals are found in weathered materials of rocks and further that Na, K. Mg. Ca, and Si are leached away, while H, Al, and Fe are concentrated in the weathered products, but it is scarcely understood from what constituent minerals of the parent fresh rock any of the clay minerals now present in the weathered material were derived. Though, a mineralogical or chemical tracing of the courses of decomposing minerals from their initial phases to subsequent modified phases was already pioneered by STEPHEN (8). such a trend is believed, by the author, to be a fourth aspect necessary for further thorough understanding of rock weathering. This way of study may also serve in bridging between experimental data on chemical reactions of specific minerals with reagent solutions on the one hand and observations of mineralogical interrelation of parent minerals to resultant weathering products on the other hand. Granitic rock offers a suitable situation for this fourth aspect because of the ease in picking up mineral grains at various weathering stages due to the coarseness of its constituent minerals and also to its unique mode of physical disintegration.     

Molecular design of antifungal agents

In a rational approach to the design of antifungal agents against Saccharomyces cerevisiae, a series of alkyl gallates (3,4,5-trihydroxybenzoates) were synthesized and assayed. Nonyl gallate (1) was found to be the most effective with a minimum fungicidal concentration (MFC) of 12.5 microg/mL (42 microM), followed by octyl gallate (2) with an MFC of 25 microg/mL (89 microM). These MFCs are little influenced by pH values. A time-kill curve study indicates that nonyl gallate exhibits fungicidal activity against S. cerevisiae at any growing stage. The antifungal activity of nonyl gallate is due primarily to its ability to act as a nonionic surface-active agent (surfactant). The length of the alkyl group is not a major contributor but plays a role in eliciting the activity to a large extent. As far as alkyl gallates are concerned, their antimicrobial spectra and potency depend largely on the hydrophobic portion of the molecules.     

Genetic resources of salt tolerance in wild Hordeum species

Salt tolerance was evaluated in 340 accessions of Hordeum, consisting of 41 brittle-rachis forms of Hordeum vulgare L. subsp. vulgare (H. agriocrithon) accessions, 154 H. vulgare L. subsp. spontaneum (H. spontaneum) accessions, and 145 accessions of ten other species or subspecies of wild Hordeum. Germination was carried out at concentrations of 171, 257, and 342 mM NaCl. The levels of salt tolerance for seed germination in wild Hordeum species were generally lower than those found by Mano et al. (1996) in cultivated barley; the NaCl tolerance level of the different species were as follows: H. agriocrithon > H. spontaneum > other wild Hordeum species. In addition, leaf injury index was used to assess tolerance at the seedling stage after treatment with 500 mM NaCl solution for four weeks. The levels of salt tolerance at the seedling stage in wild Hordeum species were generally higher than those found by Mano & Takeda (1995) in cultivated barley. Most wild Hordeum species showed high NaCl tolerance at the seedling stage and are considered good sources of germplasm for salt tolerance breeding. This revised version was published online in August 2006 with corrections to the Cover Date.     

Low-frequency spin dynamics in a canted antiferromagnet

Resistively detected nuclear spin relaxation measurements in closely separated two-dimensional electron systems reveal strong low-frequency electron-spin fluctuations in the quantum Hall regime. As the temperature is decreased, the spin fluctuations, manifested by a sharp enhancement of the nuclear spin-lattice relaxation rate 1/T1, continue to grow down to the lowest temperature of 66 millikelvin. The observed divergent behavior of 1/T1 signals a gapless spin excitation mode and is a hallmark of canted antiferromagnetic order. Our data demonstrate the realization of a two-dimensional system with planar broken symmetry, in which fluctuations do not freeze out when approaching the zero temperature limit.     

Utilization patterns of estuarine and marine habitats by the halfbeak Zenarchopterus dunckeri at Iriomote Island,southern Japan,evaluated from otolith microchemistry

Estuarine and marine habitat use patterns in the halfbeak Zenarchopterus dunckeri were examined at Iriomote Island, southern Japan, by analyzing otolith Li/Ca and Sr/Ca ratios. The ranges of both Li/Ca and Sr/Ca ratios in juvenile Z. dunckeri from the maximum (30 psu) to minimum (0.5 psu) salinity levels of brackish water estimated from rearing experiments, were compared with those of wild individuals collected from upstream and downstream stations in the Urauchi River estuary. The majority of wild-caught individuals had invariable Li/Ca and Sr/Ca ratios along an otolith transect from the core to the posterior edge, which fell within the otolith Li/Ca and Sr/Ca ranges estimated for estuarine individuals in the rearing experiments, suggesting that such individuals developed within the estuary without migrating to a marine environment at any time, although some downstream-dwelling fish had higher otolith elemental ratios than the predetermined estuarine ranges in the mid transect section. The latter fish may have been accidentally flushed from the estuary into the sea by heavy flood events, subsequently returning to the estuary. The overall results suggested that Z. dunckeri is essentially an estuarine resident, completing its life cycle within an estuarine system.     

Maturation and spawning of <Emphasis Type="Italic">Spratelloides gracilis</Emphasis> Clupeidae in temperate waters off Cape Shionomisaki,central Japan

ABSTRACT:   The reproductive ecology of Spratelloides gracilis was investigated in the temperate waters off Cape Shionomisaki, central Japan. Cape Shionomisaki is located at the northern margin of the distribution range of this species. Females of S. gracilis with gonadosomatic index (GSI) ≥ 4.0 were defined as mature based on the relationship between GSI and the histological maturity phases of their ovaries. More than 50% of females greater than 60 mm standard length (SL) were mature. Hatch dates of larvae and juveniles collected in the study area were determined by otolith daily ring counts and found to extend from April to November. The size at maturity of females (60 mm SL) and the spawning season of S. gracilis in the temperate waters off Cape Shionomisaki (April–November) was larger and shorter, respectively, than those in tropical waters in the western Pacific. The reproductive traits observed for S. gracilis off Cape Shionomisaki appear to be adaptive to northern temperate waters with seasonal changes in environmental conditions.     

Identification of juvenile abalone <Emphasis Type="Italic">Haliotis diversicolor</Emphasis> based on number of open and sealed respiratory pores

ABSTRACT:   Changes in the number of respiratory pores (open pores) and their imprints (sealed pores) in post-larvae and juveniles were observed and compared for four abalone species Haliotis diversicolor , H. discus discus , H. madaka , and H. gigantea . The first open pore was evident at a shell length (SL) of 1.5 mm in H. diversicolor , 1.9–2.0 mm SL in H. discus discus , and 2.3–2.4 mm SL in H. madaka and H. gigantea . The number of open pores in H. diversicolor gradually increased with growth, with four to five pores at 2.5–18.0 mm SL and five to six pores at 18.0–27.0 mm SL. The other three species maintained four to five open pores after they reached 3.4–4.5 mm SL. The total number of open and sealed pores (TNP) was greater in H. diversicolor than in the other species at the same SL. Juvenile H. diversicolor were identified among field-caught abalone by the difference in the relationship between SL and TNP (SL–TNP relationship) and also by the monoclonal antibody reaction method. The results of the two methods were in perfect agreement, indicating that our method using the SL–TNP relationship is reliable for the identification of H. diversicolor .