Five species of the family Cyproideidae (Crustacea: Amphipoda) from Japan, with the description of a new genus and two new species.

Shizuoka Prefecture, in the ancient Tokaido of the Goki-Shichido, is made up of the formerly named Tootoumi, Suruga, and Izu provinces. According to the 2020 national census, the population of Shizuoka prefecture was 3,633,202, a decrease of 67,103 (−1.8%) from the previous national census in 2015. It is the 10th largest, accounting for 2.9% of the total population of Japan (126,146,099). The prefecture is divided into four regions (Seibu, Chubu, Tobu, and Kamo), and comprises 35 municipalities today. Looking at the projected population increase rate from 2015 to 2045 by prefecture level, Shizuoka Prefecture is about the middle of the total 47 prefectures (−20.5% against the national average of −16.3%). However, when we analyzed it by municipality, we find a wide range of variations within the prefecture (from the highest of Nagaizumi-cho of Tobu region: −3.0%, to the lowest of Nishi Izu-cho of Kamo region: −65.4%). The municipal power indicators for each of these regions do not seem to differ from one another in any significant manner. However, the progress of shrinking Japan seems to be accelerating in the Kamo region much faster than other regions in the prefecture (−51.7% against the prefectural average of −20.5%). It is striking that for the projected population increase rates by municipality of Shizuoka Prefecture the six municipalities of the Kamo region that are all clustered around the bottom layers on the indicator, hold similar positions on the marriage power index. In fact, the marriage power (X) on the population sustaining power (Y) for 35 municipalities in Shizuoka Prefecture in 2013 is significant at 0.001 level (Y = −3.449 + 0.578X, variance explained R2 = 0.558, p = 0.000). The marriage power in 2015 of Nagaizumi-cho (5.99‰) and of Nishi Izu-cho (2.869‰) likely indicate their projected population increase rate for 2045. Thus, we can say that the theoretical hypothesis of the Goki-Shichido and regional variations is also validated for Shizuoka Prefecture. During the coronavirus pandemic, municipalities in Shizuoka Prefecture seemed to attract outmigrants from the metropolitan Tokyo area, most likely due to changes in the work style, availability of highly developed transportation facilities, and people’s preference for living in the countryside. For detailed analyses of the municipal power, we selected three municipalities: Nishi Izu-cho, a community with a shrinking population, Yoshida-cho whose population increase rate is about the average of all 35 municipalities in Shizuoka Prefecture, and Nagaizumi-cho, that represents a municipality in which the population is increasing. With the development of the Pharma Valley Nagaizumi Industrial Park, the population of Nagaizumi-cho continues to grow to 43,488 by 2020. Nagaizumi-cho provides various acclaimed child-rearing support programs, and the town has come to be known as a child friendly municipality where it is easy to give birth and raise children.

A nationwide survey of ixodid tick species recovered from domestic dogs and cats in Japan in 2011

Detection of a novel tick-borne flavivirus and its serological surveillance

Diamond squid Thysanoteuthis rhombus (Troschel, 1857), which can grow to a dorsal mantle length of ~100 cm in 1 year, is an important fisheries resource in subtropical and temperate waters worldwide. Around Japan, it is an important resource in the East China Sea, Sea of Japan, and western North Pacific Subtropical Gyre, including the Kuroshio area. It is not known if linkages occur between these habitats. To clarify the species distribution, we estimated the habitat of young squid using a generalized additive model based on trawl surveys and analyzed carbon and nitrogen stable isotope ratios (δ13C and δ15N) in tissue samples. Based on trawl observations, young squid were distributed around northeastern Taiwan and the Okinawa Islands in June–July and in the Sea of Japan and the Kuroshio extension areas in August–September. We observed ontogenetic changes in the stable isotope ratios. The δ15N values in large diamond squid (dorsal mantle length > 400 mm) were significantly lower in the Pacific than those in other areas. Considering that the δ15N of forage fish is low in the Pacific and high in the East China Sea and Sea of Japan, large diamond squid in the northwest Pacific presumably have two distinct habitats.

Ikedosoma elegans (Ikeda, 1904) (Annelida: Echiura: Thalassematidae) is a rare, large deep-burrowing spoon worm that has been observed only in Japan. This species was first described based on the specimens collected from Misaki, Sagami Bay (Kanagawa Prefecture), eastern Japan, in 1902. Since the first description, this species has not been collected until the recent studies, which reported that I. elegans was collected from Hamana Lake (Shizuoka Prefecture), Boso Peninsula (Chiba Prefecture), and probably Amakusa, Ariake Sea (Kumamoto Prefecture). Furthermore, the specimen collected from Takasu, Seto Inland Sea (Okayama Prefecture) in 1975 was identified to be I. elegans. In this study, we present a new locality of this species in Japan. We collected a large individual of I. elegans with a probably commensal scale worm (Polynoidae: Polynoinae) by using a yabby pump in a mud flat in the Doki River Estuary, which is facing the Seto Inland Sea, in Marugame (Kagawa Prefecture), northern Shikoku Island. To the best of our knowledge, the present study is the first record of I. elegans from Shikoku Island and the second record from the Seto Inland Sea, following a 42-year-old record from Takasu, Okayama.

Species-specific nested polymerase chain reaction (PCR) was used to detect the presence of possible canine ehrlichial agents (Ehrlichia canis, E. chaffeensis, E. ewingii, E. equi and E. platys) and monocytic ehrlichial agents found in Japan (E. muris and a recently discovered Ehrlichia species detected from Ixodes ovatus) in blood samples from dogs in Yamaguchi and Okinawa Prefecture, Japan. Partial sequence of E. platys was detected from 1 of 67 dogs (1.5%) tested from Yamaguchi Prefecture and 24 out of 87 (27.6%) in the subtropical Okinawa Prefecture. Dogs in Okinawa and Miyako Islands had a higher positive rate (69.2 and 45.0%, respectively) than Ishigaki Island (11.1%). Another dog in Yamaguchi Prefecture had a positive PCR reaction to the Ehrlichia sp. detected from I. ovatus. No other Ehrlichia were found in these samples.

Growth and photosynthesis temperature characteristics of the sterile Ulva pertusa (sterile type) were studied and compared with the wild U. pertusa (wild type) collected from the low water mark at Tana in Yamaguchi Prefecture and at Shimoda in Shizuoka Prefecture. The sterile type and the wild type at the Tana site in summer were cultured at 10, 15, 20, 25, 30, and 35°C. The sterile type grew faster than the wild type from 20 to 30°C. Photosynthesis temperature relationships of both types were measured with two seasons. The photosynthetic rate, measured from 5 to 35°C every 5 using the same fronds, was higher in the sterile type than in the wild type at the Tana site in autumn over 25°C. The relative photosynthetic rate, expressed as values relative to that at 20°C, was also higher in the sterile type than in the wild type both at the Tana site and at the Shimoda site in summer over 25°C, while the respiratory rate from 10 to 35°C was lower in the sterile type than in the wild type at the Shimoda site in summer. These results indicate that the rapid growth of the sterile type from 20 to 30°Cis mainly caused by a high photosynthetic rate and a low respiratory rate.

Polycyclic aromatic hydrocarbons (PAHs), originating mainly from the incomplete combustion of fossil fuels and biomass and the leakage of petroleum products, are hazardous pollutants with adverse carcinogenic and mutagenic potential for marine organisms. The Yangtze River estuarine–inner-shelf area in the East China Sea is one of the largest reservoirs of PAHs and connected with the semi-enclosed Sea of Japan through the shallow, narrow Tsushima Strait. The main sources of PAHs in the Sea of Japan are the East Asian landmass and East China Sea, with the major PAH transport pathways being atmospheric transport of the westerly and northwesterly winter monsoon and marine transport in the Tsushima Warm Current. Investigation of the environmental behavior of PAHs in the Sea of Japan is critical in assessing the ecological risks of PAHs, as the sea is among the most fertile fishing grounds, however, the contributions of surface PAHs transported via atmosphere and ocean current are unclear. This study aimed to elucidate variation factor of dissolved PAHs in the surface Sea of Japan during 2017–2022, and analyzed 1) surface PAH distribution, 2) PAH source, 3) air-sea PAH exchange flux, and 4) ocean current driven PAHs flux through the Tsushima Strait. Surface seawater samples of 10–15 L were collected at 148 sites in the Sea of Japan, and its adjacent seas including the Tsushima Strait and Kuroshio Current area (Sesoko, Okinawa Island) from 2017 to 2022. Particulate and dissolved phases were separated by filtration through 0.5 µm glass fiber filter (GFF), and the latter was concentrated in C18 disks. Particulate and dissolved PAHs were respectively extracted from the GFF and C18 disks with dichloromethane and measured by HPLC system with fluorescence detector. Total concentrations of the 14 dissolved PAHs (Σ14PAHdiss) in the central Sea of Japan were in range 0.26–5.87 ng L−1, with the mean of 3.26±0.36 ng L−1 in 2017, 3.70±1.44 ng L−1 in 2019, 0.51±0.10 ng L−1 in 2020, 1.29±0.53 ng L−1 in 2021, and 0.69±0.35 ng L−1 in 2022. In 2020, although atmospheric PAH deposition flux were increased to 4.0 ton month−1 from 2019 (3.4 ton month −1) at the Sea of Japan, mean Σ14PAHdiss in the surface seawater were parallelly decreased to 0.51 ng L−1 at the central Sea of Japan, 0.86 ng L−1 at the Tsushima Strait, and 0.46 ng L−1 at the Kuroshio Current area. The contribution of PAH-rich and low salinity continental shelf water from the East China Sea in the Tsushima Strait was decreased to 36% in 2020 from 58% in 2019 on the basis of salinity mass-balance and ocean current simulation. Moreover, PAHs inflow flux through the Tsushima Strait were in range 2.2–8.8 ton month−1, and decreased to 2.2 ton month−1 in 2020. Thus, the decrease in surface Σ14PAHdiss levels at the central Sea of Japan in 2020 was mainly caused by the decrease in PAHs flux via the Tsushima Warm Current, which flow into the Sea of Japan from the East China Sea.

Eutrophication in coastal and freshwater environments has led to increasingly frequent and intense algal blooms, posing serious threats to ecosystem health, water quality, and human activities. This study investigates the potential of fluorescence quantum yield (φ) as a dynamic indicator of phytoplankton photosynthetic activity, utilizing satellite observations from the Geostationary Ocean Color Imager (GOCI) and field measurements in Lake Taihu-a eutrophic, hydrodynamically stable lake. Under natural conditions, diurnal variations in φ revealed that phytoplankton dissipates excess energy via non-photochemical quenching (NPQ) at midday light saturation, resulting in reduced φ. These patterns closely reflected photosynthetic dynamics. Building on this foundation, the study analyzed φ dynamics during bloom events in the East China Sea, Ariake Sea, and Sea of Japan. The results demonstrated distinct diurnal patterns related to species composition and local environmental conditions. For example, φ peaked around midday during a dinoflagellate bloom in the East China Sea, while it decreased under intense solar radiation during diatom blooms in the Ariake Sea-highlighting the species-specific photoacclimation strategies. Additionally, a temporal analysis of Chl-a and φ in bloom-affected, nearshore, and offshore waters showed that increases in φ generally preceded Chl-a accumulation, indicating φ's sensitivity as an early warning signal of phytoplankton growth. These findings enhance our understanding of algal bloom dynamics and support the use of φ as a complementary tool for satellite-based bloom monitoring and ecological assessments.

Diplocirrus Haase, 1915, includes flabelligerids having cylindrical to club-shaped bodies, with cirriform papillae, multiarticulate chaetae in both parapodial rami, 8 branchial filaments of two types (thick and rarely lamellate, or cirriform), gonopodial lobes in chaetigers 5 or 6, or multiple gonopores along some anterior chaetigers. Bradiella Rullier, 1965, has included only the type species: Bradiella branchiata Rullier, 1965, described from Eastern Australia. The original description has been overlooked and it lacked enough details on branchial and chaetal features. Diversibranchius Buzhinskaja, 1993, with Diplocirrus nicolaji Buzhinskaja, 1994, as the type species, was introduced for a similar species from the Japan Sea. These two monotypic genera share the same morphologic features with Diplocirrus, and are herein regarded as its junior synonyms. As herein redefined, Diplocirrus includes, besides its type species, Diplocirrus glaucus (Malmgren, 1867)from Scandinavia : Diplocirrus branchiatus (Rullier, 1965), comb. n. from Queensland, Australia, Diplocirrus capensis Day, 1961 from South Africa, Diplocirrus erythroporus Gallardo, 1968 from Vietnam, Diplocirrus hirsutus (Hansen, 1882) from Arctic and subarctic regions, Diplocirrus incognitus Darbyshire & Mackie, 2009 from South Africa, Diplocirrus kudenovi sp. n. from off Western Mexico, Diplocirrus longisetosus (von Marenzeller, 1890) restricted to the Bering Sea, Diplocirrus micans Fauchald, 1972 from deep water off Oregon and Western Mexico, Diplocirrus nicolaji (Buzhinskaja, 1994), comb. n. from the Japan Sea, Diplocirrus normani (McIntosh, 1908), comb. n. from Scandinavia, Diplocirrus octobranchus (Hartman, 1965), comb. n. from off New England, and Diplocirrus stopbowitzi Darbyshire & Mackie, 2009 from the Irish Sea.

The Maera-clade is a group of maerid amphipod genera which has neither a falcate mandibular palp nor medially setose inner plates of maxillae 1 and 2. Two species of Maeropsis Chevreux, 1919 and four species of Orientomaera gen. nov. included in the clade, are described from Japan. Maeropsis okinawensis sp. nov. is described, based on collections from Okinawa Prefecture. It resembles M. cobia Krapp-Schickel, 2009, M. paphavasitae Wongkamhaeng, Coleman Pholpunthin, 2013, and M. serratipalma (Nagata, 1965). This new species differs from the latter three species in the long uropod 3. Maeropsis serratipalma is redescribed and newly recorded from Kanagawa, Osaka and Wakayama Prefectures. The new genus, Orientomaera, is described and is characterized by the mandibular palp article 1 without a distal tooth and the oblique palm of the gnathopod 2 with many robust setae. Orientomaera comprises four species: O. brevispina (Kim Kim, 1991) comb. nov. from Iwate, Fukui, Kyoto and Wakayama Prefectures and Ariake Sea; O. decipiens sp. nov. from Osaka and Wakayama Prefectures; O. obliquua sp. nov. from Osaka and Wakayama Prefectures; O. rotundicoxa sp. nov. from Kanagawa and Wakayama Prefectures. These species can be distinguished from one another by the coxa 1, the gnathopod 2 propodus, the pereopod 6 basis and the telson. Keys to species of Maeropsis and Orientomaera in the world are provided.

Gauge-based hourly precipitation data during the 2015-2016 warm seasons in central Japan observed with the Japan Meteorological Agency AMeDAS network and the Japanese Alps Inter-University Cooperation Project (JALPS) mountain observation network are archived. Gauge data are compared to satellite precipitation data (GSMaP_MVK and GPM/DPR) produced by Japan Aerospace Exploration Agency. The distributions of precipitation measured in gauges depend on synoptic scale disturbances showing areas of regional increases/decreases affected by large mountain ranges without year-to-year variability, except for a composite of typhoon cases. Differences in precipitation amounts are less than 2 mm/d depending on satellite product version or timing of passive microwave observations. Larger precipitation amounts of GSMaP_MVK estimated at more than 2 mm/d are distributed over inner mountain areas and northern coastal areas along the Sea of Japan, and larger amounts of gauge-measured precipitation are distributed in central Gifu and Shizuoka Prefectures. The underestimate of local sporadic heavy precipitation in mountainous areas obtained from GSMaP_MVK data was expected depending on shallow convections. Further strategies are discussed for conducting case studies to reveal the causes of discrepancies between gauge-measured and satellite-indicated precipitation.

In this study, we investigated the geographical distribution of haplotypes of Cardiocondyla kagutsuchi Terayama in Japan using COI/II mitochondrial DNA. We also examined their genealogy with C. kagutsuchi in other areas and their close relative species. Four haplotypes were found. While two of them were found in a limited area (Ishigaki and Okinawa Islands) separately, the others were distributed widely across Honsyu, Shikoku, and Kyusyu areas in Japan. The newly invaded area by C. kagutsuchi in Japan was Shizuoka prefecture. Their haplotype of Shizuoka were the same as the two haplotypes of the Honsyu, Shikoku, and Kyusyu areas. The haplotype network showed that the two haplotypes were distant from each other. The distance between them was 33, even though the two haplotypes are distributed in the same area. From the phylogenetic tree that we constructed, we found that C. strigifrons was in the same clade as C. kagutsuchi.

Benthic dinoflagellates have been the subject of extensive taxonomic research in recent decades. Studies of morphologies of already known species of benthic dinoflagellates from various geographical populations remain relevant, as these allow elucidation of some details that were overlooked in the original species descriptions or assessment of their morphological variability. In the present study, two rare species of dinoflagellates, Amphidiniella sedentaria and Pachena cf. leibnizii, have been studied, for the first time, from coastal sands of the northwestern Sea of Japan. In the cells of A. sedentaria from the Sea of Japan, we have found two anterior intercalar plates instead of one. Therefore, the original formula has been changed to APC 4′ 2a 7″ 5c 4s 6‴ 2⁗. As a result of the examination of P. cf. leibnizii from the Sea of Japan, we have counted seven precingular plates and six cingular plates, instead of six and five, respectively, indicated in the original description. The plate formula of the cells of P. cf. leibnizii from the Sea of Japan is APC 4′ 3a 7″ 6c 5s 5‴ 2⁗. It is currently difficult to judge whether these differences are morphological variations. Therefore, we have identified these cells as P. cf. leibnizii.

Teikoku Oil Co., Ltd. (TOC) completed Shizuoka-line (Koufu to Gotenba-City, 81km) at the end of 2006. Also, Shizuoka Gas Co., Ltd. (SZG), Tokyo Gas Co., Ltd. and TOC completed the Minamifuji-pipeline (Gotenba to Fuji-City, 31km) at that time. Those pipelines are in series and, with those completion, natural gas pipeline system between the Japan Sea and the Pacific Ocean was realized connecting with the Minami-nagaoka natural gas field (also with the Sekihara underground gas storage) in Niigata prefecture and the Sodeshi LNG receiving terminal of SZG in Shizuoka prefecture. Since domestic gas and imported gas (LNG) can be fed into the pipeline system, it is strongly expected that gas supply in the eastern area of Honshu Island becomes more flexible and reliable.