掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

DOI： 10.1111/jfb.14920

PubMed

掲載種別：研究論文（学術雑誌）  

DOI： 10.3389/fevo.2021.685907

担当区分：最終著者   掲載種別：研究論文（学術雑誌）  

DOI： 10.1093/beheco/araa150

担当区分：最終著者   掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/jzo.12867

その他URL： https://onlinelibrary.wiley.com/doi/full-xml/10.1111/jzo.12867

掲載種別：研究論文（学術雑誌）   共著区分：共著   国際・国内誌：国際誌  

DOI： 10.1038/s41467-021-22075-6

PubMed

担当区分：最終著者   掲載種別：研究論文（学術雑誌）   共著区分：共著   国際・国内誌：国際誌  

Siblings often compete for limited resources, such as food provided by their parents. However, although several functions of nonlethal sib- ling (nonsiblicidal) aggression have been proposed, there is currently little empirical evidence for these, apart from food monopolization. Here, we investigated the functions of nonlethal sibling aggression in the biparental-caring territorial herbivorous cichlid Varibilichromis moorii. We found that the juveniles of this species are highly aggressive and that larger juveniles are more aggressive toward their smaller siblings. Larger juveniles feed on algae more frequently than smaller siblings, thereby indicating a dominance hierarchy. Sibling aggression decreased when algae in the nest was experimentally removed. Furthermore, the removal of smaller juveniles decreased sibling aggression among the remaining larger juveniles, whereas the removal of larger juveniles increased aggression among smaller juveniles. The algal feeding rate of juveniles only increased when larger individuals were removed from the nest. Moreover, larger juveniles attained higher growth rates and remained in natal nests longer than smaller individuals. Our results indicate that sibling aggression may facilitate the mo- nopolization of resources by larger juveniles and extend the parental care period. Interestingly, a small subset of juveniles was observed to migrate to other nests. These juveniles were larger than those of the host brood, and their growth rate increased within the new nests. We suggest that subordinate juveniles may disperse from natal nests and sneak into new nests to enhance their rank, which may represent a novel example of a “best of a bad job” strategy associated with sibling competition.

DOI： 10.1093/beheco/araa150

担当区分：最終著者   掲載種別：研究論文（学術雑誌）   共著区分：共著   国際・国内誌：国際誌  

Baikal sculpins are a unique group of fishes, including both externally and internally fertilizing species. Sperm traits, such as morphology and motility, are predicted to undergo adaptive changes due to species fertilization modes. However, studies exploring such traits in Baikal sculpins are lacking. Here, we conducted a field study and investigated sperm traits of three sculpins with external fertilization (Cottocomephorus grewingkii, Leocottus kesslerii and Paracottus knerii) and one sculpin with internal fertilization (Comephorus dybowskii). Sperm head morphology was spherical in both types of fertilizing species; however, the head cross‐sectional area of the sperm of the internal fertilizer was smaller than that of external fertilizers. This result implies that sperm head morphology might be adapted to swim in a viscous ovarian fluid. The internal fertilizer, C. dybowskii, had longer and faster‐swimming sperms with longer motility duration than the external fertilizers, perhaps due to different sperm competition levels. Sperms of the internal fertilizer were only motile in isotonic solutions, whereas sperms of the external fertilizers were motile in lake waters, suggesting that sperm motilities are specialized according to their external/internal environments. To our knowledge, this is the first study to demonstrate sperm traits of Baikal sculpins, which may have evolved adaptively along with changing fertilization modes.

DOI： 10.1111/jzo.12867

掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s10228-020-00745-7

掲載種別：研究論文（学術雑誌）   共著区分：共著  

DOI： 10.1643/CE-19-271

掲載種別：研究論文（学術雑誌）  

DOI： 10.1643/CE-19-271

担当区分：最終著者   掲載種別：研究論文（学術雑誌）   国際・国内誌：国内誌  

DOI： 10.2108/zs190132

PubMed

担当区分：最終著者   掲載種別：研究論文（学術雑誌）   共著区分：共著   国際・国内誌：国際誌  

DOI： 10.2108/zs190132

PubMed

掲載種別：研究論文（学術雑誌）   共著区分：共著  

DOI： 10.1007/s10228-020-00745-7

掲載種別：研究論文（学術雑誌）   共著区分：共著   国際・国内誌：国際誌  

Although parental care is known to occur in a wide range of teleost fishes, postnatal provisioning of nutrition has been documented rarely. Here, we describe a novel example of bi-parental care in a teleost, i.e. mucus-provisioning behaviour in the scale-eating cichlid Perissodus microlepis endemic to Lake Tanganyika. Field observations revealed that young guarded by their parents frequently glanced towards the body surface of both parents. Furthermore, analyses of stomach contents of the young found the presence of ingested mucus, confirming that the young feed on the mucus secretions of their parents. The frequency of glancing behaviour increased with size of the young up to ~13 mm in standard length, but then declined with further growth. Additionally, the frequency of glancing of young towards their parents was higher when the frequency of foraging on plankton was lower. Underwater cage experiments revealed a higher rate of growth in the young kept in direct contact with their parents than in those not allowed direct contact. We conclude that glancing behaviour in young P. microlepis is a form of direct parental nourishment that confers growth benefits to the young when food abundance is low.

DOI： 10.1093/biolinnean/blz124

掲載種別：研究論文（学術雑誌）  

DOI： 10.1093/biolinnean/blz124

掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/eth.12929

掲載種別：研究論文（学術雑誌）   共著区分：共著   国際・国内誌：国際誌  

DOI： 10.1111/eth.12929

掲載種別：研究論文（学術雑誌）   共著区分：共著  

DOI： 10.1007/s00227-019-3506-4

その他URL： http://orcid.org/0000-0003-3254-7943

掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s00227-019-3506-4

担当区分：最終著者   掲載種別：研究論文（学術雑誌）   共著区分：共著   国際・国内誌：国際誌  

DOI： 10.1007/s10228-018-0672-1

掲載種別：研究論文（学術雑誌）  

DOI： 10.2108/zs180130

掲載種別：研究論文（学術雑誌）   共著区分：共著  

DOI： 10.1007/s10750-018-3768-8

掲載種別：研究論文（学術雑誌）   国際・国内誌：国内誌  

DOI： 10.2108/zs180130

PubMed

掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s10228-018-0672-1

掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s10750-018-3768-8

その他URL： http://link.springer.com/content/pdf/10.1007/s10750-018-3768-8.pdf

掲載種別：研究論文（学術雑誌）   共著区分：共著  

DOI： 10.1371/journal.pbio.3000021

PubMed

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

DOI： 10.1371/journal.pbio.3000021

PubMed

掲載種別：研究論文（学術雑誌）   共著区分：共著  

DOI： 10.3390/sym11010119

掲載種別：研究論文（学術雑誌）  

DOI： 10.3390/sym11010119

掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/eth.12813

掲載種別：研究論文（学術雑誌）  

Unravelling the evolution of complex social organization in animals is an important aim, not least because it helps to understand the evolutionary roots of human sociality. Recent advances in comparative methods allow to approach this question in a phylogenetic context. The validity of such comparative approaches depends strongly on the quality of information regarding the behaviour, sociality, and reproduction of animals in natural systems, and on the quality of the phylogenetic reconstruction. Applying a novel comparative approach, a recent study of Dey et al. (, Nature Ecology & Evolution, 1, 137) concluded that evolutionary transitions to cooperative breeding in cichlid fishes were not associated with the social mating pattern. Here we argue that this result was adversely affected by equivocal classifications of mating patterns, and inadequate phylogenetic data. In order to illustrate the impact of the mating system misclassifications, we scored mating patterns as reported in the original literature and re-analysed the dataset based on Dey et al.'s tree topology. The result suggests that the mating system does in fact significantly explain the evolutionary transition to cooperative breeding in lamprologine cichlids, but we submit that a reliable conclusion cannot be reached before improving the behavioural information and the underlying phylogenetic reconstruction. The problems identified in this case study are not unique and we urge caution in the interpretation of results from comparative phylogenetic studies in general. We do agree with Dey et al. () though that the lamprologine cichlids of Lake Tanganyika may constitute a fundamental test case for the theory of social evolution, but better information on their behaviour and phylogenetic relationships is needed to allow meaningful analyses.

DOI： 10.1111/eth.12813

掲載種別：研究論文（学術雑誌）  

J-GLOBAL

掲載種別：研究論文（学術雑誌）  

J-GLOBAL

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s10750-016-2822-7

掲載種別：研究論文（学術雑誌）  

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

掲載種別：研究論文（大学，研究機関等紀要）  

J-GLOBAL

掲載種別：研究論文（大学，研究機関等紀要）  

J-GLOBAL

掲載種別：研究論文（大学，研究機関等紀要）  

J-GLOBAL

掲載種別：研究論文（学術雑誌）  

J-GLOBAL

掲載種別：研究論文（学術雑誌）  

CiNii Article

J-GLOBAL

掲載種別：研究論文（学術雑誌）  

CiNii Article

J-GLOBAL

掲載種別：研究論文（学術雑誌）   共著区分：単著  

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

J-GLOBAL

掲載種別：研究論文（学術雑誌）  

CiNii Article

掲載種別：研究論文（学術雑誌）  

CiNii Article

J-GLOBAL

掲載種別：研究論文（学術雑誌）  

CiNii Article

J-GLOBAL

掲載種別：研究論文（学術雑誌）  

© 2015 Marine Biological Association of the United Kingdom. Two chaenopsid fishes, Neoclinus chihiroe and Neoclinus lacunicola, were collected from Sadogashima Island, the Sea of Japan. The collected specimens represent the northernmost records of the two species and the first voucher specimens from the Sea of Japan. Morphological information and colour photographs, including underwater photos, of these specimens were provided. Additional photographic evidence from Tobi-shima Island, ~100 km north-north-east of Sadogashima Island, further extended the northernmost record of Neoclinus lacunicola.

DOI： 10.1017/S1755267215001037

掲載種別：研究論文（学術雑誌）  

Two chaenopsid fishes, Neoclinus chihiroe and Neoclinus lacunicola, were collected from Sadogashima Island, the Sea of Japan. The collected specimens represent the northernmost records of the two species and the first voucher specimens from the Sea of Japan. Morphological information and colour photographs, including underwater photos, of these specimens were provided. Additional photographic evidence from Tobi-shima Island, ~100 km north-north-east of Sadogashima Island, further extended the northernmost record of Neoclinus lacunicola.

DOI： 10.1017/S1755267215001037

掲載種別：研究論文（学術雑誌）  

CiNii Article

J-GLOBAL

掲載種別：研究論文（学術雑誌）  

CiNii Article

掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s00265-014-1830-8

掲載種別：研究論文（学術雑誌）  

Cooperative breeding has been studied intensively in many species of birds and mammals but remain less well studied in fish. We report a remarkable new example of a cooperatively breeding cichlid from Lake Tanganyika, Neolamprologus obscurus. Using field observations and microsatellite DNA analyses, we studied group structure, helping behavior, relatedness, and dispersal of this species. We present four major observations. First, large territorial breeding males mated with one to eight breeding females, each of which was territorial and unrelated to another. Second, one to ten smaller fish ("subordinates") of both sexes were allowed to stay inside the breeding females' territories. Subordinates were often highly related to both the respective breeding male and female and performed territory defense and shelter maintenance, which is regarded as helping behaviors. Third, one to three subordinate males, similar in size to breeding females, were allowed to stay inside a breeding male's territory but were not tolerated in the breeding females' territories. Pairwise relatedness suggests these individuals are usually sons of the respective breeding male. Fourth, pairwise relatedness estimates suggest that juveniles delay dispersal and assist their mothers in raising offspring. As female subordinates grow up, they leave the father's territory and disperse into other groups. In contrast, male subordinates leave their mother's territory but remain within the territory of their father. The described social system makes N. obscurus a promising new model species to study the evolution of cooperative breeding.

DOI： 10.1007/s00265-014-1830-8

掲載種別：研究論文（学術雑誌）  

DOI： 10.3389/fevo.2015.00085

掲載種別：研究論文（学術雑誌）   共著区分：単著  

DOI： 10.2331/suisan.81.871

CiNii Article

掲載種別：研究論文（学術雑誌）  

DOI： 10.3389/fevo.2015.00085

掲載種別：研究論文（学術雑誌）  

We investigated the evolutionary relationship between spawning behaviour and sperm motility traits among Tanganyikan mouth-brooding cichlid species that have developed diverse mating behaviours and male sexual traits. Mouth-brooding behaviour is common among these fish, but different species demonstrate a range of spawning behaviours, bower construction, male sexual traits and timing of gamete release. We observed spawning behaviours and compared sperm motility traits of 28 Tanganyikan mouth-brooding cichlids to elucidate the evolutionary correlations between these traits. Sperm longevity was considerably longer in bower-building species that construct crater-shaped spawning sites compared with species that do not build bowers. Male bower builders released sperm in the pit of the bower prior to spawning, and the time from ejaculation to fertilization was longer. Conversely, most mouth-brooding cichlids deposited semen directly into the female buccal cavity, and spawned eggs were immediately picked up to be placed inside the cavity
thus, the time from ejaculation to fertilization was short. These observations suggest that increased sperm longevity is favoured in bower builders. Comparative phylogenetic analyses suggested that bower-building behaviour and greater time from ejaculation to fertilization are associated with the extension of sperm longevity, whereas sperm competition rank does not play a major role. In addition, bower-building behaviour preceded the emergence of increased sperm longevity. These results indicate that the extension of sperm longevity as a result of the emergence of bower builders may have acted as an evolutionary attractor for sperm longevity.

DOI： 10.1111/jeb.12522

PubMed

掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/jeb.12522

掲載種別：研究論文（学術雑誌）  

Changes in mRNA levels of prolactin (PRL) during the upstream migration were examined in fry of the amphidromous fish, ayu Plecoglossus altivelis. Quantification of mRNA has been done with real-time PCR and expressed as whole body or pituitary contents depending the body size of fry. PRL mRNA levels of ayu caught in seawater of the coastal area remained low during early spring. Prior to the start of the upstream migration, the fish caught in the coastal area in mid spring showed increased levels of PRL mRNA. There were further increases in PRL levels in the fish caught in the river. Analysis of proportions revealed that there were significant differences among PRL mRNA in the fish caught in different environmental salinities. Body weight showed a positive relation with PRL mRNA in ayu caught in seawater. A landlocked population of ayu, which migrates from lake to river, showed no significant change in PRL mRNA levels before and after upstream migration. Results in this study indicate the importance of up-regulation of PRL gene expression of ayu during the upstream migration from seawater to fresh water. There is a possible relationship between body size and PRL in the early developmental stage of ayu in seawater, but not in the fish in fresh water.

DOI： 10.2108/zs130181

掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/jzo.12125

掲載種別：研究論文（学術雑誌）  

DOI： 10.1093/jhered/esu009

PubMed

掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/eff.12045

掲載種別：研究論文（学術雑誌）  

Stream fish with low mobility are often restricted to a narrow range of a stream course, and their morphological characters tend to be affected substantially by the environmental conditions of their habitat. We examined the relationships between environmental conditions and morphological characters of Japanese fluvial sculpin (Cottus pollux), a small, benthic fish with low mobility, at seven tributaries of the same river system in eastern Japan. Discriminant function analysis (DFA) indicated significant morphological differences in sculpins amongst the seven tributaries, and over 80% of individuals were classified correctly in each tributary.The strong positive correlation/loadings on the first discriminant function (DF1: 49.9% of total variation) were anterior caudal peduncle depth (0.436) and caudal peduncle truss (0.387), both of which could be regarded as an attribute of caudal peduncle depth. The second discriminant function (DF2: 16.5% of total variation) had a high negative loading for distance between the posterior first dorsal fin and anterior anal fin (-0.454), which could be regarded as an attribute of body depth. Correlation analysis indicated that sculpin tended to have a lower caudal peduncle depth under faster bottom current velocities at the tributary scale. Individuals deviating substantially from the centroid of DF2 in each tributary had a poorer body condition. Our results suggest the possibility of changes in the morphological characters of Japanese fluvial sculpin in relation to environmental conditions even at the tributary scale within the same river system.

DOI： 10.1111/eff.12045

掲載種別：研究論文（学術雑誌）  

DOI： 10.1093/jhered/esu009

掲載種別：研究論文（学術雑誌）  

Changes in mRNA levels of prolactin (PRL) during the upstream migration were examined in fry of the amphidromous fish, ayu Plecoglossus altivelis. Quantification of mRNA has been done with real-time PCR and expressed as whole body or pituitary contents depending the body size of fry. PRL mRNA levels of ayu caught in seawater of the coastal area remained low during early spring. Prior to the start of the upstream migration, the fish caught in the coastal area in mid spring showed increased levels of PRL mRNA. There were further increases in PRL levels in the fish caught in the river. Analysis of proportions revealed that there were significant differences among PRL mRNA in the fish caught in different environmental salinities. Body weight showed a positive relation with PRL mRNA in ayu caught in seawater. A landlocked population of ayu, which migrates from lake to river, showed no significant change in PRL mRNA levels before and after upstream migration. Results in this study indicate the importance of up-regulation of PRL gene expression of ayu during the upstream migration from seawater to fresh water. There is a possible relationship between body size and PRL in the early developmental stage of ayu in seawater, but not in the fish in fresh water. © 2014 Zoological Society of Japan.

DOI： 10.2108/zs130181

PubMed

掲載種別：研究論文（学術雑誌）  

In species with alternative reproductive tactics (ARTs), males employing different tactics usually have different appearance. The clearest difference is body size: bourgeois males that monopolize access to females are larger than sneaker males that steal fertilizations from them. Sneakers are also known to be often dull in colour compared with bourgeois males and rather resemble females. However, this typical colour pattern is unlikely in the Lake Tanganyika cichlid Neolamprologus mondabu: we observed sneaking by two distinctive colour morphs, namely, black (which is apparently conspicuous against the background) and white (which is apparently background-matching). Because breeding females are black, this observation indicates that one type of sneakers contrasts female appearance. In this study, we conducted field studies to determine the expression of body colour in relation to ARTs in this fish. Body colour was dependent on size, but not sex and maturation, with black individuals being larger than white ones. Together with the presence of intermediate grey colour expressed by intermediate-sized individuals, this fish could ontogenetically changes their body colour from white to black. Both sexes of black individuals occupied feeding territories, but white individuals were non-territorial, indicating that the black body signals the possession of a feeding territory. Sexually active females were invariably black, whereas sexually active males were both black and white in colour. Few of the largest black males held harems, which included several female territories, whereas the remaining males were bachelors with no female territories. These bachelor males invested more in testes than harem males, suggesting that bachelors employ sneaking tactics, which is corroborated by our sneaking observations. To our knowledge, this is the first study showing that sneakers are entirely dissimilar to females in appearance. Herein, we discuss why sneakers are dichromatic in relation to their life histories. © 2014 The Zoological Society of London.

DOI： 10.1111/jzo.12125

掲載種別：研究論文（学術雑誌）  

　日本各地の河川では，内水面漁業者が，子ども達と一緒に魚の放流，魚の産卵場造成，川の清掃，魚釣り教室および自然観察会を行い，子ども達に自然とふれあい遊ぶ機会を提供している。本研究では，2010年8月に行われた中央水産研究所日光庁舎一般公開に来場した満20才以上の男女を対象にアンケート調査を行い，内水面漁業者による親水活動がもたらす教育的効果を評価した。調査の結果，自然との係わりおよび精神的な成長の面での教育的効果については，70 %以上の回答者が肯定的に評価し，男性よりも女性の方が高く評価する傾向にあった。社会生活との係わりでは，内水面漁業の担い手になるおよび地域に定住する意欲を高めることについて効果があると答えた回答者は50 %未満であったが，70 %以上の回答者が内水面漁業や地域社会への理解および労働の喜びや協働の意識を抱く効果を肯定的に評価した。本研究の結果は，内水面漁業者による親水活動が子どもの教育に役立つものとして多くの人に期待されていることを示唆している。

DOI： 10.3739/rikusui.74.165

CiNii Article

掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s12562-012-0592-3

掲載種別：研究論文（学術雑誌）  

It is important to select the most appropriate method for fish sampling in streams and rivers
the sampling efficiency as well as any negative effect of the method of fish sampling on fishes such as stress, injury, and mortality must be considered. This study aimed to investigate stress hormone responses in ayu Plecoglossus altivelis in reaction to direct current (DC) electrofishing, alternating current (AC) electrofishing, and cast netting in artificial streams. The mortality, injury rate, and catch efficiency of these catching methods were also compared. It was found that immediately after capture, fish caught using a cast net exhibited significantly higher cortisol levels than did control fish that were caught rapidly by a hand net. Cortisol levels did not differ between electroshocked fish and the controls. Time required to catch 12 fish was shorter when DC was used (20 s) than when AC was used (45 s). The time required to catch fish greatly increased when a cast net was used (840 s). Cortisol levels in DC electroshocked and control treatment groups were at resting levels 24 and 48 h after capture. However, higher cortisol levels were found in fish captured using a cast net at both these time points. Cortisol levels in AC electroshocked fish returned to lower levels at 24 h, but increased again at 48 h. Furthermore, 48 h following capture, the fish caught by AC electrofishing exhibited higher mortality (7. 5 %) than those captured by other methods (0 %). Spinal injury was also detected in one of the fish in this group. Considering these findings, DC electrofishing is the most effective and least damaging method for collecting P. altivelis in streams with respect to stress, physical damage, and efficiency. © 2013 The Japanese Society of Fisheries Science.

DOI： 10.1007/s12562-012-0592-3

掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/j.1600-0633.2011.00517.x

掲載種別：研究論文（学術雑誌）  

DOI： 10.2108/zsj.29.49

掲載種別：研究論文（学術雑誌）  

Social and foraging modes in fish often vary between individuals with different body sizes and between populations under different ecological conditions. We studied social and foraging behaviour of algae-grazing fish Plecoglossus altivelis ryukyuensis (Ryukyu-ayu) inhabiting Japanese subtropical island streams. Ryukyu-ayu exhibited four behavioural modes: territorial, schooling, solitary and floating. Their body sizes differed among these modes. Territorial fish predominantly foraged on benthic algae, whereas schooling and solitary individuals frequently consumed drifting materials as well. Schooling fish were smaller than territorial fish, but, unlike some other algae-grazing fish species, did not use schooling to gain access to food within territories. Territorial fish attacked smaller conspecifics but exhibited lateral display towards larger fish and schooling fish while occasionally attacking grazing gobies. Larger fish maintained larger feeding territories and occupied territories for longer periods than smaller fish did. This suggests that, in Ryukyu-ayu, intra- and interspecific food competitions and relative body size can influence diverse behavioural modes and duration of territory occupation. We also found that Ryukyu-ayu foraged more often and had larger feeding territories than ayu P. a. altivelis inhabiting temperate streams. We conclude that foraging strategies of Ryukyu-ayu may have adapted to subtropical island streams, where algal productivity is much lower than that in temperate regions. © 2011 John Wiley &amp
Sons A/S.

DOI： 10.1111/j.1600-0633.2011.00517.x

掲載種別：研究論文（学術雑誌）   国際・国内誌：国内誌  

DOI： 10.2108/zsj.29.49

PubMed

掲載種別：研究論文（学術雑誌）  

DOI： 10.1163/156853912X629139

掲載種別：研究論文（学術雑誌）  

DOI： 10.1155/2012/193235

PubMed

掲載種別：研究論文（学術雑誌）  

An algivorous cichlid, Variabilichromis moorii (Vm), defends permanent territories in Lake Tanganyika, Africa. A zoobenthivorous cichlid, Neolamprologus mustax (Nm), spends 60% of daylight hours foraging in Vm territories, from which other zoobenthivorous fishes are chased out and consequently which are much richer in prey animals than areas outside of Vm territories. We conducted a field experiment to examine whether Nm residents and non-residents received different degrees of attacks from Vm. Nm fish were caught in their territories, released at a point distant from these territories, and followed to observe interactions with Vm fish. The frequency of attacks received by the displaced Not fish was greater than attacks received by Nm residents, indicating that Nm residents had easier access to Vat territories than non-residents did. A possible mechanism for this is reduced aggression of Vm towards Nm residents, as a result of the 'dear enemy' effect that has been reported in territorial contests between rivals. An alternative mechanism is that tolerance towards Nm differs among Vm fish and Nm residents selectively visit more tolerant Vat fish due to previous experience while non-residents randomly approach both tolerant and hostile Vat fish. The ability of Vat to discriminate between Nm residents and non-residents is essential to the former mechanism but not to the latter. To more specifically examine which mechanism works in the Vm Nm commensal system, we will need to follow individually identified Vat fish interacting with Nm residents and non-residents.

DOI： 10.1163/156853912X629139

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

DOI： 10.1155/2012/193235

PubMed

掲載種別：研究論文（学術雑誌）  

富山県庄川に生息するアユを対象に、最近の体サイズの動向を把握し、また、個体の成長に影響を及ぼす条件の解明を試みた。1990年代前期および2000年代後期の9月期の漁獲データを比較したところ、過去3年間は例年を下回る小型個体が優占したため、最近の体サイズにおける小型化傾向が実証された。耳石上の輪紋数をカウントしたところ、2010年級群には遅生まれの個体が多く、さらに、Sr／Caの経時変化から、遅い時期に河川を遡上した個体が多く認められた。個体間の体サイズ変異は、海中生活期間とは無関係に、河川生活期間の長短によって説明された。小型化傾向の引金要因には、早生まれ群を消滅させるような大規模災害の関与する可能性が指摘された。

CiNii Article

掲載種別：研究論文（学術雑誌）  

富山県庄川に生息するアユを対象に、最近の体サイズの動向を把握し、また、個体の成長に影響を及ぼす条件の解明を試みた。1990年代前期および2000年代後期の9月期の漁獲データを比較したところ、過去3年間は例年を下回る小型個体が優占したため、最近の体サイズにおける小型化傾向が実証された。耳石上の輪紋数をカウントしたところ、2010年級群には遅生まれの個体が多く、さらに、Sr／Caの経時変化から、遅い時期に河川を遡上した個体が多く認められた。個体間の体サイズ変異は、海中生活期間とは無関係に、河川生活期間の長短によって説明された。小型化傾向の引金要因には、早生まれ群を消滅させるような大規模災害の関与する可能性が指摘された。

CiNii Article

掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.aquaculture.2011.01.024

掲載種別：研究論文（学術雑誌）  

It is well known that excessive suspended sediment (SS) negatively affects the fitness of fish by causing gill damage, lowered feeding efficiency, and physiological stress, all of which may impair growth, survival, and reproduction. Despite numerous researches on the effects of SS on fishes, few studies have examined its impact on stress hormone response. We conducted an experiment to test whether increased levels of SS elevate stress hormone levels in wild and low- and high-inbred hatchery strains of ayu Plecoglossus altivelis (Plecoglossidae) inhabiting clear rivers. We measured serum cortisol concentrations in fish exposed for 3. h to water with 200. mg/l of kaolin (SS treatment), fish exposed for 3. h to clear water (control treatment), and fish in stock tanks (initial control). Fish exposed to SS exhibited greater elevations in cortisol levels than control fish and initial controls. Control fish showed a small increase in cortisol levels compared with initial controls
this was probably because of the stress of handling and transfer to a novel environment. Stress response to SS in high-inbred strains was significantly lower than those in wild and low-inbred strains. These results suggest that SS is a significant environmental stressor that may increase the susceptibility of ayu to disease. Further, highly domesticated ayu may be maladaptive in nature because of lower reactivity of their stress axes as compared with those of wild or low-inbred strains. © 2011 Elsevier B.V.

DOI： 10.1016/j.aquaculture.2011.01.024

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（学術雑誌）  

同時的雌雄同体であるサラサウミウシにおいて8遺伝子座のマイクロサテライトマーカーを開発した。これらのマーカーでは，一遺伝子座あたりの対立遺伝子数は1から30，平均が15と高い多型性が認められた。多型性を示す7遺伝子座のマーカーヘテロ接合度の実測値と予測値は，それぞれ0.409から0.905，0.518から0.960の範囲であった。以上，サラサウミウシの親子判定に使用可能と考えられる多様性の高いマイクロサテライトマーカーを特定した。

CiNii Article

掲載種別：研究論文（学術雑誌）  

同時的雌雄同体であるサラサウミウシにおいて8遺伝子座のマイクロサテライトマーカーを開発した。これらのマーカーでは，一遺伝子座あたりの対立遺伝子数は1から30，平均が15と高い多型性が認められた。多型性を示す7遺伝子座のマーカーヘテロ接合度の実測値と予測値は，それぞれ0.409から0.905，0.518から0.960の範囲であった。以上，サラサウミウシの親子判定に使用可能と考えられる多様性の高いマイクロサテライトマーカーを特定した。

CiNii Article

掲載種別：研究論文（学術雑誌）  

水中における高濃度の懸濁物質は短時間であっても魚類に致死的ダメージを与える。一方、非致死的と考えられるような低濃度の懸濁物資であっても、継続時間が長期化すると、魚類に対して、摂餌頻度の減少や成長率の低下などをもたらす。さらに濁りは魚類にとってストレッサーとなり、魚の免疫機能を低下させると考えられている。しかし、濁りが魚体に与えるストレスについて実験的に証明した事例は少ない。そこで、本研究では異なる懸濁物質濃度の濁水を短時間、もしくは長時間アユに曝露し、本種におけるストレス応答の実態を調査した。

CiNii Article

掲載種別：研究論文（学術雑誌）  

水中における高濃度の懸濁物質は短時間であっても魚類に致死的ダメージを与える。一方、非致死的と考えられるような低濃度の懸濁物資であっても、継続時間が長期化すると、魚類に対して、摂餌頻度の減少や成長率の低下などをもたらす。さらに濁りは魚類にとってストレッサーとなり、魚の免疫機能を低下させると考えられている。しかし、濁りが魚体に与えるストレスについて実験的に証明した事例は少ない。そこで、本研究では異なる懸濁物質濃度の濁水を短時間、もしくは長時間アユに曝露し、本種におけるストレス応答の実態を調査した。

CiNii Article

J-GLOBAL

掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/j.1439-0310.2009.01735.x

掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s10228-009-0142-x

掲載種別：研究論文（学術雑誌）  

The effect of group size on reproductive success has long been studied in cooperatively breeding species, as it might provide an adaptive explanation for group-living in social species. Numerous studies have shown positive effects of subordinates on reproductive success ('helper effect'), but these studies have also revealed the importance of controlling statistically, or experimentally, for the effect of other factors that might affect reproductive success. Here, we first examine the relationships between group size, body size of group members and nest size in the cooperatively breeding cichlid Julidochromis ornatus, in which unrelated helpers frequently participate in reproduction and their breeding nests inside rock crevices may be crucial for reproduction and survival of all group members. Then, we subsequently investigate the relationship between group size and reproductive success, while controlling for these factors. The results showed that group size was significantly related to body size of group members rather than nest size
and larger breeders had larger helpers. It was found that group size significantly increased group reproductive output. More importantly, reproductive success of male breeders did not depend on the presence of mature helpers, whereas female reproductive success increased when two males assisted her and tended to decrease when two females bred cooperatively. We conclude that breeding groups of J. ornatus have size hierarchical societies that relate to group size, and group composition of genetically unrelated and co-breeding members affects their reproductive success. © 2010 Blackwell Verlag GmbH.

DOI： 10.1111/j.1439-0310.2009.01735.x

掲載種別：研究論文（学術雑誌）  

To investigate seasonal changes in reproductive and physical condition, sexual dimorphism, and mating tactics in the jewelled blenny Salarias fasciatus, monthly collections were conducted on the fringing reef in northern Okinawa, Japan. Monthly variation in the female gonadosomatic index suggested that the breeding season of this species is from April to June. The physical condition and hepatosomatic index of both sexes considerably deteriorated during the course of the breeding season. Such declines may be primarily due to egg production in females and brood care in males. Males' elongated anal spines were longer than females', but no other apparent sexual dimorphisms were detected, indicating that S. fasciatus exhibits a low degree of sexual dimorphism. Examinations of testes size and the testicular gland area during the estimated breeding season revealed that the gonadosomatic index values of smaller males did not differ from those of larger males. This result may differ from other blenny species that exhibit alternative male reproductive tactics. However, patterns of male testicular glands of S. fasciatus were similar to those of other blennies with alternative tactics, i.e., smaller males had poorly developed testicular glands compared with larger males. © 2009 The Ichthyological Society of Japan.

DOI： 10.1007/s10228-009-0142-x

掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/jez.587

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

DOI： 10.1002/jez.587

PubMed

掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s10228-009-0116-z

掲載種別：研究論文（学術雑誌）  

The reproductive behaviour of the Japanese ornate dragonet (Callionymus ornatipinnis) was studied at the northernmost limit of its distribution at Usujiri in southern Hokkaido, Japan. Field observations confirmed that C. ornatipinnis reproduced at Usujiri, and this is the first detailed description of the reproductive behaviour of C. ornatipinnis. Males were observed to swim continuously in a sandy area where females were abundant, persistently approaching females and performing courtship displays. Courtship behaviour consisted of males spreading their fins in front of females. If a female accepted a male for spawning, the pair would then ascend upward 0.7-1.2 m from the sandy bottom and release their pelagic eggs. Spawning, which occurred daily at dusk for approximately 1 h and ceased when it became dark, was related to water temperature and was only observed when water temperature exceeded 19°C. The breeding season of this species at Usujiri spanned only the month of September, which is considerably shorter than that of other dragonet species inhabiting temperate waters. The short breeding season was probably attributed to the fact that the water temperature at Usujiri only exceeds 19°C in the month of September. © The Ichthyological Society of Japan 2009.

DOI： 10.1007/s10228-009-0116-z

掲載種別：研究論文（学術雑誌）  

Stress hormone response to 3 h- or 24 h-exposure to different levels of suspended solids (50-500 mg/<I>l</I> of kaolin) was evaluated in ayu <I>Plecoglossus altivelis</I>. Significant increases in serum cortisol concentrations compared to control fish in clear water were detected in fish exposed for 3 h to water with 200 and 500 mg/<I>l</I> of kaolin but not in fish after 3 h exposure to 100 mg/<I>l</I> of kaolin. Additionally, 24 h-exposure to water with 50 mg/<I>l</I> of kaolin also elevated cortisol levels of ayu. The results suggest that long-time exposure to even low levels of suspended solids can stress ayu.

DOI： 10.11233/aquaculturesci.58.425

CiNii Article

掲載種別：研究論文（国際会議プロシーディングス）   共著区分：単著  

掲載種別：研究論文（国際会議プロシーディングス）  

掲載種別：研究論文（学術雑誌）  

DOI： 10.1098/rspb.2009.1175

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

DOI： 10.1098/rspb.2009.1175

PubMed

掲載種別：研究論文（学術雑誌）   共著区分：共著   国際・国内誌：国際誌  

DOI： 10.1093/icesjms/fsp145

掲載種別：研究論文（学術雑誌）  

The distribution of aquatic animals is limited by water temperature. However, little is known about migration patterns, overwintering, and reproduction at the extremities of their distribution. To investigate the sexual maturation of Japanese pygmy squid (Idiosepius paradoxus) and their ability to survive during winter at the northern limits of their distribution, we collected samples monthly at Usujiri in northern Japan and carried out experiments on low-temperature tolerance. Squid were collected during 4 months in autumn and early winter. In autumn, all squid were large and sexually mature, and many egg masses were found on the surface of seagrass, whereas in early winter, only small immature squid were collected. A warm north-flowing current reached the Usujiri area during autumn, so the squid were likely transported by the current and some of the small squid were recruits that hatched there. Field data and the results of experiments on tolerance of the species to low temperatures showed that it cannot survive at the low temperatures around Usujiri in winter. The migration pattern of I. paradoxus may differ from the traditional pattern for marine resources, where young fish are transported passively and do not reproduce at the extremities of their distribution.

DOI： 10.1093/icesjms/fsp145

担当区分：最終著者   掲載種別：研究論文（学術雑誌）   共著区分：共著   国際・国内誌：国際誌  

タンガニイカ湖のベントス食魚Neolamprologus mustaxは、藻食性のVariabilichromis mooriiの摂餌なわばり内に侵入して摂餌を行う。V. mooriiの親は黒色であるが、幼魚は黄色い体色をしており、N. mustaxの体色も黄色である。二種間での擬態の進化を明らかにするため、色の異なる魚模型を作り、V. mooriiの親魚に提示した。V. mooriiは黄色の模型に対する反応は弱かったが、黒色の模型に非常に攻撃的であった。以上より、N. mustaxはV. mooriiの幼魚の色に擬態して摂餌場所を利用している可能性が高いことが明らかになった。

DOI： 10.1163/156853909X446181

掲載種別：研究論文（学術雑誌）  

In two coexisting species with similar body colours, one species may acquire benefits from mimicking the body colour of the other species. In Lake Tanganyika, the zoobenthivorous cichlid Neolamprologus mustax preferentially exploits the territories of the algivorous cichlid Variabilichromis moorii as a feeding ground, even though other zoobenthivorous cichlid species are expelled from these territories. The yellow body colour of the guest species, N. mustax, resembles that of juveniles of the host species, V. moorii, adults of which have entirely black bodies. To estimate the effect of juvenile colour on aggression from conspecific adults, the responses of adult V. moorii to dummy fish of four colours ( black, yellow, white, and blue) were observed in this lake system. Our observations clearly demonstrated that adult V. moorii were less aggressive toward yellow, white, and blue dummies compared to black ones, with a slight difference in response to the yellow and white or blue dummies. This study indicates that resembling the colour of host juveniles can facilitate access of the guest species to host territory, but does not provide sufficient evidence for a hypothesis that the guest species mimics the body colour of the host juvenile.

DOI： 10.1163/156853909X446181

担当区分：筆頭著者   掲載種別：研究論文（学術雑誌）   共著区分：共著   国際・国内誌：国際誌  

体外受精種の場合、精子競争下ではたくさんの精子を生産すること、また、精子の鞭毛長が長く、遊泳速度の速い精子を生産することが受精に有利であると予測される。同種内でこの予測を検討した報告はあるが、ある個体が、精子競争レベルが変化した場合に精巣投資量や精子の特性を変化させられるのか検討した研究は無い。精子競争レベルを操作した水槽飼育実験の結果、精巣投資量は精子競争レベルによって劇的に変化するが、精子の特性は変えないことが示された。

DOI： 10.1007/s00265-008-0598-0

掲載種別：研究論文（学術雑誌）   共著区分：共著   国際・国内誌：国際誌  

ハッチンソン則によると、同じニッチを占める種では体サイズの重複がないことが共存できる条件となる。この原理が同種内で適用できることをシクリッドLobochilotes labiatusで発見した。L. labiatusのナワバリは同サイズクラスでは重ならないが、異なるサイズクラスでは重複した。岩の割れ目のベントスを吸い込むように摂餌し、体、口、餌の大きさは全て相関した。以上より、異なるサイズクラスは異なる岩の割れ目を利用することで、摂餌ナワバリを重複できることが初めて明らかとなった。

DOI： 10.1111/j.1365-2656.2008.01414.x

掲載種別：研究論文（学術雑誌）  

Theoretical models predict that in external fertilisers, sperm competition risk selects for larger testes and larger sperm with higher velocity, at the expense of sperm longevity. Although several empirical studies have tested this prediction within a fish species, there has been little evidence that an individual male can adjust his testis size and sperm traits according to the risk of sperm competition. Using the cooperatively breeding cichlid Julidochromis transcriptus, we examined testis size and sperm traits (sperm size, velocity and longevity) of males that were assigned to monogamous pairs (without risk of sperm competition) or cooperatively polyandrous trios composed of two males and one female (with risk); the groups were reared for breeding for 2 or more months. Our experiments showed that the polyandrous males, both siring eggs in a clutch, had larger relative testis mass than the monogamous males. However, sperm traits were unrelated to sperm competition. These results suggest that individual males of J. transcriptus can adjust their testis size but not sperm traits in response to sperm competition risk. We also examined the effect of testis investment on growth rate and the somatic condition of males. Increased investment in testes slowed growth rates, whereas testis investment did not affect somatic condition, indicating a trade-off between investment in testes and growth. We conclude that testis investment, in response to perceived sperm competition risks, occurs at the expense of growth and may be a conditional reproductive strategy that is determined by the social status (monogamous or polyandrous) of each J. transcriptus male.

DOI： 10.1007/s00265-008-0598-0

掲載種別：研究論文（学術雑誌）   国際・国内誌：国際誌  

DOI： 10.1111/j.1365-2656.2008.01414.x

PubMed

掲載種別：研究論文（学術雑誌）  

CiNii Article

担当区分：筆頭著者   掲載種別：研究論文（学術雑誌）   共著区分：共著   国際・国内誌：国際誌  

Julidochromis transcriptusは一夫一妻、一夫多妻、一妻多夫など多様な配偶システムが見られ、繁殖個体の体サイズ変異がこれらを生み出す要因の１つとして考えられる。水槽飼育実験により、性比を一定のまま、雌雄の体サイズを操作すると、雄が大きい場合は一夫多妻に、雌が大きい場合は一妻多夫に、雌雄が同サイズの場合は一夫一妻になりやすいことから、体サイズは配偶システムに大きな影響を与えることが明らかとなった。また、子の保護役割も配偶システムにより変化し、小さな個体が保護に関わる程度がより強いことが示された。

DOI： 10.1007/s10164-005-0171-5

掲載種別：研究論文（学術雑誌）  

Julidochromis species, biparental substrate-brooding cichlids in Lake Tanganyika, exhibit a variety of mating systems, including monogamy, polygyny and polyandry. A wide range of body size in both sexes is suggested to be one of the main factors inducing this variation. We studied the effect of body size on the formation of mating system in J. transcriptus in experimental aquaria with an equal sex ratio (three males, three females). In mating trials of six similar-sized fish, monogamous pairs were predominantly formed. In trials with one large male and five similar-sized fish, the large males monopolized two or three females and polygynous harems were formed. In trials with one large female and five similar-sized fish, two of five large females mated polyandrously with two males. These results suggest that body size is likely to affect the formation of mating system in this fish. We also examined parental roles of the mated fish. In monogamous pairs, both parents shared their parental tasks. In contrast, polygynous males and polyandrous females showed less parental care. These results indicate that harem owners may reduce the amount of care regardless of sex. Although the benefit of polyandrous mating remains unclear, harem males fertilized more eggs than monogamous males, indicating that polygyny may be a better option for male mating tactics. © Japan Ethological Society and Springer-Verlag 2005.

DOI： 10.1007/s10164-005-0171-5

担当区分：筆頭著者   掲載種別：研究論文（学術雑誌）   共著区分：共著   国際・国内誌：国際誌  

Julidochromis ornatusの雄ヘルパーは繁殖に参加することから、協同繁殖する雄同士には強い精子競争がはたらき、一方、一夫一妻の雄には精子競争がはたらかないことが予測される。野外で採集した異なる地位の雄の精巣投資量を調べた結果、精子競争理論から予測通り、協同繁殖する雄は精巣に多大に投資していたが、一夫一妻の雄は小さな清掃しか持っていなかった。また、精巣投資量のより高い雄はより高い繁殖成功を得るという結果が得られ、これも精子競争理論から導かれる予測と一致した。

DOI： 10.1093/beheco/arj043

掲載種別：研究論文（学術雑誌）  

Cooperatively breeding animals, in which helpers may participate in reproduction with dominant breeders, are ideal species for examining intraspecific variation in testis size because they often exhibit both monogamous breeding (low risk of sperm competition) and polyandrous breeding (high risk) within a population. However, little is known about testis investment as a result of sperm competition in these animals. The substrate-brooding cichlid fish Julidochromis ornatus has a cooperatively breeding system, in which some males mate monogamously and other males reproduce as dominant breeders or helpers within cooperatively breeding groups, in which male helpers frequently sire young. We examined the relationship between testis investment and male social status in relation to the risk of sperm competition. As predicted from sperm competition models, in groups with male helpers, both the male breeders and the male helpers invested more in testes mass, compared to breeding males without male helpers. We also found a positive relationship between the testes mass of male breeders and their male helpers, suggesting that males increase their investment in reproductive capability under the risk of sperm competition. Sperm competition models also predict that larger testes are associated with increased siring success. Our paternity analysis supported this prediction
we found a positive relationship between testis investment by male helpers and the number of offspring they sired. © The Author 2006. Published by Oxford University Press on behalf of the International Society for Behavioral Ecology. All rights reserved.

DOI： 10.1093/beheco/arj043

担当区分：筆頭著者   掲載種別：研究論文（学術雑誌）   共著区分：共著   国際・国内誌：国際誌  

Julidochromis ornatusは協同繁殖を行うことが過去の文献で示唆されていたが、野外での観察事例はこれまで全くなかった。そこで、本種の社会構造を調べた結果、一夫一妻のペア繁殖グループやヘルパーがいる協同繁殖グループ、さらにはハレムも見つかり、個体群中で多様な繁殖様式を持つことが分かった。また親子判定の結果、なわばり防衛といった手伝い行動をするヘルパーは、繁殖ペアとは血縁が無いこと、繁殖に参加していることが明らかになり、動物界全体で見ても非常に珍しい協同繁殖種であることが魚類で初めて示された。

DOI： 10.1007/s00265-005-0934-6

掲載種別：研究論文（学術雑誌）  

It is suggested that some fish of the genus Julidochromis, substrate-brooding Tanganyikan cichlids with biparental care, breed cooperatively with helpers. We studied the social system of J. ornatus in the wild and analysed genetic parentage using microsatellites. Within the studied population three patterns of social system were identified: monogamous pairs (61%, 44 of 72 groups), pairs with helpers (29%, 21), and polygamous harems with helpers (controlled by either a large female or large male owner
10%, 7). In cooperatively breeding groups, the number of helpers at each nest ranged from 1 to 6 (median 1), and male helpers were more numerous than female helpers. In both sexes, the body size was different among individuals of different social status (harem owner &gt
breeder &gt
helper). Helpers and harem owners of both sexes exhibited brood defence although its frequency was low. The molecular analysis revealed that (1) the helpers were mostly unrelated to dominant breeders, (2) many helpers of both sexes contributed genetically to the next generations, (3) male helpers had high siring success (41% of young in total), and (4) large young unrelated to group members were detected at 30% of observed nests, which may be due to breeder (or helper) replacements and immigration of young. We discuss the implications of these results for understanding the complex social system of this species, especially the low reproductive skew in comparison with other cooperatively breeding cichlids. © Springer-Verlag 2005.

DOI： 10.1007/s00265-005-0934-6

掲載種別：研究論文（学術雑誌）  

担当区分：筆頭著者   掲載種別：研究論文（学術雑誌）   共著区分：共著   国際・国内誌：国際誌  

一般的に、両親が子育てする魚類では子の保護役割が性別で決まる。しかし、タンガニイカ湖固有のシクリッドJulidochromis ornatusでは、雌が大きい繁殖ペアと雄が大きい繁殖ペアが同じ個体群中に見られ、子の保護役割には体サイズが関係している可能性が高い。そこで、この体長による保護役割決定仮説を証明するため、子の保護行動を野外観察した。その結果、性別に関係なくペアの小さい個体がより保護を行っていた。また、雌雄の体長差が小さいペアは頻繁に喧嘩をしており、雌雄の体サイズ差が繁殖ペアの維持に重要であることが分かった。以上より、体長による保護役割決定仮説が初めて支持された。

掲載種別：研究論文（学術雑誌）  

Parental roles and the amount of care in bi-parental fish have been assumed to be determined by sex. We studied the parental behaviour in a substrate brooding cichlid Julidochromis ornatus (40-90 mm in total length) in which both parents participate in care of eggs and young. In the study population, ca 80% of paired females were larger than their partners and pairs mated assortatively for size. Males spent more time with their offspring in female-largest pairs, whereas the opposite was found for male-largest pairs. These differences in the amount of care were more conspicuous when differences in body size were greater, whereas similar sized pairs shared parental tasks. These results suggest that the amount of parental care is largely affected by the relative size within pairs independent of sex in J. ornatus. However, the frequencies of defensive behaviours were not different in both female-largest and male-largest pairs. This indicates that parental roles would not completely change as the change of the body size difference within pairs. The larger parents were socially dominant over the partners regardless of sex, and observations of aggressive behaviours within pairs suggest that the larger fish are likely to make the partners perform parental care. Higher frequencies of aggressive encounters were observed in the similar-sized pairs than in the different-sized ones. Higher costs associated with frequent aggressive behaviours in the similar-sized pairs may be related to their small brood size, and may be partly responsible for the size-assortative mating with sexual size difference in this fish.

DOI： 10.1163/1568539042664623

掲載種別：研究論文（学術雑誌）   共著区分：共著   国際・国内誌：国際誌  

琵琶湖固有のハゼ、イサザの雄は岩の下に巣をかまえ、雌は岩に卵を産みつける。雄は単独で孵化まで卵保護を行う。他のハゼ科魚類の雄は、複数雌の卵塊を保護するが、イサザの雄は二匹目の雌を拒否する。この理由を明らかにするため、繁殖期に野外調査を行った。卵数の多い卵塊はより水カビに侵され、水カビに侵された卵は孵化まで至らなかった。このことから、イサザの雄は水カビに侵されないように、保護卵数を調節している可能性が高いことが示唆された。

DOI： 10.1007/s10164-004-0116-4

掲載種別：研究論文（学術雑誌）  

Like many other gobies, males of the Isaza goby, Gymnogobius isaza endemic to Lake Biwa, Japan, conduct parental care of eggs at nests, and females are likely to choose mates while visiting nests. The reproductive strategy should induce polygyny, but Isaza males never accept additional females in one breeding cycle. Sampling data of broods indicated that the egg mass areas were much smaller than the nest sizes, suggesting that nest size is not the limiting factor in obtaining further eggs from additional females. The brood size greatly decreased as the duration of care progressed. Few individuals including caring males ate eggs, and heterospecific egg predators were rarely observed. Sixty percent of egg masses at the middle stages of egg development were infected with aquatic fungi, some being covered with a fungus mat that drastically reduced survivorship. Infected egg masses contained more eggs than non-infected ones at the same stage, indicating that large egg masses are prone to be frequently destroyed by fungi. It is likely that the activity of parental males is lowered during the long care periods at low water temperature in early spring. Such lowered activity of caring males might be responsible for infections in large broods that would have needed more care. We propose the hypothesis that male rejection of additional females may be related to optimal brood size, which will be less susceptible to fungus infection and produce more hatching young than otherwise. This hypothesis will explain not only male avoidance of additional females but also some unique reproductive behaviors of this fish such as some females' spawning of a portion of of the mature eggs in one nest.

DOI： 10.1007/s10164-004-0116-4

掲載種別：研究論文（学術雑誌）  

掲載種別：研究論文（大学，研究機関等紀要）   共著区分：共著   国際・国内誌：国内誌  

タンガニイカ湖産シクリッドから作成したマイクロサテライトプライマーと今までに論文で報告されているシクリッドのプライマーをタンガニイカ湖産シクリッド4種の親子判定に使用可能かテストした。4種全てにおいて、既存のプライマーは多型性が高く使用可能であることが分かり、これら複数のプライマーは親子判定に有効であることが示された。

CiNii Article

掲載種別：研究論文（大学，研究機関等紀要）   国際・国内誌：国内誌  

タンガニイカ湖産シクリッドから作成したマイクロサテライトプライマーと今までに論文で報告されているシクリッドのプライマーをタンガニイカ湖産シクリッド4種の親子判定に使用可能かテストした。4種全てにおいて、既存のプライマーは多型性が高く使用可能であることが分かり、これら複数のプライマーは親子判定に有効であることが示された。

CiNii Article

掲載種別：記事・総説・解説・論説等（その他）   共著区分：単著  

掲載種別：記事・総説・解説・論説等（商業誌、新聞、ウェブメディア）   共著区分：単著  

会議種別：口頭発表（一般）  

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会議種別：シンポジウム・ワークショップ パネル（指名）  

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会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：ポスター発表  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

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会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：ポスター発表  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：ポスター発表  

会議種別：ポスター発表  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：口頭発表（一般）  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：口頭発表（一般）  

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会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

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会議種別：公開講演，セミナー，チュートリアル，講習，講義等  

会議種別：公開講演，セミナー，チュートリアル，講習，講義等  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：ポスター発表  

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会議種別：シンポジウム・ワークショップ パネル（指名）  

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会議種別：シンポジウム・ワークショップ パネル（指名）  

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会議種別：公開講演，セミナー，チュートリアル，講習，講義等  

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会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：公開講演，セミナー，チュートリアル，講習，講義等  

会議種別：公開講演，セミナー，チュートリアル，講習，講義等  

会議種別：公開講演，セミナー，チュートリアル，講習，講義等  

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会議種別：公開講演，セミナー，チュートリアル，講習，講義等  

会議種別：公開講演，セミナー，チュートリアル，講習，講義等  

会議種別：公開講演，セミナー，チュートリアル，講習，講義等  

会議種別：公開講演，セミナー，チュートリアル，講習，講義等  

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会議種別：口頭発表（一般）  

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会議種別：公開講演，セミナー，チュートリアル，講習，講義等  

会議種別：公開講演，セミナー，チュートリアル，講習，講義等  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：公開講演，セミナー，チュートリアル，講習，講義等  

会議種別：公開講演，セミナー，チュートリアル，講習，講義等  

会議種別：公開講演，セミナー，チュートリアル，講習，講義等  

会議種別：公開講演，セミナー，チュートリアル，講習，講義等  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

DOI： 10.2331/suisan.81.871

CiNii Article

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：シンポジウム・ワークショップ パネル（指名）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

CiNii Article

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：ポスター発表  

会議種別：ポスター発表  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

日本各地の河川では，内水面漁業者が，子ども達と一緒に魚の放流，魚の産卵場造成，川の清掃，魚釣り教室および自然観察会を行い，子ども達に自然とふれあい遊ぶ機会を提供している。本研究では，2010年8月に行われた中央水産研究所日光庁舎一般公開に来場した満20才以上の男女を対象にアンケート調査を行い，内水面漁業者による親水活動がもたらす教育的効果を評価した。調査の結果，自然との係わりおよび精神的な成長の面での教育的効果については，70 %以上の回答者が肯定的に評価し，男性よりも女性の方が高く評価する傾向にあった。社会生活との係わりでは，内水面漁業の担い手になるおよび地域に定住する意欲を高めることについて効果があると答えた回答者は50 %未満であったが，70 %以上の回答者が内水面漁業や地域社会への理解および労働の喜びや協働の意識を抱く効果を肯定的に評価した。本研究の結果は，内水面漁業者による親水活動が子どもの教育に役立つものとして多くの人に期待されていることを示唆している。

DOI： 10.3739/rikusui.74.165

CiNii Article

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

同時的雌雄同体であるサラサウミウシにおいて8遺伝子座のマイクロサテライトマーカーを開発した。これらのマーカーでは，一遺伝子座あたりの対立遺伝子数は1から30，平均が15と高い多型性が認められた。多型性を示す7遺伝子座のマーカーヘテロ接合度の実測値と予測値は，それぞれ0.409から0.905，0.518から0.960の範囲であった。以上，サラサウミウシの親子判定に使用可能と考えられる多様性の高いマイクロサテライトマーカーを特定した。

DOI： 10.18941/venus.69.3-4_214

CiNii Article

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

富山県庄川に生息するアユを対象に，最近の体サイズの動向を把握し，また，個体の成長に影響を及ぼす条件の解明を試みた。1990年代前期および2000年代後期の9月期の漁獲データを比較したところ，過去3年間は例年を下回る小型個体が優占したため，最近の体サイズにおける小型化傾向が実証された。耳石上の輪紋数をカウントしたところ，2010年級群には遅生まれの個体が多く，さらに，Sr/Ca の経時変化から，遅い時期に河川を遡上した個体が多く認められた。個体間の体サイズ変異は，海中生活期間とは無関係に，河川生活期間の長短によって説明された。小型化傾向の引金要因には，早生まれ群を消滅させるような大規模災害の関与する可能性が指摘された。

DOI： 10.11233/aquaculturesci.59.459

CiNii Article

会議種別：口頭発表（一般）  

会議種別：ポスター発表  

会議種別：ポスター発表  

会議種別：ポスター発表  

会議種別：ポスター発表  

会議種別：口頭発表（一般）  

CiNii Article

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

CiNii Article

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

DOI： 10.11233/aquaculturesci.58.425

CiNii Article

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：ポスター発表  

会議種別：ポスター発表  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：ポスター発表  

会議種別：ポスター発表  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

会議種別：口頭発表（一般）  

近年，メスによる子の父性操作が，昆虫や鳥類などの体内受精を行う動物で報告されている．体外受精を行う魚類では，２オスと１メスが共同繁殖を行うカワスズメ科魚類において，メスによる子の父性操作の可能性が示唆されている．しかし，その詳細は全く分かっていない．本研究では，共同繁殖を行う基質産卵型のカワスズメ科魚類<i>Julidochromis transcriptus</i>を用いて，水槽実験により，メスによる子の父性操作を検証することを試みた．野外観察から，この魚はクサビ形の巣で繁殖し，協同的一妻多夫の小オスは巣幅の狭い奥で，大オスは巣幅の広い入り口付近で放精するようである．このことから，メスは産卵する位置，つまり産卵位置の巣幅を変化させることで，メスが父性操作をしている可能性が考えられる．そこで，まずクサビ形の巣を作成し，大オス・小オス・メス（トリオ）で飼育・繁殖させて，産卵位置とそれぞれのオスの受精割合について検討したところ，巣幅の狭い位置で産卵した場合は，小オスの受精させた子どもの数が多かった．これにより，メスは産卵位置を選ぶことで父性操作が可能であると考えられる．さらに，産卵位置の巣幅が狭い場合に，小オスの保護行動の頻度が増加したことから，メスは小オスに受精させることで，小オスから保護の手伝いをより多く受けていることが示唆された．また，ペアでも同様に飼育・繁殖させると，ペア飼育で得られた卵塊はコンパクトに産まれているのに対し，トリオ飼育の卵塊は幅広く産まれていた．このことから，トリオのメスは2オスが受精できるように産卵位置や分布を操作しているようである．以上のことから，<i>J. transcriptus</i>のメスは受精を操作している可能性が高いと考えられる．

DOI： 10.14848/esj.ESJ52.0.111.0

CiNii Article