Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (bulletin of university, research institution)  

File： 畑啓生_小日本第44号（二校）hh.pdf

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Abstract

Regional and local habitat factors affecting the distribution and abundance of Japanese eel (Anguilla japonica) were systematically analysed in 123 reaches of 21 stream systems in south‐western Japan, with particular attention paid to human habitat modification, such as artificial barriers and concrete revetment.

The density of Japanese eel decreased upstream, and they were absent from the upper reaches of each stream system. The upper limits of their distribution were explained by the distance from the sea and the channel gradient, rather than barriers. However, the number of barriers had the highest explanatory capacity for the upstream decline in abundance of small eels (<40 cm in total length).

Analyses of the relative importance of regional and local habitat factors showed that the number of barriers (regional factor) was more important than local habitat factors in determining small eel abundance, whereas regional and local habitat factors (e.g. concrete revetment or cover habitat) were similarly important for large eel abundance.

These results suggest that: (i) barriers are not a major factor limiting the distribution (presence/absence) of the Japanese eel in the streams studied; (ii) barriers can substantially decrease the abundance of young eels; and (iii) as eels grow older and larger, local habitat factors, such as bank conditions and cover, become more important in determining their abundance.

The results for the relative importance of regional and local habitat factors suggest that in habitat restoration for the Japanese eel, priority should be given to mitigating barrier effects. The improvement of longitudinal connectivity to facilitate colonization by young eels is primarily needed for a more efficient use of the existing carrying capacity of streams. The improvement of local habitat conditions to increase the carrying capacity should be conducted in stream reaches free from barrier effects.

DOI： 10.1002/aqc.3938

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Abstract

Bitterling fish species (subfamily: Acheilognathinae) are endangered in Japan due to habitat loss. The decline of freshwater mussels also enhances the decrease of bitterlings because bitterlings lay eggs in the gills of freshwater mussels. Furthermore, loss of unionid mussels causes hybridization between bitterling species. This study aims to analyze the frequency of hybridization between congeneric species of bitterlings—Tanakia lanceolata and Tanakia limbata—at a well‐preserved site, where both species occur naturally and compare this with other regions more severely impacted by human intervention. One part of the irrigation streams of the Asahi River System, Okayama, is inhabited by a natural monument species of Japan, a benthic cobitid, Parabotia curtus, and therefore, the natural substratum and the structurally heterogeneous stream banks are maintained. We collected Tanakia individuals and surveyed mussel density at this well‐preserved site. We also developed six nuclear single‐nucleotide polymorphism (SNP) markers on different chromosomes to distinguish T. lanceolata and T. limbata. These SNP markers effectively determined individuals as being either one of these species or a hybrid. Based on genotyping, eight individuals were determined to be hybrids, whereas 90 and 173 individuals were determined as purebreds of T. lanceolata and T. limbata, respectively. The proportion of hybrid individuals was 3.0% and was relatively low compared to other regions. In addition, five species of unionids were densely distributed in this stream. Prezygotic isolation between sympatric T. lanceolata and T. limbata was established at this well‐preserved site, where unionid mussels are densely populated and provide enough breeding substrate for both species.

File： Ecological Research - 2023 - Hata - Genotyping of two congeneric bitterling fish species by nuclear SNP markers and the.pdf

DOI： 10.1111/1440-1703.12387

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1111/1440-1703.12387

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

File： Hata_et_al-2022-Hydrobiologia.pdf

DOI： 10.1007/s10750-022-04852-6

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The complete mitochondrial DNA sequence of the Japanese field vole Microtus montebelli was determined using Illumina MiSeq platform. The assembled genome was 16,307 bp in length and contained 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes. According to phylogenetic analysis of 13 protein-coding genes, M. montebelli and other Microtus species consist of paraphyletic clades and M. montebelli is most closely related to M. kikuchii, a species endemic to Taiwan.

File： Complete mitochondrial genome of the Japanese field vole microtus montebelli Milne Edwards 1872 Rodentia Arvicolinae.pdf

DOI： 10.1080/23802359.2021.1917315

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© 2020 John Wiley & Sons Ltd. Bitterling fishes (Subfamily: Acheilognathinae) spawn in the gills of living freshwater mussels and obligately depend on the mussels for reproduction. On the Matsuyama Plain, Japan, populations of unionid mussels—Pronodularia japanensis, Nodularia douglasiae, and Sinanodonta lauta—have decreased rapidly over the past 30 years. Simultaneously, the population of a native bitterling fish, Tanakia lanceolata, which depends on the three unionids as a breeding substrate, has decreased. Furthermore, a congeneric bitterling, Tanakia limbata, has been artificially introduced, and hybridisation and genetic introgression occur between them. Here, we hypothesised that decline of the unionids has enhanced this invasive hybridisation through competition for the breeding substrate. Three study sites were set in three streams on the Matsuyama Plain. We collected adult bitterling fishes (native T. lanceolata, introduced T. limbata, and foreign Rhodeus ocellatus ocellatus) once a week from April to October 2013 to measure their densities in streams and to examine seasonal differences in female ovipositor length, which elongates in the breeding season. Simultaneously, we set quadrats and captured unionids and measured environmental conditions. Each unionid individual was kept separately in its own aquarium to collect ejected bitterling eggs/larvae. Tanakia eggs and larvae were genotyped using six microsatellite markers and the mitochondrial cytochrome b gene. Introduced T. limbata was more abundant, had a longer breeding period, and produced more juveniles than native T. lanceolata. Hybrids between the two species occurred at all sites, and in total 101 of the 837 juveniles genotyped were hybrids. The density of P. japanensis was low, at most 0.42 individuals/m2. Nodularia douglasiae and S. lauta have nearly or totally disappeared from these sites. Hybrid clutches of Tanakia species occurred more frequently where the local density of P. japanensis was low. Mussels were apparently overused and used simultaneously by three species of bitterlings. Decline of freshwater unionid populations has enhanced hybridisation of native and invasive bitterling fishes through increasing competition for breeding substrate. We showed that rapid decline of host mussel species and introduction of an invasive congener have interacted to cause a rapid decline of native bitterling fish. Degradation of habitat and the introduction of invasive species interact to cause a cascade of extinctions in native species. In our study, obligate parasite species are threatened because the host species are disappearing, which means there is a serious threat of coextinction.

File： HataetalFWB2020.pdf

DOI： 10.1111/fwb.13629

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Authorship：Lead author,　Corresponding author   Language：Japanese   Publishing type：Research paper (scientific journal)  

File： 26_2111.pdf

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Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

Turf algae become the most abundant benthic group on coral reefs after mass coral bleaching. By defending feeding territories, damselfishes enhance the growth of turf algae in so-called algal farms and affect coral communities both directly and indirectly. We found several white scars (i.e., bite lesions) on massive Porites colonies around feeding territories. In this study, we examined the occurrence of white scars on corals and their function in coral–algal competition at the boundaries between algal farms of two damselfish species—the intensive farmer Stegastes nigricans, and the intermediate farmer S. lividus—and adjacent Porites corals for 3 years around Okinawa Island, Japan. White scars occurred on Porites colonies only adjacent to the territories of both damselfish species. Of the white scars on corals around S. nigricans territories, 73% of the area was covered by algae within 2 weeks, while the remaining was re-covered by Porites tissues. The coral–algal boundaries encroached further into areas of coral when the area of white scars were larger. These results suggest that both intensive and intermediate farmers bite adjacent Porites colonies causing white scars on corals, and expand their territories onto corals using algae-covered white scars as stepping stones.

File： Hataetal_SciRep2020.pdf

DOI： 10.1038/s41598-020-73232-8

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Other Link： https://www.nature.com/articles/s41598-020-73232-8

Authorship：Last author   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.parint.2019.101932

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© 2019 Hata et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Artificial transplantation of organisms and consequent invasive hybridization can lead to the extinction of native species. In Matsuyama, Japan, a native bitterling fish, Tanakia lanceolata, is known to form hybrids with another bitterling species, T. limbata, which was recently introduced from western Kyushu, Japan. These bitterlings spawn in the gills of two freshwater unionid species, Pronodularia japanensis and Nodularia douglasiae nipponensis, which have rapidly declined on the Matsuyama Plain in the past 30 years. To gauge the effect of invasive hybridization, we determined the genetic introgression between T. lanceolata and T. limbata and analyzed the morphology of these species and their hybrids to infer their niche overlap. We collected adult individuals of Tanakia spp. and genotyped them based on six microsatellite loci and mitochondrial cytochrome b sequences. We analyzed their meristic characters and body shapes by geometric morphometrics. We found that 10.9% of all individuals collected were hybrids. Whereas T. lanceolata were more densely distributed downstream and T. limbata were distributed upstream, their hybrids were widely distributed, covering the entire range of native T. lanceolata. The body height and anal fin length of T. limbata were greater than those of T. lanceolata, but their hybrids were highly morphologically variable, covering both parental morphs, and were widely distributed in the habitats of both parental species. Hybridization has occurred in both directions, but introduced T. limbata females and native T. lanceolata males are more likely to have crossed. This study shows that invasive hybridization with the introduced T. limbata is a potential threat to the native population of T. lanceolata via genetic introgression and replacement of its niche in streams.

File： journal.pone.0212452.pdf

DOI： 10.1371/journal.pone.0212452

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DOI： 10.1242/jeb.191676

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

© 2018 Uemura et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The distributions of two bitterling fish (subfamily: Acheilognathinae), Tanakia lanceolata and T. limbata, overlap in western Japan. Acheilognathinae fish lay their eggs in the gills of freshwater bivalves, and the early juvenile stage develops in the gills. Populations of freshwater bivalves are declining worldwide, which has limited the number of spawning substrate for bitterlings. T. limbata has been artificially introduced to some rivers in Ehime, Japan, where it coexists with native T. lanceolata, and some hybrids have been observed. We collected both species from several sites in western Japan, and from the Kunichi River system in Ehime, and analyzed genetic population structure based on six microsatellite loci and sequences of the mitochondrial cytochrome b gene. Structure analysis identified three genetically distinct populations: T. lanceolata, T. limbata “West Kyushu”, and T. limbata “Setouchi”. Two clades of T. limbata were also supported by molecular phylogenetic analyses based on cytochrome b. Hybrids in Ehime originated mostly from interbreeding between male T. lanceolata and female T. limbata “West Kyushu”, and made up 10.2% of all collected fish, suggesting that hybrids occurred frequently between females of colonizing species and males of native species. On the other hand, interspecific hybrids were detected at rates of 40.0%, 20.0%, and 17.6% in the Ima River (Fukuoka), Midori River (Kumamoto), and Kase River (Saga), respectively, which are naturally sympatric regions. We found a few T. limbata “Setouchi” in the Midori and Kase Rivers, which were supposed to be introduced from other regions, coexisting with native T. limbata “West Kyushu”, and this cryptic invasion may have triggered the interspecific hybridization. These results suggest that artificial introduction of a fish species, a decline in the unionid population, and degradation of habitat have caused broad hybridization of bitterlings in western Japan.

File： Uemuraetal2018.pdf

DOI： 10.1371/journal.pone.0203423

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File： 11_原著_吉見 color.pdf

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ZOOLOGICAL SOC JAPAN  

Laterality has been studied in several vertebrates, mainly in terms of brain lateralization and behavioral laterality, but morphological asymmetry has not been extensively investigated. Asymmetry in fishes was first described in scale-eating cichlids from Lake Tanganyika, in the form of bilateral dimorphism in which some individuals, when opening their mouths, twist them to the right and others to the left. This asymmetry has a genetic basis, and is correlated with lateralized attack behaviors. This has subsequently been found in fishes from numerous taxa with various feeding habits. The generality of such morphological laterality should thus be investigated in as wide a range of fishes as possible. Using specific indicators of lateral differences in mandibles and head inclination, we find that representative species from all 60 orders of extant gnathostome fishes (both bony and cartilaginous) possess morphological laterality. Furthermore, we identify the same laterality in agnathans (hagfish and lamprey), suggesting that this trait appeared early in fish evolution and has been maintained across fish lineages. However, a comparison of asymmetry among groups of bony fishes reveals, unexpectedly, that phylogenetically more recent-groups possess less asymmetry in body structures. The universality of laterality in fishes indicates a monophyletic origin, and may have been present in the ancestors of vertebrates. Ecological factors, predatorprey interactions in particular, may be key drivers in the evolution and maintenance of dimorphism, and may also be responsible for the cryptic trend of asymmetry in derived groups. Because lung-fish and coelacanths share this trait, it is likely that tetrapods also inherited it. We believe that study of this morphological laterality will provide insights into the behavioral and sensory lateralization of vertebrates.

DOI： 10.2108/zs160196

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File： 桑原ほか2017.pdf

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Animals in a population consistently differ from one another in behavioural types over time and this difference can affect intra- and interspecific relationships. However, empirical studies about roles of behavioural individual variation in interspecific interactions are scarce. Here, we provide evidence that inter-individual variation of a cichlid in aggression affects access to its territory by a heterospecific cichlid. In Lake Tanganyika, a zoobenthivorous cichlid Neolamprologus mustax (Nm) is admitted into territories of an algivorous Variabilichromis moorii (Vm) to prey on benthic invertebrates, while other zoobenthivorous fishes are chased from the territories. We conducted an experiment in which caged Nm fish were exposed twice to each Vm fish in natural habitats. Results indicated repeatable individual variations in Vm aggression towards Nm. Moreover, diving observations indicated that Nm fish frequently used some of Vm territories inside their own territories, but rarely or never used others. This uneven use of Vm territories by the Nm fish was negatively correlated with individual variations in Vm aggression. We conclude that the preferential access of Nm to Vm territory is gained by Nm's recognising more tolerant Vm fish or discriminating among sites for their territories.

DOI： 10.1007/s10750-016-2822-7

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In Lake Tanganyika, several lineages of cichlids have diversified into 200 species. Tribe Tropheini contains the greatest richness of herbivorous species that are classified into four ecomorphs: grazers, browsers, suckers, and pickers. All of these ecomorphs coexist on littoral rocky shores. To reveal the differences among species within ecomorphs, we analysed fish shape and functional morphology related to feeding habits, using geometric morphometrics, and measured intestine length. Furthermore, we tested the relationship between genetic and morphological distances. As a result, diversities of functional morphology among ecomorphs, and among species within ecomorphs, were revealed. In grazers, morphological diversity was greatest in jaws and the opening direction of mouth, suggesting that these species have adapted to feed on various substrata. In browsers, intestine length varied among species, indicating that this ecomorph consists of species with various specializations in herbivory. Morphological divergence was found only in the mandible and occlusal facet in grazers. No clear relation was found between morphological and phylogenetic distances in browsers, which are a polyphyletic group, indicating that their traits were acquired by convergence in multiple lineages. Our data suggest that the observed morphological variation among species enable sympatric species to separate their feeding niches.

File： Tada_et_al_2017.pdf

DOI： 10.1007/s10750-016-2761-3

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER HEIDELBERG  

In host-parasite coevolution, parasite innovations including the acquisition of new habitats and novel traits can trigger evolutionary breakthroughs and enhance parasite diversification via accumulation of new hosts. All species of the family Cymothoidae are obligate fish parasites, attaching to exterior body surfaces of fish, the buccal or opercular cavities, or burrowing into abdominal muscle tissue. In the present study, we constructed a molecular phylogeny of 27 cymothoid species that parasitise 38 fish species, combined with 2 prior cymothoid datasets, based on the sequences of mitochondrial 16S rRNA and COI genes. We explored the evolution of the host attachment mode, and the habitat shift from saline water to freshwater. Our evolutionary trees include two freshwater clades, an abdominal burrower clade, and cymothoid clades that are closer to the base of Cymothoidae than those initially analysed. We found that the basal clade of Cymothoidae was Elthusa sacciger, which is parasitic in the opercular cavity of synaphobranchid eels. This result suggests that cymothoids may have originated in deep seas, subsequently expanded to shallow seas, and then to brackish and/or freshwater, by shifting host species. Invasion of freshwater habitats has occurred at least twice; freshwater abdominal muscle burrowers living on armoured catfish constitute a clade allied to E. sacciger. The ancestral host attachment site, based on our dataset, was the opercular cavity, followed (sequentially) by buccal colonisation and attachment to the external body.

File： Hata et al (2017).pdf

DOI： 10.1007/s00227-017-3138-5

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Solitary scleractinian corals of the genera Heterocyathus and Heteropsammia inhabit soft marine bottoms without attaching to hard substrata. The corallums of these genera contain a coiled cavity inhabited by a sipunculan that roams the seafloor, carrying the host coral with it. The coral serves as a sturdy shelter that protects the sipunculan from possible predators. At the same time, the sipunculan maintains the coral in an upright position on the soft bottom. This coral-sipunculan association is unique because two phylogenetically distant coral genera have developed convergent associations with sipunculans. We investigate the process of convergent evolution of two coral species, Hc. aequicostatus and Hp. cochlea, in Okinawa, Japan, with their symbiotic sipunculans, using phylogenetic and morphological analyses. Phylogenetic analyses clarified that the symbiotic sipunculans comprise two distinct clades, surprisingly both of which are associated with both coral species. The bodily habitus of the sipunculan differed between coral species and fit the morphologies of the coiled cavities of their respective host corals. Our results suggest that the two coral species share two sipunculan clades and that sipunculan morphology is plastic and determined by the internal structure of their host corals.

File： IgawaHataKato2017.pdf

DOI： 10.1371/journal.pone.0169825

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Language：English   Publisher：AMER ASSOC ADVANCEMENT SCIENCE  

DOI： 10.1126/science.aal1722

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC  

Cichlid fish in Lake Tanganyika represent a system of adaptive radiation in which eight ancestral lineages have diversified into hundreds of species through adaptation to various niches. However, Tanganyikan cichlids have been thought to be oversaturated, that is, the species number exceeds the number of niches and ecologically equivalent and competitively even species coexist. However, recent studies have shed light on niche segregation on a finer scale among apparently equivalent species. We observed depth and substratum preferences of 15 herbivorous cichlids from four ecomorphs (i.e. grazer, browser, scraper and scooper) on a rocky littoral slope for 14 years. Depth differentiation was detected among grazers that defended feeding territories and among browsers with feeding territories. Cichlid species having no feeding territory also showed specificity on depth and substratum, resulting in habitat segregation among species that belong to the same ecomorph. Phylogenetically close species did not occupy adjacent depths, nor the opposite depth zones. Our findings suggest that apparently equivalent species of the same ecomorph coexist parapatrically along depth on a few-metre scale, or coexist with different substratum preferences on the rocky shore, and this niche segregation may have been acquired by competition between encountering equivalent species through repetitive lake-level fluctuations.

File： Hata&Ochi2016.pdf

DOI： 10.1098/rsos.160229

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：INTER-RESEARCH  

Cymothoid isopods (family Cymothoidae) are commonly found parasitizing diverse fishes, including commercial species. However, the effects of these parasites on host body condition are still poorly known. Here we investigated the spatial variation of the effects of parasite infection on host body condition, using the parasitic load of the cymothoid Mothocya parvostis on the Japanese halfbeak Hyporhamphus sajori at 4 sampling sites in western Japan. M. parvostis prevalence at each site (41.6-74.4%) was higher than that known for other fish host-cymothoid systems (usually less than 30%). The number of isopods in infected hosts, the reproductive status of female isopods (i.e. ovigerous/non-ovigerous), and the body size of female and male isopods relative to the size of their hosts were not significantly different among sites. However, at the site where human activity was most intense, M. parvostis infection had a significantly negative effect on host body condition. These results suggest that the effect of cymothoid infection on host body condition might be benign under natural conditions but becomes detrimental in habitats that are unsuitable for the host, such as highly human-impacted areas.

DOI： 10.3354/dao03064

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Publishing type：Research paper (scientific journal)   Publisher：Biology of Damselfishes  

DOI： 10.1201/9781315373874

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File： Hata2015_ZoolLett.pdf

DOI： 10.1186/s40851-015-0016-1

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Authorship：Last author,　Corresponding author   Language：Japanese   Publisher：The Ichthyological Society of Japan  

<p>Phylogeographic analysis of the bitterling <i>Tanakia limbata</i> in western Japan was conducted to identify the origin of the fish population in Ehime, Shikoku Island. A survey of rivers and spring-fed ponds on the Matsuyama Plain, Ehime, indicated that <i>T. limbata</i> had become distributed on the plain over a period of 19 years to the present day. Sequences of the mitochondrial cytochrome <i>b</i> gene indicated that the 42 individuals sampled included 4 haplotypes, which were shared with a <i>T. limbata</i> population in the Yabe River, Fukuoka, Kyushu Island. All 4 haplotypes belonged to the West Kyushu group of <i>T. limbata</i>. On the other hand, <i>T. limbata</i> comprising the West Seto clade inhabits western Honshu and eastern Kyushu, which regions shared the same paleoriver system with Ehime 20,000 years BP. These results suggest that individuals of <i>T. limbata</i> presently collected in Ehime originated from the Yabe River or adjacent waters, having artificially transported over the mountain chain that may act as a natural barrier separating the West Kyushu and West Seto groups. To conserve an endangered native bitterling, <i>T. lanceolata</i>, in Ehime, management of the introduced <i>T. limbata</i>, so as to prevent competition and hybridization with the former, is necessary.</p>

File： 松葉ら2014.pdf

DOI： 10.11369/jji.61.89

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：BIOMED CENTRAL LTD  

Background: Lake Tanganyika, an ancient lake in the Great Rift Valley, is famous for the adaptive radiation of cichlids. Five tribes of the Cichlidae family have acquired herbivory, with five ecomorphs: grazers, browsers, scrapers, biters and scoopers. Sixteen species of the herbivorous cichlids coexist on a rocky littoral slope in the lake. Seven of them individually defend feeding territories against intruding herbivores to establish algal farms. We collected epiphyton from these territories at various depths and also gathered fish specimens. Algal and cyanobacteria community structures were analysed using the amplicon-metagenomic method.
Results: Based on 454-pyrosequencing of SSU rRNA gene sequences, we identified 300 phototrophic taxa, including 197 cyanobacteria, 57 bacillariophytes, and 31 chlorophytes. Algal farms differed significantly in their composition among cichlid species, even in the same ecomorph, due in part to their habitat-depth segregation. The algal species composition of the stomach contents and algal farms of each species differed, suggesting that cichlids selectively harvest their farms. The stomach contents were highly diverse, even between species in the same tribe, in the same feeding ecomorph.
Conclusions: In this study, the amplicon-metagenomic approach revealed food niche separation based on habitat-depth segregation among coexisting herbivorous cichlids in the same ecomorphs in Lake Tanganyika.

File： Hata2014_BMCBiol.pdf

DOI： 10.1186/s12915-014-0090-4

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The left-right asymmetry of scale-eating Tanganyikan cichlids is described as a unilateral topographical shift of the quadratomandibular joints. This morphological laterality has a genetic basis and has therefore been used as a model for studying negative frequency-dependent selection and the resulting oscillation in frequencies of two genotypes, lefty and righty, in a population. This study aims were to confirm this laterality in Perissodus microlepis Boulenger and P. straeleni (Poll) and evaluate an appropriate method for measuring and testing the asymmetry. Left-right differences in the height of the mandible posterior ends (HMPE) and the angle between the neurocranium and vertebrae of P. microlepis and P. straeleni were measured on skeletal specimens. Snout-bending angle was also measured using a dorsal image of the same individuals following a previous method. To define which distribution model, fluctuating asymmetry (FA), directional asymmetry (DA), or antisymmetry (AS), best fit to the lateral asymmetry of the traits, we provided an R package, IASD. As a result, HMPE and neurocranium-vertebrae angle of both species were best fitted to AS, suggesting that P. microlepis and P. straeleni showed a distinct dimorphism in these traits, although snout-bending angle of P. microlepis was best fitted to FA. Measurement error was low for HMPE comparing the snout-bending angle in P. microlepis, indicating that measuring HMPE is a more accurate method. The scale-eating tribe Perissodini showed distinct antisymmetry in the jaw skeleton and neurocranium-vertebrae angle, and this laterality remains a valid marker for further evolutionary studies. © 2013 The Authors.

File： Hata2014_ece3849.pdf

DOI： 10.1002/ece3.849

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Tuna-farming is expanding worldwide, necessitating the monitoring/managing of its effects on the natural environment. In Japan, tuna-farming is conducted on coral reefs that have been damaged by mass-bleaching events and crown-of-thorns starfish (COTS) outbreaks. This study focused on the coral community on an artificial substrate of tuna-farm to reveal the possible effects of tuna-farming on the natural environment. Corals flourished on ropes suspended in the farm in the Amami Islands, southern Japan. These were moored 3 m below the sea-surface in 50-m-deep water. The coral community on the rope was analyzed and compared with those on natural substrata on two adjacent COTS-damaged reefs and with that in a protected reef. Corals were monitored throughout a year. Sixty coral species grew on the ropes, that corresponds to 27.3% of the 220 species known from Amami. The coral community was unique, dominated by massive faviid corals. On the ropes, the water temperature rarely exceeded 30.0 degrees C and no corals on the rope were severely bleached or covered by sedimentation during the observations. The tuna-farm infrastructure provided corals with a suitable habitat, and species-rich coral communities were established. These coral communities are an important node connecting tuna-farms and the natural environment. (C) 2012 Elsevier Ltd. All rights reserved.

File： Hata et al. 2013.pdf

DOI： 10.1016/j.marenvres.2012.12.009

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Recent phylogenetic studies of Chlorella-like algae revealed that this group has diversified into free-living and endosymbiotic niches, the latter within protists and invertebrate organisms. Our previous studies using a long-term culture composed of an alga (Chlorella vulgaris, rDNA sequence unknown), a bacterium (Escherichia coli) and a ciliate (Tetrahymena thermophila), suggested that some clones in the algal population developed an endosymbiotic ability with T. thermophila while others developed an ectosymbiotic ability with E. coli from a non-associated stage. In this paper, an rDNA (18S, ITS1, 5.8S, ITS2)-based phylogeny of the ancestral strain and derived clones isolated from 5-year microcosm cultures was constructed and revealed that the alga belongs to the genus Micractinium. This result was supported by analysis of the secondary structure of the rRNA gene. No difference was observed in the sequence between the ancestral and derived clones. On the other hand, some morphological and physiological traits of the ancestral strain and the derived clones were analysed and revealed that several phenotypic changes had occurred among the algal clones. In particular, the derived clones obtained from long-term cultures had increased in cell size, changed in their ability to grow at pH 4.0, and developed a tendency for cell-aggregation or sedimentation. © 2013 © British Phycological Society.

DOI： 10.1080/09670262.2013.860482

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We present a mathematical model of the maintenance of polymorphism of fluvial and amphidromous types in a fish population. Downstream drifting of offspring after hatching and their subsequent upstream migration have an important effect on the maintenance of an upstream population. This model, which assumes a linear relationship of offspring mortality rate, nutritional conditions, and flow rate or inclination with the distance from the river mouth, enables us to calculate the number of recruits to the mother population. From the present analysis, we can predict that the fluvial type producing large embryos is selected in the upper reaches under conditions where there are large differences in offspring mortality and flow rate between the upper and lower reaches, and a small difference in nutritional conditions between these sites. Therefore, the fluvial type can be more easily evolved in tropical regions than temperate regions where the difference in nutritional conditions is relatively larger. This selection is promoted when offspring mortality decreases greatly with their size. Conversely, at the lower reaches of the same river, the amphidromous type producing many small embryos is favored. These two populations can be the polymorphism of a single population species in a river, and can be established as different species in terms of pre- or post-reproductive isolation mechanisms, such as assortative mating or habitat preference, even if their members mate with each other in a river. We can assert that sympatric speciation is common in fluvial environments, when this process really works, because other taxonomic groups, such as Annelida. Crustacea, and Mollusca, also have the same sympatric pair of fluvial and amphidromous species derived from marine origin, that is, so called the evolutionary invasion from marine to terrestrial environments. (C) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.ecolmodel.2012.06.006

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Authorship：Lead author,　Corresponding author   Language：Japanese  

CiNii Books

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Authorship：Lead author,　Corresponding author   Language：Japanese  

CiNii Books

J-GLOBAL

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ZOOLOGICAL SOC JAPAN  

The asymmetry of mouth morphology, in which the mouth opens either leftward or rightward, is a unique example of antisymmetry that is widely found in fishes, such as Tanganyikan scale-eating cichlids, herbivorous cichlids, and the Japanese freshwater goby. This dimorphism is thought to be heritable in a Mendelian manner similar to that of the dominance of the lefty allele over righty, with homozygotes of lefty alleles being absent. This study aims to reveal whether this trait is inherited in the same Mendelian manner in fishes other than those examined to date, and whether the absence of the dominant homozygote is due to a lethal effect. We conducted F-1 and F-2 breeding experiments using the Tanganyikan cichlid Julidochromis transcriptus and Japanese medaka Oryzias latipes. For both J. transcriptus and O. latipes, the F1 generations produced by incrossing lefty parents showed a lefty: righty ratio of 2:1, whereas incrosses of righties produced only righty offspring. Test crosses between lefty and righty produced a 1:1 ratio of lefty and righty offspring. These results are consistent with the inheritance model in which righty is homozygous for a recessive righty allele and lefty is heterozygous for dominant lefty and recessive righty alleles, in agreement with previous observations. The F-2 test cross also confirmed this pattern. Furthermore, no lethal effects on hatchability of O. latipes were detected, refuting the suggestion that the dominant homozygote is embryonic lethal. We conclude that mouth laterality is inherited in the same Mendelian manner in these two species, similar to that other fish species studied previously. However, the reason for absence of the dominant homozygote remains unclear.

DOI： 10.2108/zsj.29.49

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：PSYCHOLOGY PRESS  

The inheritance patterns of asymmetry in mouth opening in zebrafish were investigated using crossing experiments. Zebrafish exhibit asymmetric laterality in mouth opening, with each individual having either a leftward (righty) or rightward (lefty) bias. All righty incrosses produced only righty F-1, whereas all lefty incrosses resulted in an F-1 L:R ratio of 2:1. All test crosses between lefty and righty individuals resulted in an F-1 L:R = 1:1. These results were consistent with the hereditary pattern for Japanese medaka, three Tanganyikan cichlids, and a Japanese riverine goby. The pattern suggests a one-locus two-allele Mendelian model of inheritance, with the lefty allele being dominant over righty and the dominant homozygote being lethal. To determine the reason for the absence of lefty homozygotes, the survival rates of the offspring were examined according to developmental stage. Survival did not differ among combinations of parent laterality. Thus the mechanism underlying the lethality of the dominant homozygote remains unclear. This study showed that the mouth-opening laterality of zebrafish is genetically determined and that the direction follows a Mendelian inheritance pattern that is shared among cypriniform zebrafish, beloniform medaka, perciform cichlids, and a goby, suggesting a common genetic background in mouth-opening laterality among these species.

DOI： 10.1080/1357650X.2011.626563

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：PUBLIC LIBRARY SCIENCE  

Background: Asymmetry in animal bodies and behavior has evolved several times, but our knowledge of their linkage is limited. Tanganyikan scale-eating cichlids have well-known antisymmetry in their bodies and behavior; individuals open their mouths leftward (righty) or rightward (lefty), and righties always attack the right flank of the prey, whereas lefties attack the left. This study analyzed the morphological asymmetry in a scale-eating characiform, Exodon paradoxus, and its behavioral handedness.
Methodology/Principal Findings: Each eight E. paradoxus was observed for 1-h with a prey goldfish in an aquarium to detect the behavioral handedness. Following the experiment, the lateral differences in the mandibles and head-inclination of these eight and ten additional specimens were analyzed. Both measurements on the morphology showed a bimodal distribution, and the laterality identified by these two methods was always consistent within a given individual, indicating that the characin has morphological antisymmetry. Furthermore, this laterality significantly corresponded to behavioral handedness; that is, lefties more often rasped scales from the right flank of the prey and vice versa. However, the correlation between laterality and handedness is the opposite of that in the cichlids. This is due to differences in the feeding apparatus and technique. The characin has cuspids pointing forward on the external side of the premaxilla, and it thrusts its dominant body side outward from its body axis on the flank of the prey to tear off scales. By contrast, the cichlids draw their dominant body side inward toward the axis or rotate it to scrape or wrench off scales with the teeth lined in the opened mouth.
Conclusions/Significance: This study demonstrated that the antisymmetry in external morphology and the corresponding behavioral handedness have evolved in two lineages of scale-eating fishes independently, and these fishes adopt different utilization of their body asymmetry to tear off scales.

File： Hata2011_journal.pone.0029349(3).pdf

DOI： 10.1371/journal.pone.0029349

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER TOKYO  

The territorial damselfish, Stegastes nigricans, maintains algal farms by excluding invading herbivores and weeding unpalatable algae from its territories. In Okinawa, Japan, S. nigricans farms are exclusively dominated by Polysiphonia sp., a highly digestible filamentous rhodophyte. This study was aimed at determining the diet of S. nigricans in Okinawa and its dependency on these almost-monoculture algal farms based on stomach content and chemical analyses. Stomach content analyses revealed that all available food items in the algal farms (i.e., algae, benthic animal inhabitants, trapped detritus) were contained in fish stomachs, but amorphous organic matter accounted for 68% of the contents. Therefore, carbon and nitrogen stable isotope ratios and fatty acid (FA) compositions were analyzed to trace items actually assimilated in their bodies. Stable isotope analyses showed that benthic animals were an important food source even for this farmer fish. Two essential fatty acids (EFAs), 20:4n6 and 20:5n3, which are produced only by rhodophytes among available food items, were rich in the muscle tissue of S. nigricans as well as in algal mats and detritus, suggesting that algal mats contribute EFAs to S. nigricans directly and indirectly through the food web. In conclusion, S. nigricans ingested algal mats, detritus, and benthic animals maintained within its farm. Algae and detritus were original sources of EFAs, and benthic animals, which were much more abundant in the farms than in outside territories, provided a nitrogen-rich dietary source for the fish.

File： Hata&Ume_2011.pdf

DOI： 10.1007/s11284-011-0840-5

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：BIOMED CENTRAL LTD  

Background: On coral reefs, damselfish defend their territories from invading herbivores and maintain algal turfs, from which they harvest filamentous algae. In southern Japan, intensive weeding of indigestible algae by Stegastes nigricans results in overgrowth by one filamentous alga, Polysiphonia sp. 1. Because this alga is highly susceptible to grazing and is competitively inferior to other algae, it survives only within the protective territories of this fish species, suggesting an obligate mutualism between damselfish and their cultivated alga. The wide distribution of damselfish species through the Indo-Central Pacific raises the question of whether this species-specific mutualism is maintained throughout the geographic range of the fish. To address this question, from all 18 damselfish species we conducted comprehensive surveys of algal flora within their territories throughout the Indo-West Pacific, and identified species of Polysiphonia using morphological examination and gene sequencing data.
Results: Several species of the genus Polysiphonia were observed as a major crop in territories throughout the geographic range of S. nigricans. Polysiphonia sp. 1 occurred only in territories of S. nigricans in central areas of the Indo-Pacific. However, its occurrence was low from the Great Barrier Reef and Mauritius. In contrast, other indigenous Polysiphonia species, which formed a clade with Polysiphonia sp. 1, occurred in the territories of fishes from Egypt, Kenya, and the Maldives. The other Polysiphonia species in the clade only inhabited damselfish territories and were never found elsewhere.
Conclusions: Cultivation mutualism between the damselfish S. nigricans and algae of Polysiphonia was maintained throughout the Indo-West Pacific, although algal crop species and the mode of cultivation (e.g., presence/absence of selective weeding, the species composition of algal turfs) varied among localities. This finding implies that damselfish utilize indigenous Polysiphonia species in newly colonized habitats in different ways, and therefore the algal composition and means of cultivation have diverged.

File： Hata2010_BMCEvolBiol.pdf

DOI： 10.1186/1471-2148-10-185

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：BLACKWELL PUBLISHING  

Underwater observations conducted in the shallow waters of the southern part of Lake Tanganyika showed that a zoobenthos-eating cichlid Neolamprologus mustax preferentially foraged in the permanent territory of an algivorous cichlid Neolamprologus moorii, even though other zoobenthos-eaters were chased out. Benthic invertebrates were much richer within the territory of N. moorii than outside, suggesting that the territory was an attractive feeding ground for zoobenthos-eaters. Stomach contents analysis showed that N. mustax rarely ate fish broods, although other zoobenthos-eaters often did so. It is concluded that the differential tolerance of N. moorii towards zoobenthos-eaters based on their harmfulness to broods benefits harmless N. mustax by allowing its use of the prey-rich territory. (c) 2007 The Authors Journal compilation (c) 2007 The Fisheries Society of the British Isles.

DOI： 10.1111/j.1095-8649.2007.01493.x

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOCIETY  

In cultivation mutualisms, farming animals prepare fields for cultivars, enhance their growth and harvest them. For example, in terrestrial ecosystems, plant-herbivore cultivation mutualisms arose between humans and their crops only relatively recently. We discovered an obligate cultivation mutualism between a damselfish and an alga in a coral reef ecosystem. The damselfish, Stegastes nigricans, manages algal farms through territorial defence against the invading grazers and through weeding of unpalatable algae. As a result, the algal farms of S. nigricans are dominated by one species, Polysiphonia sp. We performed an exhaustive survey of algal assemblages inside and outside the territories of five damselfish species around the Ryukyu Islands, Japan, using molecular and morphological characteristics. Polysiphonia sp. 1 grew exclusively inside the farms of S. nigricans, and never elsewhere. Since only Polysiphonia sp. 1 is harvested and consumed by the damselfish as a staple food, this interdependent relationship is an obligate cultivation mutualism. This is the first record of an obligate plant-herbivore cultivation mutualism in a marine ecosystem. Our data also suggest that three other Polysiphonia species are facultatively mutual with, commensal with, or parasitic on other damselfish species.

File： Hata2006_Biol. Lett.-2006-Hata-593-6.pdf

DOI： 10.1098/rsbl.2006.0528

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Algal farms maintained by different species of territorial herbivorous damselfishes vary in size, algal biomass, and species composition. To determine the factors that affect the structure of these farms, we compared fanning behavior and intensity between two sympatric damselfish species, Stegastes nigricans (Lacepede) and S. obreptus (Whitley), which maintain two different types of farms in the Okinawa Islands, southern Japan. By weeding of indigestible algae and prompt exclusion of herbivorous fishes and grazing sea urchins, S. nigricans manage relatively small farms largely dominated by one algal crop species, Polysiphonia sp. In contrast, by delayed exclusion of herbivores, S. obreptus maintain larger farms invaded by diverse indigestible algae, such as Chondria sp. and Padina sp. As a result of intensive management, S. nigricans attains a higher algal biomass per area than does S. obreptus. This study provides a new perspective, as it suggests that damselfishes practise both intensive and extensive fanning. The former results in small and highly productive monoculture farms of one palatable alga, while the latter leads to large, species-rich, mixed-culture farms. (C) 2004 Elsevier B.V. All rights reserved.

File： Hata2004_JEMBE.pdf

DOI： 10.1016/j.jembe.2004.08.009

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：INTER-RESEARCH  

Resident herbivorous damselfishes exclude other herbivores from their territories and maintain dense stands of filamentous algae as algal farms. The damselfish Stegastes nigricans occupies coral reefs in the Okinawa Islands, southern Japan, and is unique in maintaining monocultural algal farms of the filamentous rhodophyte Polysiphonia sp. One of the mechanisms by which S. nigricans maintains these unique algal farms is by selective weeding of indigestible algae. This study tested the hypothesis that, were it not for management by S. nigricans, monocultures would be taken over by algal succession, even without grazing by other herbivores. We set up S. nigricans-exclusion cages inside and grazer-exclusion cages outside the territories of S. nigricans, and monitored algal succession. After exclusion of S. nigricans, the Polysiphonia sp. monoculture deteriorated rapidly and algal biomass decreased simultaneously. Filamentous rhodophytes replaced Polysiphonia sp. within 2 wk, and were in turn displaced by corticated macrophytes and calcareous algae (which are usually selectively weeded by S. nigricans). Monocultures of Polysiphonia sp. did not appear in the grazer-exclusion cages; pioneer Polysiphonia sp. colonized the areas just after caging, but thereafter was replaced by other filamentous rhodophytes, corticated macrophytes, and calcareous algae. Our experiments demonstrated that S. nigricans maintained monocultures and high biomass of palatable pioneer Polysiphonia sp. against algal succession by intensive farm-management, involving selective weeding.

File： Hata2003_m263p159.pdf

DOI： 10.3354/meps263159

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

We compared the community structure of benthic algae inside and outside pomacentrid damselfish (Stegastes nigricans) territories in a moat at Sesoko Island, Okinawa, Japan. S. nigricans maintained "algae farms" that were dominated by the filamentous rhodophyte, Womersleyella setacea. Species richness and biomass were higher inside damselfish territories than outside, while species diversity and evenness were higher outside. Detrended correspondence analysis (DCA) based on species composition showed that the dominance of W. setacea was maintained throughout the year in all samples collected from inside damselfish territories. The observed strong dominance of filamentous rhodophytes was consistent with the findings of most studies on damselfish territories worldwide. However, the dominance of a single species of alga and low species diversity inside the territories was in contrast to the findings of previous studies, in which the reduction of grazing pressure caused intermediate disturbance and enhanced algal species diversity. This discrepancy in algal species diversity inside the damselfish territories seems to have been caused by unique characteristics of the alga and the fish. W setacea traps sediment, which reduces the availability of firm substrata for attachment and inhibits the recruitment of some algae. Moreover, S. nigricans "weeds" indigestible calcareous and thicker algae. The algal assemblage outside damselfish territories varied among samples, and included mat-forming cyanophytes (Calothrix aeruginosa and Calothrix codicola), a prostrate laminar phaeophyte (Padina sp.), thin and small-scaled algae (Cladophora sp. and Feldmannia indica), finely branched filamentous rhodophytes (Taenioma perpusillum and Herposiphonia obscura), and a coarsely branched rhodophyte (Gelidiopsis variabilis).
We placed artificial slate plates inside and outside damselfish territories, and showed that the W setacea inside territories gradually increased in biomass, reaching the same levels of biomass and dominance as W setacea on natural substrata. Outside the territories, the algal assemblage underwent succession from early colonizers, i.e., thin and small-scaled algae, to grazing-resistant algae such as mat-forming cyanophytes and prostrate laminar Padina sp. Under heavy grazing, the flora outside the territories was composed of early colonizers, grazing-resistant algae, and scattered erect algae that had probably escaped grazing by chance.
Our findings suggest that sediment trapped by the turf of W setacea inhibited recruitment of some algae, and that moderate cropping and selective weeding by S. nigricans excluded grazing-resistant algae and prevented early colonizers and competitively superior algae from out-competing W setacea. Consequently, low species diversity and a high-biomass "farm" suitable for harvesting was maintained. (C) 2002 Elsevier Science B.V. All rights reserved.

File： Hataetal2002.pdf

DOI： 10.1016/S0022-0981(02)00395-7

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：INTER-RESEARCH  

Resident herbivorous damselfishes (Pisces: Pomacentridae) exclude other herbivores from their territories and reduce the grazing pressure within these territories. Among the damselfish, Stegastes nigricans is unique in that it manages a virtual monoculture dominated by the erect filamentous rhodophyte Womersleyella setacea, whereas many other herbivorous damselfishes maintain species-rich farms. We observed the behavior of S. nigricans in a lagoon in Okinawa, Japan, and discovered that this species intensively weeded out specific algae. To analyze weeding selectivity, we compared the algae picked up and discarded by S. nigricans to the algal assemblage found inside the territory. To examine the digestibility of each algal species, 10 damselfish were collected, and algae removed from their stomachs were compared with those found in the intestine and faeces. Inside their territories, S. nigricans selectively weeded out indigestible algae. These algae were late-colonizing Species, and the intensive weeding suppressed algal growth beyond early successional stages. Consequently, selective weeding enabled the fish to maintain virtual monocultural farms of a digestible early colonizer, W setacea, inside their territories.

File： Hata&Kato2002.pdf

DOI： 10.3354/meps237227

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The structures of benthic foraminiferal communities inside and outside the territory of the pomacentrid damselfish Stegastes nigricans on coral rocks in a moat of Sesoko Is. (26degrees38' N, 127degrees52' E) in Okinawa, Japan were compared. Inside the territory, an algal farm, i.e., a dense stand of a filamentous rhodophyte, Womersleyella setacea, was maintained throughout the year. Outside the territory, in areas subjected to intensive and continuous grazing by various grazers, the flora was composed of mat-like cyanophytes, a prostrate turf-form Padina sp., microscopically thin filaments and scattered filamentous rhodophytes. Algal biomass was greater inside the territory than outside the territory of the damselfish. These differences were reflected by the structure of the associated foraminiferal communities. We classified foraminiferal species based on their microhabitat use around algal communities into four life types: free-living type, crawling type, sedentary type, and sessile type, The abundance of foraminifera, especially the free-living type (e.g,, Peneroplis pertusus and Quinqueloculina seminulum) and sedentary type (Rosalina globularis and Cymbaloporetta squammosa), was greater inside the territory of the damselfish than outside the territory. Species richness was also higher inside the territory, mainly due to an increase in species richness of the free-living and sedentary types. These increases in abundance and species richness were caused by habitat structuring. TV setacea is a relatively tall and complicated alga with tangled rhizoids. Its dense stand inside the territory trapped a larger amount of sediment, which provided free-living foraminifera with heterogeneous and stable habitats. In addition, the dense stand of TV setacea provided sedentary-type foraminifera with a large, complex substratum, providing refuge and food inside the territory. This assumption was confirmed by the results of plate experiments showing that foraminiferal community structures were controlled by associations between foraminifera and algae. We showed that habitat-conditioning is an important process in biotic habitat-structuring and that habitat-conditioning by territorial damselfish maintains and enhances multi-species coexistence of foraminifera on coral rocks in a coral reef, (C) 2002 Elsevier Science B.V. All rights reserved.

File： Hata&Nishihira2002.pdf

DOI： 10.1016/S0022-0981(02)00029-1

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Language：Japanese   Publisher：日本微生物生態学会  

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DOI： 10.14848/esj.ESJ52.0.721.0

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Language：Japanese   Publisher：日本生態学会  

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Event date： 2022.5

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