Effects of water depth and structural complexity on survival and settlement of white-spotted charr (Salvelinus leucomaenis)

Hydrobiologia - Both climate change and dam operations are affecting water levels in river systems worldwide and their influence can be especially drastic in upper streams, where juvenile salmonids...     

Occurrence of mature male white-spotted charr (Salvelinus leucomaenis) in spring,an unusual season

Ichthyological Research -     

Synchronous female spawning and male mating behavior in a land-locked population of Japanese charr, Salvelinus leucomaenis japonicus

In resource-based promiscuous mating systems, synchronous spawning of females affects competition among males and variation in the reproductive success of males. We documented the mating behavior of Japanese charr (Salvelinus leucomaenis japonicus) through an annual breeding season to examine the relationship between female spawning synchrony and male mating behavior. Females spawned highly synchronously in the population studied, i.e., approximately half the spawning was finished within the first three days of the entire spawning season (11 days). The daily operational sex ratio (OSR) was nearly 1:1 through the spawning period. The number of males around a spawning female was very small (1.21+/-0.49 males per female) over the spawning ground and period, suggesting that a competitive male could effectively chase subordinate males away from a spawning female. A few males attempted to sneak near the oviposition site of females (16%; 9 of 57 breeding groups), while some males adopted sneaking tactics in the initial phase of females' spawning (24%). We did not observe any males to succeed in sneak fertilizations. We conclude that in this Japanese charr population, the synchronous spawning of females was related to the unbiased daily OSR, male aggregation around females, and consequently whether and how efficiently males engaged in sneak mating behavior.     

Spatial and temporal changes in genetic structure and diversity of isolated white-spotted charr (Salvelinus leucomaenis) populations

Hydrobiologia - In Japan, numerous artificial dams constructed for erosion control or hydroelectric power generation have affected almost all rivers and resulted in isolation and fragmentation of...     

A novel acid ribonuclease from white-spotted charr (Salvelinus leucomaenis): purification and characterization of the homogeneous enzyme

An novel acid ribonuclease has been purified approx. 1300 fold from acid extract of developing white-spotted charr (Salvelinus leucomaenis) testes. The final preparation of the enzyme was homogeneous on polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate (SDS). The molecular weight was determined to be 20,000 with both Sephadex gel filtration and SDS-polyacrylamide gel electrophoresis. The isoelectric point was determined to be 6.4 and the hydrolytic activity was stimulated with low concentration of phosphate. The enzyme has an optimal pH at 5.5 and hydrolyzed yeast RNA and several synthetic homopolyribonucleotides. Under appropriate conditions, the enzyme hydrolyzed substrates, yeast RNA, poly (I), poly (A) and poly (U), in a ratio of 100:900:30:20, respectively. However, poly (C) could not be hydrolyzed under any conditions tested so far. Yeast RNA was hydrolyzed into monoto pentanucleotides. The range of substrate-specificity of this enzyme will be discussed on the basis of the analysis of these products.     

Incidence of a skeletal deformity (truncated upper jaw) in an isolated population of white-spotted charr Salvelinus leucomaenis

Although dorsal and caudal fin deformities (curvature), abnormal body color patterns, and fluctuating asymmetry of meristic characters have been previously reported for white-spotted charr (Salvelinus leucomaenis), the incidence of skeletally deformed individuals in the wild are extremely rare. Here, we report on skeletally deformed individuals of white-spotted charr with extremely truncated upper jaw, in a headwater reach of the Yoneshiro River, northern Honshu, Japan. In this study, we examined the genetic diversity of deformed and non-deformed populations of white-spotted charr using polymorphic microsatellite DNA markers. We also compared individual growth histories of deformed individuals with normal individuals using a back-calculation of fish lengths at previous ages from otolith annuli. We collected 41 and 100 individuals from the below- and above-waterfall sites, respectively. Of these, two individuals from the above-waterfall site were skeletally deformed, whereas the other individuals had a normal morphology. Microsatellite DNA genetic diversities of the above-waterfall population were notably lower than those of the just below-waterfall population. Individuals of the above-waterfall population had significantly higher internal relatedness and lower standardized heterozygosity values compared with those of the below-waterfall population, indicating higher inbreeding situation of the above-waterfall individuals compared with individuals in the below-waterfall site. Back-calculation of individual growth using otoliths revealed that deformed individuals grew significantly slower than sympatric normal individuals. Although incidence of deformed individuals in the wild might be related with accumulated inbreeding as suggested for other fishes, mechanisms for their long-term persistence in the wild remain unclear.     

Introgressive hybridization between Dolly Varden Salvelinus malma and white‐spotted charr Salvelinus leucomaenis on Hokkaido Island, Japan

Intra‐ and interspecific phylogenetic analysis of Dolly Varden Salvelinus malma and white‐spotted charr Salvelinus leucomaenis throughout Hokkaido Island was conducted using nucleotide sequences of the mitochondrial DNA control region and three nuclear DNA markers [ribosomal DNA (ITS‐1), microsatellite ( u ‐85), SINE ( Fok ‐223)]. A total of 19 mtDNA haplotypes from 271 individuals of Dolly Varden, nine haplotypes from 134 white‐spotted charr were defined, and identified two well‐supported monophyletic clades for each species. Two haplotypes of Dolly Varden, however, were clustered together in the white‐spotted charr clade. Those haplotypes were found only from several rivers in the Shiretoko Peninsula, and a neighbouring river of that region. Analyses of ribosomal DNA and Fok ‐223 loci revealed that both species are characterized by having completely species‐specific diagnostic sequence and fragment patterns. Dolly Varden of the Shiretoko populations are typically allopatric in distribution where white‐spotted charr do not currently occur. In addition, incongruence in genetic relationships between mtDNA and nuclear DNA markers give strong evidence of historical mtDNA introgression between Dolly Varden and white‐spotted charr. Some white‐spotted charr diagnostic alleles in a nuclear microsatellite locus ( u ‐85) were found in some Shiretoko Dolly Varden populations, suggesting that introgressive hybridization might have also occurred in relatively recent contact and potentially ongoing evolutionary event. The present study presents an example of historical hybridization and introgression at the southernmost distribution limits of Dolly Varden.     

Immunohistochemical demonstration of urotensins I and II in the caudal neurosecretory system of the Japanese charr,Salvelinus leucomaenis,retained in sea water

This paper is concerned with part of the role and function of the caudal neurosecretory system of the charr,Salvelinus leucomaenis, studied by immunohistochemistry. In order to elucidate the different histologic changes, we examined the immunoreactivities of urotenisn I (UI) and urotensin II (UII) in 3 experimental groups: the feral (river) fish, the fresh-water aquarium-, and sea water aquarium-retained fish. Coexistence of UI and UII was demonstrated in most of the smaller and larger neurons distributed in and near the urophyseal system of all 3 groups. However, some of the larger neurons were immunoreactive only to a single hormone, UI or UII. Merely a few neurons indicated no reactivity for either UI or UII. No such clearcut differences were encountered immunohistochemically in the 3 groups. Neuronal and urophysial immuno-reactivity to UI of feral and fresh-water-retained fish was slightly stronger than that of sea water-retained fish. Moreover, in sea water-retained fish, the intensity of immunoreactivity for UI was variable, and the number of neurons positive for UII only was somewhat larger than that in feral and fresh-water-retained fish. A series of UII-positive cerebrospinal fluid (CSF)-contacting neurons were seen in the ependymal and subependymal layers ventral to the central canal of the spinal cord in every group. These CSF-contacting neurons might constitute another neurosecretory system aside from the ordinary caudal neurosecretory system equipped with urophysis. In contrast to the hypothalamohypophysial neurosecretory system, the caudal neurosecretory system did not show any significant changes among the 3 groups. This suggests that urotensins I and II have no essential role in osmoregulation of the charr.     

Effects of competitor density and physical habitat structure on the competitive intensity of territorial white spotted charr Salvelinus leucomaenis

This study compared the effects of interference competition in habitats of different complexity and in different densities. The influence of fish density and habitat structure was examined in manipulative experiments using young-of-the-year white spotted charr Salvelinus leucomaenis as a model species. The difference of specific growth rate ( G ) range, an index of interference competitive intensity, was significantly smaller in the structurally complex treatments than structurally simple treatments, while there were no significant difference between high-density and low-density treatments. Thus, physical habitat structure was more effective for mitigating interference competition than manipulating competitor density. Although interference competition was not affected by competitor density, mean G were suppressed in the high-density treatments. This implied that exploitative competition may cause the decrease of G rather than interference competition does in the high-density treatments. Mean G were also suppressed in the structurally complex treatments. Chaotic flow pattern created by physical habitat structures may decrease G by reducing foraging success of experimental fish in the complex treatments.     

Effect of ozone on erythrocyte membrane adenosine triphosphatase.

Human erythrocyte membrane fragments were exposed to O3 over varying lengths of time. Ozone was found to have a deleterious effect on the ouabainsensitive ATPase (EC 3.6.1.3) in the membrane fragments. After 1 min of exposure to O3, which was generated at a rate of 4.0 mumol/min, ouabain-sensitive ATPase activity decreased to 26% of the control. Ouabain-insensitive ATPase was found to be unaffected by O3 exposure under the test conditions. Additions of ascorbic acid or cysteine, prior to O3 exposure, partially protected the enzyme from inactivation. However, the inactivating effect of O3 could not be reversed by addition of either ascorbic acid or cysteine after exposure. Superoxide dismutase or catalase did not afford significant protection. The enzyme could not be protected by Ellman's reagent. The inactivating effect of O3 on the ouabain-sensitive ATPase was also demonstrated in exposure of intact erythrocytes. No detectable change was observed in glycolytic activity in the hemolysate prepared from O3-treated erythrocytes, however. It was postulated that inactivation of the membrane ATPase by O3 may be responsible for the destructive effect of O3 on the red cell.     

Marine growth and survival of white-spotted charr,Salvelinus leucomaenis, in relation to smolt size

The relationships between marine growth and survival, and smolt sizes were examined for white-spotted charr (Salvelinus leucomaenis) populations in the Nairo River, Rebun Island, off northern Hokkaido Island, and the Haraki River, southern Hokkaido Island, Japan. Smolts in the Haraki River were much larger in size than those in the Nairo River, despite being similar size among age cohorts and between the sexes in each population. From scale analyses, smolt size-specific growth rates and survival were estimated by utilizing both observed and back-calculated size-frequencies. Inverse correlations between specific growth rates at sea and smolt size were found in both populations. However, the expected size increments at a given size of smolts in the Haraki River were significantly larger than of those in the Nairo River. For both populations, there were no significant effects of smolt ages (2 to 5 or 6 years) on growth rates at sea. Larger smolts had a consistent survival advantage, although the degree of size-dependent survival function seemed to differ between populations. The results suggested that growth and survival of individuals at sea are determined ultimately by size-, rather than age-, dependent factors depending upon local environmental conditions, supporting the hypothesis of a threshold size for smolting within populations.     

Occurrence of deformed fish and their fitness-related traits in Kirikuchi charr, Salvelinus leucomaenis japonicus, the southernmost population of the genus Salvelinus

Kirikuchi charr, Salvelinus leucomaenis japonicus, is the southernmost population of the genus Salvelinus. It is endemic to the Kii Peninsula, central Honshu Island, Japan. As a consequence of anthropogenic disturbances, a few populations of Kirikuchi charr with low genetic diversity now survive only in small, isolated habitats. This study investigated the occurrence of deformed individuals and assessed differences between deformed and nondeformed fish in fitness-related traits, i.e., body size, body condition, growth rate, reproductive traits, survival rate, and habitat use, for two small isolated populations of Kirikuchi charr in the upper drainage of the Totsu River system of the Kii Peninsula. The two populations contained deformed fish in the respective proportions of 8.0-17.4% and 3.0-5.8% between 2003 and 2005. Annual survival rates of deformed fish were approximately half those of nondeformed fish. Other traits were not significantly different between deformed and nondeformed fish. These results indicate that the occurrence of deformities is an important ecological indicator that reflects the decline in fitness of small, isolated populations.     

Effect of electrical brain stimulation on erythrocyte membrane lipids

Biliary obstruction was induced in rats by intermittent stimulation of the lateral hypothalamus for periods of 2 and 6 hours. Cholesterol and phospholipid concentrations of circulating red blood cells were found to be decreased, whereas in the plasma these lipids were elevated. The mechanism of membrane lipid depletion associated with early biliary obstruction is currently unknown. It is possible, however, that cells other than erythrocytes undergo similar changes. In previous experiments plasma membrane degeneration of endothelial cells was observed in rats subjected to hypothalamic stimulation for 6 hours. Thus, central nervous system stimulation may have a deleterious effect on cell membrane structure and function and be mediated through biliary obstruction.     

Isolation and characterization of tri‐ and tetra‐repeat microsatellite loci in the white‐spotted charr Salvelinus leucomaenis (Salmonidae)

Tri‐ and tetra‐motif repeat microsatellite marker loci were developed for the white‐spotted charr Salvelinus leucomaenis. The 454 pyrosequencing was used to discover repeat arrays, and eight microsatellite‐primer sets, available for the estimation of polymorphisms, were identified. The number of alleles in a wild population ranged from two to four and the observed and expected heterozygosities were 0·180–0·600 and 0·188–0·599, respectively.     

Phylogeography of white-spotted Charr (Salvelinus leucomaenis) inferred from mitochondrial DNA sequences

The white-spotted charr (Salvelinus leucomaenis) is a coldwater-adapted fish distributed in far-eastern Asia. To assess phylogeographic patterns of this species over most of its range in the Japanese archipelago and Sakhalin Island, Russia, we examined nucleotide sequences of the mitochondrial DNA (mtDNA) cytochrome b region (557 bp) in 141 individuals from 50 populations. A total of 33 (5.5%) nucleotide positions were polymorphic and defined 29 haplotypes. Phylogenetic analysis assigned the observed haplotypes to four main clades, which were characterized by the idiosyncrasies and discontinuity of geographic distributions. The nested clade analyses revealed that the geographical distribution patterns of some haplotypes and clades were explained by historical event such as past fragmentation. Although substantial genetic differentiation was found among the four main clades, their geographic distributions overlapped extensively in several regions. Since white-spotted charr can potentially use both freshwater and marine environments, coexistence among different lineages can be attributed to secondary contact through range expansion by migratory individuals during multiple glacial periods after interglacial isolation. Finally, our data demonstrate that the current subspecies designation does not reflect the phylogeography of this species based on mtDNA analysis. Hierarchical analysis (AMOVA) also showed that genetic variation was far more pronounced within subspecies than among subspecies (i.e., among discrete regions). These results suggest that each population, rather than each subspecies, must be treated as an evolutionarily significant unit.     

Evidence for interspecific hybridization between native white-spotted charr Salvelinus leucomaenis and non-native brown trout Salmo trutta on Hokkaido Island, Japan

Hybrids between native white-spotted charr Salvelinus leucomaenis and non-native brown trout Salmo trutta were identified in streams of Hokkaido, Japan, using both appearance and genetic characters. The DNA analyses indicated that the specimens were hybrids between female S. leucomaenis and male S. trutta . Occurrence of such hybrids implies increased mating opportunities between these species in wild streams.     

Parasites of arctic charr Salvelinus alpinus (Linnaeus) and their use in separating sea-run and non-migrating charr

Metazoan parasites of arctic charr, Salvelinus alpinus , from the Nettilling Lake–Koukdjuak River system, Baffin Island, were studied. Non-migrating charr hosted 9 species of parasites while sea-run charr hosted 15 species of parasites. Diphyllobothrium spp., Eubothrium salvelini , and Proteocephalus longicollis were found to be good indicators of non-migrating charr and Brachyphallus crenatus, Bothrimonus sturionis and Prosorhynchus squamatus were good indicators of sea-run charr. Using these parasites as biological tags, the proportion of charr caught by the commercial fishery at the outlet of the Koukdjuak River were determined to be approximately 80% sea-run and 20% non-migrating charr. Step-wise discriminant statistical analysis on morphic characters of charr, designated as sea-run and non-migrating by their parasites, showed these charr to differ morphologically.     

Aging of the erythrocyte IV. Spin-label studies of membrane lipids,proteins and permeability

Spin-label studies demonstrated age-related alterations of the erythrocyte membrane concerning both lipid and protein components. Decrease in fluidity of membrane lipids correlated with decreased membrane permeability to a hydrophobic spin label TEMPO, permeability to a more hydrophilic TEMPOL being less affected. The rigidification of membrane lipids was much more pronounced in whole membranes than in liposomes composed of membrane lipids, suggesting changes in lipid-protein interactions as an important factor in the decrease of lipid fluidity in aged red cells. ESR spectra of membrane-bound maleimide spin label evidenced alterations in the state of membrane proteins during cell aging in vivo.