Phylogeography of the Japanese eight-barbel loach <Emphasis Type="Italic">Lefua echigonia</Emphasis> from the Yamagata area of the Tohoku district,Japan

The Japanese eight-barbel loach Lefua echigonia, which is a freshwater fish native to Japan, is distributed from the Tohoku to Kinki districts and is divided into six regional populations according to mtDNA analysis. In this study, we investigated L. echigonia collected from several locations in Yamagata Prefecture and neighboring prefectures using mtDNA control region sequences and confirmed the spatial distribution pattern among the new regional population (Yamagata population). The new population was limited to the Mogami river system in the inland area of Yamagata Prefecture and is distinguished from other regional populations by high sequence divergences.     

Wild stock structure of <Emphasis Type="Italic">Girella punctata</Emphasis> in Japan revealed shallow genetic differentiation but subtle substructure in subsidiary distributions

Twelve populations of Girella punctata, from widespread locations of the species’ range in Japan and Korea, were screened for sequence variability within the mitochondrial DNA (mtDNA) control region (n = 128) and at five polymorphic microsatellite loci (n = 547) to determine the genetic structure maintaining population integrity. mtDNA variability of 132 variable sites within a 334-bp region reveals shallow genetic differentiation across populations. The weak differentiation of G. punctata was partly supported by the screening of five polymorphic microsatellite loci. However, hierarchical analysis of molecular variance and principal component analysis on the basis of allele frequencies in microsatellite loci extracted a subtle substructure in a subsidiary population and in near-subsidiary populations in the semi-enclosed Seto Inland Sea.     

Genetic control of intra-ring wood density variation in hybrid larch (Larix gmelinii var. japonica × L. kaempferi) F1

Genetic parameters for various wood density traits were estimated in 29-year-old trees of 18 full-sib families of hybrid larch (Larix gmelinii var. japonica × Larix kaempferi) F₁. Intra-ring density variation (IDV) was also evaluated using a model that expresses the pattern curve from earlywood to latewood as a power function. A high IDV indicates an abrupt change in wood density from earlywood to latewood. The ring width and wood density traits of individual rings were determined by X-ray densitometry. Overall wood density (RD) was shown to increase with increasing ring number, ranging from 0.42–0.59 g/cm³, whereas IDV of individual rings decreased gradually from pith outwards. Estimates of individual tree narrow-sense heritability of RD and IDV were 0.66 and 0.67, respectively. IDV showed negative genetic and phenotypic correlations with RD (r _g = −0.99, r _p = −0.72). The predicted genetic gains in latewood proportion and IDV were higher than that of RD. These results suggest that the intra-ring density variation is under moderate genetic control equivalent to wood density. The trend of increasing wood density from earlywood to latewood was associated with changes in both tracheid diameter and cell wall thickness.     

Tree mortality and habitat shifts in the regeneration trajectory underneath canopy of an old-growth subalpine forest

To better understand tree regeneration trajectories and the resultant coexistence of Abies with co-dominants, Picea jezoensis var. hondoensis, Tsuga diversifolia and Betula ermanii, in an old-growth subalpine forest, we investigated spatial mortality patterns during the regeneration of Abies mariesii and A. veitchii, which are abundant in the understory reflecting their shade tolerance. Regeneration of these Abies spp. from shaded understory to canopy status is affected by other canopy co-dominants. Snags of understory Abies spp. were common, suggesting that the primary mortality agent is suppression by the overstory. Although live, small Abies trees in the understory were positively associated with a Picea canopy, the long-term survival was reduced among Abies trees close to the canopy, suggesting that shading by large Picea in the overstory negatively affects understory Abies plants. The existence of shade-intolerant canopy co-dominants such as Picea and also Tsuga, which are larger and longer lived than the shade-tolerant Abies, may play an important role in preventing the Abies spp. from competitively displacing these other tree species, which are much rarer in the understory, though common in the canopy. Moreover, in spite of the fact that Betula canopies fostered recruitment and growth of Abies saplings, Abies showed no association with Betula canopy and their survival at later-stage was rather reduced near or beneath Betula canopies at the subsequent understory small tree stage. Based on spatially significant events related to tree death, this study detected such “habitat shifts” in the trajectory of tree regeneration. Accordingly, it can be concluded that careful consideration of the regeneration habitat is required for a fuller understanding of ecological processes in spatially complex old-growth forest systems.     

Vermiculite in Some Japanese Soils

Since Gruner's pioneer work in 1934¹⁾, vermiculite has been attracting the attention of mineralogists and soil scientists with much interest, probably because of its unique behaviour on cation exchange and of a component common in most soils derived from various parent rocks. A number of papers thereafter dealt with the mineral, revealing its properties, diagenesis, and distribution in soils. However, as information has been accumulated on vermiculite, especially on clay vermiculite, it became evident that the difference between vermiculite and montmorillonite is due simply to the difference in layer charge and that the division is essentially an arbitrary one²⁾. Walker suggested that the Mg plus glycerol test would be the only one which appeared to be universaIlY valid in the identification of vermiculite, and that although the K test was still of value as an aid in the differentiation, it could no longer be reo commended as of universal validity. In recent years, several workers^4-12) indicated that interlayer materials, especially Al-hydroxyls, prevented vermiculite from contracting to 10 Å in the K test and prevented montmorillonite from expanding to 18 Å in the Mg-glycerol test. This suggests that in the light of new evidences the 14 Å mineral hitherto believed as vermiculite, chlorite, or montmorillonite by the classical test should be reexamined after removal of interlayer materials.     

Measurement of the shear modulus of wood by static bending tests

When measuring the shear modulus of wood by static bending tests, the basic theory is dependent on Timoshenko's bending theory. The shear modulus obtained by static bending is a much smaller value than that derived by other methods. We examined the applicability of Timoshenko's theory and propose an empirical equation that can derive the shear modulus properly. Three softwoods and three hardwoods were used for the tests. First, the Young's modulus and shear modulus were measured by free-free flexural vibration tests. Then the three-point static bending tests were undertaken, varying the depth/span ratios. Additionally, the bending tests were simulated by the finite element method (FEM). The shear moduli obtained by these methods were then compared. The deflection behaviors in static bending were not expressed by the original Timoshenko bending theory because of the stress distortion near the loading point. Based on the experimental results and numerical calculations, we modified the original Timoshenko bending equation. When using our modified equation the stress concentration must be carefully taken into account.     

Severe oxidative stress is thought to be a principal cause of jaundice of yellowtail Seriola quinqueradiata

The jaundiced yellowtail Seriola quinqueradiata had yellow discolored skin and hyperbilirubinemia. Histology revealed that hemosiderin and ceroid occurred in the spleen. In the vascular system, there were vasculitis and sinusoidal dilatation. Hepatic cells showed degenerative figures with pyknotic or karyolytic nuclei, basophilic cytoplasm, cytoplasmic vacuoles in various sizes, and ceroidosis. In the bile duct system, however, there was no noticeable change. Hemoglobin contents of jaundiced fish were similar to those of control fish. Plasma taurine levels of jaundiced fish were significantly lower than those of control (p0.05). Judging from 2-thiobarbituric acid reactive substance values, in vivo lipid peroxidation progressed in the liver of jaundiced fish. In the plasma of jaundiced fish, contents of unconjugated bilirubin were significantly higher than those of conjugated bilirubin. A large amount of substance Xs, breakdown products of bilirubin scavenging active oxygen species, existed in the plasma of jaundiced fish. Therefore, jaundiced fish may suffer from severe oxidative stress, which might be a principal cause of jaundice. Liver superoxide dismutase and glutathione peroxidase activities of jaundiced yellowtail were significantly lower than those of controls.     

Release of dissolved free amino acids from biofilms in stream water

We investigated the origin of dissolved free amino acids (DFAA) in stream water focusing on biofilms in the river bed by means of incubation experiments in the laboratory. Stones were placed in the Toyohira River, Hokkaido, Japan, for 3 months, allowing formation of biofilms, and then incubated for 24 h in the laboratory at stream water temperature. After incubation, the composition and concentrations of DFAA in the incubation solution and total hydrolyzed amino acids (THAA) in biofilms were measured by high-performance liquid chromatography. The amount of chlorophyll a (Chl. a) and the number of bacteria were also measured. The DFAA concentration increased greatly in the biofilm incubation solution, but the DFAA composition (mol %) did not change relative to the inception of incubation, where it was similar to stream water. There was no correlation between the increase in DFAA concentration and the THAA concentration, Chl. a amount, or the number of bacteria in biofilms. These results suggest that biofilms are one of the major sources of DFAA in stream water.     

Estimating larval supply of Ezo abalone <Emphasis Type="Italic">Haliotis discus hannai</Emphasis> in a small bay using a coupled particle-tracking and hydrodynamic model: insights into the establishment of harvest refugia

Most juveniles of Haliotis discus hannai have been found to be descendants of wild individuals, although most adults were artificially produced (released) individuals as a result of restocking inside the refugium located near the head of Oshoro Bay, Hokkaido, Japan. To estimate the larval supply from released and wild individuals into the refugium and to compare the suitability of locations as larval sources, we simulated larval dispersal using a coupled hydrodynamic and particle-tracking model. The simulation results indicated that more larvae may be supplied from the wild adults inside the bay to the refugium than from the released adults. These results are consistent with the observed high abundance of wild juveniles in the refugium. Most larvae from the refugium were predicted to disperse out of the bay. We found that larval retention in the bay was at least one order of magnitude higher than that in the refugium. Thus, it may be more effective in terms of self-replenishment and reproduction if the refugium were to be expanded to the bay scale. There were only minor differences among the compared sites at the head of the bay in terms of their suitability as larval sources. Consequently, the establishment of new refugia in this area could be expected to provide an effectiveness equal to that of the current refugium.     

The incidence of Campylobacter contamination levels through Chicken-Sashimi Processing steps in A Small-scale Poultry processing plant applying the External stripping method

This study aimed to analyze the incidence of Campylobacter in a small-scale chicken meat processing plant producing “chicken-sashimi”, and determine the effectiveness of surface burning as a treatment during processing. The most probable number (MPN) method was used to analyze the load of Campylobacter in 48 samples from four different processing steps (de-feathering, chilling, surface burning, and final-products; 12 samples each). We found the highest load of isolated bacteria in chicken skin after de-feathering. Campylobacter was not detected after the surface burning step despite a large load of bacteria present in the cecum content. Campylobacter was absent in the final products. Adequate surface burning can avoid Campylobacter contamination of chicken sashimi in the processing plant by applying the external stripping method.