A search for introgressive hybridization in the rudd, Scardinius erythrophthalmus (L.), and the roach, Rutilus rutilus (L.)

Rudd, roach and their hybrids from an interbreeding population at Norwich were examined electrophoretically for seven enzymes; an examination of pharyngeal teeth supplemented the data. The rudd were compared to rudd from Lake Trawsfynydd, Wales, a lake free from roach. No differences were observed between the rudd from the two localities and no evidence was found of introgression within the fish from Norwich.     

Epidemiology of squamous cell carcinomas in rudd Scardinius erythrophthalmus from SE Ireland

An epidemiological study was carried out to investigate the possible aetiology of squamous cell carcinomas which occur in a population of rudd Scardinius erythrophthalmus (L.) from Lough Aderry in south-east Ireland. A total of 1343 rudd were sampled from Lough Aderry and 2 nearby small lakes in spring, summer, autumn, and winter over 2 yr, 1986 to 1988. Fish were weighed, measured, sexed, aged, and examined for lesions. Water quality parameters and natural radioactivity were assessed as possible influencing factors in the disease. The prevalence of squamous cell carcinoma was 6.1% overall, with no significant difference between the lakes, seasons or years. Both male and female fish were affected, of ages from 1+ to 5+ yr. No fish of 6+ or 7+ yr was found with tumours, indicating that the neoplasm caused premature death. The female:male sex ratio of rudd with tumours was higher than that of healthy rudd overall, suggesting that males are more susceptible to the neoplasm. Of the parasites observed, Posthodiplostomum cuticola was common, but rarely found in rudd with tumours. Sphaerospora sp.was also common, but not in sufficient densities for statistical inference, and Argulus sp. was present on 7 fish. No viral particles were found. Natural radiation levels in the vicinity of the lakes were low. The lakes sampled are in an agricultural catchment, and the waters were eutrophic. While rudd are tolerant, it is likely that environmental conditions were stressful at least some of the time, with possible consequences for the immunocompetence of the rudd. The aetiology of the carcinoma is still unknown, but the possibilities of carcinogenic compounds resulting from the high nutrient levels, or of carcinogenic algal toxins produced during algal blooms, should be examined.     

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.     

Squamous cell carcinoma in rudd Scardinius erythrophthalmus: histopathology, ultrastructure, and transmission

The histopathology and ultrastructure of a skin neoplasm in rudd Scardinius erythrophthalmus (L.) are described and the neoplasm is diagnosed as squamous cell carcinoma. In the early stage, tumour cells appear singly or in clusters close to the epidermis; then tumour cells are seen in the dermis as epithelial pearls/nests, cords or sheets with central keratin; and with further development of the neoplasm, tumour cells appear as large sheets and masses, enclosing extensive keratinous formations and foci of necrotic cells, infiltrating deeper into the dermis and penetrating the muscle layers. Increasing vascularity and inflammation are associated with all stages of progression. In some cases metastases are observed in the viscera. Electron microscopic examination shows that the neoplastic cells are joined by desmosomes; the cytoplasm contains abundant mitochondria and rough endoplasmic reticulum. The neoplasm was successfully transmitted experimentally to healthy rudd when tumour cells were inoculated subcutaneously. Eight of 19 surviving test fish developed tumour growth at the site of tumour cell injection and/or in a corresponding site on the opposite of the body. One of these 8 fish, which developed a neoplasm, also showed a microscopic internal tumour in the viscera. One of the 19 test fish showed a microscopic tumour in the spleen, even though no skin tumour was visible in this fish. No tumours were found in control fish. In contrast, intraperitoneal injection of tumour cells into healthy rudd did not result in transmission of the neoplasm.     

Implications of rudd (Scardinius erythrophthalmus) herbivory on submerged macrophytes in a shallow eutrophic lake

The role of rudd (Scardinius erythrophthalmus) herbivory was studied in Kirkkojärvi, a shallow and turbid basin in Lake Hiidenvesi, Finland. The submerged species dominating in the rudd diets were Potamogeton obtusifolius, Ranunculus circinatus, Sparganium emersum, bryophytes, and filamentous algae. Plant consumption estimated with bioenergetics modelling increased with fish age, being highest in late summer concomitant with the macrophyte biomass peak. Depending on the age structure, a rudd biomass of 20 kg ha^?1 consumes 18–23 kg of macrophytes ha^?1 a^?1, while a rudd biomass of 100 kg ha^?1 results in plant consumption of 92–115 kg ha^?1 a^?1. Although, rudd seemed to feed rather unselectively on suitable-sized and edible plants, some species abundant in the littoral, such as Myriophyllum verticillatum and pleustophytic Ceratophyllum demersum, were not found in rudd guts, indicating selective plant consumption. In Kirkkojärvi, selective grazing by rudd and increased turbidity and high nutrient levels partly caused by bottom dwelling cyprinid fish, may promote the inedible and pleustophytic macrophytes, which have increased in Kirkkojärvi during the past decades.

     

Electrophoretic identification of roach (Rutilus rutilus L.), rudd (Scardinim erythrophthalmus L.), bream (Abramis brama L.) and their natural hybrids

Roach, rudd, bream and their natural hybrids of 2 cm standard length or larger can be definitively identified by their enzyme electrophoretic patterns. Zymograms of lactate dehydrogenase and esterases as produced by vertical starch gel electrophoretic analysis of whole fry or adult eye extracts are the most useful in this respect. The lactate dehydrogenase isozymes, containing B sub-units, migrate more anodally in rudd and bream than in roach. Due to the tetrameric structure of lactate dehydrogenase, in hybrid rudd x roach and roach x bream, eleven isozymes can be observed as compared with six in the parental patterns. Esterases show unique patterns for all species and hybrids. With the exception of one fraction in rudd x bream, the esterase patterns of hybrids show summations of the parental phenotypes.     

The adaptation of digestive enzymes to temperature, season and diet in roach Rutilus rutilus L. and rudd Scardinius erythrophthalmus L. Cellulase

The cellulolytic activity of the contents of the intestinal tract of populations of roach and rudd in four Tyrolean lakes was studied. Much of the activity was taken up with the diet. In fish feeding on plants and detritus a lower cellulolytic activity was found than in fish feeding on zooplankton or on arthropods. A seasonal pattern of cellulolytic activity was demonstrated with a peak in the autumn. It is assumed that the cellulolytic activity found in the intestinal contents of cyprinids is insufficient for the digestion of fibre, but that is suffices—particularly in omnivorous species—to support the breakdown of cell walls.     

Seasonal variation in cone sensitivity and short-wave absorbing visual pigments in the rudd Scardinius erythrophthalmus

Summary Microspectrophotometric and electroretinographic investigation of photoreceptor spectral sensitivity in the rudd Scardinius erythrophthalmus has revealed four spectral classes of cone with peak sensitivity in the ultra-violet, violet, green and red regions of the spectrum. These peak sensitivities were found to vary seasonally, and in response to artificial illumination, as a result of a change in the ratio of A1 to A2-based visual pigment in the cells. Short daylengths favoured the A2 pigment whereas long daylengths favoured the A1 analogue. Both the ultra-violet and violet-sensitive pigments have not previously been reported for the rudd. Evidence is presented supporting the hypothesis that the ultra-violet class of cells is not present in older fish.Abbreviation rvi response versus intensity (curve)     

Health status of rudd (Scardinius erythrophthalmus hesperidicus H.) in Lake Vrana on the Island of Cres, Croatia

The health status of rudd ( Scardinius erythrophthalmus hesperidicus H.) in Lake Vrana, the largest Croatian karstic lake, was evaluated. Studies comprising parasitological, haematological and bacteriological surveys were conducted over a 2-year period. Parasitological examination revealed a light infestation of 27% of the examined fish, mostly Dactylogyrus and Ichthyophthirius species. Haematological studies showed that haematocrit values were lower than the physiological limit. A haematocrit coefficient of correlation in all research periods was higher than 15%, indicating that the majority of fish in the study were susceptible to the development of bacterial and other diseases. Indeed, a diverse array of bacteria were isolated from rudd, mainly Flavobacterium spp. and Aeromonas spp., but also some specific fish pathogens, notably Pasteurella piscicida, Yersinia ruckeri , and Edwardsiella ictaluri , were identified. Under stress conditions, detected bacterial species can give rise to disease outbreaks.     

On the populations of roach (Rutilus rutilus), rudd (Scardinius erythrophthalmus), and their hybriin Esthwaite Water, with notes on the distinctions between them

Samples of cyprinid fishes from Esthwaite Water, Westmorland, have been examined and identified as roach ( Rutilus rutilus ), rudd ( Scardinius erythrophthalmus ), with a high degree (37%) of hybridization between these species. The distinguishing features of roach and rudd are discussed in the light of the difficulty of distinguishing the roach x rudd hybrid from the roach. It is concluded that the only reliable characters are the number and external morphology of the pharyngeal teeth.     

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.     

The adaptation of digestive enzymes to temperature, season and diet in roach, Rutilus rutilus and rudd Scardinius erythrophthalmus; Proteases

The seasonal changes of proteolytic activity in the gut content of roach R. rutilus and rudd S. erythrophthalmus in four Tyrolean lakes and the adaptation of the proteases to constant temperatures and different natural diets were studied. In rudd proteolytic activity remains nearly constant throughout the year. In roach proteolytic activity increases and then decreases during the first three months after the thaw in spring. This period appears to be endogenously controlled and is followed by a second stage in which proteolytic activity is influenced by environmental factors. Under natural conditions both species have a higher proteolytic activity when feeding on animals than on detritus. Under laboratory conditions there is a slight maximum at an environmental temperature of 16° C when the fish had been fed on meal worms. With plant food a significant dependence of proteolytic activity on environmental temperature was only found in roach.     

The influence of simulated aquatic macrophytes on the zooplankton consumption rate of juvenile roach, Rutilus rutilus, rudd, Scardinius erythrophthalmus, and perch, Perca fluviatilis

Laboratory experiments showed that, of zooplanktivorous roach, rudd and perch, in the absence of any environmental structure roach were the most efficient feeders, but high densities of simulated submerged marcrophytes elevated perch to this position; rudd matched the performances of perch and roach only at intermediate structure densities. These changes in efficiency rankings with increased structure were the result of overall decreases in the performances of roach and rudd. Simulated water lilies and emergent reeds had their own influences on consumption rate. These effects were largely mediated through relationships between structure density and swimming speed; roach and rudd, not perch, showed reduced swimming speeds in the more structured environments. Observations of the routine behaviour of the fish suggest that their assessment of predation risk may be an important factor in determining their activity level and hence foraging strategy.     

Further information on fish parasites from Lake Trasimeno. II. Observations on the population of Scardinius erythrophthalmus L

An investigation was carried out to identify the actual state of parasitism in the Scardinius erythrophthalmus L. population of Trasimeno lake (Umbria, Italy). Seasonal samples of fishes were taken in different points of the litoral and pelagic zones. The parasites found, together with the somatometric values and the characteristics of their localizations are reported. It has been found: a high number of infested specimens; eleven species of parasites, of which five were not yet known to be in the lake; frequency variations of certain species. The species of parasites observed are distributed in the Paleartic region. The five species, whose presence was not known in the lake, are considered to be allochtonous. The organs most frequently involved were, in descending order, the gills, the ureters, the gonads, the intestinal and mesenteric serous membranes, the liver. The most marked histologic alterations and reactions were observed as a consequence of Ergasilus sieboldi Nord. action and, in several cases, with the presence of Ligula intestinalis L. larvae.     

Hybrids of Abramis brama with Scardinius erythrophthalmus and Rutilus rutilus from Lake Volvi, Macedonia, Greece

Two specimens of the hybrid Abramis brama × Scardinius erythrophthalmus and a single specimen of the hybrid A. brama × Rutilus rutilus are reported and described from Lake Volvi, Macedonia, Greece. This is the first occurrence of either hybrid in Greek fresh waters.     

Identification, phylogenetic relationships and a new maximum size of two rudd populations (Scardinius, Cyprinidae) from the Adriatic Sea drainage, Croatia

In order to determine an unknown fish population from the Vrana Lake, mitochondrial cytochrome b gene and non-coding nuclear region Cyfun P were investigated. Stabile population of Bulldog rudd, Scardinius dergle Heckel & Kner, the endemic Croatian freshwater fish in the Krka River, was genetically characterized with the same markers in order to compare it with the material from the Vrana Lake. Genetic markers were sequenced and aligned with the similar ones obtained from the GenBank in order to determine taxonomic and phylogenetic position of these two species. A significant discrepancy between nuclear genetic markers of our specimens and the sequence from the GenBank was found. Phylogenetic analysis suggested that the specimens from the Vrana Lake belong to the species S. hesperidicus. Morphometric characteristics, the maximum length and body mass showed new maximum values for both S. dergle and S. hesperidicus.     

Estimating the accuracy of psychological scales using longitudinal data

This article presents a method for estimating the accuracy of psychological screening scales using receiver operating characteristic curves and associated statistics. Screening scales are typically semicontinuous within a known range with distributions that are nearly symmetric when the target condition is present and highly skewed when the condition is absent. We model screening scale outcomes using truncated normal distributions that accommodate these different distributional shapes and use subject-specific random effects to adjust for multiple assessments within individuals. Using the proposed model, we estimate the accuracy of the Symptom Checklist as a measure of major depression from a repeatedly screened sample of patients.