Water quality as a determinant of the composition of fish parasite communities

To investigate the relationship between fish parasite communities and water quality level, metazoan parasites were examined in 157 specimens of chub (Leuciscus cephalus L.), sampled in four lowland water courses (northern Italy): Ticino river (unpolluted), Naviglio Pavese Canal (slightly polluted), Lambro river near the Merone village (polluted) and near Monza (severely polluted). Dactylogyrus vistulae, Paradiplozoon ergensi, Bucephalus polymorphus, Acanthocephalus anguillae and larval stages of Tylodelphys clavata were found in all the sampled sites. The distribution of Lamproglena pulchella and Pomphorhynchus laevis was limited to the unpolluted and slightly polluted river sectors, while Asymphylodora tincae, glochidia, along with larval stages of Diplostomum spathaceum, were absent in the severely polluted site. The variability of the calculated infection indices (prevalence, mean abundance and mean intensity), the degree of interactivity among parasites, as well as parameters of species richness and diversity suggest that the structure of parasite communities are affected by the water contamination level.     

Origin, radiation, dispersion and allopatric hybridization in the chub Leuciscus cephalus

The phylogenetic relationships of 492 chub (Leuciscus cephalus) belonging to 89 populations across the species' range were assessed using 600 base pairs of cytochrome b. Furthermore, nine species belonging to the L. cephalus complex were also analysed (over the whole cytochrome b) in order to test potential allopatric hybridization with L. cephalus sensu stricto (i.e. the chub). Our results show that the chub includes four highly divergent lineages descending from a quick radiation that took place three million years ago. The geographical distribution of these lineages and results of the nested clade analysis indicated that the chub may have originated from Mesopotamia. Chub radiation probably occurred during an important vicariant event such as the isolation of numerous Turkish river systems, a consequence of the uplift of the Anatolian Plateau (formerly covered by a broad inland lake). Dispersion of these lineages arose from the changes in the European hydrographic network and, thus, the chub and endemic species of the L. cephalus complex met by secondary contacts. Our results show several patterns of introgression, from Leuciscus lepidus fully introgressed by chub mitochondrial DNA to Leuciscus borysthenicus where no introgression at all was detected. We assume that these hybridization events might constitute an important evolutionary process for the settlement of the chub in new environments in the Mediterranean area.     

Hybrids of bleak, Alburnus alburnus, and chub, Leuciscus cephalus in English rivers

The occurrence of hybrids between bleak, Alburnus alburnus , and chub, Leuciscus cephalus is reported from four discrete river systems in England. The hybrids are described and illustrated, and means of identification from the parent species are given. Bleak × chub hybrids appear to be moderately common and on superficial examination resemble the bleak parent species more than the chub.     

Genetic divergence in Greek populations of the genus Leuciscus and its evolutionary and biogeographical implications

In 23 populations of Greek Leuciscus ( Squalius ), the percentage of polymorphic allozyme loci ranged between 0·034 and 0·379 (P=0·19) and expected heterozygosity was 0·011–0·166 (H_e=0·067). Current taxonomy is confusing and does not correspond to genetic data that support the presence in Greece of at least seven different species: L. cephalus , L. peloponnensis , L. prespensis , L. moreoticus , L. borysthenicus , L. keadicus and Leuciscus sp. from Euboea Island. The maximum Nei modified genetic distance was found among L. keadicus and the rest of subgenus Squalius populations D * Nei=0·446–0·705). Accepting the molecular clock hypothesis, speciation for the genus Leuciscus in Greece must have occurred during the Cenozoic period (between the Middle Miocene and the Later Pliocene). The two main biogeographical events causing speciation on mainland Greece were the Uplift of the Pindic cordillera and the isolation of the southern part of Peloponnesus. The faunistic composition of the lakes studied, in which new taxa are reconsidered, suggests the same faunistic origin in the Early Pliocene for Lakes Prespa and Stymphalia and a younger one in the Late Pliocene for Lake Trichonis. Euboea Island was not a zoogeographical unit during the Cenozoic. The isolation of all the freshwater fish fauna of Euboea has occurred since the Pliocene. The biogeographical model proposed here differs from classical hypotheses in considering of lesser importance the dispersion of L. cephalus on the Greek mainland during the Neogene and Quaternary.     

Variability in the growth rate of chub Leuciscus cephalus along a longitudinal river gradient

An increase in individual growth rate of chub Leuciscus cephalus along a longitudinal river gradient of the Rhône River basin was observed and supported by significant differences between mean growth rates of successive river size groups. The potential implications of the results for studies on species traits variability along large-scale environmental gradients are discussed.     

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 ).     

Leuciscus cephalm (Linnaeus), with records of fingerling adult males, Leuciscus plemobipunctatus (Stephanidis) and their hybrids from western Greece

The spawning season of chub, Leuciscus cephalus , in western Greece starts in January-February when males are aged at least 2 + and females 3 + (rarely 2 +) years. In the R. Ermitsa (Achelos R. basin) a population is reported with fingerling adult males with developed gonads and breeding tubercles at a size of 42 72 mm s.l . Leuciscus pleurobipunctatus breeds between February and the first half of May, when males are aged at least 1 + and females 2 + (sometimes also 1 +); their life span is about 4 years. L. cephalus × L. pleurobipunctatus hybrids were found in the R. Ermitsa (five specimens) and R. Louros (one specimen). In the former the contemporary presence of adult fingerling male chub, the smallest adults of L. pleurobipunctatus , and hybrids between the two species, may be related to channel width and the human interference which has resulted in considerable disturbance of the habitat.     

Hybrids of chub and roach (Leuciscus cephalus and Rutilus rutilus) in English rivers

The occurrence of hybrids between chub, Leuciscus cephalus , and roach, Rutilus rutilus , from three rivers in England is reported. The hybrids are described and illustrated, and means of identification are indicated. Chub X roach hybrids, like those between other leuciscine cyprinid species, can be positively identified by the number and form of the pharyngeal teeth.     

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.     

Description of Myxobolus gayerae sp. n. and re-description of M. leuciscini infecting European chub from the Hungarian stretch of the river Danube

Myxobolus gayerae sp. n. and M. leuciscini González-Lanza & Alvarez-Pellitero, 1985 (Myxozoa: Myxobolidae) have been described and re-described from European chub Leuciscus cephalus L. from the Hungarian stretch of the river Danube. The ellipsoidal plasmodia of M. gayerae sp. n. were found in the mucosa of the intestinal wall, whereas the large, elongated plasmodia of M. leuciscini infected the afferent arteries of the gill filaments. The spores of M. gayerae sp. n. are relatively large, slightly oval and almost rectangular in shape. On the basis of spore morphology and 18S rDNA sequences, the most similar species was M. cycloides Gurley, 1893, but the 2 species differed in host and tissue tropism as well as in the size of the spores. The spores of M. leuciscini from L. cephalus, having no intercapsular appendix or occasionally a very small one, showed a high morphological similarity to spores collected from L. cephalus cabeda, Chondrostoma polylepis and Rutilus arcasi in Spain and described as M. leuciscini González-Lanza & Alvarez-Pellitero, 1985.     

Population dynamics of Lernaea cyprinacea (Crustacea: Copepoda) on four cyprinid species

A total of 217 Barbus graellsii, 54 Barbus haasi, 417 Cyprinus carpio and 85 Leuciscus cephalus captured at 9 sampling stations in the central basin of the Llobregat River (NE Spain) were studied for Lernaea cyprinacea parasitism. Prevalence (B. graellsii 39.2, B. haasi 31.5, C. carpio 8.4, L. cephalus 48.2), intensity of infection (B. graellsii range 1 to 39, mean 4.6; B. haasi range 1 to 7, mean 2.6; C. carpio range 1 to 16, mean 3.1; L. cephalus range 1 to 8, mean 2.4), and abundance (B. graellsii 1.80; B. haasi 0.83; C. carpio 0.26; L. cephalus 1.15) varied with the fish species studied. Correlations between abundance and host size were positive and significant for B. graellsii and L. cephalus. Correlation was positive but non-significant for B. haasi. Correlation between intensity and fish size was positive but not significant for B. graellsii, C. carpio, and L. cephalus. This is the first record of L. cyprinacea infecting B. graellsii and B. haasi.     

Isolation and characterization of microsatellites in Leuciscus cephalus (Cypriniformes,Cyprinidae) and cross‐species amplification within the family Cyprinidae

Thirteen polymorphic microsatellites were isolated from Leuciscus cephalus, a widespread cyprinid species with great ecological tolerance. Together with the cross‐species amplification of six additional loci originally published for three cyprinid fish species, we optimized a multiplex panel for L. cephalus allowing the genotyping of 19 polymorphic loci. Number of alleles and heterozygosity per locus in a sample of 20 fish individuals ranged from two to 16 and from 0.05 to 0.90, respectively. These primers will be useful in determining the population structure of L. cephalus. In addition, successful cross‐amplification was obtained for several species of Cyprinidae.     

Helminth communities of the rudd Scardinius erythrophthalmus (Cypriniformes, Cyprinidae) from Srebarna Biosphere Reserve, Bulgaria

A total of 180 individuals of Scardinius erythrophthalmus from Srebarna Lake, north-east Bulgaria, were examined for helminth parasites during spring, summer and autumn of 2005-2006 (30 specimens per season). Helminth parasites were recorded in 166 individuals (92.2%). Ten helminth species were found: trematodes--metacercariae of Posthodiplostomum cuticola, Diplostomum chromatophorum and D. spathaceum; monogeneans--Dactylogyrus difformis, D. difformoides and Diplozoon scardinii; cestodes--metacestodes of Paradilepis scolecina; nematodes--larvae of Spiroxys contortus and Rhabdochona denudata and adults of Schulmanela petruschewskii. Significant seasonal differences in the mean abundance were recorded for D. difformis, D. difformoides and D. scardinii. Significant seasonal differences in prevalence were recorded for P. cuticola, D. difformis, D. difformoides and D. scardinii. Dominant species in the component communities were P. cuticola, D. difformis and D. difformoides. The species composition of the component community essentially differs from that in the adjacent Danube River; a possible reason is the specific hydrobiological situation of the lake, characterized by a low density of benthic molluscs and crustaceans.     

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.     

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.     

Myxosporidian Parasites from the Fish of the River Lugg

SYNOPSIS. Six different species of Myxosporidia were recorded from fish of the River Lugg. Myxobolus muelleri, M. artus, M. macrocapsularis, Henneguya zschokkei, H. psorospermica and H. oviperda .
Leuciscus cephalus, L. leuciscus and Rutilus rutilus infected with M. muelleri were common; of these 3 hosts, L. cephalus had the highest intensity of infection and the greatest number of infected organs and tissues. M. muelleri was compared from all the different infection sites each month where possible, from the same host ( i.e., L. cephalus ) and from the same site on different hosts (i.e. from the gills of all 3 hosts). No seasonal variation in occurrence, spore shape or size was found for M. muelleri , but spore size varied depending on the host and site of infection.
Tailed and tailless forms of H. zschokkei were found on L. leucicus and H. oviperda on E. lucius . Only tailless H. psorospermica were found.
Variations in spore form and size are discussed in relation to their use as taxonomic characters.     

Hybridization between Alburnus albidus (C.) and Leuciscus cephalus cabeda R. in Italy

Thirty-six specimens of hybrid between the cyprinid species Alburnus albidus and Leuciscus cephalus cabeda were recognized from samples collected from five rivers in southern Italy. In the Alento river hybridization was marked and in a single sample of 66 specimens, 23 were found to be hybrids. The identification of hybrids is easy due to the combination of intermediate characters such as body pigmentation, gill rakers, branched rays of anal and pelvic fins, and some proportional measurements. The growth rate of hybrids is intermediate between the parental forms. Males are more numerous than females.     

Spatial and temporal variations in fish populations in the upper Thames estuary

Between February 1989 and August 1990, the upper Thames estuary contained 23 species of fish. Fish numbers were higher and relatively constant in the uppermost part of the estuary. Number of species was augmented in summer from fresh water and from downstream, coinciding with high temperature, low flow and high salinity. The eight most abundant species contributed to 98·5% of the total number. Flounder Pleuronectes flesus , dace Leuciscus leuciscus and perch Perca fluviatilis , recruited from May to August, and common goby Pomatoschistus microps , roach Rutilus rutilus and chub Leuciscus cephalus , from August to November. The upper estuary (salinity 0·34–2·96 p.s.u.) formed a species transition area between the freshwater but salinity-resistant roach, chub, and gudgeon Gobio gobio upstream, and the estuarine eurhyhaline common goby and flounder downstream. The three-spined stickleback Gasterosteus aculeatus and cyprinids were more abundant at upstream while perch was more abundant at downstream sites. High abundances of gudgeon, chub and roach were associated with high transparency and dissolved oxygen and low salinity, while high abundances of perch were associated with high salinity and low transparency. Dace and three-spined stickleback were associated with high dissolved oxygen and low pH, and common goby with high pH. Flounder showed no clear preferences.     

A neurofibrillar body in the perikaryon of nervus terminalis ganglion cells in teleosts

Summary In three species of Teleosts (Tinea tinea L., Leuciscus cephalus cabeda Risso, Epinephelus guaza L.) a round strongly argentophilic body of considerable size occurs in the cytoplasm of the nervus terminalis ganglion cells. In Tinea, surgical interruption of functional connections of the ganglion cells does not produce any apparent change either in the number or in the size of these cytoplasmic bodies.Electron microscopical observations show that the neurofibrillar body is made up of densely packed and irregularly arranged bundles. In cross section, each of these bundles appears to be composed of neurofilaments (100 Å in thickness) and neurotubules (diameter: 300 Å). Each tubule is surrounded by 9–10 filaments equi-distant from one another, and at a distance of 30–40 Å from the central tubule.The authors are indebted to Prof. G. Palladini for helpful histochemical advice, to Prof. B. Bertolini for electron micrographs and to Mr. D. Scorsini for skilful technical assistance.