Late winter larval mesopelagic fish assemblage in the Kuroshio waters of the western North Pacific

The larval mesopelagic fish assemblage and its distribution patterns were investigated in the Kuroshio region off southern Japan in late winter. A total of 8690 fish larvae was collected, 85.8% of which were mesopelagic fish larvae. Mesopelagic fish larvae were significantly more abundant in the area east of the Kuroshio axis than west of the Kuroshio axis (660.6 versus 194.5 ind 10 m^?2). Sigmops gracile, Bathylagus ochotensis, Notoscopelus japonicus, Diaphus slender type and Myctophum asperum were the five most abundant larvae and accounted for 16.9, 16.4, 15.2, 13.9 and 9.3% of the total catch in numbers, respectively. We conclude that these larvae were transported by the Kuroshio Current to the more productive transition waters, where they spend their juvenile stage from spring to early summer. The possibility of expatriation and southward long‐distance spawning migrations of N. japonicus and B. ochotensis are discussed, based on the geographic distribution patterns of their larvae, juveniles and adults.     

An atypical bHLH protein encoded by POSITIVE REGULATOR OF GRAIN LENGTH 2 is involved in controlling grain length and weight of rice through interaction with a typical bHLH protein APG

Grain size is an important yield component in rice, however, genes controlling the trait remain poorly understood. Previously, we have shown that an antagonistic pair of basic helix-loop-helix (bHLH) proteins, POSITIVE REGULATOR OF GRAIN LENGTH 1 (PGL1) and ANTAGONIST OF PGL1 (APG), is involved in controlling rice grain length. Here, we report the involvement of another atypical bHLH protein gene, POSITIVE REGULATOR OF GRAIN LENGTH 2 (PGL2), in the regulation of rice grain length. Over-expression of PGL2 in the lemma/palea increased grain length and weight in correlation with the level of transgene expression. Observation of the inner epidermal cells of lemma of PGL2-overexpressing lines revealed that the long grain size is caused by an increase in cell length. PGL2 interacts with a typical bHLH protein APG, a negative regulator of rice grain length and weight, in vitro and in vivo. It was reported that overexpression of BU1 (BRASSINOSTEROID UPREGULATED 1), the closest homolog of PGL2, caused an increase in grain length. However, we detected no interaction between BU1 and APG. These findings suggest that PGL2 and PGL1 redundantly suppress the function of APG by forming heterodimers to positively regulate the rice grain length, while the pathway through which BU1, the closest homolog of PGL2, controls grain length is independent of APG.     

Multiple cohorts of juvenile jack mackerel Trachurus japonicus in waters along the Tsushima Warm Current

The jack mackerel, Trachurus japonicus, has a prolonged spawning season and widely spread spawning grounds. The population in the coastal waters of Japan seems to be composed of several cohorts spawned seasonally from different waters. To understand its population structure along the Tsushima Warm Current, we analysed hatchdates and growth histories of fish from Kunda Bay, the southern, central and northern East China Sea (ECS), the southern Sea of Japan, and Maizuru Bay. Seven cohorts were detected from fish collected between June 2005 and June 2006 in Kunda Bay. Comparing hatchdate distributions and growth trajectories of the seven cohorts with those of the other five regional samples, we did not find that cohorts collected in Kunda Bay originated in the southern ECS. Therefore, these coastal waters of Japan appear to be significant spawning grounds for juvenile jack mackerel.     

Transport and survival processes of eggs and larvae of jack mackerel <Emphasis Type="Italic">Trachurus japonicus</Emphasis> in the East China Sea

ABSTRACT:   Recent surveys showed substantial aggregation of larvae of jack mackerel in the southern East China Sea, indicating intensive spawning grounds near Taiwan. A numerical model was applied to investigate transport and survival processes of eggs and larvae of jack mackerel from the spawning area to the nurseries. The results show that: (i) the distributions of larvae simulated by the model agreed well with those obtained by field survey; (ii) the stock of jack mackerel in the Sea of Japan is composed of both groups from north of Taiwan and from the western coast of Kyushu. It takes more than two months for the former to reach the Sea of Japan, while it is within 40 days for the latter; and (iii) large proportions of the eggs and larvae spawned off the north of Taiwan are transported rapidly to the Pacific side of Kyushu by the Kuroshio Current, and the rest slowly to the east or north-east along the continental slope in the East China Sea. In contrast to the larval flux, survivors are more abundant in the northern East China Sea than in the Pacific Ocean, indicating that survival in the northern East China Sea would determine the jack mackerel stock in Japan.     

Correlation between cytochrome P450 1A (cyp1a) mRNA expression and ambient phenanthrene and pyrene concentration in Javanese Medaka Oryzias javanicus

Fisheries Science - Cytochrome P450 1A (Cyp1a) catabolizes polycyclic organic compounds. In this study, we sequenced the cyp1a gene from two Javanese medaka&nbsp;Oryzias...     

Molecular mechanism of the S-RNase-based gametophytic self-incompatibility in fruit trees of Rosaceae

Self-incompatibility (SI) is a major obstacle for stable fruit production in fruit trees of Rosaceae. SI of Rosaceae is controlled by the S locus on which at least two genes, pistil S and pollen S, are located. The product of the pistil S gene is a polymorphic and extracellular ribonuclease, called S-RNase, while that of the pollen S gene is a protein containing the F-box motif, SFB (S haplotype-specific F-box protein)/SFBB (S locus F-box brothers). Recent studies suggested that SI of Rosaceae includes two different systems, i.e., Prunus of tribe Amygdaleae exhibits a self-recognition system in which its SFB recognizes self-S-RNase, while tribe Pyreae (Pyrus and Malus) shows a non-self-recognition system in which many SFBB proteins are involved in SI, each recognizing subset of non-self-S-RNases. Further biochemical and biological characterization of the S locus genes, as well as other genes required for SI not located at the S locus, will help our understanding of the molecular mechanisms, origin, and evolution of SI of Rosaceae, and may provide the basis for breeding of self-compatible fruit tree cultivars.     

Neutralizing antibodies against feline parvoviruses in nondomestic felids inoculated with commercial inactivated polyvalent vaccines

The virus neutralization (VN) antibody titers of serum samples from 18 individuals representing 8 carnivore species vaccinated with commercial polyvalent vaccines optimized for domestic cats containing inactivated feline panleukopenia virus (FPLV) were evaluated against canine parvovirus type 2 (CPV2). In addition, the titers among 5 individuals from 4 carnivore were evaluated against antigenic variants of feline parvoviruses; FPLV, CPV2, CPV2a, CPV2b, CPV2c, mink enteritis virus type 1 (MEV1) and MEV2. The polyvalent vaccines induced cross-reactive VN titers against antigenic variants of feline parvoviruses in nondomestic felids. However, we observed very low cross-reactive VN antibody in lions and Siberian tigers, therefore we should pay attention to CPV infections in these animals even if they were vaccinated with inactivated FPLV vaccines.     

Horizontal and vertical distribution patterns of larval myctophid fishes in the Kuroshio Current region

The horizontal and vertical distribution of myctophid fish larvae is described based on discrete depth sampling from the surface down to 200 m at seven stations on a transect crossing the Kuroshio Current on 6–9 July 1977. A total of 7819 larvae was collected. Myctophid larvae accounted for 72% of the total fish larvae and included 18 species or types belonging to 12 genera. Based on horizontal distribution patterns these species (or types) were categorized into three groups, i.e. Kuroshio-axis group ( Myctophum asperum , M. orientale , Lampadena luminosa and Symbolophorus evermanni ), Kuroshio east group ( Hygophum reinhardtii , Lampanyctus alatus , Diogenichthys atlanticus , Lobianchia gemellarii , M. nitidulum , Benthosema suborbitale , Lampadena sp. and Ceratoscopelus warmingii ) and Pan- Kuroshio group [ Diaphus stubby type (mostly D. garmani ) and D. kuroshio ]. Larvae of the subfamily Lampanyctinae were distributed in shallower (0–30 m) waters than those of the subfamily Myctophinae (50–150 m), while this relationship was opposite of the night-time depth distribution of adults of the two subfamilies.     

Linking environmental drivers,juvenile growth,and recruitment for Japanese jack mackerel Trachurus japonicus in the Sea of Japan

Growth traits of juvenile Japanese jack mackerel (Trachurus japonicus) were estimated based on otolith daily increments in spring during 2011–2016 in the southwestern part of the Sea of Japan (SWSJ). Spatial variability in growth traits was examined between the western and eastern areas of the study area. Back-calculated body length at 50 days post hatch varied among areas and years between 26 and 40 mm. Body lengths at age in the eastern area were significantly smaller than those in the western area. Slower growth rate in the eastern area was associated with the lower ambient temperature in the eastern area than in the western area. In the eastern area, interannual variations in the instantaneous growth rate positively correlated with ambient temperature. Furthermore, interannual variations in back-calculated body length during the late larval and early juvenile stages positively correlated with the juvenile abundance. These results suggest that the thermal conditions in the eastern area are indicative of the growth rate and abundance of juvenile T. japonicus in SWSJ. We further examined relationships between juvenile abundance and thermal conditions during 2003–2019 using archived data of this survey and found that the ambient temperature in the eastern area positively correlated with the juvenile abundance and also the strength of the Tsushima Warm Current. Thus, higher temperatures derived from the Tsushima Warm Current result in a faster growth rate during the late larval and early juvenile stages and subsequently higher abundance of T. japonicus juveniles in SWSJ.     

Biomass fluctuation of two dominant lanternfish <Emphasis Type="Italic">Diaphus</Emphasis><Emphasis Type="Italic">garmani</Emphasis> and <Emphasis Type="Italic">D. chrysorhynchus</Emphasis> with environmental changes in the East China Sea

Acoustic surveys have been conducted for estimating the biomass of commercially important fish (e.g., anchovy, jack mackerel), lanternfish (Diaphus garmani and D. chrysorhynchus), and pearlside (Maurolicus japonicus) in summer in the East China Sea (ECS) since 1997. The biomass of lanternfish and pearlside was 2.26–19.16 times that of commercially important fish, and these species represented substantial biomass in the ECS. Though there were no correlations between biomass of pearlside and environmental indices, significant correlations between biomass of lanternfish and southern oscillation index (SOI) in March (positive correlation), arctic oscillation (AO) in March (negative) and October (positive), monsoon index (MOI) in February (positive), and Kuroshio flow mass in winter (positive) were observed. Weak AO and strong MOI would cool down the sea temperature and would lead to increased primary and secondary production in the ECS, thereby enhancing larval survival of lanternfish. The SOI would affect the Kuroshio meander in the ECS, and strong SOI and Kuroshio flow mass would transport larvae of lanternfish to the present survey area. This is the first report on the lanternfish standing stock and its fluctuation in the ECS.