Estimating the spawning season of black sea bream Acanthopagrus schlegelii in Hiroshima Bay,Japan, from temporal variation in egg density

Fisheries Science - We aimed to determine the spawning period of black sea bream Acanthopagrus schlegelii in Hiroshima Bay, Japan, based on the distribution of its eggs, to assist in the resource...     

Changes in the plasma levels of several bone markers in newborn calves during the first two days of life

The fluctuations in the plasma levels of several bone markers were investigated in newborn calves. Experiment 1 monitored the postnatal changes in the plasma levels of tartrate-resistant acid phosphatase isoform 5b (TRAP5b), total alkaline phosphatase (t-ALP) and bone-specific alkaline phosphatase (BAP) in four calves. These markers increased significantly from 9−20 hr after the first colostrum-suckling compared with the values immediately after birth. Experiment 2 evaluated changes in the plasma TRAP5b, t-ALP, BAP and type I collagen cross-linked N-telopeptide (NTx) levels within 2 days post-birth in five calves with successful passive immunization via colostrum (non-deficient group) and five others with poor colostrum intake (deficient group). The non-deficient group had significantly higher plasma levels of the four parameters around 12 hr of life compared with the deficient group. The results suggest that the increase in plasma bone markers in calves in the first day of life is related to the colostrum intake.     

Effects of dietary lipid and phosphorus levels on nitrogen and phosphorus excretion in young yellowtail Seriola quinqueradiata: A preliminary observation

ABSTRACT:   A feeding trial was conducted to investigate the effect of dietary lipid and phosphorus levels on nitrogen and phosphorus excretion of young yellowtail under on-site conditions for 4 months. Three levels of dietary lipid (200, 250 and 300 g/kg) and four levels of supplemental phosphorus (0, 2, 4 and 7 g/kg) were tested in a complete randomized design with a 3 × 4 factorial arrangement. Each net cage of 170 yellowtail were fed the experimental diets for 4 months and the fish grew from approximately 346–912 g, at water temperatures between 18 and 23°C. Dietary phosphorus levels did not cause any difference in weight gain, specific growth rate, feed conversion ratio and nitrogen retention. However, its increasing supplemental levels reduced phosphorus retention, consequently increasing its excretion, whereas nitrogen excretion remained uninfluenced. In contrast, increasing the dietary lipid level resulted in its greater deposition in the whole body of young fish leading to a reduction in nitrogen excretion. This study has shown that phosphorus levels need not necessarily be high in the diets of young yellowtail. In addition, dietary lipid can be manipulated favorably to produce environmentally suitable diets.     

Population genetic structure and variability of Pacific herring <Emphasis Type="Italic">Clupea pallasii</Emphasis> in the stocking area along the Pacific coast of northern Japan

ABSTRACT:   The genetic diversity of wild and hatchery-released Pacific herring Clupea pallasii collected from three brackish lakes and two bays in Honshu and Hokkaido, Japan was examined with five microsatellite loci. All loci showed high genetic variability with expected heterozygosities ranging from 0.815 to 0.945. Significant differences in genotypic and allelic distributions were detected among all locations except for between the two bays in Honshu Island. Pairwise population analysis based on the F _ST values showed close genetic relationships among the locations in Hokkaido Island, and the hierarchical analyses of molecular variance showed significant genetic difference between the two islands. Those results suggest the existence of subpopulations due to natal homing. In addition, stocked fish showed as much genetic diversity as the wild fish. The pairwise population analyses also showed close relationships between the hatchery fish and the wild fish in respective stocking areas, showing that no effects of stocking programs on genetic diversity of wild populations were detected.     

Abundance and composition of ammonia oxidizers in response to degradation of root cap cells of rice in soil microcosms

Purpose

Nitrification is a key process in the global nitrogen cycle, of which the first and rate-limiting step is catalyzed by ammonia monooxygenase. Root cap cells are one of substrates for microorganisms that thrive in the rhizosphere. The degradation of root cap cells brings about nitrification following ammonification of organic nitrogen derived from the root cap cells. This study was designed to gain insights into the response of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) to mineralized N from root cap cells and the composition of active bacterial and archaeal ammonia oxidizers in rice soil.

Materials and methods

Rice callus cells were used as a model for root cap cells, and unlabelled (¹²C) and ¹³C-labelled callus cells were allowed to decompose in aerobic soil microcosms. Real-time quantitative polymerase chain reaction (PCR), DNA-based stable isotope probing (SIP), and denaturing gradient gel electrophoresis (DGGE) were applied to determine the copy number of bacterial and archaeal amoA genes and the composition of active AOB and AOA.

Results and discussion

The growth of AOB was significantly stimulated by the addition of callus cells compared with the growth of AOA with a much lesser extent. AOB communities assimilated ¹³C derived from the callus cells, whereas no AOA communities grew on ¹³C-callus. Sequencing of the DGGE bands in the SIP experiments revealed that the AOB communities belonging to Nitrosospira spp. dominated microbial ammonia oxidation with rice callus amendment in soil.

Conclusions

The present study suggests that root cap cells of rice significantly stimulated the growth of AOB, and the active members dominating microbial ammonia oxidation belonged to Nitrosospira spp. in rice rhizosphere.     

Stand structure and plant species occurrence in forest edge habitat along different aged roads on Okinawa Island, southwestern Japan

We compared stand structure and plant species occurrence on the shoulders of 3-, 10- and 20-year-old roads in a subtropical evergreen broad-leaved forest to document temporal changes in edge effects of forest roads. We recorded 154 vascular species in the study plots, including 3 non-native species. We used generalized linear mixed models to analyze changes in forest structure and plant species composition in relationship to the distance from forest roads. The spatial patterns in stand structure at different distances from roads differed with road age. The large canopy openness on the edge of 3-year-old roads decreased with time after the construction. A progressive decrease in tree height on roadsides was observed after the road construction, suggesting tall trees could not withstand the dry and windy roadside environment. The edge effect on the canopy tended to be larger at higher elevation sites. The spatio-temporal pattern of species occurrence based on distance from roads differed by species. Typical pioneer species such as Schima wallichii and Eurya japonica increased along the edge, while less aggressive pioneer species and understory species decreased. As time passed after the road construction, some climax and understory species decreased at the forest edge, while other climax and understory species increased. The modeling methods proposed in this study could be applied to different roadside and edge study sites.     

The effect of soil water flow and soil properties on the motility of second-stage juveniles of the root-knot nematode (Meloidogyne incognita)

The movement of root-knot nematode Meloidogyne incognita second-stage juveniles was investigated in a column filled with two types of fillings, andisol or sand, under a saturated condition. After incubation with or without soil water flow, the changing distribution of nematodes was monitored. As a result, we observed a tendency for different movement traits of nematodes between andisol and sand. The distance of nematodes movement in sand was always greater than that in andisol in both a percolation test and non-percolation test. In the percolation test, distance of nematodes movement in sand gradually began to increase with increasing time. We attribute this result to a gradual decrease in nematodes activity with time. Nematodes were always affected by the water flow rate, but the distance of nematodes movement did not correspond to water flow volume. We also observed that mobility of nematodes in sand were always greater than that in andisol at both percolation test and non-percolation test. These results are attributed to differences in soil structure and pore distribution of andisol and sand. This study demonstrates a difference in the movement of nematodes influenced by water flow. However, this study also presents evidence that nematodes can resist soil water flow rates that are possible in actual field conditions. Moreover, mobility of nematodes changed considerably with soil structure or pore distribution. All these may contribute to a more stable positioning of nematodes around the rhizosphere of their host plants, and therefore increase the possibility of successful parasitization.     

Intraspecific phenotypic variation associated with nuclear DNA content in Lolium perenne L.

The variation in nuclear DNA content and its association with phenotypic traits were examined in 15 cultivated populations of perennial ryegrass (Lolium perenne L.), including herbage and turf populations. Nuclear DNA contents of 15 populations were measured by a flow cytometric method using DAPI (4′-6-diamidino-2-phenylindole) as a fluorochrome. DNA contents were also measured using PI (propidium iodide) for six populations that showed large differences in DAPI values to confirm the difference. There were significant differences in nuclear DNA contents among the populations for both dyes. Of the total variation in nuclear DNA content measured with DAPI, 29% was ascribed to the inter-population variation, 46% was ascribed to the intra-population variation, 24% was ascribed to the random error variation. Herbage populations tended to have larger DNA content than did turf populations. 2C DNA content was positively correlated with cell size, seed size and single leaf size, although significant correlations were mainly due to a small number of populations with large and small DNA contents. These results suggest that intraspecific variation in nuclear DNA content plays important roles in determining phenotypic differences between cultivated populations of L. perenne. This revised version was published online in August 2006 with corrections to the Cover Date.