Changes in growth,higher salinity tolerance and behavioral traits in Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis> after repeated cross-breeding

ABSTRACT:     To improve stock enhancement strategies, the influences of repeated cross-breeding on several traits were studied in hatchery-reared juveniles of the Japanese flounder. Ten families (seven caught in the wild and three from cross-bred brood fish) were produced by artificial fertilization. Ninety-four days after hatching, we investigated settlement, burying in the sand and escape behavioral traits, and then measured tolerance of high salinity and six morphological traits. Juveniles from the repeatedly cross-bred brood fish showed significantly higher growth and tolerance than those from the wild-caught brood fish. Among the behavioral traits, a significantly lower settling speed and incidence of burying in the sand were observed in the juveniles from the repeatedly cross-bred families. Heritability ( h ²) of growth traits was more than 0.2 in both origins, while that of other traits was close to zero. These results suggest that repeated cross-breeding of Japanese flounder under hatchery conditions improves growth performance and leads to the loss of certain behavioral traits that are considered essential to survival in wild environments.     

Seasonal dynamics of the pink root fungus (Setophoma terrestris) in rhizosphere soil: Effect of crop species and rotation

Setophoma terrestris, a ubiquitous inhabitant of soil, causes pink root rot in various crops. In the present study, the density of S. terrestris was estimated by quantitative real-time PCR in onion and non-onion fields of Hokkaido, the northernmost island of Japan. Three-year observations in monoculture and rotation fields demonstrated that the fungus grew significantly from the third year onwards, and declined in fields planted with poor hosts (e.g., sugar beet and soybean) that produced few or no chlamydospores of S. terrestris. Seasonal analysis revealed that the population of S. terrestris consistently increased when the tops of onions fell over in summer, which is when root activity declines. However, the soil inoculum potential estimated by a seedling bioassay showed distinct seasonal patterns, which rose from post-harvest in winter and remained high until the subsequent planting in spring. Detailed surveys on depth distribution in an onion field detected a high population of S. terrestris in the effective layer (10–30 cm deep) but not below the hardpan (40 cm), implying that the fungus is intimately associated with roots. These results indicate that the proliferation of the fungus is closely related to root senescence and that over-wintered propagules play an important role in primary infections, affecting disease severity. The present study shows that the temporal dynamics of S. terrestris depend exclusively on the activity of infecting roots and provides circumstantial evidence on the deleterious impact of monoculture on crop production.     

Epidemic progress of beet necrotic yellow vein virus: Evidence from an investigation in Japan spanning half a century

Beet necrotic yellow vein virus (BNYVV) is the causal agent of rhizomania, the most serious sugar beet disease worldwide. Since the first finding in Japan in 1969, BNYVV became widespread throughout Hokkaido in a few decades and led to the introduction of Rz1-resistant sugar beet cultivars in the 1990s. Here, we report the historical progress of the BNYVV epidemic in Hokkaido from 1969 to 2019. Previous analysis on samples from 1991 showed that BNYVV isolates were classified into three strains (named O, D, and T) based on the RNA3-encoded p25 gene. The O-type viruses were widely detected in Hokkaido, while the D- and T-type viruses were detected in limited areas. The RNA5, encoding the p26 gene, was initially contained in some D- and O-type isolates but not in any T-type isolates. Interestingly, recent sample analysis revealed that RNA5-containing T-type viruses, seemingly more virulent than the other two strains, were widely detected in Hokkaido. Additionally, a small group of virus isolates harbouring a new p25 gene (named C) was found in limited areas. These results suggest that the T-type viruses, which accompanied RNA5, have been preferentially spread from a limited area to other districts over the last few decades and that this spread might be strongly associated with the recent introduction of Rz1-resistant sugar beet cultivars. BNYVV-positive samples also contained mainly beet soil-borne virus and traces of beet virus Q, both of which are the first to be recorded in Japan.     

Chromospheric anemone jets as evidence of ubiquitous reconnection

The heating of the solar chromosphere and corona is a long-standing puzzle in solar physics. Hinode observations show the ubiquitous presence of chromospheric anemone jets outside sunspots in active regions. They are typically 3 to 7 arc seconds = 2000 to 5000 kilometers long and 0.2 to 0.4 arc second = 150 to 300 kilometers wide, and their velocity is 10 to 20 kilometers per second. These small jets have an inverted Y-shape, similar to the shape of x-ray anemone jets in the corona. These features imply that magnetic reconnection similar to that in the corona is occurring at a much smaller spatial scale throughout the chromosphere and suggest that the heating of the solar chromosphere and corona may be related to small-scale ubiquitous reconnection.     

Water in Earth's lower mantle

Secondary ion mass spectrometry measurements show that Earth's representative lower mantle minerals synthesized in a natural peridotitic composition can dissolve considerable amounts of hydrogen. Both MgSiO3-rich perovskite and magnesiowüstite contain about 0.2 weight percent (wt%) H2O, and CaSiO3-rich perovskite contains about 0.4 wt% H2O. The OH absorption bands in Mg-perovskite and magnesiowüstite were also confirmed with the use of infrared microspectroscopic measurements. Earth's lower mantle may store about five times more H2O than the oceans.     

Automated acoustic method for counting and sizing farmed fish during transfer using DIDSON

Counting and sizing large farmed fish such as tuna is often performed during their transfer from one net cage to another. Dual-frequency identification sonar (DIDSON) provides an automated fish counting and sizing tool. However, its counter and sizer are not suitable for measuring farmed fish because of net movements due to currents and subsequent frequent image breakups. This paper presents a fully automated acoustic method to count and size farmed fish during fish transfer by using DIDSON imaging. The background is subtracted from the image after being stabilized by an image phase-only correlation method. The segmentation of the fish is obtained by tracing the edges with a contour tracing method. To prevent recounting the same fish, a Kalman filter algorithm was designed and adapted to predict fish movements. Automated counting was performed by analyzing the spatiotemporal trajectory of the track. The separated fish images were searched for and body length was obtained by summing down the centerline segments from the head to the tail of the fish. The proposed system was verified using farmed yellowtail, Seriola quinqueradiata (mean total length 83.1 cm) to obtain a sizing error of mean total length within 2.4 cm.     

Successive use of different habitats during the early life stages of Pacific herring <Emphasis Type="Italic">Clupea pallasii</Emphasis> in Akkeshi waters on the east coast of Hokkaido

Distributions of eggs, larvae and juveniles of Pacific herring Clupea pallasii were surveyed in Lake Akkeshi and the connecting Akkeshi Bay on the Pacific coast of eastern Hokkaido. Eggs were found attached to seagrasses and seaweeds in the densely vegetated eastern inner lake. Larvae (7.1–34.9 mm total length) were distributed in the less densely vegetated inner lake during April and June. Juveniles (35.0–89.6 mm) were collected in the central and western parts of the lake. The sites containing juveniles were less densely vegetated with water temperatures lower than 20 °C from June to August. When the water temperature of the entire lake rose to 20 °C in late summer, juveniles appeared to move from the lake to the bottom layer of Akkeshi Bay, which has lower temperatures. Thus, in Akkeshi waters, C. pallasii successively used different habitats during its egg, larval and juvenile stages. A comparison of the current limited distribution of eggs and larvae with the distribution over the entire lake and bay areas in the 1950s and 1960s (periods of large catch size) indicates that the spawning grounds and larval habitats of C. pallasii have contracted to the lake area due to low spawning stock biomass in recent years.     

Expression and localization of tight junction-related proteins in adult rat pituitary stem/progenitor cell niches

Pituitary endocrine cells are supplied by Sox2-expressing stem/progenitor cells in the anterior lobe of the adult pituitary gland. These SOX2-positive cells are maintained in two types of microenvironments (niches): the marginal cell layer (MCL)-niche and the parenchymal-niche. Recently, we isolated dense SOX2-positive cell clusters from the parenchymal-niche by taking advantage of their resistance to protease treatment as parenchymal stem/progenitor cell (PS)-clusters. In the present study, by analyzing these isolated PS-clusters, we attempted to identify novel structural characteristics of pituitary stem/progenitor cell niches. Quantitative real-time PCR showed that tight junction-related genes were distinctly expressed in the isolated PS-clusters. Immunocytostaining showed that the tight junction molecules, ZO-1 and occludin, were localized in the apical membrane facing the pseudo-follicle-like structure of the isolated PS-clusters regardless of the expression of S100β, which distinguishes the sub-population of SOX2-positive cells. Furthermore, immunohistochemistry of the pituitary glands of adult rats clearly demonstrated that ZO-1 and occludin were densely present in the parenchymal-niche encircling the pseudo-follicle, while they were observed in the apical membrane in the MCL-niche facing the residual lumen. Collectively, these tight junction-related proteins might be involved in the architecture and maintenance of the plasticity of pituitary stem/progenitor cell niches.     

Establishment of a reverse genetics system for rabies virus strain Komatsugawa

The rabies virus strain Komatsugawa isolated from a dog in Tokyo in the 1940s retains biological properties as a field strain, providing an effective model for studying rabies pathogenesis. To facilitate molecular studies on the pathogenesis, this study aimed to establish a reverse genetics system for the Komatsugawa strain. By transfecting the full-length genome plasmid of this strain, infectious virus with artificially introduced genetic markers in its genome was rescued. The recombinant strain had biological properties similar to those of the original strain. These findings indicate that a reverse genetics system for the Komatsugawa strain has successfully been established.