Rhodeus Ocellatus Research Articles

Metacercaria Infection Status of Fishborne Zoonotic Trematodes, Except for Clonorchis sinensis in Fish from the Heilongjiang Province, China.

To investigate the metacercarial infections of fishborne zoonotic trematodes (FZT), a total of 6815 freshwater fish (in representing 13 species of 5 families) were collected from Songhua river (n = 2636), Nenjiang river (n = 1935), Mudanjiang river (n = 301), and other lakes or ponds (n = 1943) in 36 representative regions in Heilongjiang Province, China, from August 2012 to December 2015. Metacercariae of four FZT species, that is, Clonorchis sinensis, Metorchis orientalis, Isthmiophora hortensis, and Metagonimus yokogawai, metacercariae were detected in the examination by the artificial digestion method. As the partial data for C. sinensis were previously reported, the remaining three FZT species are to be treated in this study. The overall prevalence of M. orientalis, I. hortensis, and M. yokogawai, metacercariae was 10.54%, 0.28%, and 1.35%, respectively. Metacercariae of M. orientalis were detected in seven fish species, that is, Pseudorasbora parva, Hemiculter leucisculus, Saurogobio dabryi, Rhynchocypris lagowskii, Carassius auratus, Rhodeus ocellatus and Perccottus glehnii. Their prevalences were the highest in false dace, P. parva (26.81%), and in fish from Songhua river (17.94%). Metacercariae of I. hortensis were detected in only one fish species, Misgurnus anguillicaudatus, from Nenjiang river only. Metacercariae of M. yokogawai were detected in three fish species, that is, P. parva, H. leucisculus and S. dabryi. Their prevalences were the highest in sharpbelly, H. leucisculus (6.05%), and in fish from Mudanjiang river (5.65%). This study first demonstrated the existence of M. orientalis, I. hortensis, and M. yokogawai in freshwater fish from Heilongjiang Province, posing a major public health concern. Eight fish species, namely M. anguillicaudatus, P. parva, H. leucisculus, S. dabryi, R. lagowskii, C. auratus, R. ocellatus, and P. glehnii, cannot be eaten raw. Moreover, the findings of this study not only extended the second intermediate host range of FZT, but also improve the information of the distribution of FZT in China.

Avoidance of host resistance in the oviposition-site preferences of rose bitterling

A contemporary outcome of dynamic host–parasite coevolution can be driven by the adaptation of a parasite to exploit its hosts at the population and species levels (parasite specialisation) or by local host adaptations leading to greater host resistance to sympatric parasite populations (host resistance). We tested the predominance of these two scenarios using cross-infection experiments with two geographically distant populations of the rose bitterling, Rhodeus ocellatus, a fish brood parasite of freshwater mussels, and four populations of their mussel hosts (two Anodonta woodiana and two Unio douglasiae populations) with varying degrees of geographic sympatry and local coexistence. Our data support predictions for host resistance at the species level but no effect of local coexistence between specific populations. Rhodeus ocellatus showed a preference for allopatric host populations, irrespective of host species. Host mussel response, in terms of ejection of R. ocellatus eggs, was stronger in the more widespread and abundant host species (A. woodiana) and this response tended to be higher in sympatric populations. These outcomes provide support for the importance of host resistance in bitterling oviposition-site decisions, demonstrating that host choice by R. ocellatus is adaptive by minimizing egg ejections. These findings imply that R. ocellatus, and potentially other bitterling species, may benefit from exploiting novel hosts, which may not possess appropriate adaptive responses to parasitism.

Digesting or swimming? Integration of the postprandial metabolism, behavior and locomotion in a frequently foraging fish

Fish that are active foragers usually perform routine activities while digesting their food; thus, their postprandial swimming capacity and related behavior adjustments might be ecologically important. To test whether digestion affect swimming performance and the relationships of digestion with metabolism and behavior in an active forager, we investigated the postprandial metabolic response, spontaneous swimming activities, critical swimming speed (Ucrit), and fast-start escape performance of both fasted and digesting (3h after feeding to satiation) juvenile rose bitterling (Rhodeus ocellatus). Feeding to satiation elicited a 50% increase in the oxygen consumption rate, which peaked at 3h after feeding and returned to the prefeeding state after another 3h. However, approximately 50% and 90% of individuals resumed feeding behavior at 2 and 3h postfeeding, respectively, although the meal size varied substantially. Digestion showed no effect on either steady swimming performance as suggested by the Ucrit or unsteady swimming performance indicated by the maximum linear velocity in fast-start escape movement. However, digesting fish showed more spontaneous activity as indicated by the longer total distance traveled, mainly through an increased percentage of time spent moving (PTM). A further analysis found that fasting individuals with high swimming speed were more inclined to increase their PTM during digestive processes. The present study suggests that as an active forager With a small meal size and hence limited postprandial physiological and morphological changes, the swimming performance of rose bitterling is maintained during digestion, which might be crucial for its active foraging mode and anti-predation strategy.

Phylogeography, Historical Demography, and Genetic Structure of the Rose Bitterling, Rhodeus ocellatus (Kner, 1866) (Cypriniformes: Acheilognathidae), in East Asia.

Yao-Feng Tsao, Wen-Wen Lin, Chia-Hao Chang, Takayoshi Ueda, Nian-Hong Jang-Liaw, Ya-Hui Zhao, and Hsiao-Wei Kao (2016) Rose bitterling, Rhodeus ocellatus, is a small cyprinid fish distributed in East Asia. To infer its phylogeography and genetic structure, specimens from Taiwan, China, and Japan were collected, and complete mitochondrial cytochrome b (cyt b) DNA sequences were amplified and sequenced. Phylogenetic analyses identified seven mitochondrial lineages (A-G). Among them, three lineages (A, B, and C) distributed in mainland China. Lineages D, E, and F distributed in Japan, Korea, and Taiwan, respectively. Lineage G distributed in both China and Japan. The results of the Bayesian Binary MCMC analysis (BBM) suggested that the most recent common ancestor of R. ocellatus was from Lower Yangtze region. Divergence times among lineages inferred by molecular clock ranged from 7.55 to 1.44 million years ago. We propose that topography and climate changes by uplift of the Tibetan Plateau in the Late Miocene-Pliocene and the glacial-interglacial cycles in the Pleistocene might account for population expansion and genetic differentiation. Divergence times among lineages A, B, and C in Yangtze River basin ranged from 7.55 to 2.27 million years ago that might result from changes of flow directions of rivers from westward to eastward driven by the uplift of the Tibetan Plateau. The glacial-interglacial cycles in the Pleistocene might further cause population expansion to the northward of lineage G at about 0.19 million years ago. Lineage D in Japan was dispersed from the mainland China before the opening of the Sea of Japan, and lineage F in Taiwan was dispersed from the mainland China through the land bridge in the Pleistocene. Because of the genetic differentiation is statistically significant among populations, protection of genetic diversity and distinctness of R. ocellatus should be considered in the future conservation management.

Interspecific comparison of movement patterns among bitterling species in an agricultural ditch system

Patterns of movement are related to life history and/or species traits. Understanding movement patterns of multiple species sharing the same niche may clarify coexistence mechanisms. Therefore, the movement patterns of three bitterling species, Acheilognathus tabira erythropterus, Acheilognathus melanogaster, and Rhodeus ocellatus ocellatus, were examined between June and November 2009 in an agricultural ditch system associated with Lake Kasumigaura in central Japan. The mark–recapture method was used with a fixed releasing point in an approximately 5.5 km-long ditch. Movement distances of A. t. erythropterus and A. melanogaster were longer than that of R. o. ocellatus, but the direction of movement was similar among the three species. However, R. o. ocellatus moved to locations with a low dissolved oxygen concentration and deeper water. These results suggest that R. o. ocellatus may adapt better to environmental fluctuations, because its tolerance to hypoxia is the highest of the three species. Compared with R. o. ocellatus, A. t. erythropterus and A. melanogaster may move relatively longer distances to search for suitable habitats following an environmental fluctuation.

A Cell Line Derived from Early Embryos of Rose Bitterling (Teleostei: Cypriniformes: Acheilognathinae)

<p class="1Body">A cell line was established from embryo cells of rose bitterling <em>Rhodeus ocellatus ocellatus</em> (Teleostei: Acheilognathinae). This cell line is maintained for more than seven years in my laboratory. Karyotype in it does not have the change either. In maintenance of the biological diversity, it is an important problem to demand a method to prevent the extinction of the species. This cell line will become the clue of the study of the embryonic stem cell in endangered species. On the other hand, this cell line which karyotype is stable in its will be a useful tool for a mutagenicity assay.</p>

The effects of starvation on fast-start escape and constant acceleration swimming performance in rose bitterling (Rhodeus ocellatus) at two acclimation temperatures.

To investigate the effects of starvation and acclimation temperature on the escape ability of juvenile rose bitterling (Rhodeus ocellatus), we measured the fast-start escape and constant acceleration swimming performance of fish fasted for 0 (control), 1 and 2weeks and half-lethal periods (6 or 4weeks) at two temperatures (15 and 25°C). Fish acclimated at a high temperature exhibited shorter response latency (R), higher maximum linear velocity (V max) and longer escape distance during escape movement (D 120ms) than those at the low temperature. Starvation resulted in a significant decrease in V max and D 120ms at either low or high temperature and a significant increase in R at only the high temperature in the half-lethal period groups (P<0.05). The relationship between V max (Y, ms(-1)) and starvation time (X, week) was Y 15=-0.062X+1.568 (r=-0.665, n=36, P<0.001) at low temperature and Y 25=-0.091X+1.755 (r=-0.391, n=40, P=0.013) at high temperature. The relationship between U cat (Y, cms(-1)) and starvation time (X, week) was Y 15=-1.649X+55.418 (r=-0.398, n=34, P=0.020) at low temperature and Y 25=-4.917X+62.916 (r=-0.793, n=33, P<0.001) at high temperature. The slopes of equations showed a significant difference between low and high temperature (F 1,63=9.688, P=0.003), which may be due to the different energy substrate utilization when faced with food deprivation at different temperatures.

Four Members of Heat Shock Protein 70 Family in Korean Rose Bitterling (Rhodeus uyekii).

Heat shock protein (HSP) 70, the highly conserved stress protein families, plays important roles in protecting cells against heat and other stresses in most animal species. In the present study, we identified and characterized four Hsp70 (RuHSP4, RuHSC70, RuHSP12A, RuGRP78) family proteins based on the expressed sequence tag (EST) analysis of the Korean rose bitterling R. uyekii cDNA library. The deduced RuHSP70 family has high amino acid identities of 72-99% with those of other species. Phylogenetic analysis revealed that RuHsp70 family clustered with fish groups (HSP4, HSC70, HSP12A, GRP78) proteins. Quantitative RT-PCR analysis showed the specific expression patterns of RuHsp70 family members in the early developmental stages and several tissues in Korean rose bitterling. The expression of 4 groups of Hsp70 family was detected in all tested tissue. Particularly, Hsp70 family of Korean rose bitterling is highly expressed in hepatopancreas and sexual gonad (testis and ovary). The expression of Hsp70 family was differentially regulated in accordance with early development stage of Rhodeus uyekii.

Molecular and Functional Characterization of Thioredoxin 1 from Korean Rose Bitterling (Rhodeus uyekii).

Thioredoxin is a multifunctional antioxidant enzyme that belongs to the reductase family. In this study, we cloned and characterized thioredoxin 1 cDNA from the Korean rose bitterling Rhodeus uyekii (RuTrx). The full-length RuTrx cDNA consists of 674 bp with a 324 nt open reading frame (ORF) encoding a 107 aa protein. The deduced RuTrx amino acid sequence indicated a characteristic redox active site, 31WCGPC35. Pairwise alignment revealed RuTrx amino acid identity (55.1%–83.2%) with orthologs from various species of mammalia, amphibia, fish and bird. Phylogenetic analysis was conducted to determine the evolutionary position of RuTrx. Expression analysis showed that RuTrx transcripts were present in all of the tissues examined, and was high in the hepatopancreas of R. uyekii. During early development, the expression of RuTrx transcripts was increased. Recombinant RuTrx protein (rRuTrx) was tested for its capacity to serve as an antioxidant enzyme using a metal-catalyzed oxidation (MCO) system. The ability of rRuTrx to protect against supercoiled DNA cleavage due to oxidative nicking increased in a dose-dependent manner. In Raw264.7 cells, Dihydroethidium (DHE) staining for ROS production indicated the antioxidant activity of rRuTrx. Together, these findings suggest that RuTrx may play a role in maintaining the redox state balance in Korean rose bitterling R. uyekii.

Complete mitochondrial genome of Rhodeus ocellatus (Cypriniformes: Cyprinidae)

The complete mitogenome sequence of Rhodeus ocellatus (Kner) was determined using the next-generation sequencing (NGS). The genome was 16 761 bp in length and contained 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes and a control region. The overall nucleotide composition was 30.43% A, 27.50% T, 25.94% C, and 16.13% G, with an A + T bias of 57.93%. The gene composition and the arrangement of the R. ocellatus mitochondrial genome were similar to that of most other vertebrates. The complete mitochondrial genome sequence will help to study the evolutionary relationships and population genetics of Rhodeus fish.

New species of Cypriniform fishes (Cypriniformes) in the fauna of the Balkhash–Ili basin, Kazakhstan

Based on the results of morphological studies of materials on bitterlings (genus Rhodeus) and loaches (genus Misgurnus) collected in the Ili River basin (Kazakhstan) in 2011, it is shown for the first time that the rosy bitterling R. ocellatus and Nikolsky’s loach M. nikolskyi have naturalized in the Balkhash–Ili basin.

Cognitive ability is heritable and predicts the success of an alternative mating tactic.

The ability to attract mates, acquire resources for reproduction, and successfully outcompete rivals for fertilizations may make demands on cognitive traits--the mechanisms by which an animal acquires, processes, stores and acts upon information from its environment. Consequently, cognitive traits potentially undergo sexual selection in some mating systems. We investigated the role of cognitive traits on the reproductive performance of male rose bitterling (Rhodeus ocellatus), a freshwater fish with a complex mating system and alternative mating tactics. We quantified the learning accuracy of males and females in a spatial learning task and scored them for learning accuracy. Males were subsequently allowed to play the roles of a guarder and a sneaker in competitive mating trials, with reproductive success measured using paternity analysis. We detected a significant interaction between male mating role and learning accuracy on reproductive success, with the best-performing males in maze trials showing greater reproductive success in a sneaker role than as a guarder. Using a cross-classified breeding design, learning accuracy was demonstrated to be heritable, with significant additive maternal and paternal effects. Our results imply that male cognitive traits may undergo intra-sexual selection.

Stergilization against Water Mold Disease in Artificial Breeding of Rosy Bitterling Rhodeus ocallatus by the Schale’s Method

Stergilization against Water Mold Disease in Artificial Breeding of Rosy Bitterling Rhodeus ocallatus by the Schale’s Method

黄山陈村水库上游河源溪流的鱼类群落及其纵向梯度格局

PDF HTML阅读 XML下载 导出引用 引用提醒 黄山陈村水库上游河源溪流的鱼类群落及其纵向梯度格局 DOI: 10.5846/stxb201304140706 作者: 作者单位: 安徽师范大学生命科学学院,安徽师范大学生命科学学院,安徽师范大学生命科学学院,安徽师范大学,安徽师范大学生命科学学院,安徽师范大学生命科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金(31172120, 31372227); 国家重点基础研究发展计划项目(2009CB119200) Fish assemblages and longitudinal patterns in the headwater streams of the Chencun Reservoir in the Huangshan Area Author: Affiliation: Provincial Key Laboratory of Biotic Environmental and Ecological Safety,College of Life Sciences,Anhui Normal University,Provincial Key Laboratory of Biotic Environmental and Ecological Safety,College of Life Sciences,Anhui Normal University,Provincial Key Laboratory of Biotic Environmental and Ecological Safety,College of Life Sciences,Anhui Normal University,Provincial Key Laboratory of Biotic Environmental and Ecological Safety,College of Life Sciences,Anhui Normal University,Provincial Key Laboratory of Biotic Environmental and Ecological Safety,College of Life Sciences,Anhui Normal University,Provincial Key Laboratory of Biotic Environmental and Ecological Safety,College of Life Sciences,Anhui Normal University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:确定鱼类群落的分布格局及其对人类活动的响应,是合理保护、恢复和管理鱼类多样性的基础。基于2011年5月和10月自黄山陈村水库上游3条河源溪流共39个样点的调查数据,比较研究了溪流间鱼类群落及其纵向梯度格局的异同,着重探讨了人类活动对溪流鱼类群落纵向梯度格局的影响。研究结果显示,同人为干扰较轻的舒溪相比,人为干扰严重的浦溪和麻溪中水宽、底质和植被覆盖率等局域栖息地条件显著变化,这造成了后者的鱼类多样性显著下降及物种组成的显著变化,主要表现为敏感性的地方物种(如宽鳍鱲、光唇鱼、原缨口鳅等)数量减少、耐受性的广布物种(如泥鳅、麦穗鱼、高体鰟鲏等)数量增多。舒溪的鱼类物种数及其组成均与海拔显著相关,但这种"海拔-鱼类群落"关系在麻溪和浦溪中削弱甚至消失。底质、植被覆盖率对舒溪鱼类群落具有重要影响,但对浦溪和麻溪鱼类群落却无显著影响。研究结果表明,在子流域空间尺度上,诸如城镇化发展、土地利用、河道治理等人类活动可通过对局域栖息地条件的影响,导致溪流鱼类多样性下降及其物种组成的变化,破坏鱼类群落的纵向梯度格局,并改变栖息地与鱼类群落之间的联系。 Abstract:Studying the spatial and temporal patterns of stream fish assemblages and identifying how human land-use activities impact these patterns are crucial for fish species conservation, ecosystem restoration and management. The objectives of this study were (1) to examine the influences of human perturbations on the longitudinal patterns of fish species diversity and assemblage structures in headwater streams, (2) to assess the correlations between local habitat factors and fish assemblages, and their longitudinal and temporal patterns. We sampled fish at 39 segments during May and October 2011 from three headwater streams of the Chencun Reservoir in the Huangshan Area, which were influenced by different extents of human activities. A total of 4041 fish were collected, representing four orders, 10 families, and 28 species, among which family Cypriniformes comprised 67.9% of total species richness. 24, 22 and 24 species were sampled from the Shuxi, Puxi and Maxi Streams, respectively. Two-way ANOVA was used to test the influences of streams and seasons on habitat and fish-diversity variables, respectively. Results showed that habitat variables varied significantly across three streams and in different seasons. Results from the Shuxi Stream showed lower numbers in dissolved oxygen and wetted width but higher levels in substrate size and canopy cover than those from the Puxi and Maxi Streams, and May showed lower pH but higher water temperature and discharge than October. However, species richness, fish abundance and the Shannon's index varied significantly across streams but not between seasons. In overall, fish diversity was higher in the Shuxi Stream than that in the Puxi and Maxi Streams. Results of two-way crossed ANOSIM indicated that fish assemblage structures varied substantially across streams but not between seasons. The assemblage structures in the Puxi and Maxi Streams did not show significant differences, however, they significantly differed from those in the Shuxi Stream. SIMPER analysis indicated that some endemic specialized species (e.g., Zacco platypus, Acrossocheilus fasciatus, Vanmanenia stenosoma) were more abundant in the Shuxi Stream, while those cosmic generalized species (e.g., Misgurnus anguillicaudatus, Pseudorasbora parva, Rhodeus ocellatus) were more in the Puxi and Maxi Streams. The results of Pearson's correlation and redundancy analysis showed that fish species richness in the Shuxi Stream significantly increased with elevation decreasing in both May and October, respectively. However, this "species richness-elevation" correlation lessened in the Maxi Stream and even disappeared in the Puxi Stream. Similarly, elevation showed significant correlation with assemblage structures in the Shuxi and Maxi Streams but not the Puxi Stream. In addition, the effects of local habitat variables on fish assemblage structures were examined using linear regression model and redundancy analysis, respectively. Results showed that fish assemblages in the Shuxi Stream were significantly affected by substrate and canopy, but those in the Puxi and Maxi Streams were related to water temperature and wetted width. In conclusion, our results suggest that, at the sub-watershed scale, the alteration of local habitat conditions in headwater streams associated with human activities (e.g., urbanization, land-use and river-regulation) may decrease stream fish diversity, modify the correlations between local habitat and fish assemblage, and change the longitudinal pattern of fish assemblages. 参考文献 相似文献 引证文献

The parasitic copepod Lernaea cyprinacea from freshwater fishes, including alien species (Gambusia affinis and Rhodeus ocellatus ocellatus), in central Japan

愛知県名古屋市と西尾市にある池沼と河川で採集した淡水魚を調べたところ，カイアシ類の1種，イカリムシLernaea cyprinacea Linnaeus, 1758の寄生を認めた。寄生を受けていたのはカダヤシGambusia affinis，タイリクバラタナゴRhodeus ocellatus ocellatus，モツゴPseudorasbora parvaおよびフナ属の1種Carassius sp.である。わが国で，国外外来魚のカダヤシとタイリクバラタナゴにイカリムシの寄生を認めたのは本論文が最初である。

Length-weight relationships for four small fish species caught in wetlands of central Yangtze River, China

Summary Length–weight relationships for four native species (Oryzias latipes Temminck & Schlegel, 1846; Rhodeus ocellatus Kner, 1866; Rhinogobius giurinus Rutter, 1897; and Micropercops swinhonis Gunther, 1873) were determined. The fish were collected from the wetlands of the central Yangtze River, in Wuhan, Hubei Province, China. Samples were obtained from May 2012 to January 2013. Length–weight relationships for O. latipes were determined for the first time.

The function of multiple ejaculations in bitterling.

In some taxa, males perform multiple ejaculations, which may function in sperm competition or in maintaining a baseline density of spermatozoa in the female reproductive tract to ensure fertilization, a process that has been termed 'topping up'. We investigated the function of multiple ejaculations in two species of bitterling, the European bitterling (Rhodeus amarus) and Chinese rose bitterling (Rhodeus ocellatus). Bitterling oviposit in living freshwater mussels, with fertilization taking place within the mussel gill cavity. Thus, although fertilization is external, the mussel is analogous to the female reproductive tract in an internally fertilizing species. We measured the frequency of ejaculations and mussel inspections by individual males of two bitterling species in 28 replicated mesocosms and examined focal male responses to rival ejaculations and the presence of females in spawning condition. We used a model of ejaculatory behaviour to simulate the temporal abundance of spermatozoa in mussels. Male R.amarus exhibited high rates of ejaculation and inspection of the siphons of mussels and increased their ejaculation rate in response to the presence of females in spawning condition. Rhodeus ocellatus showed lower overall rates of ejaculation, but significantly elevated ejaculation rate in response to rival ejaculations. The ejaculatory strategy of R.amarus is one that maintains a minimum level of spermatozoa in mussels, which is elevated when the probability of oviposition increases. In contrast, R.ocellatus engages more directly in sperm competition with rivals. We discuss these results in the context of the function of multiple ejaculations and male mating tactics.

Prevalence of Clonorchis sinensis infection in freshwater fishes in northeastern China

The prevalence of Clonorchis sinensis infection in freshwater fishes was surveyed in Heilongjiang Province, northeastern China, between August 2011 and September 2013. Thirteen species of freshwater fish (n=3221) and one species of shrimp (n=93) were collected from Songhua river, Nenjiang river and other lakes or ponds in 37 sites of 15 representative cities in Heilongjiang Province. They were individually examined by digestion technique, and the C. sinensis metacercariae were identified morphologically followed by confirmation using sequences of the second internal transcribed spacer of ribosomal DNA. Ten of the 13 examined species of freshwater fishes were infected with C. sinensis metacercariae, while all shrimps were negative. The overall prevalence of C. sinensis infection in 3221 examined freshwater fishes was 19.96%, with 42.57% (272/639) in Pseudorasbora parva, 22.55% (83/368) in Hemicculter leuciclus, 20.44% (121/592) in Carassius auratus, 17.71% (68/384) in Saurogobio dabryi, 10.85% (23/212) in Rhodeus ocellatus, 10.54% (48/455) in Phoxinus lagowskii, 8.20% (21/256) in Perccottus glehnii, 6.25% (5/80) in Misgurnus anguillicaudatus, 4.55% (1/22) in Xenocypris davidi, and 1.49% (1/67) in Cyprinus carpio. The average infection intensity in P. parva was 103.3 encysted metacercariae per gram of fish meat in Zhaoyuan city. The average prevalence of C. sinensis infection in Songhua river, Nenjiang river and lakes or ponds were 31.96% (503/1574), 11.30% (102/903) and 7.93% (59/744), respectively. The prevalence of C. sinensis infection in Zhaoyuan city (43.68%) was the highest among all sampling locations. These results revealed a high-prevalence of C. sinensis infection in freshwater fishes in Heilongjiang Province, northeastern China, posing significant public health concern.

Reproductive behaviour of female rosy bitterling Rhodeus ocellatus in response to a female-biased operational sex ratio

While the effect of Operational Sex Ratio (OSR) on reproductive behaviour of males has been studied extensively, little is known of the response of females facing a female-biased OSR. We investigated the effect of different OSRs on female reproductive behaviour using the rosy bitterling, Rhodeus ocellatus, a freshwater fish that lays its eggs inside the gills of living freshwater mussels. Three levels of OSR (male/female ratio 1:1, 1:3 and 1:5) were tested. We demonstrated that inspection of the mussel (spawning substrate) by individual females increased with increasingly female-biased OSR, but that the rate of following territorial male decreased. Aggression towards other females was not affected by the OSR. Interestingly, when a male bitterling led a non-dominant female towards the mussel, the dominant female would become aggressive to the male and chase the non-dominant female away. Aggression towards male followed a bell-shaped pattern and was highest at an OSR of 1:3. In both the female-biased OSRs examined, almost 50% of dominant females tended to chase away other females and defend the mussel, showing territoriality in a similar manner to males. These observations suggest that female reproductive behaviour is strongly affected by the OSR, and their reproductive tactics during courtship change from a passive role in courtship (following a male) to an active role in courtship (approaching a male), with presence of female territorial behaviour as the OSR becomes increasingly female-biased. This study provides strong evidence that a female-biased OSR has an important effect on female reproductive behaviour.

マイクロサテライトマーカーから見た大阪産ニッポンバラタナゴ溜池集団の遺伝的特徴

溜池に生息する大阪産ニッポンバラタナゴについてマイクロサテライトマーカーを用いた遺伝的特徴の推定を行った。平均アリル数は何れの集団も約 2 と低い値を示したが，ヘテロ接合度と血縁度は集団間で大きく異なり，その要因として創始者効果と生息地の規模の違いが考えられた。また，アリル組成において集団間の違いは殆ど見られなかったが，南北間で遺伝的分化が認められた。これらの結果は大阪集団が単一起源である一方，ボトルネックにより遺伝的分化が生じており，近親交配の回避において環境収容力が重要であることを意味する。