Functional responses of five cyprinid species to planktonic prey

Synopsis The functional responses of five species of cyprinids (Chalcalburnus chalcoides, Vimba vimba, Abramis brama, Rutilus rutilus, and Scardinius erythrophthalmus) feeding on four planktonic prey types were measured in the laboratory. Although no alternative prey types were present, the response curves were sigmoid in most cases, because attack rates were not independent of prey density. The findings are explained as being the overt expression of the fishes& foraging tactics. The chief way of maximizing food uptake, according to our interpretation, is accelerating attack rates with increasing prey density. The ability of prey to escape or relative prey size may interfere with this strategy. C. chalcoides, the only obligatory planktivore among the species studied, attacks at higher rates and responds most markedly to changes in prey density.     

Fish drift in a Danube sidearm‐system: I. Site‐, inter‐ and intraspecific patterns

A total of 10 649 larval and juvenile fishes of 24 species were caught in the drift at Marchfeldkanal, a man‐made side branch of the Danube River near Vienna, Austria, with tubenose goby Proterorhinus marmoratus being the dominant species. Distinct differences in inter‐ and intraspecific drift patterns among different sampling stations along the course of the channel were found. The percentage of the rheophilic and rheoparous ecological guild was highest at the inlet of the channel, where it is directly fed with water from the Danube. For individual species, significant differences in drift densities among sites were found for tubenose goby, barbel Barbus barbus , ide Leuciscus idus , roach Rutilus rutilus and for the two most abundant percids, the pike‐perch Sander lucioperca and zingel Zingel zingel combined. The occurrence of larval and juvenile fishes in the drift was related to certain developmental stages and differed between species and sites. Most species (common bream Abramis brama , bleak Alburnus alburnus , gudgeon species Gobio spp., chub Leuciscus cephalus , ide and roach) occurred with highest densities at the earliest developmental larval stage, but some species ( e.g . common bream and roach) were also found abundantly in drift at later developmental stages. Application of Ivlev's index of electivity as a drift index describing the propensity of the different species to drift, yielded the highest indices for the gudgeon species, common bream and bleak and the lowest for perch Perca fluviatilis , Prussian carp Carassius auratus gibelio and rudd Scardinius erythrophthalmus .     

The influence of temperature on the embryonic development of three cyprinid fishes, Abramis brama, Chalcalburnus chalcoides mento and Vimba vimba

The influence of temperature on the embryonic development of three European cyprinid fishes, Abramis brama, Chalcalburnus chalcoides mento and Vimba vimba , was studied with respect to hatching efficiency and the functional relationship with the duration of development. The functional dependance of the duration of development on temperature is well described by a power function with a correcting constant for temperature. Comparison with published data for other cyprinids shows that the response of embryos to temperature, together with the various temperature controlled responses of adult fishes, is a valuable aid for the ecological characterization of the different species.     

Cross‐species amplification of zebrafish and central stoneroller microsatellite loci in six other cyprinids

One hundred and twenty Danio rerio and Campostoma anomalum microsatellite loci were tested for amplification in the cyprinids Phoxinus phoxinus, Scardinius erythrophthalmus, Rutilus rutilus, Abramis brama, Carassius carassius and Gobio gobio . The PCR amplification products were recorded in 35 to 50 loci, depending on focal species. Eight to 28 of the amplifying loci were also polymorphic, establishing potential sets of genetic markers for population genetics studies.     

Fish drift in a Danube sidearm‐system: II. Seasonal and diurnal patterns

Seasonal and diurnal patterns of larval and juvenile fish drift were investigated in the Marchfeldkanal, a man‐made side branch of the Danube River near Vienna, Austria. A clear seasonal pattern with peak densities in mid‐June was found. Species composition varied over time, showed a site specific pattern and was dominated by tubenose goby Proterorhinus marmoratus . Water temperature was the main factor responsible for the increase of drift densities until the median drift date and repeated occurrence of early larval stages in drift indicated repeated spawning for many species. Significant differences in drift densities between different time periods of the day (day, dusk, night and dawn) were found for common bream Abramis brama , barbel Barbus barbus , chub Leuciscus cephalus , tubenose goby and roach Rutilus rutilus . The highest drift rates occurred at night (2200–0400 hours), with 86% of all larvae drifting during the hours of darkness. Fish larvae of different lengths drifting at different phases of the day were found for common bream, bleak Alburnus alburnus and chub, with largest larvae drifting during dusk (chub) and day (bleak and common bream). For bleak, all gudgeon species Gobio spp., tubenose goby, roach and for all cyprinid species combined, one 2 h night sample was found to be sufficient to predict the total 24 h drift.     

Cryopreservation of spermatozoa in cyprinid fishes

The present study investigated semen cryopreservation in cyprinid fish using computer-assisted sperm motility analysis for viability control. Spermatozoa of the bleak, Chalcalbumus chalcoides, were used as a basic model to describe the toxic and cryoprotective effects of internal and external cryoprotectants, their most effective concentrations and combinations, the freezing and thawing conditions, and the effects of equilibration. We also used these data to develop a cryopreservation protocol for Barbus barbus, Chondrostoma nasus, Ctenopharyngodon idella, Cyprinus cario, Hypohtalmichthys molitrix, Leuciscus cephalus, Rutilus meidingerii, and Vimba vimba. For all investigated species the optimal extender composition was a buffered physiological sperm motility-inhibiting saline solution containing 10% DMSO and 0.5% glycin. The optimal sperm equilibration period in the extender was < or = 5 min. Freezing was performed in an insulated box in liquid nitrogen vapor and it was optimal at 4 to 5 cm above the surface of the liquid, depending on the species. Thawing was optimal in a 25 degrees C water bath whereby the thawing time ranged depending on species from 15 to 45 sec. This cryopreservation protocol resulted in frozen-thawed semen with 35 to 65% motile and 5 to 25% locally motile spermatozoa depending on the quality of fresh semen.     

Maximum daily ration of juvenile fish fed on living natural zooplankton

Juveniles of five species of cyprinids of body length 15–90 mm as well as juvenile perch, Perca fluviatilis L., were fed on living natural zooplankton over periods of 2 or 3 days. For all species the correlation of the daily ration (% body weight) with body weight showed a maximum curve. The maximum was reached at a body weight (wet weight) of 0.6 g for Leuciscus leuciscus (L.) and 0.1 g for a group consisting of varying numbers of Rutilus rutilus (L.), Abramis brama (L.) and Alburnus alburnus (L.). For L. leuciscus , the maximum was 220% body weight (wet weight), corresponding to 40% on a dry weight basis. For the mixed species group the maximum was about 500% (wet weight) and about 140% on a dry weight basis. The highest daily ration coincided with the occurrence of the spring bloom of zooplankton.     

DNA reassociation kinetics in diploid and phylogenetically tetraploid cyprinidae.

Four diploid and three phylogenetically tetraploid Cyprinidae (Ostariophysi) have been characterized as for nuclear DNA content, modal chromosome number and DNA reassociation kinetics (hydroxyapatite chromatography). Among the diploid species nuclear DNA content (10(-12) g DNA/2C) was 1.62 for Tinca tinca, 1.87 for Scardinius erythrophthalmus, 2.53 for Leuciscus cephalus and 2.75 for Alburnus alburnus, while the phylogenetically tetraploid species Carassius auratus, Barbus barbus and Cyprinus carpio attained 3.40, 3.66 and 3.80 respectively. Modal chromosome number was 2n = 48-50 for diploid individuals and 2n = 100-104 for phylogenetically tetraploid ones. In all the species 5--8% of the genome is represented by highly repetitive and foldback DNA. In DNA reassociation kinetics of phylogenetically tetraploid Cyprinidae a distinct plateau separates an intermediate reassociating sequence fraction (about 22% of the genome; with average repetition frequencies between 1,000 and 1,400) from a slow reassociating one (unique DNA; about 72% of the genome). These two genome fractions are not clearly distinguishable from each other in Cot curves of the diploid Cyprinidae, where a similar plateau is not evident. Since simple ploidy changes are not expected to affect DNA reassociation kinetics we suggest a different evolution in the genome organization of the two ploidy groups. Some possible hypotheses are discussed.     

Fish community structure in mesotrophic and eutrophic lakes of southern Finland: the relative abundances of percids and cyprinids along a trophic gradient

In 36 south Finnish lakes, the number of species, as well as the cyprinids:percids ratio, was dependent, not only on total phosphorus (TP), but also on lake size. Total fish biomass and cyprinid biomass increased along the TP gradient, whereas the dependence of percid biomass was less evident. Perch Perca fluviatilis and roach Rutilus rutilus strongly dominated mesotrophic lakes; in eutrophic lakes the proportion of other cyprinids and percids, such as white bream Blicca bjoerkna , bream Abramis brama , pikeperch Stizostedion lucioperca and ruffe Gymnocephalus cernuus , increased. Perch biomass was weakly related to abiotic factors but depended on roach biomass. Lake size and fish species composition are essential factors affecting fish community changes in relation to TP, and may be important as well in regulating the responses of a fish community to biomanipulation.     

The testicular main ducts and the spermatic ducts in some cyprinid fishes—II. Composition of the seminal fluid

The composition of the organic compounds of the seminal fluid, pH values and osmolalities were investigated in three cyprinid species, the bleak ( Alburnus alburnus ), the chub ( Leuciscus cephalus ) and the zaehrte ( Vimba vimba ). The seminal fluid contains monosaccharides (glucose, fructose, galactose, xylose), lipids (cholesterol, fatty acids, phosphatidylcholine, glycolipids) and proteins, and exhibits activities of acid phosphatase, β-glucuronidase, proteases and to some extent of alkaline phosphatase. The composition of free amino acids reveals species specific differences.     

Karyotypes of some Cypriniform fishes from the water bodies of Armenia

Karyotypes of six species of Cypriniformes from the water bodies of Armenia—blackbrow Acanthalburnus microlepis, white bream Blicca bjoerkna transcaucasica, chub Leuciscus cephalus orientalis, stone moroco Pseudorasbora parva, mursa Barbus mursa, and Angora stone loach Barbatula angorae were studied. The karyotype of A. microlepis is represented by 50 chromosomes (2n = 50), 10M + 28SM + 12STA, NF = 88; of B. bjoerkna transcaucasica, by 2n = 50, 12M + 24SM + 14STA, NF = 86; of L. cephalus orientalis, by 2n = 50, 12M + 18SM + 20STA, NF = 80; of P. parva, by 2n = 50, 8M + 16SM + 26STA, NF = 74; of B. mursa, by 2n = 100, 6M + 36SM + 58STA, NF = 142; and of B. angorae, by 2n = 50, 8M + 24SM + 18STA, NF = 86. The intraspecific and interspecific chromosome polymorphism of species of the genera Blicca, Leuciscus and Pseudorasbora is described.     

Life styles and patterns of development of gills and muscles in larval cyprinids (Cyprinidae; Teleostei)

A morphometric study of gill structures and of the body musculature during the first weeks after hatching was carried out on larvae of six cyprinid species: Leuciscus cephalus, L. leuciscus, Rutilus rutilus, Alburnus albumus, Chondrostoma nasus and Abramis brama . In all species a unicellular layer of red muscle fibres covers the central muscle mass; this layer is of greatest extent shortly after hatching but diminishes gradually in mass by contracting towards the lateral region of the body until it merges with (or gives rise to) the adult red muscle fibres proper. There is a close relationship between the rate of differentiation of gill structures and the rate at which the larval red muscle layer disappears, the pattern of this relationship reflecting the life style of the species. The longer the larvae delay the start of their free-swimming existence after hatching (which in A. alburnus may be as long as 10 days) the longer does the red layer of muscle fibres serve as the organ of gas exchange and the longer is gill development suppressed. It appears that the metabolism of the swimming muscles is almost entirely aerobic so long as gas exchange takes place across the whole body surface, the glycolytic capacity of the central muscle mass developing only slowly in conjunction with the switch from red layer to gills as the major respiratory organ.     

Physiological and biochemical investigations on egg stickiness in common carp

The properties and behaviour of common carp, Cyprinus carpio, eggs in water and in ovarian fluids were studied at different temperature, pH, and with divalent cation concentrations. The biochemical composition of zona radiata externa (ZRE) was analyzed qualitatively and quantitatively on amino acids, carbohydrates, uronic acid and sialic acids using chemical assays; on proteins using electrophoresis. Comparative biochemical studies were performed on the chub, Leuciscus cephalus, the vimba, Vimba vimba and the bleak, Chalcalburnus chalcoides. Eggs of common carp became sticky within seconds after mixing with water. Egg stickiness was not affected by water pH in a range of 6-9, by water temperatures between 4 and 30 degrees C, by divalent cations in concentrations < or =20 mmol/l, and by sodium chloride concentrations < or =50 mmol/l. Our investigations indicated that specific proteins of the cyprinid ovarian fluid are controlling (inhibiting) the initiation of egg stickiness: egg stickiness did not develop as long as the eggs were incubated in ovarian fluid. When however the ovarian fluid proteins were removed from the ovarian fluid by heat treatment, eggs developed stickiness within seconds, like they do in water. Biochemically, the ZRE consisted of nine types of proteins whereby four of them were glycoproteins. Glucose, fructose, galactose, and uronic acids were the major carbohydrates. Treatment of the egg membrane with invertase or amyloglucosidase did not affect the egg stickiness. Treatment with protease prevented stickiness. From these results and from additional histochemical results, we conclude that glycoproteins are likely to be the molecules responsible for stickiness.     

Molecular characterization of Diplozoidae populations on 5 species of Cyprinidae: new data on parasite specificity

The genus Diplozoon (Platyhelminth) exhibits one of the most striking modes of reproduction. Adults reproduce after the permanent fusion of two larval hermaphrodites, which play a symmetrical role. The Diplozoidae are also exceptional among the Monogenea Polyopisthocotylea for two other reasons. They represent the only group really diversified on continental freshwater fishes; however, this diversification is difficult to evaluate since few morphoanatomical criteria are available to distinguish species and their host specificity is atypically variable among the Monogenea. For the first time in the Diplozoidae, the problems of species definition and of host specificity are examined using molecular tools. Two ribosomal markers (ITS2 and 28S rDNA (D1)) have been sequenced in five Diplozoidae, interacting with five Cyprinidae host species: the corresponding parasite-host systems have been well characterised, revealing some contrasting situations in the relations between Diplozoidae and Cyprinidae. Some species are effectively strictly host specific, but Diplozoon scardinii initially considered as a specific species on Scardinius erythrophtalmus and D. homoion on Rutilus rutilus are proposed to be a single species on the basis of their identical ITS2 and 28S rDNA sequences. On the same basis we proposed that D. paradoxum is able to parasitize two fish species, Abramis brama and Blicca bjoerkna, despite the morphological differences observed between the two xenopopulations. Phylogenetic relationships among Diplozoidae species were estimated with ITS2 sequences while cytochrome b sequences were used for their fish hosts. Finally, the comparison between these two molecular phylogenies seems to exhibit the phenomenon of cospeciation.     

Variations in the spawning periodicity of eight fish species in three English lowland rivers over a 6 year period, inferred from 0+ year fish length distributions

The spawning periodicity of eight fish species was investigated in three English lowland rivers over a 6 year period from patterns in 0+ year fish standard length ( L _S) distributions. A single cohort of 0+ year dace Leuciscus leuciscus , roach Rutilus rutilus and perch Perca fluviatilis was observed each year, suggesting that these species spawned only once annually. By contrast, populations of chub Leuciscus cephalus , bleak Alburnus alburnus , bream Abramis brama , gudgeon Gobio gobio and minnow Phoxinus phoxinus were inferred to spawn on more than one occasion each year. Annual and intercatchment variations occurred in the L _S distribution patterns of some of the fish species. In chub, for example, although a minimum of two 0+ year cohorts occurred in all years in the River Trent, 'multiple' spawning (either at the individual or population level) was most apparent in 1999, 2003 and 2004. By contrast, 'multiple' spawning events were not evident in all years in the Warwickshire Avon and Yorkshire Ouse, with recruitment presumably based upon a single spawning event in some years. There is effectively a trade-off between early spawning (extended growing season), and the possibility that environmental conditions will impact upon recruitment success, and the potential for reduced overwinter survival of smaller individuals with lower lipid resources from later spawning events. Notwithstanding, fishes as small as 15 mm L _S survived the winter in some years, suggesting that progeny from later spawning events may make important contributions to fish recruitment success.     

A molecular approach to detect hybridization between bream Abramis brama, roach Rutlius rutilus and rudd Scardinius erythrophthalmus

Hybridization between roach Rutilus rutilus , bream Abramis brama and rudd Scardinius erythrophthalmus was investigated using morphological and genetic analysis employing both nuclear (ITS1) and mitochondrial (cytochrome b ) markers. Allele-specific amplification (ASA) reactions for both markers were developed and ITS1 sequence data for all three species are presented. Sequencing detected two ITS1 haplotypes within both roach and bream which most likely evolved in isolation and were subsequently brought together as a result of restocking by anglers. Analysis of cloned hybrid nuclear ribosomal DNA revealed evidence of recombination between parental ITS1 sequences. ASA proved to be an effective method for identifying hybrids and detected multiple ITS1 copies in fishes identified as purebred by morphological analysis. In addition this suggests post-F1 hybridization and introgression may be occurring between roach and bream, and rudd and bream, although some barriers appear to be suppressing backcrosses within the hybrid population. Analysis of the hybrid population demonstrated that hybridization has occurred in both directions.     

Anthropogenic changes in the freshwater fish fauna of Italy, with reference to the central region and Barbus graellsii, a newly established alien species of Iberian origin

In a survey of the west-central Italian rivers Ombrone, Fiora, Albegna and Bruna, among established exotic species, the Iberian barbel Barbus graellsti was recorded in Italian fresh waters for the first time. Morphological identification was supported by comparison of cytochrome b sequences with those from related barbel species. Other exotics of particular note were Barbus barbus, Pseudorasbora parva and Leuciscus cephalus , together with the Padano-Venetian Chondrostoma genei and Padogobius bonelli. Native species still present included Leuciscus lucumonis, Telestes muticellus, Rutilus rubilio and Padogobius nigricans , but were now more restricted to upper reaches and smaller watercourses. The deleterious effect of alien species on native forms is discussed with particular reference to probable competition between C. genei and L. lucumonis , and between the two gobies. The checklist of species introduced to the fresh waters of Italy is now updated to 34. For the Italian freshwater fish fauna in general, the conservation status of three native species ( Acipenser naccari, Salmo marmoratus and Knipowitschia punctatissima ) has been improved but five species are believed to be at risk ( Salmo carpio, L. lucumonis, Scardinius scardafa, Gobio benacensis and P. nigricans ) and four anadromous species ( Petromyzon marinus, Lampetra fluviatilis, Acipenser sturio and Huso huso ) no longer breed in Italian fresh waters. The processes of change in the composition of the Italian freshwater fish fauna as a whole may be summarized as successively 'padanization', 'danubization' and now 'globalization'.     

Comparative analysis of glucosephosphate isomerase, lactate dehydrogenase and malate dehydrogenase isozymes in 9 cyprinid species from Italy

The developmental and the tissue-specific expression of glucosephosphate isomerase (GPI), lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) multilocus isozymes were analyzed in samples of Leuciscus cephalus and the adult patterns compared with those of 8 additional Italian cyprinid species: Alburnus alburnus alborella, Chondrostoma genei, L. lucumonis, L. souffia, Rutilus rubilio, R. erythrophthalmus, Scardinius erythrophthalmus and Tinca tinca, the taxonomic status of many of them being uncertain and highly debated. The spatial and temporal patterns of expression obtained generally agree with literature data. Main exceptions are the single expression of GPI-A* and MDH-A* loci of the liver in L. cephalus and the GPI pattern of the eye in all species examined. Since delayed appearence of the subunits coded by the GPI-B* locus and the very early ontogenetic expression of the sMDH-B* locus were found in L. cephalus, the onset of expression of orthologous loci can vary in related species. Genetic structure comparisons support a high genetic divergence of T. tinca from all other species.     

Male primer endocrine responses to preovulatory female cyprinids under natural conditions in Sweden

This study investigated two related aspects of male-female reproductive interactions in the family Cyprinidae: (1) whether ovulating female rudd Scardinius erythrophthalmus (subfamily Leuciscinae) induce endocrine and gonadal priming responses in conspecific males, a phenomenon which has been described only in species from the subfamily Cyprininae such as goldfish, Carassius auratus, crucian carp Carassius carassius and common carp, Cyprinus carpio and (2) whether the stimuli mediating these responses are species-specific. Field studies of three sympatric European cyprinids, two leuciscins (S. erythrophthalmus and white bream Blicca bjoerkna) and one cyprinin (C. carassius), were conducted on fishes captured in Sweden in the spawning season and held in net pens under natural conditions. As previously reported in C. carassius, male S. erythrophthalmus increased milt (sperm and seminal fluid) volume and plasma concentrations of the sperm maturation hormone 4-pregnen-17,20β-diol-3-one (17,20β-P) when they were held with female S. erythrophthalmus induced to ovulate by injection of Ovaprim (GnRH analogue plus dopamine antagonist). Male S. erythrophthalmus had larger milt volumes than male C. carassius prior to and following exposure to ovulatory conspecifics, but exhibited a smaller proportional milt increase in response to stimulation, suggesting species differences in sperm allocation at spawning. The presence of female S. erythrophthalmus and B. bjoerkna did not affect milt volumes of C. carassius under two experimental conditions: (1) ovulating S. erythrophthalmus and B. bjoerkna did not increase the milt volumes of C. carassius and (2) S. erythrophthalmus and B. bjoerkna did not interfere with the milt volume increase induced in male C. carassius by ovulating conspecifics. These results suggest that, as in C. auratus, C. carassius and C. carpio (subfamily Cyprininae), female S. erythrophthalmus (subfamily Leuciscinae) release a preovulatory pheromone that exerts priming effects on male hormones and sperm allocation. The findings also indicate that C. carassius discriminate between the reproductive odours of conspecifics and heterospecifics.     

Observations on the distribution, specificity and pathogenicity of the acanthocephalan Pomphorhynchus laevis (Müller)

The distribution, specificity and pathogenicity of the acanthocephalan Pomphorhynchus laevis (Müller) were studied in the River Avon, Hampshire. The parasite occurred in every fish species, but three categories of hosts could be distinguished. Using growth and maturation as criteria of specificity, only chub Leuciscus cephalus (L.) and barbel Barbus barbus (L.) were recognized as its preferred hosts. Parasites occasionally matured in trout Salmo trutta (L.) and dace Leuciscus leuciscus (L.), but none grew or matured in other host species. Changes in the abundance of P. laevis along the river were related to changes in the abundance of both the intermediate host, Gammarus pulex , and the preferred hosts, and its occurrence in fish to the importance of G. pulex in their diet. In the upper reaches of the River Avon and in other localities populations could be maintained at a low level by parasites maturing in trout, and presence and abundance at any site depended upon the presence and abundance of both intermediate and definitive hosts especially and upon the dietary preferences of the latter. The absence of P. laevis from many parts of Britain is nevertheless still inexplicable. The parasite caused local damage to the intestinal wall of fish, the extent of which varied from species to species, but did not affect host growth rate or cause direct mortality and P. laevis cannot be regarded as an important pathogen in the River Avon or any other British River.