Taxonomic review of East Asian <Emphasis Type="Italic">Pleuronichthys</Emphasis> (Pleuronectiformes: Pleuronectidae), with description of a new species

A review of East Asian frog flounders, genus Pleuronichthys (family Pleuronectidae), recognized Pleuronichthys japonicus sp. nov. and P. cornutus (Temminck and Schlegel 1846). Pleuronichthys japonicus sp. nov. is characterized by small, dark, rounded spots or marbled markings on the ocular side of the body, rounded cycloid scales somewhat irregularly arranged, usually 12 abdominal vertebrae, 67–80 (modally 75) dorsal-fin rays, 48–59 (modally 55) anal-fin rays, and a short branch of the supratemporal lateral line usually present on both sides. Pleuronichthys cornutus is characterized by densely distributed small, dark, irregular spots on the ocular side of the body, elongate cycloid scales somewhat regularly arranged, usually 13 abdominal vertebrae, 72–88 (modally 77) dorsal-fin rays, 52–65 (modally 58) anal-fin rays, and a branch of the supratemporal lateral line usually absent on both sides. Whereas P. cornutus is distributed from Miyagi Prefecture (Tohoku District) southward along the Pacific coast of Japan to the Bungo Channel, from Akita Prefecture (Tohoku District) southward along the Sea of Japan coast through the Tsushima Strait to the East China Sea, Yellow and Bohai Seas, the Taiwan Strait, and northern Chinese coast of the South China Sea, P. japonicus is distributed from southern Hokkaido southward along the Sea of Japan and Pacific coasts of Japan to the southern East China Sea. Geographic variations were found in caudal vertebrae and anal-fin ray counts, and caudal-peduncle depth in P. cornutus, and in ocular side body coloration, body depth, and head length in P. japonicus. Pleuronichthys lighti Wu 1929 was regarded as a junior synonym of P. cornutus.     

Secondary contact in the Sea of Japan: the case of the <Emphasis Type="Italic">Careproctus rastrinus</Emphasis> species complex (Liparidae)

The Careproctus rastrinus species complex, widely known from the North Pacific, has been revealed recently to include nine genetically divergent groups on the basis of mitochondrial DNA (mtDNA) sequence variations. Herein we describe an AFLP analysis that focuses on three closely related groups in order to clarify the evolutionary history of the species complex in the Sea of Japan and off the Pacific coast of Japan. A principal coordinate analysis indicated the absence of nuclear divergence in two groups defined by mtDNA variations in the Sea of Japan, whereas another group from the Pacific coast of northern Japan was clearly distinct. This suggests extensive gene flow between two groups in the Sea of Japan as a result of secondary contact.     

Revision of the bathyal fish genusHomostolus (Ophidiiformes,Ophidiidae)

The ophidiid fish genusHomostolus is revised on the basis of 44 specimens. Meristic and morphometric characters strongly indicate that the genus as presently known contains a single species,Homostolus acer Smith et Radcliffe, 1913, withHomostolus japonicus Matsubara, 1943, reduced to synonymy. Geographical variations found in certain meristic characters indicate thatH. acer expanded its range from Philippine waters into both northern and southern waters. The species is distributed on deep-sea floors from the Pacific Ocean off central Japan, to the Indian Ocean off northern Western Australia, and to the Tasman Sea off New South Wales, at bathyal depths from about 400 to 700 m.     

Population structure in Chilean hake Merluccius gayi as revealed by mitochondrial DNA sequences

Genetic variation and divergence among samples of Chilean hake Merluccius gayi, from three localities off the coast of Chile and one locality off the coast of northern Peru, were assessed using sequences from the control region of mitochondrial DNA. Homogeneity tests revealed occurrence of at least three distinct genetic stocks of M. gayi within the region sampled. Factors potentially contributing to genetic divergence among M. gayi probably include hydrodynamics and behaviour.     

Multiplex PCR system applied for analysing microsatellite loci of Schlegel's black rockfish,Sebastes schlegeli

Two multiplex PCR amplifications were performed to analyse six microsatellite loci of Schlegel's black rockfish, Sebastes schlegeli, an important commercial fish in the northern part of Japan and an important species for the stock enhancement program in this area. We analysed 67 wild samples from Yamada Bay, Iwate Prefecture, Japan. The observed genotype frequencies agreed with the Hardy–Weinberg expectations at all loci, and the observed heterozygosities ranged from 0.072 to 0.897.     

A new species of <Emphasis Type="Italic">Lycenchelys</Emphasis> (Perciformes: Zoarcidae) from the Pacific coast of northern Japan

 Lycenchelys tohokuensis sp. nov. is described from five specimens, 199–270 mm SL. Unknown before 1997, specimens were collected along the Pacific side of the Tohoku coast, from off Aomori to Fukushima prefectures at depths of 543–709 m. The species differs from all congeners in the northwestern Pacific chiefly in the lack of pelvic fins, having a double lateral line configuration, relatively low vertebral counts, two rows of palatine teeth, and its head pore pattern. The new species does not appear to be closely related to any other northwestern Pacific Lycenchelys including the only other one without pelvic fins, Lycenchelys fedorovi Anderson and Balanov, 2000. Received: March 26, 2002 / Revised: July 8, 2002 / Accepted: July 9, 2002 Acknowledgments We are indebted to Dr. Daiji Kitagawa, Tohoku National Fisheries Research Institution, and participants in his research cruises, including Drs. T. Hattori, Y. Shimizu, K. Uchikawa, and T. Nobetsu, for collecting and supplying the five specimens described here. We also thank the crews of the R/V Wakataka-Maru and T/V Tanshu-Maru for their help aboard ship. Elaine Heemstra, J.L.B. Smith Institute, South Africa, rendered the figures. Correspondence to:M. Eric Anderson     

Genetic Variation at the Mitochondrial 16S rRNA Gene among Trichiurus lepturus (Teleostei:Trichiuridae) from Various Localities: Preliminary Evidence of a New Species from West Coast of Africa

The taxonomic classification of large head hairtail (Trichiurus lepturus) is controversial because of similar body appearance and silvery coloration. Ten samples of T. lepturus caught off the west coast of Africa and 43 samples of T. lepturus caught off the western Atlantic coast and Indo-Pacific waters were used for sequence comparison of mitochondrial DNA encoded partial 16S ribosomal RNA(16S rRNA) gene. Ten samples of T. japonicus (obtained from various parts of southern Japan) were also included in the comparative analysis. For the 509 bp sequence determined, 58 sites were variable, of which 53 were parsimony informative. Phylogenetic analyses using maximum parsimony, maximum likelihood and Bayesian algorithm with Eupleurogrammus muticus as outgroup, showed that the haplotypes of T. lepturus obtained from the West coast of Africa, Indo-Pacific and Western Atlantic coast constituted clearly distinct and well supported lineages without any sharing and overlapping between them. Previous morphological analyses and this genetic study strongly indicate that the morphotypes of T. lepturus obtained from the West African coast are genetically distinct and probably represents a separate species.     

Genetic relationships among populations of the Argentine ant Linepithema humile introduced into Japan

Since some colonies of Argentine ant Linepithema humile were discovered in Japan in 1993, populations of this invasive alien ant species have been expanding their distribution. To resolve the number of invasions and the genetic structure in the early stages of introduction, we inferred the genetic structure and relationships among colonies from eight localities, from analyses of eight nuclear microsatellite DNA markers. F _ST analysis, principal component analysis and assignment test showed that at least three highly genetically differentiated groups of Argentine ants are present in Japan. Populations from Hiroshima Bay were grouped together (Hiroshima, Hatsukaichi, Otake, Iwakuni Central and Iwakuni Kuroiso), while those from Kobe and Yanai were both genetically distant from each other and from the Hiroshima Bay group. Hatsukaichi and Kobe are international seaports, suggesting that the by-ship invasion occurred at least twice. The invasion route of the Yanai population is unknown at this moment. The Aichi population was genetically distant from that of the Hiroshima Bay group by the difference in allele frequencies, and it was plausible that the Aichi population was introduced from the Hiroshima Bay group by human-mediated jump dispersal.     

Cryptic diversity of Melanochlamys sea slugs (Gastropoda,Aglajidae) in the North Pacific

North Pacific specimens of Melanochlamys sea slugs were examined morphologically (including the male reproductive morphology, shell and external coloration) and were sequenced for three genes (mitochondrial COI and 16S and nuclear H3). Phylogenetic and species delimitation analyses were used to determine the evolutionary relationships and species diversity among the specimens examined. Both molecular and morphological data revealed an unexpected high level of cryptic diversity. At least four distinct species occur on the Northwestern Pacific. Melanochlamys ezoensis occurs in Russia and temperate and cold areas in Japan. Three additional undescribed species occur in Japan and/or South Korea. One of the undescribed species occurs both in South Korea and in Japan, but only in Tokyo Bay, suggesting that it could be non‐native in Japan. Two distinct species occur on the Northeastern Pacific coast; Melanochlamys diomedea is widespread from Southern California to Alaska, whereas M. ezoensis was found only in San Francisco Bay, suggesting a human‐mediated introduction. This is further supported by the absence of records of M. ezoensis in San Francisco prior to 2001. The species diversity of Melanochlamys in the Northwestern Pacific is much greater than in the Northeastern Pacific; it is hypothesized that differences in geographic and ocean current system complexity might account for different responses to glacial extinction and postglacial expansion.     

Highly differentiated population structure of a Mangrove species, Bruguiera gymnorhiza (Rhizophoraceae) revealed by one nuclear GapCp and one chloroplast intergenic spacer trnF–trnL

To evaluate the genetic diversity of a mangrove species and clarify the genetic structure of its populations, we studied nucleotide polymorphism in two DNA regions of Bruguiera gymnorhiza collected from the southern islands of Japan, Thailand, Malaysia, Indonesia, Micronesia, and India. The two DNA sequences were the chloroplast (cp) intergenic spacer between trnL and trnF genes (ca. 300 bp), and a part (ca. 550 bp) of the nuclear gene coding for glyceraldehyde-3-phosphate dehydrogenase (GapCp). Little polymorphism was found within each of the three geographical regions, Pacific Ocean, Bay of Bengal and Arabian Sea. Throughout the vast regions east of the Malay peninsula including Indonesia, Thailand, Micronesia and the southern islands of Japan (Pacific Ocean), essentially only one haplotype (apart from variation in number of a T repeat) was present. A second haplotype was present on the western coast of Malay Peninsula and the eastern coast of India (Bay of Bengal). On the southwest of Malay Peninsula both of these haplotypes were present. Finally a third haplotype was found only on the western coast of India (Arabian Sea). When taken over all geographic populations, total nucleotide variation within the species was large (μ = 0.006, average of the two genes). Our results are consistent with the hypothesis that this low genetic diversity within any local population and differentiation between the different oceans or regions are caused by very low gene flow between each of the different oceans coupled with frequent fluctuation of population sizes due to the change in sea level. The significance of these results is discussed from evolutionary point of the mangrove forests.     

Cryptic species in Pacific sipunculans (Sipuncula: Phascolosomatidae): east‐west divergence between non‐sister taxa

Cryptic diversity, i.e. diversity observable in genetic but not in morphological traits, is prevalent in marine invertebrates and presents one of the greatest obstacles to obtaining accurate estimates of species richness. Sipunculans, commonly called peanut worms, are marine annelids in which high levels of cryptic diversity have previously been documented. In this study, we use genetic identification techniques to examine divergence of two lineages of Pacific sipunculans, both known under the name Phascolosoma agassizii. One lineage is isolated to the eastern Pacific coast while the other one inhabits the western Pacific coast. These clades are reciprocally monophyletic and are not recovered as sister taxa, suggesting relatively early divergence within Phascolosoma. Furthermore, we did not find support for a genetic distinction between the western Pacific Phascolosoma agassizii agassizii and Phascolosoma agassizii kurilense, a subspecies reported from the Kuril Islands. Considering that the type locality for P. agassizii is in the Eastern Pacific, we suggest that the western clade, including the samples from the Kuril islands, represent a new, undescribed species.     

Taxonomic reassessment of Chondrus verrucosus (Rhodophyta,Gigartinales), with a description of Chondrus retortus sp. nov

Phylogenetic and morphological reinvestigation of Chondrus verrucosus Mikami was conducted in the Pacific coast of southeastern Honshu, Japan, including the holotype specimen and samples near the type locality. Two entities were recognized by phylogenetic analyses of plastid rbcL and nuclear EF2 sequences. In morphological analyses, the two entities were distinguished by: (i) thallus size and form, and (ii) cell shape of the medullary layer surrounding young carposporangia: one has larger thalli, is regularly canaliculated, with linear medullary cells (large‐type); the other is smaller, canaliculated with crispation and has roundish medullary cells (small‐type). The large‐type was common in southern to eastern Boso Peninsula including near the type locality; the small‐type was typical in the southwest Boso Peninsula and Sagami Bay. The large‐type was shown to be equivalent to C. verrucosus by examination of the holotype specimen. The small‐type is described as a new species, C. retortus Matsumoto et Shimada.     

Impact of the Fukushima nuclear accident on obesity of children in Japan (2008–2014)

This study used prefecture-level panel data from Japan for the period 2008–2014 to investigate the influence of the 2011 Fukushima nuclear accident on the body mass index (BMI) z-score and obesity rates of children over time. I adopted a difference-in-differences approach and found the following: (1) for the cohort aged 5–7 years in 2010, the BMI z-score and obesity rates in disaster-affected areas were higher than in other areas, although this was not observed for the other cohorts; (2) for the cohort aged 5–7 years in 2010, the influence of the accident persisted even after 3 years; and (3) the differences in the BMI z-score and obesity rate before and after the accident were greater for Fukushima Prefecture than for the other affected areas (Iwate and Miyagi prefectures). I infer that health-conscious parents, whose children had lower BMIs, may have moved from Fukushima, thereby increasing the BMI z-score of the child population living in Fukushima by around 0.05 for the cohort aged 5–7 years. The enforced reduction in physical activity increased the BMI z-score of children living in Fukushima by around 0.19 for that cohort.     

DISTINCTION OF SOUTH AMERICAN HAPLOGLOIA ANDERSONII AND CHORDARIA LINEARIS (PHAEOPHYCEAE) BASED ON DIFFERENCES IN SEXUAL REPRODUCTION,MORPHOLOGY, ECOPHYSIOLOGY,AND DISTRIBUTION1

Haplogloia andersonii (Farlow) Levring is an anti-tropical species that occurs on cold and warm-temperate Pacific coasts of both Americas. In its habit it resembles the subantarctic species Chordaria linearis (Hooker et Harvey) Cotton. Culture studies show that the species differ in morphology and ecophysiology of their microscopic gametophytes and in gamete behavior. Details of sporophyte anatomy are presented that also allow the distinction of field plants. In South America, H. andersonii occurs only on the Pacific coast, from central Perú (14°S) to southern Chile (50°S). Chordaria linearis occurs on the Pacific coast from Chiloé Island (43°S) to Cape Horn (56°S). In the shared area the species may co-occur. On the Atlantic coast, C. linearis was newly collected at a locality in northern Patagonia (41°S). In addition, C. linearis occurs in Antarctica. Haplogloia moniliformis Richer, recently described from Macquarie Island, is probably synonymous with Chordaria linearis.     

Genus Alexandrium Halim, 1960 (Dinophyta) from the Pacific coast of Russia: Species composition, distribution, and dynamics

At present 8 species of Alexandrium genus have been found in seas and adjacent waters of Russia: A. acatenella, A. catenella, A. insuetum, A. margalefii, A. ostenfeldii, A. pseudogonyaulax, A. tamarense, and A. tamutum. The distribution and population density of Alexandrium species varied within the surveyed area of the Pacific: in the Sea of Japan and Sea of Okhotsk, 7 species were recorded; 3 species were recorded along the Pacific coast of Kamchatka; and 2 species were found in the Bering Sea. A. tamarense was the most widespread and abundant species over the area. A. insuetum was recorded only in the Sea of Japan, and A. catenella, in the Sea of Okhotsk (Terpeniya Bay). The highest concentration of Alexandrium spp. (2–7 million cells/l) was recorded along the Pacific coast of Kamchatka and in the Bering Sea; in the Sea of Okhotsk, a rather high concentration (51000 cells/l) was registered in Aniva Bay; in the Sea of Japan, the highest concentration was recorded in Peter the Great Bay (6000 cells/l). The distribution of cysts (spores) in surface sediments of the Pacific coast of Russia as a whole reflected the pattern of distribution of vegetative cells of Alexandrium. Cysts of Alexandrium cf. tamarense prevailed all over the area, with the maximum concentration along the Pacific coast of Kamchatka. Beyond that type of cysts, insignificant numbers of cysts of Alexandrium cf. minutum were recorded in Peter the Great Bay and Aniva Bay. Analysis of seasonal dynamics revealed that cells of Alexandrium spp. occurred in Peter the Great Bay from June up to September, and along the Pacific coast of Kamchatka from April to October. In the first region, the maximum density was recorded in August; it was provided by A. pseudogonyaulax (59% of the total density of Alexandrium), A. tamarense (35%), and A. insuetum (6%). In the second region, it was recorded in July, thanks only to development of A. tamarense.     

Intraspecific Genetic Diversity of Undaria pinnatifida in Japan, based on the Mitochondrial cox3 Gene and the ITS1 of nrDNA

The intraspecific genetic diversity of the kelp Undaria pinnatifida (Harvey) Suringar (Laminariales, Phaeophyceae) was investigated using DNA sequences of the mitochondrial cytochrome oxidase subunit 3 (cox3) gene and internal transcribed spacer 1 (ITS1) of nuclear ribosomal DNA in plants collected from 21 localities along the Japanese coast between 2001 and 2003. Morphological variation was also examined and compared with the genetic diversity. Cox3 analyses of 106 plants revealed 9 haplotypes (I–IX) that differed from each other by 1–7 bp (all synonymous substitutions). Haplotype I was distributed in Hokkaido and the northern Pacific coast of Honshu, while haplotype III was found along the Sea of Japan coast of Honshu. Other types were found along the central and southern coast of Honshu. ITS1 analyses of 42 plants revealed 0–1.7% nucleotide differences, but plants from the Sea of Japan coast and northern Japan had similar sequences. The lower genetic differentiation along the Sea of Japan and northern coasts might be due to the recent establishment (after the middle of the last glacial period) of the Sea of Japan flora. The cox3 haplotype of cultivated plants was found in natural populations occurring close to cultivation sites (Naruto, Tokushima Pref., and Hokutan, Hyogo Pref.). This suggests that cultivated plants possibly escaped and spread or crossed with plants of natural populations. Morphological analyses of variation in 10 characters were conducted using 66 plants. The results showed no significant local variation owing to the wide variation in each population and did not support any forma previously described. No correlations between the morphological characters and cox3 haplotypes were detected.     

Development of microsatellite markers for an extremely limited distributed rare diving beetle species,Acilius kishii,and a widely distributed species,Acilius japonicus (Coleoptera: Dytiscidae)

Acilius kishii Nakane, 1963 (Coleoptera: Dytiscidae) is an endangered diving beetle species distributed in only one location, Lake Yashaga‐Ike, Honshu Island, Japan. Acilius japonicus, which is related to A. kishii, is distributed widely in northern Honshu Island and Hokkaido Island in Japan. In this study, we identified 14 microsatellite loci for A. kishii and A. japonicus, including both polymorphic and monomorphic loci, using the next‐generation sequencing method. We observed that 5 and 10 loci showed polymorphisms in 31 and 32 individuals of A. kishii and A. japonicus, respectively. The observed and expected heterozygosities were 0.00–1.00 and 0.00–0.74, respectively. These microsatellite loci could be useful for future conservation genetic studies, including monitoring of genetic diversity and extinction risk of A. kishii.     

Genetic differences among three species of the genus Trichiurus (Perciformes: Trichiuridae) based on mitochondrial DNA analysis

The mitochondrial DNA segment encoding the 16S ribosomal RNA (16S rRNA) gene sequence (ca. 600 bp) was compared among Trichiurus sp. 2 (sensu Nakabo, 2002) (obtained from various areas of Japan), T. japonicus Temminck and Schlegel (collected from various localities within Japan), and true T. lepturus Linnaeus (caught off the Atlantic coast of the United States and Brazil) of the family Trichiuridae using 10, 10, and 15 specimens, respectively. Based on phylogenetic analysis using a neighbor-joining (NJ) algorithm, the haplotypes of Trichiurus sp. 2, T. japonicus, and T. lepturus indicated three distinct monophyletic lineages, being supported by 100% bootstrap values with no haplotypes overlapping or sharing among the lineages. Trichiurus sp. 2, T. japonicus, and T. lepturus are genetically different from each other, suggesting that they are three distinct species.     

PCR-RFLP genotyping for Japanese and Korean populations of Pacific oyster using mitochondrial DNA noncoding region

Production of Pacific oyster Crassostrea gigas in Miyagi and Hiroshima (Japan) has gradually increased, with a marked increase in imported oysters from Goseong (Korea), and then cultured oysters of the Miyagi, Hiroshima, and Goseong populations accounting for most oyster consumption in Japan. In this study, we developed a simple PCR-RFLP analysis of a mitochondrial DNA noncoding region (mtDNA-NCR) for differentiating cultured oysters of these populations. PCR amplification yielded a 818 bp fragment comprising the entire mtDNA-NCR and parts of adjacent tRNA^Cys and tRNA^Asn genes from all the specimens. By use of a wide restriction test using 30 different restriction enzymes, only a single enzyme only, AluI, produced a unique RFLP pattern enabling us to discriminate Miyagi and Hiroshima oysters from Goseong oysters. This difference is probably because of nucleotide alteration at the presumptive AluI recognizing site on position 439 of the mtDNA-NCR. Our simple, robust and cost-effective PCR-RFLP analysis is potentially useful for population genetic investigation of cultured Pacific oyster, particularly when large numbers of specimens must be analyzed.     

A new species of the deep-sea fish genusParabrotula (Parabrotulidae) from Sagami Bay with notes on its ecology

Parabrotula tanseimaru sp. nov. (Zoarcoidei: Parabrotulidae) is described from Sagami Bay, central Japan, as the second species of the genus. The new species is readily distinguished from the known species,P. plagiophthalma, by dorsal fin ray counts (44–50 vs. 37–43) and higher total vertebral counts (64–73 vs. 54–64).P. tanseimaru is viviparous, occurring in pseudoceanic meso-/bathypelagic depths and feeding primarily on copepods.