Comparative morphology and ecomorphology of the gut in European cyprinids (Telostei)

The patterns of coiling of the gut were compared in 22 species of Eurasian Cyprinidae. In selected species, also the length of gut and mucosal surface structure were compared. Piscivorous ( Aspius aspius ), planktivorous ( Abramis ballerus ) fishes as well as species feeding mainly on plankton and wind-borne' drift'( Alburnus alhurnus, Pelecus cultratus ) have the relatively shortest guts, with only a single loop. The same simple arrangement of a short gut is present in many euryphagous species with more or less carnivorous tendencies ( Abramis sapa, Alburnoides bipunctalus, Abramis brama, Blicca bjoerkna, Chalcalburnus chalcoides memo, Gobio gobio, Leuciscus cephalus, Leuciscus leuciscus, Rutilus rutilus, Scardinius erythrophthalmus. Tinea tinea, Vimba vimba ). Some benthivorous winnowers (oropharyngeal sorters) and species with herbivorous feeding tendencies have relatively long guts showing a more complex pattern of loops and coils ( Barbus barbus, Carassius carassius, Chondrostoma nasus, Ctenopharyngodon idella, Cyprinus carpio ). The goldfish, Carassius auratus , has the most complex coils. Scanning electron microscopy of the mucosal surface revealed five types of folding in the intestinal bulb which were only loosely related to feeding: 1, smooth surface ( Aspius aspius, Leuciscus cephalus, Vimba vimba ); 2, irregularly branching folds ( Alhurnus alburnus, Barbus barbus, Blicca bjoerkna, Chalcalburnus chalcoides memo, Leuciscus leuciscus, Rutilus rutilus, Scardinius erythrophthalmus ); 3, curl-like folds ( Tinea tinea ); 4, net-like folding pattern ( Abramis brama ); 5, honeycomb-like mucosal structure ( Cyprinus carpio ).     

Molecular phylogeny of congeneric monogenean parasites (Dactylogyrus): a case of intrahost speciation

Dactylogyrus species (Dactylogyridae: Monogenea) are a group of monogenean gill parasites that are highly specific to freshwater fish of the family Cyprinidae. Dactylogyrus species were sampled from 19 cyprinids and one percid collected in Europe. Using partial 18S rDNA and ITS1 sequences, a phylogeny of 51 Dactylogyrus species was reconstructed to investigate the patterns of parasite speciation and diversification. Three main Dactylogyrus lineages were recognized from all phylogenetic trees, that is, analysis of 18S rDNA alone and combined 18SrDNA and ITS1. The first lineage associates the Dactylogyrus species of Cyprinus carpio and Carassius auratus of the Cyprininae; the second associates Dactylogyrus species of the Gobioninae, Pseudorasbora parva of the Rasborinae, and Ctenopharyngodon idella of the Cyprininae; and the third associates Dactylogyrus species of the Leuciscinae and Alburninae and Barbus barbus of the Cyprininae. Our results suggest that the genus Dactylogyrus is of quite recent origin and that these three lineages separated from each other in a very short period of time. Host subfamily mapping onto the parasite tree inferred from analysis of the combined dataset showed that the Cyprininae could be plesiomorphic hosts for Dactylogyrus. Dactylogyrus parasites would have secondarily colonized the Percidae and representatives of the Leuciscinae, Alburninae, Gobioninae, and Rasborinae. Comparison of host and parasite phylogenetic relationships indicated that a very high number of parasite duplications occurred within two of the three Dactylogyrus lineages. Dactylogyrus diversification can be mainly explained by sympatric intrahost speciation events that seem to be correlated to strict host specificity. Moreover, the present study shows that the congeneric parasites speciating within one host tend to occupy niches within hosts differing at least in one niche parameter.     

NORs and counterstain-enhanced fluorescence studies in Cyprinidae of different ploidy level

The ribosomal RNA gene expression in the genomes of evolutionary diploid (Scardinius erythrophthalmus, Leucaspius delineatus, Tinca tinca) and polyploid species (Cyprinus carpio, Carassius carassius, Carassius auratus gibelio, Carassius auratus auratus) of Cyprinidae has been investigated by means of a silver nitrate technique. The diploid species investigated exhibited only one pair of chromosomes with nucleolus organizers (NOR). Higher numbers of rRNA-expressing chromosomal sites in several evolutionary polyploid species (Carassins) gave evidence against a complete functional diploidization, at least with regard to the NOR bearing chromosomes in these species. The NORs displayed a heterochromatic brilliant chromomycin A₃ fluorescence. No distamycin-A/DAPI-bright heterochromatic blocks were detected in the genomes of the Cyprinidae.     

Evidence for the paternal mitochondrial DNA in the crucian carp-like fish lineage with hybrid origin

In terms of taxonomic status, common carp(Cyprinus carpio, Cyprininae) and crucian carp(Carassius auratus, Cyprininae) are different species; however, in this study, a newborn homodiploid crucian carp-like fish(2n=100)(2nNCRC) lineage(F1–F3) was established from the interspecific hybridization of female common carp(2n=100)×male blunt snout bream(Megalobrama amblycephala, Cultrinae, 2n=48). The phenotypes and genotypes of 2 n NCRC differed from those of its parents but were closely related to those of the existing diploid crucian carp. We further sequenced the whole mitochondrial(mt) genomes of the 2n NCRC lineage from F1 to F3. The paternal mt DNA fragments were stably embedded in the mt-genomes of F_1–F_3 generations of 2n NCRC to form chimeric DNA fragments. Along with this chimeric process, numerous base sites of F1–F3 generations of 2 n NCRC underwent mutations. Most of these mutation sites were consistent with the existing diploid crucian carp. Moreover, the mt DNA organization and nucleotide composition of 2n NCRC were more similar to those of the existing diploid crucian carp than those of the parents. The inheritable chimeric DNA fragments and mutant loci in the mt-genomes of different generations of 2nNCRC provided important evidence of the mt DNA change process in the newborn lineage derived from hybridization of different species. Our findings demonstrated for the first time that the paternal mt DNA were transmitted into the mt-genomes of homodiploid lineage, which provided new insights into the existence of paternal mt DNA in the mt DNA inheritance.     

Large and persistent effect of a female steroid pheromone on ejaculate size in goldfish Carassius auratus

This study determined if ejaculate size in male goldfish Carassius auratus is increased by the female preovulatory steroid pheromone 4‐pregnen‐17,20β‐diol‐3‐one (17,20βP), which previously has been shown to affect male behaviour and to increase sperm motility and stripped sperm number, and also to increase paternity in competitive spawning and competitive in vitro fertilization. Experimental males were exposed overnight to 17,20βP whereas control males were not. The morning following exposure, each male was placed with a reproductively active female and, after one to 20 spawning acts, aquarium water was sampled to quantify released sperm. Although exposure to 17,20βP induced a five‐fold difference in the number of sperm that could be stripped, the median number of sperm in first ejaculates of pheromone‐exposed males was >60 sixty times that of control males, a pheromonal effect on ejaculate size that persisted for at least 20 spawning acts. The magnitude of the pheromone effect on ejaculate size indicates that it is a critical component of C. auratus sperm allocation, and that examining this effect in concert with other factors (e.g. presence of competitors, male and female size and frequency of spawning) will reveal the contribution of the preovulatory pheromone to male fitness in this promiscuous species.     

Identification of natural hybrids of gibel carp Carassius auratus gibelio (Bloch) and crucian carp Carassius carassius (L.) from lower Dyje River floodplain (Czech Republic)

Morphometric and genetic variation were examined in parental Carassius auratus gibelio and Carassius carassius individuals, and their natural hybrids. Of meristic traits, only the number of gill rakers clearly distinguished hybrids (39·4 ± 1·4) from parental C. a. gibelio (48·3 ± 0·7) and C. carassius (28·6 ± 1·1). MtDNA sequences showed that the hybrids were descendants of female C. a. gibelio . Microsatellite analysis confirmed the presence in hybrids of variants typical of C. a. gibelio and C. carassius .     

Hybridization of crucian carp, Carassius carassius (Linnaeus, 1758), in Ukrainian reservoirs and genetic structure of hybrids

Hybridization of crucian carps Carassius carassius in polyspecific crucian populations of reservoirs of Ukraine and genetic structure of the hybrids were investigated using biochemical gene marking and cytometric procedure. The fact of wide hybridization between C. auratus and C. carassius was proved to be true by large number of hybrids which can form populations consisting only from hybrid individuals. Hybrids C. auratus x C. carassius were diploid, tryploid and in exceptional cases tetraploid; females and males which most likely breed by hybridogenesis. Besides, some clonal hybrids C. carassius x C. gibelio-1 appearing as tetraploid females, and one triploid female C. carassius x Tinca tinca were revealed. It is supported that hybridization of alien C. auratus with endemic C. carassius became one of mechanisms of replacement and depressions of populations of the last.     

Towards the conservation of crucian carp Carassius carassius: understanding the extent and causes of decline within part of its native English range

The extent and causes of crucian carp Carassius carassius decline were assessed during an initial study of c. 25 ponds in north Norfolk, eastern England, U.K., which was then replicated (a validation study) on another c. 25 ponds in an adjacent area. Of these ponds, c. 40 are known to have contained C. carassius during the 1970s-1980s. In the initial and validation studies, C. carassius were found in only 11 of these ponds, yielding declines of 76% (five of 21 ponds) and 68% (six of 19 ponds), respectively (72% decline overall). Non-native cyprinids, including goldfish Carassius auratus and common carp Cyprinus carpio and their hybrids with C. carassius, were observed in 20% of the ponds. Causes of C. carassius local extinction from 21 ponds were confidently determined as desiccation due to drought, terrestrialization and habitat deterioration, hybridization and competition with non-native cyprinids, agricultural land reclamation and predation (after the introduction of pike Esox lucius). This study led to C. carassius being designated as a Biodiversity Action Plan (BAP) species in the county of Norfolk, the first formal conservation designation for the species in the U.K. The C. carassius BAP plan aims to halt the decline of this much overlooked species through reintroductions and selective stocking of suitable ponds within the native range of the species.     

Phylogeny and biogeography of the family Cyprinidae in the Middle East inferred from cytochrome b DNA- evolutionary significance of this region.

The phylogenetic relationships of cyprinid species from the Middle East and neighboring biogeographical areas were investigated using cytochrome b sequence variation in order to test hypotheses that consider the Middle Eastern area as an important interchange area or a center of speciation for the freshwater fauna. A total of 62 cyprinid species were analyzed over the complete cytochrome b fragment (1140 bp); 28 belong to the Leuciscinae subfamily and 34 to the Cyprininae. All the Leuciscinae lineage fish recorded in the Middle East are also found in Europe, which was interpreted as an important Palearctic influence in the Middle Eastern ichthyofauna consistent with the Lago Mare dispersion. However, it has also been suggested that several Danube species have their origins in the Middle East. In contrast, the Cyprininae subfamily showed three highly divergent lineages, one shared with the Euro-Mediterranean area (Barbus/Luciobarbus genus) relict of the Lago Mare dispersion, one shared with Africa (Carasobarbus/Varicorhinus subgenus), and the third shared with Asia (Garra genus). Furthermore, clades observed in the phylogenetic reconstructions are not consistent with morphometric or karyological data and disagree with previous taxonomic assumptions. Lastly, the dispersion history in the Middle East of this subfamily appears much more complicated and ancient than that of the Leuciscinae. However, taking into account Cyprininae and Leuciscinae distribution, the Middle East appears more like an important interchange area for the freshwater ichtyofauna than a center of speciation.     

Isolation increases milt production in goldfish

Milt volume in goldfish is increased by female steroid and prostaglandin pheromones, by exposure to males with elevated gonadotropin levels, and by isolation from conspecifies. This study examined various aspects of the isolation effect on milt volume and serum gonadotropin II (GTH II). The latency of isolation-induced milt increase in this study (12-24 hr) was longer than the latencies to pheromone-induced milt increase in previous work (0.5-6.0 hr), was not affected by the time of day at which males were isolated, persisted for at least 72 hr in isolated males, and was terminated within 24 hr in males that were returned to groups. Isolated males maintained high milt production when separated from tank mates by a perforated barrier or when exposed to visual and odor cues from males in other tanks, suggesting that the unknown conspecific cues that maintain low milt production in groups operate at close range. Isolation appears to increase milt through a mechanism different from that mediating response to female pheromones because: (1) unlike female pheromones, which consistently increase serum GTH II, no isolation or regrouping treatment in this study affected male GTH II concentration; and (2) the effects of isolation and of exposure to the female pheromone 17 alpha, 20 beta-dihydroxy-4-pregnen-3-one (17,20 beta-P) are additive. Finally, males that were previously isolated or exposed to 17,20 beta-P increased milt (but not GTH II) in grouped males, suggesting that the effects of isolation and pheromone exposure can indirectly stimulate male conspecifics. Although the biological function of the isolation effect is not clear, we propose that it illustrates the effect of removal from inhibitory cues normally received from male conspecifies.     

鲫鱼的人工和天然雌核发育

用照射处理的草鱼或华南鲤的精液授精的鲫鱼卵为单倍体雌核发育;所有单倍体胚胎都是畸形,并在孵化前死亡。如果用照射精液授精的鲫鱼卵在18—19℃的水中放置2分钟,然后在0—3℃的冰水中放置20分钟,再放回室温水中孵化,可以从每百颗受精卵中得到4.5—11.9(平均8.34)尾成活的二倍体仔鱼。根据38尾银鲫(其中33尾捕自黑龙江省方正县双凤水库)的细胞学和胚胎学检查,证实它们是雌核发育繁殖的。       

Genetic analysis of offspring from intra‐ and interspecific crosses of Carassius auratus gibelio by chromosome and RAPD analysis

The ploidy of silver crucian carp Carassius auratus gibelio individuals, originating from nine natural habitats of Hungary, was estimated by erythrocyte nucleus area analysis. On the basis of DNA polymorphism, the genetic homogeneity or heterogeneity and the chromosome number of different offspring derived from the crossing of triploid and diploid populations and of two types of silver crucian carp females with other cyprinid males ( Cyprinus carpio, Carassius carassius, Carassius auratus and Barbus conchonius ) were determined. The results of chromosome and RAPD analysis demonstrated that diploid females could reproduce sexually with silver crucian carp and other cyprinid males and that the offspring of intra‐ and interspecific crosses contained the paternal DNA. Triploid females usually reproduced by gynogenesis and their offspring were clones, however, in very rare cases paternal genes were actually transmitted ( i.e . paternal leakage) to the offspring and the progeny were triploid interspecific hybrids. RAPD analysis showed that while the paternal DNA appeared in the offspring, the maternal phenotype was strongly expressed.     

Occurrence of Monogenea in Italian freshwater fish (Po river basin)

Sixteen Monogenean species were found on the skin and gills of 10 different fish species collected from north Italian water bodies. Cleidodiscus pricei from Ictalurus melas; Dactylogyrus alatus from Alburnus alburnus; D. anchoratus, D. formosus and D. vastator from Carassius carassius; D. difformis from Scardinius erythrophthalmus; D. rutili from Rutilus aula; D. tincae and Gyrodactylus gasterostei from Tinca tinca; D. ergensi from Leuciscus cephalus and Telestes muticellus; D. vistulae and Paradiplozoon rutili from Leuciscus cephalus; D. extensus and G. katharineri from Cyprinus carpio; G. lucii and Tetraonchus monenteron from Esox lucius. All species are new records for Italy with the exception of D. difformis, D. ergensi, D. vistulae and T. monenteron.     

Genetic Diversity in Crucian Carp (Carassius auratus)

A survey of restriction fragment polymorphism in mitochondrial DNA of three subspecies of Carassius auratus throughout four provinces in China was undertaken using 17 restriction enzymes. Two carp, Cyprinus carpio rubbrofuscus and Cyprinus carpio carpio, were included as the outgroup. A total of 16 haplotypes was observed: 5 in tetraploids of C. auratus auratus; 8 in hexaploids of C. auratus auratus; and 2 in C. auratus gibelio and C. auratus cuvieri, respectively. The tetraploids and hexaploids share three common haplotypes as I, V, and VI. C. a. Cuvieri may have diverged first among the three subspecies. Interestingly, C. a. auratus and C. a. cuvieri did not form monophyletic clades, which indicated that the classification of Carassius auratus required further studies. The current hypothesis, that hexaploids originated from tetraploids by a polyploidy event, is less favorable, based on the distribution of haplotypes and the lower diversity in tetraploids than in hexaploids. Our data also indicate that divergence of hexaploids and tetraploids might be recent and mtDNA polymorphism existed before the divergence. Meanwhile, genetic isolation exists between the hexaploids and the tetraploids.     

指环虫属的早期辐射及其与宿主鲤科鱼类的协同进化关系

本研究利用28SrDNAC1-D2区序列分析采自鲤科鱼类中6亚科宿主和寄生在花鲈、梅花鲈上的共17种指环虫的系统发育关系。同时,通过比较宿主鲤科鱼类与指环虫的系统发育树,检验指环虫与其宿主是否存在协同进化关系。结果表明:17种指环虫形成5个进化支(Clade),其中寄生在团头鲂(亚科)和鲢、鳙(鲢亚科)上的6种指环虫聚为一支(Clade1),而它们的宿主鱼类在系统发育分析中也表现为近缘关系;寄生在鲮鱼(野鲮亚科)上的D.quanfami(Clade5)位于系统树最基部,鲫鱼和鲤鱼(鲤亚科)的寄生指环虫处在系统树的次基部位置,而鲤亚科与野鲮亚科组成的姐妹群在宿主系统树上同样处在基部位置,寄生虫和宿主在进化上较为原始的地位得到了很好地相互印证。因而,本研究首次利用分子系统学手段分析指环虫属远缘物种间的系统关系,揭示了指环虫属与宿主鱼类之间存在协同进化关系。另外,本研究首次发现,野鲮亚科鱼类也可能是指环虫类的早期宿主,这与先前认为鲤亚科鱼类为指环虫类的祖先宿主的推测有所不同。     

杞麓湖鲤鱼鳞片表面结构的扫描电镜观察

采用扫描电镜技术对鲤科鱼类鳞片表面结构进行观察研究,目前国内尚未见报道。本工作主要以杞麓湖的鲤鱼为研究对象,同时观察了鲤亚科其他属鱼类的鳞片表面结构,发现鳞纹上的齿状粒突可能是从无到有,同时探察此结构有无可能作为分类的一项指标。鉴于杞麓鲤的鳞纹上具齿状粒突,而华南鲤则无,再综合考虑二者骨骼性状的差异,作者认为,这些性状可作为将杞麓鲤由普通鲤的一个亚种提升为一个独立种级地位的证据。从鳞片辐射沟的亚显微结构推测,辐射沟具有两方面的功能,一方面可对鳞片的热胀冷缩起缓冲作用:另一方面可增强鳞片的柔软弯曲性。     

Reproduction mode of an artificial allotetraploid carp (Pisces; Cyprinidae)

Mature eggs of allotetraploid carp were activated by inactive sperm or crossed with normal sperms of common carp (Cyprinus carpio), crucian carp (Carassius auratus), Chinese blunt snout bream (Megalobrama amblycephala), Hemiculter leucisculus and Pseudorasbora parva. Chromosome counts showed that all offspring of these crosses presented a mode number of 200 chromosomes (4n = 200), and their morphological traits are much like maternal. Microsatelite marker and RAPD patterns between allotetraploid maternal and its offspring, reproduced from different paternal species, were identical. Cytological, morphological and molecular evidences suggested that allotetraploid carp female nucleus would not fuse with any male nucleus and its reproduction mode might be gynogenesis and therefore their offspring are retaining their tetraploidy and give origin to clonal individuals.     

复合四倍体异育银鲫两种不同生殖方式的细胞学观察

在复合四倍体异育银鲫（）×银鲫（）的受精过程中,精子入卵后经过解凝、核化,最终形成雄性原核,并可与卵子的雌性原核融合,证明了复合四倍体异育银鲫卵子具有与两性融合生殖极为相似的拟两性融合生殖的能力;而在复合四倍体异育银鲫（）×兴国红鲤（）的组合中,精子入卵后以固缩状态存在,又表现出典型的雌核发育型生殖行为。因此我们认为复合四倍体异育银鲫具有两种不同的生殖发育机制。此外,我们还观察到在第一次有丝分裂中期有核物质被排斥到纺锤体之外的现象。本文就复合四倍体异育银鲫生殖发育的机制进行了初步的探讨。     

天然雌核发育银鲫卵子控制异源精核发育的受精学机制

作者对两性融合生殖鱼和雌核发育银鲫脱膜卵受精的精核发育进行了观察,并采用鱼类卵子无细胞系对以上两类卵质提取物体外诱导经Ｔｒｉｔｏｎ—Ｘ１００处理的精子及其发育进行了初步研究,结果表明在两性融合生殖型脱膜鱼卵中精核通过解凝最终形成原核,而在雌核发育的银鲫脱膜卵子中部分精核体积虽有一定程度的增加,但始终没有观察到原核的发育;在体外诱导实验中,经Ｔｒｉｔｏｎ—Ｘ１００处理的精子在两类卵质提取物中充分发育,都出现了类似体内原核的状态。该现象提示在银鲫卵质中存在有促使精核形成原核的因子,但在正常受精状态下,由于银鲫卵质促使精核核膜解体的功能的异常,使覆盖精子头部的核膜不能象在两性融合生殖受精卵子中进行崩解,精核进一步的原核发育受到抑制。另外,建立体外诱导系统的重要意义,在于它为研究雌核发育调控的分子学机制提供了一条有效途径。     

海口地区集贸市场淡水鱼华枝睾吸虫囊蚴感染调查

用直接压片法和人工消化法检查了海口集贸市场上5种淡水色(鲫色、罗非鱼、鲤鱼、土鲮色、白鲳)感染华枝睾吸虫囊蚴情况。结果表明：5种淡水色的总感染率为53．66％。其中,鲤鱼、土鲮色、鲫鱼、罗非鱼、白鲳的感染率分别为68．75％、58．82％、58．06％、48．57％和36．67％;平均每克鱼肉含囊蚴数最高的是鲫鱼(9．47个／g),平均每尾阳性鱼含囊蚴数最高的是土鲮鱼(43个／尾)。