Some biological characteristics of the endemic Neretvan nase, Chondrostoma knerii Heckel, 1843, in the Hutovo Blato wetlands (Bosnia and Herzegovina)

The paper presents for the first time important information regarding population structure, growth rate, length‐weight relationships and reproductive aspects of the Neretvan nase, Chondrostoma knerii, a fish species endemic to the Neretva River. Chondrostoma knerii is mainly distributed in the lower parts and delta of the Neretva River wetlands and its tributaries (Krupa River, Hutovo Blato wetlands) shared between Croatia and Bosnia Herzegovina. Samples were collected between 2000 and 2001 during the reproduction period of the species in the Hutovo Blato wetlands area. Population structure analysis indicates that all ages appear, from 0 to 7+. Longevity was estimated at 7.5 years. Main age classes were 3, 4 and 5 years, totalling 91.00% of all individuals. Males ranged between 2 and 5+ years of age, and females between 1 and 7+ years of age. Maximum length was 28.04 cm and maximum weight, estimated from the length‐weight relationship, as 206.8 g. Found scattered in streams of high water velocity, eggs were attached to the substrate (aquatic plants or solid objects). Correlation between egg number and length and weight was extremely low. The gonad‐somatic index distribution showed an inverse proportionality with total length. Main length classes for reproduction ranged from 20 to 24 cm, while fecundity ranged between 2000 and 16 000 eggs per female.     

Age, growth and reproduction of the Caspian roach (Rutilus rutilus caspicus) in the Anzali and Gomishan wetlands, North Iran

The hypothesis of environmentally related life history variations between two Rutilus rutilus caspicus populations was investigated by comparing Gomishan and Anzali populations along the southern shores of the Caspian Sea. The roach growth rate in the Anzali wetland was higher than in the Gomishan wetland. There were significant differences in growth patterns between males and females from both wetlands, however the sex ratios were not significantly different. Fecundity or reproductive investment (Gonadosomatic index – GSI) of the Gomishan roach was significantly more than the Anzali roach. In both areas the absolute fecundity was significantly positive correlated to age and total length.     

Occurrence of an intersex condition in the roach Rutilus rutilus (L)

The roach, Rutilus rutilus , is normally a dioecius species. During an experimental study of reproduction in this species, a condition of apparently functional intersex was discovered. Anatomically the gonad was a testis, exhibiting various normal stages of spermatogenesis. A group of oocytes was found during the microscopical examination of the gonad, interspersed between lobules of normal testicular tissue. A few small oocytes were found to be in the chromatin-nucleolus stage, while the rest were in the perinucleolus stage. In addition, some large oocytes with an average diameter of 40 μm were randomly distributed among the lobules of the testis.     

Loss of genetic variability in reintroduced roach (Rutilus rutilus) populations

Genetic variation at five microsatellite loci and in mtDNA was surveyed in reintroduced and 'control' populations of roach ( Rutilus rutilus ) in Sweden. Microsatellite allelic richness and allele size ranges were significantly reduced in reintroduced populations, and mtDNA diversity was nearly significantly reduced in reintroduced populations. These measures of genetic variability were strongly correlated with lake characteristics that influence population size and food availability.     

Satiation-dependent, intra-cohort variations in prey size selection of young roach (Rutilus rutilus)

The tolerance to freezing and thawing of Leucodon sciuroides, a moss growing in mountainous areas of the Mediterranean (south-east Spain), was investigated by means of CO₂ gas exchange, modulated chlorophyll (Chl) a fluorescence and pigment analysis by high-performance liquid chromatography. Evidence is presented for freezing-induced decreases in CO₂ fixation that enhance non-radiative dissipation of absorbed light energy, a process which protects the photosynthetic apparatus. The photosynthetic apparatus of L. sciuroides remained fully recuperable after freezing, as indicated by the recovery of photosynthetic CO₂ fixation and Chl fluorescence parameters to pre-freezing values during thawing. The rapid recovery of photosynthesis activity during thawing in L. sciuroides suggests that this moss is capable of tolerating freeze-thaw cycles in a manner similar to that found at higher latitudes or in the Antarctic. The resistance of the photosynthetic apparatus of this moss to freezing might be achieved, at least partially, through the employment of dissipative pathways, such as non-radiative dissipation of absorbed light energy. Received: 4 June 1998 / Accepted: 15 February 1999     

Genetic diversity of Garra rufa Heckel, 1843 (Teleostei: Cyprinidae) in Anatolia

In the present study, mitochondrial DNA polymerase chain reaction-restriction-fragment length polymorphism (PCR-RFLP) and nuclear DNA inter-simple sequence repeat (ISSR) assays were used to assess the phylogenetic and phylogeographic relationships among Garra rufa samples from Anatolia. The complete mtDNA NADH 3/4 dehydrogenase (ND-3/4) gene amplified by PCR was digested with eight restriction enzymes. These enzymes produced 20 composite haplotypes for G. rufa populations. All the mtDNA haplotypes detected were highly diverged from each other and each lineage had a unique genetic profile. The evaluation of mtDNA PCR-RFLP data coupled with geological history of Anatolia indicated a deep genetic divergence among the mtDNA haplotypes of G. rufa populations from drainages of the Mediterranean and Persian Gulf, suggesting an early isolation of Tigris-Euphrates with Orontes river and other rivers draining into the Mediterranean Sea. In general, data from both mtDNA and nDNA were congruent.     

Parasite community and mortality of overwintering young-of-the-year roach (Rutilus rutilus)

The composition and development of the parasite community of overwintering young-of-the-year (YOY) roach (Rutilus rutilus) was studied in outdoor artificial ponds. Cumulative mortality of the roach from November until May was about 20%. The prevalences of the epizoic ciliates Trichodina sp. and Apiosoma sp., and of the monogeneans Dactylogyrus suecicus, Dactylogyrus nanus, and Gyrodactylus sp. in general tended to peak in the beginning of April at a water temperature of about 8 C. However, mean parasite intensity remained constant over this interval. Prevalence of metacercariae of the digeneans Diplostomum cf. spathaceum and Tylodelphys clavata remained constant with values around 60% and 10%, respectively. Larvae of the nematode Philometra obturans and the cestode Ligula intestinalis and females of the copepod Neoergasilus japonicus were found sporadically. A concept of 2 thresholds, a critical condition factor (attained by a temperature-induced energy deficiency), and a condition-dependent critical infection intensity, which determine winter mortality of YOY, is suggested.     

Histochemical characterization of myotomal muscle in the roach, Rutilus rutilus (L.)

A histochemical study of the myotomal muscles in the roach revealed three main muscle regions: red, intermediate and white. These were distinguished on the basis of glycogen content, succinate dehydrogenase (SDH), and myofibrillar ATPase (mATPase) activity. Except for the red fibre region, none of these described regions is homogeneous. The principal new findings are the toniclike fibre, the presence of a transitional zone with two fibre types, and the mosaic organization of the white fibre region. The significance of this type of myotome architecture in relation to the locomotion of the species is discussed.     

Size-dependent over-winter mortality of young-of-the-year roach, Rutilus rutilus

Over-winter survival of starved and fed young-of-the-year roach from two lakes in central Finland was examined in the laboratory between November 1992 and May 1993. The mortality rate of starving YOY roach (total length 38 ± 2 mm) from small (ca. 0.5 km²), eutrophic Lake Isojärvi was 50%, whilst roach (total length 32 ± 3 mm) from large Lake Päijänne (1106 km²) suffered 42% mortality. Mortality was size-dependent among roach from Lake Isojärvi, smaller individuals being more vulnerable. There was not strict size limit for survival as proposed previously. However, it seems that within populations approximately the same proportion of smallest roach died independent of the absolute lengths of the fish. Mortality of fed roach from both lakes was always < 5%. This good survival indicates indirectly the importance of energy reserves in wintering. Lipid and protein content of fasting roach from lake Isojärvi decreased during the winter. In the group of fasting roach from Lake Päijänne the amount of lipids stored increased between November and March and decreased thereafter. No change in protein content of fasting fish from Lake Päijänne was observed.     

Embryonic fissure and photoreceptor differentiation in the eye of adult Garra rufa Heckel 1843 (Cyprinidae, Teleostei)

The retina of the adult teleost Garra rufa retains a curved, open embryonic fissure indicating an asymmetrical postembryonic retinal growth. Undifferentiated, oval photoreceptors are observed on both sides of the middle of the fissure with their larger diameter running parallel to the fissure to which they may attach by desmosomes. They detach from the fissure, rotate to become perpendicular to it and begin an active process of differentiation as they slide along the temporal side of the outer half of the fissure. This process is divided into stages for simplicity. The photoreceptors develop stumpy inner segments extending into a ventricular space that appears between the retinal pigment epithelium and the photoreceptors. Calycal processes arise from the inner segments and the distal centriole of each photoreceptor forms a connecting cilium. The proximal centriole is retained for some time after the outer segment develops. The formation of rod spherules and cone pedicles takes place almost concomitantly with the outer segments. Double cones appear first as single cones before pairing. One or more of the principal cone mitochondria accumulate electron-dense material and merge to form the ellipsosome. The retinal pigment epithelium undergoes a parallel differentiation. The developmental events described in the present work conform those recorded in embryonic teleostean retinas.     

Homing precision of roach Rutilus rutilus in Lake Arungen,Norway

Synopsis The present study tests the precision of repeat homing of roach, Rutilus rutilus, to two tributaries of a small Norwegian Lake, Årungen. A sample of 19 959 spawners was tagged or marked in the spawning area. After spawning the roach intermingled with other spawning demes in the lake. The year after marking, 2515 (12.6%) roach were recaptured during spawning in the five tributaries, 340 (13.5) of these were strayers. This straying is considerably larger than found in comparable autumn spawning species, but approximately the same as reported for other spring spawning species. The recapture rate was lower for females than for males, probably due to increased female mortality induced by the tagging manipulation.     

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.     

The morphology and histology of the pineal organ in roach, Rutilus rutilus (L.)

The pineal organ in the roach, Rutilus rutilus (L.), is covered by a semi-transparent area, the pineal window. Beneath this the pineal is attached to a long robust stalk, lying just under the parietal bone. The pineal is attached to the brain through the dorsal sac. Three cell types have been identified histologically. These are the sensory cells, supporting cells and the ganglia cells. The inner segment of the sensory cells respond to PAS and AF staining, while the remaining cells respond to Orange G, LG, or Acid Fuchsin. The evidence suggests that the roach pineal may have a dual photosensory and glandular function.     

Reproductive disturbance in a roach (Rutilus rutilus) population affected by cooling water discharge

To analyse a recruitment failure in a roach ( Rutilus rutilus ) population exposed to cooling water from a Swedish nuclear power plant, histopathological examinations were made on female gonads. Several disorders were documented, corresponding to effects previously seen in Lithuanian, Moldavian and Russian heated waters, The relative gonad size (GSI) was generally lower in the exposed population. Oocyte degeneration was observed in about 50% of the females, potentially seriously reducing their reproductive capacity. The gameto- and gonadogeneses also were clearly affected and generally occurred at a faster rate. Sexual maturity was earlier and was accompanied by an increased occurrence of asynchionic gonad and oocyte growth. A normal gonad development should pass through different stages, coupled to the seasons, and the difference between individuals in a population should be small. However, in some exposed fish, the sequence of seasonal development was disturbed and a simultaneous, intensive, growth of sex cells in different stages of development could be seen. An increase of variation in gonad development both within, as well as between, fish thus was documented. Conclusively, the histopathological analysis provided evidence that the observed recruitment deficit could be related to gonad failure.