Comparative studies on the seasonal occurrence,nymphal development and food menu in two giant water bugs,Diplonychus japonicus vuillefroy andDiplonychus major esaki (Hemiptera: Belostomatidae)

We compared the seasonal changes in population density and nymphal development at different water temperatures and under different food conditions between two giant water bugs, Diplonychus japonicus and D. major, in Okayama, Japan. D. japonicus produced 1–2 generations a year, while D. major was strictly inivoltine. The developmental velocity was higher in D. japonicus than in D. major. The thermal constant of D. japonicus was less than that of D. major. These results suggest that D. japonicus is adapted, to higher water temperature than D. major. In the field, D. japonicus preyed predominately on Lymnaeidae and Physidae snails, while D. major preyed on aquatic insects such as dragonfly nymphs.     

Life history,distribution and molecular phylogenetics of the Upward-Mouth Spikefish Atrophacanthus japonicus (Teleostei: Tetraodontiformes: Triacanthodidae)

Ninety-six juvenile specimens (37–54 mm standard length; L_S) of the rarely collected Upward-Mouth Spikefish Atrophacanthus japonicus (Triacanthodidae) were obtained from the stomachs of three Yellowfin Tuna Thunnus albacares collected off Guam in the Mariana Islands in the central Pacific Ocean. These specimens extend the range of A. japonicus eastward into Oceania. We review the systematic characters of the monotypic genus Atrophacanthus and present colour photographs of freshly collected specimens. The diet of the juvenile specimens of A. japonicus consisted of thecosome pteropods and foraminiferans. We present a range map of A. japonicus based on all known specimens and show that specimen size is related to whether specimens were collected in the pelagic zone or on the bottom. Our results support that, compared to all other Triacanthodidae, A. japonicus has an unusually extended pelagic larval and juvenile period, up to 54 mm L_S, before settling to the bottom as adults. Lastly, we provide a multilocus phylogeny addressing the phylogenetic placement of Atrophacanthus based on eight of 11 triacanthodid genera and six genetic markers. Our results reveal that Atrophacanthus is the sister group of Macrorhamphosodes and they provide new insights about the evolutionary history of the family.     

The complete mitochondrial genome sequence of the cutlassfish Trichiurus japonicus (Perciformes: Trichiuridae): Genome characterization and phylogenetic considerations

Mitochondrial genome sequence and structure analysis has become a powerful tool for studying molecular evolution and phylogenetic relationships. To understand the systematic status of Trichiurus japonicus in suborder Scombroidei, we determined the complete mitochondrial genome (mitogenome) sequence using the long-polymerase chain reaction (long-PCR) and shotgun sequencing method. The entire mitogenome is 16,796 bp in length and has three unusual features, including (1) the absence of tRNA^Pro gene, (2) the possibly nonfunctional light-strand replication origin (O_L) showing a shorter loop in secondary structure and no conserved motif (5'-GCCGG-3'), (3) two sets of the tandem repeats at the 5' and 3' ends of the control region. The three features seem common for Trichiurus mitogenomes, as we have confirmed them in other three T. japonicus individuals and in T. nanhaiensis. Phylogenetic analysis does not support the monophyly of Trichiuridae, which is against the morphological result. T. japonicus is most closely related to those species of family Scombridae; they in turn have a sister relationship with Perciformes members including suborders Acanthuroidei, Caproidei, Notothenioidei, Zoarcoidei, Trachinoidei, and some species of Labroidei, based on the current dataset of complete mitogenome. T. japonicus together with T. brevis, T. lepturus and Aphanopus carbo form a clade distinct from Lepidopus caudatus in terms of the complete Cyt b sequences. T. japonicus mitogenome, as the first discovered complete mitogenome of Trichiuridae, should provide important information on both genomics and phylogenetics of Trichiuridae.     

The effect of bacteria on interspecific relationships between the euryhaline rotifer Brachionus rotundiformis and the harpacticoid copepod Tigriopus japonicus

Inconsistent results have been obtained on the population growth of Brachionus rotundiformis and Tigriopus japonicus, when results from single-species and two-species mixed cultures are compared. Bacteria growth was not regulated in these experiments, which could be the cause for this. In order to test this possibility, we conducted similar experiments under axenic and synxenic (with presence of one species of bacteria) conditions. The population growth of B. rotundiformis was suppressed by the presence of T. japonicus in axenic cultures. T. japonicus could not persist in axenic cultures, but its population increased when grown in synxenic cultures. T. japonicus used RT bacteria strain as a food source, while these bacteria were toxic to B. rotundiformis. These results suggest that bacteria can modify the interspecific relationship between B. rotundiformis and T. japonicus.     

不同生境下川麦冬根围土壤丛枝菌根真菌多样性北大核心CSCD

采用高通量(Illumina Miseq)测序技术对栽培和野生2种生境下川麦冬根围的丛枝菌根(AM)真菌多样性和群落结构进行测定,并结合土壤理化因子进行相关性分析,以明确两种生境下川麦冬根围土壤AM真菌多样性和优势群落的分布特点,探讨AM真菌群落分布差异的驱动因子,为AM真菌应用于麦冬生产提供理论依据和技术支持。结果表明:(1)不同生境下川麦冬根围土壤中共鉴定出AM真菌3属10种,其中野生川麦冬根围土壤鉴定出的AM真菌3属7种,分别隶属于无梗囊霉属(Acaulospora)、多孢囊霉属(Diversispora)和球囊霉属(Glomus),而栽培环境下鉴定出AM真菌1属6种,隶属于球囊霉属。2个生境优势属均为球囊霉属。(2)不同生境下川麦冬根围AM真菌之间存在显著差异,野生生境下川麦冬根围土壤AM真菌多样性指数ACE和Shannon均显著高于人工栽培生境,而Simpson指数则相反。(3)相关性分析表明,AM真菌多样性指数及群落组成结构均与土壤理化因子存在相关性,其中全钾(TK)、全磷(TP)、全氮(TN)对AM真菌多样性指数和群落结构组成均存在显著影响。研究认为,不同生境下川麦冬根围AM真菌群落存在显著差异,球囊霉属为川麦冬互利共生的关键属,TK、TP、TN是不同生境川麦冬根围AM真菌群落差异的主要驱动因子。     

Comparative studies on the reproductive systems ofMazus japonicus andM. miquelii (Scrophulariaceae)

Mazus japonicus is predominantly self-pollinated,M. miquelii mostly cross-pollinated, with a low degree of self-incompatibility. Correlated differences effect structure, development and seismonasty of the stigma, spatial relationships of stigma and anthers, and pollinator visits.M. japonicus produces numerous and light,M. miquelii fewer and heavier seeds. Growth experiments under different temperature regimes demonstrate thatM. japonicus dies after flowering and fruiting, and behaves as an annual, whileM. miquelii has additional asexual propagation and is clearly perennial.M. japonicus grows in somewhat drier and more disturbed habitats thanM. miquelii.     

Microbial diversity in the tick Argas japonicus (Acari: Argasidae) with a focus on Rickettsia pathogens

The soft tick Argas japonicus mainly infests birds and can cause human dermatitis; however, no pathogen has been identified from this tick species in China. In the present study, the microbiota in A. japonicus collected from an epidemic community was explored, and some putative Rickettsia pathogens were further characterized. The results obtained indicated that bacteria in A. japonicus were mainly ascribed to the phyla Proteobacteria, Firmicutes and Actinobacteria. At the genus level, the male A. japonicus harboured more diverse bacteria than the females and nymphs. The bacteria Alcaligenes, Pseudomonas, Rickettsia and Staphylococcus were common in nymphs and adults. The abundance of bacteria belonging to the Rickettsia genus in females and males was 7.27% and 10.42%, respectively. Furthermore, the 16S rRNA gene of Rickettsia was amplified and sequenced, and phylogenetic analysis revealed that 13 sequences were clustered with the spotted fever group rickettsiae (Rickettsia heilongjiangensis and Rickettsia japonica) and three were clustered with Rickettsia limoniae, which suggested that the characterized Rickettsia in A. japonicus were novel putative pathogens and also that the residents were at considerable risk for infection by tick‐borne pathogens.     

Synopsis of biological, fisheries and aquaculture-related information on mulloway Argyrosomus japonicus (Pisces: Sciaenidae), with particular reference to Australia

Argyrosomus japonicus is a member of the family Sciaenidae, which are commonly known as drums and croakers. A. japonicus occurs in estuarine and nearshore Pacific Ocean and Indian Ocean waters surrounding Australia, Africa, India, Pakistan, China, Korea and Japan. The biology of A. japonicus is relatively well studied in South Africa, and more recently studied in Australia, but no information is readily available from other areas of its distributional range. The early life history distribution of A. japonicus may differ among regions, with their distribution in estuaries linked to salinity, turbidity, freshwater flows and depth of water. Studies in South Africa and Australia found that juvenile fish grow rapidly, attaining 35 cm TL in 1 year and 87–90 cm TL in 5 years. Sexual maturity also differs among regions and is attained at 2–3 years of age and >50 cm in eastern Australia, 5–6 years of age and >80 cm TL in western Australia and southern Africa. The maximum reported length and age of A. japonicus is 175 cm and 42 years, respectively. Spawning most likely occurs in nearshore coastal waters although there is evidence to suggest that it may also occur in the lower reaches of estuaries. Time of spawning varies among geographic localities and is probably linked to water temperature and oceanography. Juvenile fish (<2 years) appear to be relatively sedentary, but sub‐adults and adults can move relatively long distances (>200 km) and such movements may be linked to pre‐spawning migrations. A. japonicus is important in many recreational and commercial fisheries, but like other sciaenids, is prone to overfishing. It is classified as recruitment overfished in South Africa and overfished in eastern Australia. Although much research has been done to minimize the capture of juveniles in Australian prawn‐trawl fisheries, greater protection of spawners and improved fishing practices to enhance survival of discarded juveniles, particularly from prawn trawling, may be required. An aquaculture industry is developing for A. japonicus in Australia and preliminary research on the impacts and success of re‐stocking wild populations has begun in an attempt to arrest the apparent decline in populations.     

Lotus japonicus, an autogamous, diploid legume species for classical and molecular genetics

In the Leguminosae plant family, few of the individual plant species have been used for plant molecular biology research. Among the species investigated no obvious representative ‘model’ legume has emerged. Here a member of the tribe Loteae, Lotus japonicus (Regel) Larsen is proposed as a candidate. L. japonicus is a diploid, autogamous species, with a good seed set, and a generation time of approximately 3 months. The haploid genome consists of six chromosomes and the genome size was estimated to be relatively small (0.5 pg per haploid complement). L. japonicus is susceptible to Agrobacterium tumefaciens and transgenic plants can be regenerated after hygromycin or kanamycin selection. Tissue culture conditions and procedures for transformation and regeneration are described. Stable transformation is demonstrated by segregation of the hygromycin selectable marker after selfing of transgenic plants or test crosses. The possibility of mapping polymorphic DNA markers inbred lines of L. japonicus is also discussed.     

Effect of the ascidian Styela clava on the growth of small holothurians of the species Apostichopus japonicus

We studied the effect of the common ascidian Styela clava on the growth of small holothurians of the species Apostichopus japonicus (Selenka, 1867). In a traditional aquaculture system, the oxygen consumption rates, ammonia excretion rates, and ingestion rates of small A. japonicus were reduced significantly, which suggested that this group was stressed by the presence of large A. japonicus, and that this stress grew stronger with time. Oxygen consumption rates, ammonia excretion rates, and ingestion rates of small A. japonicus in an integrated aquaculture (IA) system with S. clava, microalgae, and A. japonicus were higher than those observed in the traditional culture system. Metabolic and digestive enzymes were more active in small A. japonicus in the IA system than in those in the traditional aquaculture system. These results suggest that the IA model did not affect the growth of large A. japonicas, but produced a marked positive impact on the growth of small individuals.     

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.     

A MOLECULAR ANALYSIS OF ANALIPUS AND RALFSIA (PHAEOPHYCEAE) SUGGESTS THE ORDER ECTOCARPALES IS POLYPHYLETIC1

We report partial 18S ribosomal DNA sequences of Analipus japonicus (Harvey) Wynne and Ralfsia fungiformis (Grunnerus) Setchell et Gardner. These sequences were compared with the corresponding sequences of 13 brown algae representing six phaeophycean orders: Dictyotales, Ectocarpales, Fucales, Laminariales, Sphacelariales, and Syringodermatales. These 15 brown algae included 10 ectocarpoids representing nine ectocarpacean (sensu Gabrielson et al. 1989) families: Chordariaceae, Dictyosiphonaceae, Ectocarpaceae, Elachistaceae, Heterochordariaceae, Leathesiaceae, Punctariaceae, Ralfsiaceae, and Scytosiphonaceae. We addressed the controversial taxonomic placement of A. japonicus and R. fungiformis in the Ectocarpales by analysis of DNA sequences. Neighbor-joining and maximum parsimony-inferred phylogenies provided evidence that A. japonicus and R. fungiformis are not closely associated with the other representatives of the Ectocarpales. Bootstrap analyses suggest polyphyly of the order Ectocarpales (sensu Gabrielson et al.). However, our analysis failed to resolve the phylogenetic relationship between A. japonicus and R. fungiformis. Our results suggest that the ectocarpoids are just as distantly related to A. japonicus and R. fungiformis as they are to members of the advanced orders Desmarestiales, Dictyotales, Fucales, Laminariales, Sphacelariales, and Syringodermatales.     

Bioenergetic responses of sub-adult sea cucumber Apostichopus japonicus (Selenka) (Echinodermata: Holothuroidea) to temperature with special discussion regarding its southernmost distribution limit in China

1. This paper investigated the bioenergetic responses of the sea cucumber Apostichopus japonicus (wet weights of 36.5±1.2 g) to different water temperatures (5, 10, 15, 20, 25 and 30 °C) in the laboratory.

2. Results showed that theoretically the optimal temperatures for energy intake and scope for growth (SFG) of sub-adult A. japonicus was at 15.6 and 16.0 °C, respectively. The aestivation threshold temperature for this life-stage sea cucumber could be 29.0 °C by taking feeding cessation as the indication of aestivation.

3. Our data suggests that A. japonicus is thermo-sensitive to higher temperature, which prevents it from colonising sub-tropical coastal zones. Therefore, water temperature plays an important role in its southernmost distribution limit in China.

4. The potential impact of global ocean warming on A. japonicus might be a northward shift in the geographical distribution.

Rapid PCR-RFLP method for discrimination of imported and domestic mackerel

With the ever-decreasing domestic fishery catch of Japanese mackerel Scomber japonicus, alternative Atlantic mackerel Scomber scombrus has been increasingly imported and currently accounts for approximately 34% of mackerel consumption in Japan. As there is no morphologic difference between the species after removal of their skin, not only fresh and frozen fillets but also processed seafood of S. scombrus are frequently marketed with mislabeling as S. japonicus. In this study, a rapid and reliable polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) analysis was developed to discriminate imported mackerel S. scombrus and domestic mackerel S. japonicus. PCR amplification for the nuclear 5S ribosomal DNA nontranscribed spacer was performed using Scomber-specific primers. Direct digestions of the PCR products using either PvuII or HaeIII restriction enzymes generated species-specific profiles, indicating that both enzymes enable the accurate identification of S. scombrus and S. japonicus. This robust and reproducible method can serve as molecular-based routine food inspection program to enforce labeling regulations.     

A comparison of the effects of light intensity on movement and growth of albino and normal sea cucumbers (Apostichopus japonicus Selenka)

Albinism in the sea cucumber Apostichopus japonicus (Selenka) may be a significant biomarker that can be used to obtain information about behaviors and growth of this species. The goal of this study was to compare the behaviors and growth rate between albino and normal A. japonicus. Total light intensity and specific growth rate were used as statistical indices. Diverse light intensities were tested in the laboratory and in the field to identify ecological characteristics of albino A. japonicus. Experimental results revealed that: (1) both albino and normal specimens had negative phototaxis; (2) normal A. japonicus were more responsive to intense light than albino species, and the latter could withstand longer periods of exposure to intense light; (3) normal A. japonicus grew faster than albino specimens; and (4) both normal and albino A. japonicus grew faster in natural light than in the other light intensities tested.     

Revision of the wobbegong genus <Emphasis Type="Italic">Orectolobus</Emphasis> from Japan,with a redescription of <Emphasis Type="Italic">Orectolobus japonicus</Emphasis> (Elasmobranchii: Orectolobiformes)

The wobbegong genus Orectolobus occurring from Japan and its adjacent waters was reviewed, and O. japonicus was redescribed using ten specimens including a syntype. Only one species, O. japonicus, was regarded as valid among three species previously recorded from Japan. Orectolobus maculatus had been erroneously described from Japan because of the past nomenclatural confusion with O. japonicus. The specimen called “Karakusa-oose,” which had been identified with O. ornatus, was regarded as an irregular form of O. japonicus. Orectolobus japonicus was distinguished from the other congeners by having no tubercles on the body, five to eight dermal lobes in the preorbital group, two distally notched lobes in the postspiracular group, no dermal lobes on lower jaw, nasal barbel with a branch, no supraocular knob, relatively high dorsal fins with usually concave posterior margins, a lower number of precaudal vertebrae and intestinal valve turns, saddles on the back without black borders and yellowish and variously shaped blotches, not forming white O-shaped spots.