Koji Tojo

• Doctor of Philosophy
• Professor (Full) at Shinshu University

The Japanese islands were originally included in the Eurasian Continent as part of the southern and northern landmasses. The two landmasses were detached from the continent 18 million years ago. After that, the former was repeatedly connected to the Korean peninsula during glacial periods, but most of the latter was under seawater. Thus, all Japane...

Long‐term biodiversity monitoring is necessary for conservation and management. In such circumstances, environmental DNA (eDNA) surveys can enable easy and effective biomonitoring of aquatic insects. However, previous studies of aquatic insects based on the mtDNA COI region have revealed incomplete taxonomic coverage, and frequent amplification of...

Three new species of Leptoceridae were described from the Lower Mekong tributaries, namely Ceraclea luangnamthaensis n. sp., Setodes xangthevadaensis n. sp. from Laos, and Setodes mongkondechsawati n. sp. from Cambodia. The male genitalia of Ceraclea luangnamthaensis n. sp. are distinguished from those of other species by its preanal appendages, wh...

Organisms inhabiting mountainous regions can experience large vertical environmental changes, and show different ecological characteristics between altitudes, thus facilitating allopatric fragmentation even in geographically close populations. This study compared the life‐history patterns of a species of limnephilid caddisfly, Asynarchus sachalinen...

Taxonomical and ecological knowledge of stoneflies (Order: Plecoptera) is important biological indicator of riverine environments. A genus Utaperla was established by Ricker in 1952 when he described U. sopladora Ricker 1952. The Utaperla stoneflies have been recorded in North America, Russia and China and consists of the species, U. sopladora, U....

Diving beetles play an important role in fishless freshwater communities. The genus Cybister is included in the Japanese Red Data List owing to its diminished population size. The phylogenetic relationships and genetic structures of Cybister chinensis and Cybister brevis, whose populations are declining, and Cybister tripunctatus lateralis, whose p...

How subsurface hyporheic zone (HZ) of rivers is connected to riparian zones remains largely unknown. We collected benthic macroinvertebrates and adult aquatic insects for six years, including those at 30-cm depth in the HZ to identify insect taxa having a high level of habitat affinity for HZ (HZ taxa). Adults of HZ taxa were identified with the ai...

When gene flow has been restricted between populations, the genetic structure of such species often reflects geohistory and climate changes. Populations of species inhabiting high-altitude regions, known as ‘Sky Islands’, are isolated and exhibit restricted gene flow, so they often have habitat-specific genetic structures that correspond to their s...

Three new species of Trichosetodes , namely T. carmelae sp. nov. , T. katiengensis sp. nov. and T. ratanakiriensis sp. nov. are described and illustrated by male specimens. The male genitalia of T. carmelae sp. nov. can be distinguished from the other 16 species of the genus found in Southeast Asia by the shape of the phallicata. The phallicata of...

In river systems, frequent floods generally decrease the abundance of riverine species, and recent studies have reported that the degree of flood disturbance changes along agricultural gradients. However, the interactive impacts between anthropogenic and flood disturbances on migration dynamics are not well tested. In a forest–agricultural landscap...

Dispersal is an important factor that determines the potential for colonization to pioneer sites. Although most decapods employ seaward migration for reproduction with a planktonic larval phase, true freshwater crabs spend their entire life cycle in freshwater. Therefore, it is expected that genetic regionality can be easily detected. In this study...

Long-term biodiversity monitoring is necessary for the conservation and management of water resources. Notably, aquatic insects have been used as an indicator of water quality because they provide important basic information about freshwater ecosystems and water resources. Although environmental DNA (eDNA) surveys can enable easy and effective biom...

Organisms that inhabit the alpine zone tend to have distribution areas that are isolated and scattered in patches, in effect ‘sky islands’. We focused on Pseudostenophylax caddisflies, a typical alpine aquatic insect group. Phylogenetic analyses were conducted on all eight Japanese species, with the monophyletic lineage of each strongly supported....

Floods affect the population structure of organisms that inhabit streams. In recent decades, the scale of floods has become larger due to climate change. Under these circumstances, on 12 October 2019, the largest typhoon in the history of observation in Japan struck the Japanese Archipelago. This typhoon caused heavy rainfall in various places, and...

Elucidating the mechanism of formation of biota on islands will contribute to our understanding of the evolutionary mechanisms that generate biodiversity. In this study, we focus on the evolutionary history of Ephemera orientalis, which is distributed in East Asia. Phylogenetic analyses were performed using the mitochondrial DNA 16S rRNA, cytochrom...

Dorcus montivagus is a Japanese endemic stag beetle that feeds exclusively on dead beech wood, and its distribution is almost completely coincidental with that of beech forests. Japanese beech, Fagus crenata, is the dominant tree species of the cool‐temperate deciduous broad‐leaved forests in Japan. Historical changes in the distribution of beech f...

DNA barcoding is a powerful tool that provides rapid, accurate, and automatable species identification using standardized genetic region(s), such as for revealing the existence of cryptic species and/or rare species in biodiversity monitoring. DNA barcoding techniques require the development of sets of universal PCR primers for DNA barcoding. We tr...

Japanese macaques, Macaca fuscata, of Kamikochi in the Japanese Alps endure one of the coldest and harshest environments during winter when scarcity of food puts them at risk. However, various behaviors have evolved to mitigate potential mortality. These macaques typically eat bamboo leaves and the bark of woody plants in winter, but our previous s...

Aim Dispersal is an important factor that determines the potential for colonization to pioneer sites. Most decapods employ seaward migration for reproduction with a planktonic larval phase. However, true freshwater crabs spend their entire life cycle in freshwater. Therefore, it is expected that genetic regionality can be easily detected. In this s...

Little is known about the ecology of insect species in the hyporheic zone of rivers, despite its importance in understanding how species survive in specialized habitats. We report on the life history and trophic characteristics of the hyporheic stonefly species Alloperla ishikariana Kohno, 1953 (Order: Plecoptera, Family: Chloroperlidae) in a grave...

In this study we present evidence of an ongoing speciation event in the Japanese Archipelago. The Kisaura nozakii species complex (Philopotamidae) is a group of a small trichopteran insects, and it has been reported that this species has large differences between populations in the copulatory organs (genitalia) of males. Therefore, we conducted mol...

Insect silk is a versatile biomaterial. Lepidoptera and Trichoptera display some of the most diverse uses of silk, with varying strength, adhesive qualities, and elastic properties. Silk fibroin genes are long (>20 Kbp), with many repetitive motifs that make them challenging to sequence. Most research thus far has focused on conserved N- and C-term...

Insect silk is an incredibly versatile biomaterial. Lepidoptera and their sister lineage, Trichoptera, display some of the most diverse uses of silk with varying strength, adhesive qualities and elastic properties. It is well known that silk fibroin genes are long (> 20 kb) and have many repetitive motifs. These features make these genes challengin...

Niche differentiation between closely related species leads to differentiation of their habitats. Segregation based on slight differences in environmental factors, that is niche differentiation on the microhabitat scale, allows more species to inhabit a certain geographic space. Therefore, such fine scale niche differentiation is an important facto...

To deepen understanding the evolutionary process of lucanid–yeast association, the lateral transmission process of yeast symbionts among stag beetle genera Platycerus and Prismognathus around the border between Japan and South Korea was estimated based on molecular analyses and species distribution modelings. Phylogenetic analyses were based on yea...

The Japanese macaque ( Macaca fuscata ) is native to the main islands of Japan, except Hokkaido, and is the most northerly living non-human primate. In the Chubu Sangaku National Park of the Japanese Alps, macaques live in one of the coldest areas of the world, with snow cover limiting the availability of preferred food sources. Winter is typically...

DNA barcoding is a powerful tool that provides rapid, accurate, and automatable species identification by using standardized genetic region(s). It can be a powerful tool in various fields of biology such as for revealing the existence of cryptic species and/or rare species and in environmental science such as when monitoring river biota. Biodiversi...

The intermediate stages of speciation are important for understanding the processes involved in the creation of biodiversity, and also comprise a number of interesting phenomena. However, difficulties are associated with dividing clear speciation stages because speciation is a continuous process. Therefore, the elucidation of speciation is an inter...

The distribution area of a species is determined by a combination of factors and since each species of aquatic insect has adapted to drastically changing environments along river channels, they are excellent targets for study. Considering these factors, we focused on three Ephemera mayflies inhabiting the Japanese Archipelago and investigate their...

The unique hydrology and physicochemistry of alpine streams provide an important influence on the structure and function of inhabiting biological communities. A substantial body of research exists on alpine streams across many regions of the globe (e.g. Europe, North and South America and Greenland). To date, however, there have been few studies in...

In general, population genetics theory predicts that a fragmented smaller population will contain relatively less genetic diversity than a larger population, and so will have a higher rate of genetic fixation due to random genetic drift or inbreeding. However, in this study, having analysed the genetic structure of the mitochondrial DNA COI region...

A new mayfly species, Bleptus michinokuensis sp. nov. (Ephemeroptera: Heptageniidae) is described on the basis of specimens of male and female adults and mature nymphs collected at a seepage zone of a small freshwater branch of the ‘Tachiya-zawa-gawa’ River located amongst the northern foothills of Mt. Gassan (Shonai-machi Town, Yamagata Prefecture...

Knowledge of the factors that determine the distribution ranges of organisms is necessary to understand their evolutionary and ecological significance and contribution to biodiversity. A very effective mean of studying such factors is to compare the distribution characteristics and genetic structures of closely related species with differing habita...

Changes in river environments due to elevation gradients have a great impact on living organisms. In particular, with respect to aquatic insects, it has been recognized that even in closely related species there is a tendency for species to be replaced between upstream and downstream environments. Such a distribution tendency has also been suggeste...

In August 2017, an outbreak of the stick insect, Ramulus mikado (Rehn, 1904), was observed in the Akashina area in Central Japan. This stick insect is a wingless, non‐flying species that inhabits East Asia. Although it seems that the occurrence of many individuals emerging together had been observed in the 2 or 3 years prior, the outbreak in 2017 w...

We developed microsatellite markers for Appasus japonicus (Heteroptera: Belostomatidae). This belostomatid bug is distributed in East Asia (Japanese Archipelago, Korean Peninsula and mainland China) and often listed as an endangered species in the Red List or the Red Data Book at the national and local level in Japan. Here, we describe twenty novel...

We focused on Meloe beetles that have lost all flight ability, and conducted molecular phylogeographic analyses based on their mitochondrial DNA COI and nuclear DNA EF1-α regions. Meloe beetles infiltrate bumblebee nests by attaching to bumblebees as they pollinate flowers and thereafter have a unique and specific life history as they complete thei...

Oviparous, ovoviviparous and viviparous reproduction are interesting subjects for understanding animals' evolutionary pathways and adaptation to their life history and habitat conditions. In this study, we examined the reproductive mode of the ovoviviparous mayfly Cloeon dipterum, particularly comparing embryogenesis between hand-pairing and unmate...

The soricid water shrew Chimarrogale platycephalus is a mammalian species endemic to the Japanese Islands. The animals inhabit the islands of Honshu and Kyushu, and are considered to be extinct in Shikoku. Information on this water shrew from Honshu and Kyushu is scarce, and C. platycephalus is registered on many local governments' red lists as an...

The acquisition of wings in insects is the most significant subject in considering the diversification and adaptive radiation of insects, that is, the “macro‐evolution” of insects. In the discussion of the origin of insect wings, Palaeoptera has attracted particular attention in phylogenetic and evolutionary studies. In particular, Ephemeroptera ha...

Alpine streams are typically fed from a range of water sources including glacial meltwater, snowmelt, groundwater flow, and surface rainfall runoff. These contributions are projected to shift with climate change, particularly in the Japanese Alps where snow is expected to decrease, but rainfall events increase. The overarching aim of the study was...

Environments such as floodplains and the marshlands of rivers, lakes and ponds, are important habitats for aquatic insects adapted to lentic water conditions. In addition, ponds and paddy fields artificially created for agriculture are also important alternative habitats for lotic water-dependent wildlife. In this study, we focused on aquatic insec...

We developed microsatellite markers for Appasus japonicus (Hemiptera: Belostomatidae). This belostomatid bug is distributed in East Asia (Japanese Archipelago, Korean Peninsula, and Mainland China), and often listed as endangered species in the 'Red List' or the 'Red Data Book' at the national and local level in Japan. Here we describe twenty novel...

The soricid water shrew, Chimarrogale platycephalus , is a mammal species endemic to the Japanese Islands. They inhabit the islands of Honshu and Kyushu, and are considered to be extinct in Shikoku. Information on this water shrew from Honshu and Kyushu is also scarce, and C. platycephalus is registered on the Japanese Government′s red list as an e...

DNA barcoding has been actively used as a method for species identification, and it will become an increasingly important method in the future. However, DNA barcoding can occasionally encounter a major problem, namely “nuclear mitochondrial DNA pseudogenes (NUMTs)”. In this paper, we report the discovery of a pseudogene in the mitochondrial COI reg...

The Japanese wrinkled frog Glandirana rugosa is separated into five genetically different groups. One group in western Japan is further divided into three subgroups, found in Kyushu, Shikoku, and western Honshu. We collected G. rugosa frogs at 39 sites in Kyushu and determined nucleotide sequences of the mitochondrial 12S and 16S rRNA genes for phy...

In the present study, we add genetic data of the mayfly Cloeon dipterum collected from the Japanese Islands to the established molecular phylogenetic knowledge in the mitochondrial COI gene of Cloeon mayflies. Cloeon dipterum is a typical cosmopolitan species that includes six intraspecific haplotype groups. The present phylogenetic analysis reveal...

Adult caddisflies were collected weekly from a spring-fed brook of Shimauchi-yusui from 11 April 2013 to 5 June 2014. A total of 11867 specimens belonging to 39 species, 18 genera and 14 families were identified. The most abundant species collected in 1 year (the first 52 weeks) were Agapetus sibiricus Martynov 1918 (60%), Apatania aberrans (Martyn...

Sexual reproduction is overwhelmingly the most common reproductive mode among Metazoans, although it has been secondarily lost in some organisms. Ephoron shigae is a geographically parthenogenetic mayfly. Here, we provide details of the frequency of bisexual and parthenogenetic strains of E. shigae together with data on their sex ratios in the Abuk...

Elucidation of the diversification process of organisms is one of the important tasks of biology. From the viewpoint of species diversity, insects are the most successful group among the diverse organisms on earth and evolutionary adaptation is one of the important factors driving this pattern. Evolutionary adaptation is one of the important factor...

Insects are the most diverse organisms in the world and have been in existence since ca. 480 Ma; given this, they can provide profound insights into evolution. Among them, the order Ephemeroptera is one of the most basal clades of winged insects. This makes Ephemeroptera a significant key taxon in understanding the macro-evolution or the insect gro...

The DNA-based identification of aquatic insects, which show high species diversity, is becoming increasingly popular because these insects are excellent indicators of the condition of the aquatic environment. Spiny crawler mayflies (Ephemerellidae) are aquatic insects known for their altitudinal stratified distribution patterns and niche partitioni...

The Japanese Islands have a high degree of biodiversity, with almost the entire area being designated as a 'global hotspot of biodiversity'. There is no doubt that many complex factors have contributed to this, particularly the complex history of the geological formation of the Japanese Islands. As such, we have focused on the genetic structure and...

Phylogeographic studies based on molecular information have been attracting attention because they have come to play a significant role in the elucidation of the population structure and phylogenetic relationships of species. Furthermore, molecular tools have helped to reveal evidence for cryptic biodiversity, including in many cases the discovery...

Each vertebrate species, as a general rule, has either the XX/XY or ZZ/ZW chromosomes by which sex is determined. However, the Japanese Rana (R.) rugosa frog is an exception, possessing both sex-determining combinations within one species, varying with region of origin. We collected R. rugosa frogs from 104 sites around Japan and South Korea and de...

The use of environmental DNA (eDNA) has recently been employed to evaluate the distribution of various aquatic macroorganisms. Although this technique has been applied to a broad range of taxa, from vertebrates to invertebrates, its application is limited for aquatic insects such as aquatic heteropterans. Nepa hoffmanni (Heteroptera: Nepidae) is a...

Agricultural activities have increased environmental homogenisation in stream ecosystems. These alterations reduce the availability of flow refugia during flooding and increase the effects of flood disturbances on aquatic insects. Thus, we examined the effects of the agricultural development (percentage of pasture cover within the catchment) and fl...

Japan is considered a global hot spot of biodiversity. With regard to species diversity, insects are no exception. To date, more than 32,000 insect species have been identified in Japan, while around 100,000 species of insects are estimated to inhabit this country. In this paper, we outline background factors having contributed to diversification o...

Four species of the genus Ephemera mayflies are recorded in the Japanese Islands. Among them, Ephemera japonica McLachlan, 1875 is an endemic species to Japan, they inhabit Hokkaido, Honshu, Shikoku, and Kyushu. Both Ephemera strigata Eaton, 1892, and Ephemera orientalis McLachlan, 1875 inhabit Hokkaido, Honshu, Shikoku, Kyushu, and also inhabit co...

Japan is often referred to as a global hotspot of biodiversity. With regard to species diversity, insects are no exception. To date, more than 30,000 insect species have been identified in Japan, and yet about 100,000 species of insects are considered to inhabit this country. In this chapter, we outline background factors contributing to the degree...

A list of the caddisflies obtained during the 14th International Symposium on Trichoptera, 2-7 July 2012, Vladivostok, Russia, is presented. Imago and immature stages were collected in different places in South Primorye during the symposium (5 July 2012) and post-symposium excursion (8-13 July 2012). The list of collected caddisflies includes 98 sp...

The channels of almost all rivers in Japan have been fixed through the construction of artificial riverbanks to control flooding. In addition, to prevent flooding, maintenance works including the removal of gravel from the channels must be conducted regularly. As a result, the level of most riverbeds within river channels has been lowered, and rive...

We investigated the molecular phylogeny of isonychiid mayflies inhabiting the East Palearctic region, Isonychia (Isonychia) japonica, Isonychia (Isonychia) ignota, Isonychia (Isonychia) ussurica and Isonychia (Prinoides) shima. We discuss their genetic structures, phylogeny and phylogeography. We collected a total of 100 specimens of isonychiid may...

Larvae and females of two Stenopsyche species, S. formosana Kobayashi and S. drakon Weaver, are described for the first time. They were associated with the adult male through mitochondrial DNA sequence comparisons. The male of S. formosana, which has been recorded as Stenopsyche banksi Mosely from Taiwan, is redescribed. The males of S. formosana a...

In Lake Suwa, various eutrophication control measures have been taken to reduce external loads of phosphorus and nitrogen. As a result, the composition of the phytoplankton in the lake has also changed. Since 1999, blue-green algae have decreased, and Mougeotia have appeared August–December in 2011. DNA analysis of the 18S rRNA region of Mougeotia...

In October 2015, a wing degenerated female of limoniid cranefly, genus Prionolabis was collected at Kamikochi. Although we could not identify this female at the species level, this is considered to be either Prionolabis nigrilunae or Prionolabis imanishii, based on the characteristic of its degenerated wings. We herein report its morphological chara...

We focused on the genetic structure and evolutionary divergence of a typical habitat generalist mayfly, Isonychia japonica, inhabiting rivers widely distributed across eastern Asia. In the Japanese Archipelago, they are distributed across a wide range of environments, including up- and downstream areas in 1 river basin. We analyzed DNA sequences of...

Evaluating the relative connectivity of populations within and among streams in a riverine landscape is crucial to developing a better understanding of stream ecology. Molecular markers provide a reasonable approach to assess the connectivity of populations and to evaluate inherent properties of populations, such as genetic diversity. Many previous...

ミトコンドリアのチトクロームb遺伝子は魚類の系統解析に広く用いられ、多くの研究が報告されているが、ホトケドジョウ類では分子系統学的研究の初期に唯一の研究がみられるだけである。この研究報告の後、新たな集団が発見されるなどホトケドジョウ類について知見が加わったため、改めてチトクロームb遺伝子を用いて系統解析を行う必要が生じた。そこで本研究では、新たに発見された集団のサンプルなどを加え、Lefua pleskeiを除くすべての種とすべての種内集団を用いて、チトクロームb遺伝子による系統解析を行った。その結果、エゾホトケドジョウ、ヒメドジョウ、トウカイナガレホトケドジョウ、ホトケドジョウの7地方集団、ナガレホトケドジョウの2地方集団が各々高い信頼性をもって単系統群を形成し、トウカイナガレホトケドジョ...

ThecaddisfliesofthespeciesHydatophylax nigrovittatus (McLachlan,1872) are distributed sporadically and in extremely isolated areas, intheJapaneseArchipelago.In addition,thisspecieshasbeenregisteredasaRedListspecies,i.e., in category“DD(data deficient)”intheNaganoPrefecture.Wereportanewlyfoundhabitatatanextremelyhigh densityinNaganoPrefecturein2014....

Aim Pelophylax frogs in East Asia provide an opportunity to explore the impact of glacial cycling on demographic and genetic dynamics, because it has been suggested that they experienced distribution shifts and subsequent mt DNA introgression from Pelophylax plancyi to Pelophylax nigromaculatus in association with climatic oscillations. However, th...

Facultative parthenogenesis is important for mayflies with short alate stages because females are able to reproduce without mating. We studied facultative parthenogenesis in Ephoron eophilum, a mayfly with an extremely short alate stage. We examined the survival rates of embryos from unfertilized eggs, in addition to investigating the number of chr...

Figure S2 A Bayesian analysis tree of Ephoron shigae based on the 16S rRNA gene (373 bp). Operational taxonomic units (OTUs) are indicated by sequence and population numbers (in parentheses)(figure 1, table S1 and S2). All specimens from parthenogenetic unisexual populations across Japan were found to possess the same respective sequence types in e...

Figure S1 Distribution of E. shigae in Japan. Blue open circles indicate bisexual populations, red solid circles unisexual, purple open stars weakly female-biased, and orange solid stars strongly female-biased. Population numbers are referred to in table S1 (Supporting information).

Figure S3 A Bayesian analysis tree of Ephoron shigae based on the COI gene (636 bp). Operational taxonomic units (OTUs) are indicated by sequence and population numbers (in parentheses)(figure 1, table S1 and S3). All specimens from parthenogenetic unisexual populations across Japan were found to possess the same respective sequence types in each g...

Ephoron shigae is distributed in Far East Russia, Korea and Japan, where it inhabits rivers, streams and lakes. Although this mayfly is a geographically parthenogenetic species, unisex populations have been observed only in Japan. We aimed to answer the following three questions: (i) whether there is a unisex population of E. shigae in Korea; (ii)...

The burrowing polymitarcyid mayfly Ephoron shigae is distributed across Japan, Korea, northeast China and far east Russia. Some populations are bisexual, and others are unisexual, i.e. geographically parthenogenetic throughout Japan. In general, parthenogenetic organisms are often found in harsh environments, such as at high latitudes and altitudes...

Appasus japonicus and A. major, two belostomatid species of the giant water bug found in parts of East Asia, have very similar morphological characteristics and ecological niches, and also overlapping habitats. However, the results of our previous published study utilising molecular phylogenetic analyses of mitochondrial and nuclear DNA revealed ex...

The East Asian giant water bug species Appasus japonicus Vuillefroy and Appasus major Esaki are aquatic hemipteran insects whose ranges overlap, particularly in the Japanese Archipelago and on the Korean Peninsula. In rare cases, the two species co‐occur. Furthermore, they are very similar ecologically and also morphologically, making their identif...

In East Asia, the mayfly genus Ephoron, a member of Polymitarcyidae, has been classified into three species: Ephoron eophilum, Ephoron limnobium, and Ephoron shigae. Using the nuclear histone 3 and internal transcribed spacer 1 and mitochondrial 16S rRNA and cytochrome c oxidase subunit I genes, we investigated the phylogenetic relationships of the...

Cryptoperlan stoneflies inhabit the headwaters or upper stream areas of rivers. A molecular phylogeographic study of cryptoperlans in the Japanese archipelago and on Taiwan Island has been conducted. Altogether the mtDNA 16S rRNA region of 71 individuals from 61 populations, the mtDNA COI region of 76 individuals from 41 populations, and the nDNA H...

RNA interference (RNAi) is a powerful and convenient tool not only for functional analysis of specific genes, but also for large-scale screening of gene function in insects; however, reports on its efficiency throughout development in a single species are limited. We demonstrate here that non-cell autonomous RNAi by injection of double-stranded RNA...

The polymitarcyid mayfly Ephoron shigae is widely distributed in Japan, and inhabits burrows in gravel riverbeds in the mid and lower regions of rivers. This mayfly is renowned for synchronized mass emergences at dusk in early autumn, which have been frequently observed in various Japanese rivers since the 1970s. Although much geographic documentat...

Pelophylax nigromaculatus, P. porosus porosus, and P. p. brevipoda are three pond frog species distributed in Japan. Their distributions overlap at two basins in central Japan (P. nigromaculatus and P. p. porosus in the Matsumoto basin, and P. nigromaculatus and P. p. brevipoda in the Ina basin), and hybrid descendants have been found in these area...

The heptageniid mayflies Epeorus latifolium and Epeorus l-nigrus are often the dominant species in the upper and midstream areas of Japanese rivers; as such, they play a significant role in river ecosystems. However, although these two species have been identified using the morphological characteristics of the male in its adult stage, it is impossi...

The freshwater amphipod Crangonyx floridanus (Amphipoda: Crangonyctidae) is considered to have been recently introduced from North America to Japan, and the recorded sites at which it has been collected now cover nearly all of Japan except for the northern part. In this study, we surveyed further areas outside of its known distribution range, and e...

抄録 長野県において，小河川に形成されたワンド・タマリの魚類群集を調査したところ，合計で 12種の魚類が採捕された。本流の魚類と比べると，ドジョウとシマドジョウが多く，ウグイとオイカワが少なかった。ワンド・タマリでは，魚類の種数や個体密度は主な餌となる底生動物の豊富さとは相関しなかったが，物理化学的環境要因と強く相関した。魚類の種数は，6月にはワンド・タマリの溶存酸素飽和度が高い場合に，9月にはワンド・タマリの面積や水深が大きい場合に多かった。魚類の全個体密度は，9月にはどの環境要因とも相関しなかったが，6月にはワンド・タマリの流速が大きいほど高かった。ワンド・タマリにおいて，魚類はユスリカ科及びカゲロウ目の幼虫と底生藻類及びデトリタスを主に摂食していた。本流と比べると，魚類の食性に占めるデ...