Effects of silvering state on induced maturation and spawning in wild female Japanese eel <Emphasis Type="Italic">Anguilla japonica</Emphasis>

ABSTRACT:   The effects of silvering state of wild female Japanese eels Anguilla japonica on the success of induced maturation and the following spawning were examined. Thirty-eight females, collected in Mikawa Bay, were divided into four stages based on their silvering state: yellow (Y1), late-yellow (Y2), silver (S1) and late silver eels (S2). Despite injections of salmon pituitary extract (SPE) through the standard technique, Y1 and Y2 eels did not respond to the treatment with undeveloped gonad (gonad-somatic index [GSI]: 0.3–0.9), and all these females died by 5 weeks, probably due to an abnormal physiological condition. Most S1 (81%) and S2 eels (100%) matured completely (GSI: 17.8–51.4), and finally spawned successfully (69% for S1, 89% for S2). S2 eels fully matured with oocytes of over 750 μm in diameter by significantly smaller number of injections of SPE (5–6 times) than the case of S1 eels (6–8 times). The amount of eggs released by S2 eels (0.65 ± 0.11 g/fish per body weight [BW]) was significantly larger than those by S1 eels (0.54 ± 0.09 g/fish per BW). There was no difference in fertilization and hatching rates between eggs released by S1 eels and those of S2 eels. These results indicate that the success of induced maturation and spawning in wild female Japanese eels depends on their silvering state, and matured eggs can be obtained efficiently through the use of S2 eels rather than other stages.     

Reproductive season and female maturity size of coconut crab <Emphasis Type="Italic">Birgus latro</Emphasis> on Hatoma Island,southern Japan

Information about reproductive season, size at sexual maturity and size-dependent reproductive potentials is important for efficient resource management. Such information is necessary to determine seasonal closures and minimum legal size limits. To conserve resources of coconut crab Birgus latro, which are in danger of extinction due to excessive exploitation, their reproductive season, female size at functional maturity and relationship between female size and reproductive potentials were investigated. The reproductive season started in early June and ended late August, and females with higher reproductive potentials showed a tendency to spawn early in the reproductive season. The prohibition of exploiting the resources during the reproductive season, especially early in the season, would be appropriate for sustainability of high reproductive outputs. Fifty percent of investigated females matured functionally at 24.5-mm thoracic length (TL). However, the size at which all females reached functional maturity was 32.3 mm TL, and there was a wide variation in the size of functional maturity among individuals. We must determine minimum legal size by taking the variation into account to allow all individuals to mate at least once before they are caught, which may prevent serious depression in reproductive rate and genetic diversity.     

Recreational fishery as a conservation tool for endemic Dolly Varden <Emphasis Type="Italic">Salvelinus malma miyabei</Emphasis> in Lake Shikaribetsu,Japan

Recreational angling is a popular leisure activity globally and can be a threat or useful conservation tool depending on the management strategy. Miyabe charr Salvelinus malma miyabei is an endemic fish that inhabits Lake Shikaribetsu, and a management program was established to harmonise recreational fishery and conservation. To examine the suitability of this program, population assessment was conducted with the cooperation of anglers. The population size in 2014 as assessed by tag-and-release angling was estimated to be 105,300 [95% confidence interval (CI) 37,300–178,600], much higher than the reported estimate in 1995. Further, angling mortality was estimated to be quite low. Moreover, no decreasing population trend was detected on analysing 8 years of anglers’ catch data. Consequently, angling has facilitated stock assessments of Miyabe charr under the current program. This case is a good example of recreational angling acting as a conservation tool under appropriate management.     

Long-term case study of myelodysplastic syndrome in a dog

A 10-year-old, female shih tzu was diagnosed as having myelodysplastic syndrome (MDS) based on the presence of a nonregenerative anemia, dysplastic changes in the three hematopoietic cell lines, a normal to hypercellular bone marrow, and less than 30% blast cells of all nucleated cells in the bone marrow. Low-dose aclarubicin, a differentiation-induction therapy for MDS and atypical leukemias in humans, was administered. Hematological improvement was observed, and the dog lived for 809 days after the first presentation.     

Entomosporium leaf spot of Pomoideae (Rosaceae) in Japan. III. Additional basis for identification of the fungus,and distribution of the disease

Treatment by Sivanesan and Gibson (1976), that combined all species of Entomosporium into one species E. mespili (DC. ex Duby) Sacc, was supported through the investigation of many exsiccati and fresh specimens.Morphologically, all specimens and isolates of Entomosporium, which had been differentiated into 4 species, could not be divided into clearly separated groups.The fungus has been recorded on 50 host species and the disease is widespread throughout the world.     

EMG telemetry studies on upstream migration of chum salmon in the Toyohira river,Hokkaido, Japan

The movements of 28 adult chum salmon, Oncorhynchus keta (Walbaum) tagged with electromyogram (EMG) transmitters were tracked along the Toyohira river, Hokkaido, Japan, in October of 2007 and 2008 to investigate and evaluate the upstream migratory behavior through the protection bed and fishway of ground sills. The approach time of fish that ascended successfully through the protection bed and fishway was shorter than that of unsuccessful fish. The unsuccessful fish were observed to swim in currents with high water velocity and shallow water depth at swimming speeds that exceeded their critical swimming speed (U _crit) during the approach to these structures. In consequence, unsuccessful fish frequently alternated between burst and maximum sustained speeds without ever ascending the fishway, and eventually became exhausted. It is important that fishway are constructed to enable chum salmon to find a passage way easily, so that they can migrate upstream rapidly without wasting excessive energy.     

Predicting the rate of range expansion of an invasive alien bumblebee (Bombus terrestris) using a stochastic spatio-temporal model

To develop effective strategies for managing biological invasions, it is important to understand and be able to predict patterns of invasion and range expansion, and particularly the rate of spread and factors controlling this rate. To predict the spatial dynamics of invasion by an alien bumblebee (Bombus terrestris) in Hokkaido, Japan, we explicitly constructed a stochastic spatio-temporal model that incorporates immigration and establishment processes. Using a Bayesian approach, we parameterized the model based on spatio-temporal presence/absence data collected by citizen volunteers and used the model to predict control of the near-future spread of the bumblebee under several management strategies. The range expansion dynamics of B. terrestris were significantly negatively affected by two aspects of environmental heterogeneity: the land-use pattern (the proportion of woodland) and climate (the snow depth). Of the several spatial management strategies, suppressing the outlying (edge) colonies would be the most efficient strategy to reduce the bumblebee’s spread, irrespective of the level of effort, and would significantly slow the bumblebee’s range expansion during the next 30 years. The modeling approach employed in the present study will be broadly useful for studying real-world biological invasion problems, for which prediction of the progress of an invasion, even in the very near future, is urgently needed to support effective spatial management options and countermeasures. In addition, the model demonstrates that incorporating the dynamics of environmental heterogeneity is a fundamental requirement for prediction and risk assessment during biological invasions, especially in the context of recent rapid changes in the environment at regional and global scales.     

Quantum criticality without tuning in the mixed valence compound beta-YbAlB4

Fermi liquid theory, the standard theory of metals, has been challenged by a number of observations of anomalous metallic behavior found in the vicinity of a quantum phase transition. The breakdown of the Fermi liquid is accomplished by fine-tuning the material to a quantum critical point by using a control parameter such as the magnetic field, pressure, or chemical composition. Our high-precision magnetization measurements of the ultrapure f-electron-based superconductor β-YbAlB(4) demonstrate a scaling of its free energy that is indicative of zero-field quantum criticality without tuning in a metal. The breakdown of Fermi liquid behavior takes place in a mixed-valence state, which is in sharp contrast with other known examples of quantum critical f-electron systems that are magnetic Kondo lattice systems with integral valence.     

Comparison of Ni/Zn Accumulation Ability of Thlaspi japonicum from Three Different Areas in Hokkaido

Thlaspi japonicum is a Japanese Ni-hyperaccumulator plant growing in areas with serpentine soil containing a high level of Ni. In the present study, we investigated the ability of wild Thlaspi japonicum plants inhabiting non-ultramafic soil areas of Hokkaido to accumulate Ni/Zn. Wild T. japonicum plants growing on Rebun Island (Rebun-T) accumulated small amounts of Ni, while the plants cultivated on ultramafic rock soil accumulated large amounts of Ni, like T. japonicum growing on Mt. Yubari (Yubari-T), and this change was also observed for T. japonicum growing on Mt. Tengu (Tengu-T). All the T. japonicum plants transplanted on both ultramaflc soil or Andosol accumulated over 100 mg kg⁻¹ Zn, especially the Ni/Zn content of Tengu-T plants tended to be higher than that of the plants growing in the other two areas. In contrast, transplanting of Yubari-T plants from ultramafic soil with a high level of Ni to soil with a lower-Ni content decrease of the Ni concentration in the leaves. Wild Rebun-T plants showed a smaller biomass than the Yubari-T and Tengu-T plants, and some individuals of the Rebun-T population were smaller than those of the other populations, with tiny radical leaves. Zinc content of the small leaves was not significantly different from that in large leaves. These results suggested that T. japonicum plants are able to accumulate high Ni/Zn accumulation, regardless ecotype, habitat and leaf size.