Albino Rainbow Trout Research Articles

Effects of body color luminance and behavioral characteristics on predation risk in salmonid fishes

We investigated the effects of body color luminance and behavioral characteristics of stocked juvenile white-spotted charr, masu salmon, rainbow trout, albino rainbow trout, and non-spotted rainbow trout on their predation risk by predatory land animals. Body color luminance and behavioral characteristics were scored before starting the predation test. The dorsal color luminance of the albino rainbow trout was brighter than that of the other fish. The white-spotted charr and non-spotted rainbow trout were less active than the masu salmon and rainbow trout, and the non-spotted rainbow trout stayed in the open more than the white-spotted charr during behavioral observations in an aquarium. A piscivorous bird, the grey heron was the most frequently observed land animal during the predation test conducted at a semi-natural stream study site. The survival rate of total fish groups was 21.4 %, only 3 % albino rainbow trout and 11 % non-spotted rainbow trout survived, which were significantly lower than the survival rate of the other fish. These results suggest that the body color luminance of albino rainbow trout and the behavioral characteristics of non-spotted rainbow trout were important vulnerability factors.

Karyotype variation in the albino rainbow trout (Oncorhynchus mykiss(Walbaum))

A Robertsonian polymorphism resulting in diploid chromosome number ranging from 59 to 61 and constant chromosome arm number (fundamental number = 104) was observed in the albino rainbow trout (Oncorhynchus mykiss (Walbaum)) from the yellow color strain. In one individual, 90 mitotic chromosomes and 156 chromosome arms were counted, indicating the fish as a triploid. Morphology of the chromosomes, DAPI staining, and the cytogenetic location of 5S rDNA sequences showed sex-related chromosomal heteromorphism in the specimens. Additionally, length polymorphism of the X chromosome was detected in the studied individuals and two morphs of the X chromosome were described, XL and XS, according to the size of its short arm (p). The XS was observed in the female as well as male albino rainbow trout; however, among females, no XSXS genotype was found. After primed in situ labeling with 5S rDNA primers, the p-arms of both types of the X chromosome showed similar hybridization signals. On the other hand, fluorescence in situ hybridization with telomeric PNA (peptide nucleic acid) probe exhibited weak hybridization spots on the p-arm of the XS chromosome compared with the distinct hybridization spots observed on the XL p-arm. This could reflect a different telomere length on the p-arm of the XS and XL chromosomes. Partial translocation and deletion of the X chromosome p-arm are considered to be responsible for the p-arm length difference between the two morphological variants of X chromosome.

Comparison of Paraoxonase Activity, Malondialdehyde and HighDensity Lipoprotein Levels in Cultuvated Normal and Albino Rainbow Trout Reared in the Same Conditions

In this study, serum paraoxonase activity (PON), malondialdehyde (MDA) and high-density lipoprotein (HDL) levels of culture rainbow trout (NRT) and albino rainbow trout (ART) have been compared. In this research, ART and NRT which have average weights of 130±10.7g and 150±11.9g respectively have been used. During the research, fish (ART and NRT) have been fed with commercial trout feed, twice a day. Fish used in the analysis have been random-ly caught from pools and five fish (three times replicated) for each group have been sampled. PON activity, HDL and PON/HDL levels determined in serum samples of NRT group have been found higher than the ART group. Mean MDA level in NRT group has been found lower than the ART group, however, these differences have been found statistically insignificant. Finally, the different species and size, dominance status may be reason for the change of PON activity, MDA and HDL levels.

Effects and Interaction of Phenotype and Rearing Density on Growth and Fin Erosion in Rainbow Trout

AbstractIntensively reared rainbow trout Oncorhynchus mykiss that receive formulated feed frequently exhibit torn, ragged, and eroded fins. To better understand the factors affecting fin erosion, two rainbow trout phenotypes (albino and pigmented) were reared to verify reports that albino rainbow trout suffer less dorsal fin erosion than do pigmented fish. A 12‐month study was conducted to evaluate the effects of phenotype, rearing density, and the phenotype × density interaction on fin erosion. Extremes in rearing density were tested using group rearing (maximum density = 200 fish/tank) and individual rearing as the treatments. To evaluate interactive effects of phenotype, rainbow trout were reared either in mixed populations (MPs) containing equal proportions of albino and pigmented fish or in separate populations (SPs) containing only albino or pigmented individuals. Group rearing treatments were each applied to three tanks at 200 first‐feeding fish/tank. Eight albino and eight pigmented fish were reared in individual rearing chambers. At 3‐month intervals, fish were measured for weight, total length, condition factor, and dorsal and pectoral fin lengths. Survival exceeded 90% in all treatments, but albino fish had lower survival than did pigmented fish in both MPs and SPs. Albino fish from MPs were significantly smaller (37 g) than MP‐reared pigmented fish (77.5 g) at the end of the study. Dorsal fin index scores were greater (i.e., indicated less fin erosion) for MP‐reared albino fish (7.5%) than for MP‐reared pigmented fish (5.6%), but considerable erosion occurred in both phenotypes reared in MPs and SPs. Rainbow trout that were reared individually had complete dorsal fins and pectoral fins during the entire study (i.e., dorsal fin and pectoral fin indices [fin lengths expressed as a percentage of total length] > 11%). This study demonstrates that albinism does not directly affect the occurrence or rate of dorsal fin erosion, but less fin erosion is observed in albino fish than in pigmented fish when reared in MPs.

Photic history modifies susceptibility to retinal damage in albino trout

Albino vertebrates exposed to intense light typically lose photoreceptors via apoptosis, and thus serve as useful models of retinal degeneration. In contrast, albino rainbow trout exposed to intense light maintain populations of rod and cone nuclei despite substantial damage to rod outer segments (ROS). The aim of this study was to differentiate between two hypotheses that could account for this divergent result: (1) trout rod nuclei remain intact during light damage, or (2) rod nuclei die but are replaced by cell proliferation. A further aim was to examine whether photic history modulates retinal damage, as in rodents. Albino and normally pigmented trout were moved from defined photic regimes into full daylight, while some were not moved to serve as protected controls. ROS were always maintained in pigmented fish and in albinos protected from full daylight. In albinos exposed to full daylight, ROS were removed over most of the central retina, whereas rod nuclei were maintained in the outer nuclear layer over 10 days. Pyknotic and TUNEL-labeled rod nuclei were abundant in affected albinos at all time-points tested. Rod death occurred without a decrease in the number of rod nuclei, confirming that proliferation must be replacing cells. Indeed a transient increase in proliferation was observed in retinal progenitors of albinos receiving 5 days of damaging light. This proliferative response was decreased with further damage. Cones remained intact even in areas where rod nuclei had degenerated. Pretreatment with light of moderate versus low intensity light affected the cell death and proliferative responses, and the ectopic localization of rod opsin. We conclude that apoptotic demise of rods, but not cones, occurred during light damage in retinas of albino trout and proliferative responses have a limited a capacity to replace lost rods.

A minichromosome carrying a pigmentation gene and brook trout DNA sequences in transgenic rainbow trout.

We describe the transmission of an introduced minichromosome of brook trout (Salvelinus fontinalis) origin, carrying a pigmentation gene, through three generations in rainbow trout (Oncorhynchus mykiss). The minichromosome was originally introduced into gynogenetic albino rainbow trout using gamma-irradiated brook trout sperm. In the third generation, the presence of the minichromosome was correlated with pigmentation. A brook trout specific interspersed repeat DNA sequence, Fok I, was also correlated with pigmentation in these individuals. This system, the first clearly documented example of induced chromosome mediated gene transfer at the organismal level, could have applications in studies of gene mapping, development, gene regulation, and chromosome function.

Solar pruning of retinal rods in albino rainbow trout.

Morphology of the central retina and scotopic visual sensitivity were compared in juvenile albino and normally pigmented rainbow trout living under natural and reduced daylight. Outdoor albinos avoided exposing their eyes to direct sunlight, whereas normals were indifferent to it. After 4 months outdoors (approximately 10,000 lux in albinos, approximately 100,000 lux in normals), albinos had severely truncated or missing rod outer segments (ROS) and some missing rod ellipsoids, but normal numbers of photoreceptor nuclei and fully intact cones. Albino estimated ROS volume was only 7.1% of normal in July, but increased to 20% by the following February, mainly via an increase in numbers of ROS. However, in albinos moved indoors October 7 and exposed to 10-30 lux ambient daylight, both the number and length of ROS increased significantly, with estimated ROS volume reaching 95% of normal by 34 days. Albinos generally had more phagosomes (approximately 3 x normal) and more macrophages (approximately 2 x normal) in their outer retina. An optomotor reflex was used to define the effect of ROS volume on the ability to respond visually during dark adaptation. In July, albinos and normals from outdoor raceways (3 months) or indoor raceways (35 days) showed equal sensitivity after first being placed in darkness, but after 1 h in darkness, outdoor albinos with 6% of normal ROS volume were 2.0 log units less sensitive than indoor or outdoor normals, whereas indoor albinos with 53% of normal ROS volume were only 0.7 log units less sensitive. This verifies that most rod cell bodies of albino trout can persist without functional ROS in indirect sunlight, and can regrow functional outer segments in dim daylight. This finding is distinct from the extensive retinal light damage observed in albino rats exposed to more moderate cyclic light, in which entire rod cells degenerate early on.

Fin Condition and Health Profiles of Albino Rainbow Trout Reared in Concrete Raceways with and without a Cobble Substrate

Abstract Fingerlings of albino rainbow trout Oncorhynchus mykiss were reared for 200 d in concrete raceways with either concrete (controls) or cobblestone bottoms. Health and condition profiles were performed on 20 fish/treatment on four occasions. For fish in cobble-bottom raceways, there was no fin erosion as measured by fin indices (ranked from 0 to 2) applied to the fish as a whole or relative fin lengths (% of body length) of individual fins. For control fish, however, considerable erosion was evident for caudal, dorsal, anal, both pectoral, and both ventral fins. Condition factor, fat levels, and total length were reduced in cobbled raceways. Results are compared with previous experiments with normally pigmented rainbow and cutthroat trout O. clarki. Overall, cobble substrates markedly reduced fin erosion, which suggests that cobble-bottom raceways are especially suitable for rearing albino rainbow trout, if a slight reduction in growth is acceptable.

Incidence of albinos as a monitor for induced triploidy in rainbow trout

Albinism is a recessive trait in rainbow trout ( Oncorhynchus mykiss). We tested for complementation at the albino locus among six USA rainbow trout strains and found that albinos from four domesticated strains and one Idaho steelhead strain are mutant at the same locus. These strains apparently are tyrosinase-deficient albinos. An albino steelhead strain from Washington State and an albino brook trout ( Salvelinus fontinalis) strain are apparently mutant at other loci because they produce pigmented progeny when crossed to the common form of albino rainbow trout. We determined using gynogenesis that the albino locus common in domesticated rainbow trout maps very near the end of a chromosome; virtually all the gynogenetic progeny of heterozygous females were pigmented. In contrast, the Golden locus of rainbow trout appears centromere-linked. Female rainbow trout heterozygous for the albino gene have 50% albino offspring when crossed to albino males but a high proportion of pigmented offspring after a heat shock is applied to induce triploidy. The proportion of pigmented offspring would be expected to correlate directly to the proportion of triploid individuals in such crosses. However, pigmented diploids can sometimes be found in such crosses in higher than predicted frequencies, apparently because heat shock can sometimes induce rejection of the sperm. This indicates that diploids observed among lots treated to induce triploidy may result from sperm rejection as well as from failure of second polar body retention.

Maintenance of foreign gene expression and independent chromosome fragments in adult transgenic rainbow trout and their offspring.

Transgenic rainbow trout (RT) were generated in earlier experiments by an in vivo modification of the chromosome-mediated gene transfer technique. This involved fertilizing albino RT eggs with gamma-irradiated brook (speckled) trout (ST) sperm and then heat shocking the eggs to induce second polar body retention. Striped pigment patterns were stable in six mosaic individuals between the ages of 7 and 14 months. We estimated the total ST DNA contribution in adult transgenic fish using DNA dot blot analyses. An average of 7% ST DNA was obtained in analyses of 11 transgenic individuals. Nine of 55 transgenic individuals examined expressed a ST-specific isozyme in adulthood; some were mosaic for foreign gene expression. Variable numbers of autonomous chromosome fragments were maintained in 10 adult transgenic individuals examined. Five transgenic RT were backcrossed to albino RT. Chromosome fragments were inherited by 29 of 31 backcross embryos examined. Additional active nucleolar organizer regions (NORs) were present on some fragments and may also have been integrated into some host chromosomes. This method may have numerous applications for basic and applied genetic research in fish.

Development of a simple method to optimize the conditions for producing gynogenetic offspring, using albino rainbow trout, Salmo gairdneri Richardson, females as an indicator for gynogenesis

Gynogenetic offspring of rainbow trout were produced by means of UV‐irradiation of the sperm from a normal male. In order to indicate the destruction of the chromosomes of the sperms, eggs of albinos were used. The gynogenetic offspring showed no pigmentation while normal progeny showed pigmentation.

Intergeneric gene transfer of six isozyme loci in rainbow trout by sperm chromosome fragmentation and gynogenesis

AbstractTransgenic rainbow trout were produced by fertilizing albino rainbow trout eggs with gamma‐irradiated brook trout (ST) or rainbow trout (RT) sperm and then heat shocking the eggs at 29°C for 10 minutes to induce second polar body retention. Electrophoretic analyses of the RT × ST crosses confirmed the expression of paternal (brook trout specific) alleles at Ldh‐4, Mdh‐3,4, Mdh‐2, Aat‐1,2, Gpi‐3, and 6‐Pgd; the transfer frequency of these loci varied from 2 to 17%. These loci range from 8 to 48 cM from the centromere; proximity of introduced genes to a centromere does not appear to be a factor in retention and expression of foreign genes. Cytogenetic analyses of these same crosses revealed variable numbers and types of chromosome fragments and rings within individuals. Survival and pigment transfer in the resultant gynogenetic offspring varied considerably due to the individual female used in a particular cross. This female effect may have obscured effects due to dose of irradiation and species of male.

Induction of diploid gynogenesis in Atlantic salmon and rainbow trout using irradiated sperm and heat shock

Three experiments were carried out to investigate the possibility of producing inbred lines of Atlantic salmon (Salmo salar) and rainbow trout (Salmo gairdneri) by gynogenesis using irradiated sperm and heat shock. In experiment I, tolerance of eggs to heat shock was investigated. In experiment II, eggs were inseminated with irradiated sperm and effects of temperature level, duration of shock, and time from insemination to heat shock were investigated. Heat shock administered for 10 or 20 min during the first 30 min after insemination increased the frequency of gynogenetic fry. Time from insemination to heat shock did not influence the results. The highest frequencies of gynogenetic fry were produced when Atlantic salmon and rainbow trout eggs were heat shocked at 24 and 26 °C, respectively. In experiment III, eggs from albino rainbow trout (recessive homozygote for a depigmentation gene) were inseminated with irradiated sperm from wild-type coloured males and heat shocked. All fry produced in this experiment were of the yellow albino phenotype. It is concluded that induction of diploid gynogenesis by heat shock is a rapid and practical method of producing high numbers of inbred lines in Atlantic salmon and rainbow trout.

A comparison of antibody responses of rainbow trout, sea run rainbow trout, and mutants.

Immune responses to formalin-killed Aeromonas salmonicida cells and goldfish red blood cells (GFRBC) were assessed by assaying agglutinin titre and haemolysin titre, using a few different types of rainbow trout Salmo gairdneri (yearlings weighing 50-80g). These included steelhead trout, which is sea run rainbow trout, albino rainbow trout, obtained as a mutant, and unspotted rainbow trout (which is called “Horai masu”), a mutant lacking black-pigmented spots in the skin. The anti-A. salmonicida agglutinin reached the maximal titre after 2 weeks and still maintained a detectable titre level after 4 weeks. The anti-GFRBC haemolysin, however, formed a peak after 1 week and became undetectable after 3 weeks in antibody titration. Thus, a dissimilarity in antibody responses was produced by applying the two kinds of particulate antigens. In the comparative assessment of antibody responses of the trout, no significant difference between antibody assays could be traced, even though there were different types of rainbow trout among the immunized fish. The results appear to show that the types bear a close resemblance to each other in immunological potentiality, especially in antibody productivity.

Preliminary report on hybridization experiments in trout — Growth and survival of F 1 hybrids

Hybridization experiments were carried out by crossing females of common rainbow trout with the males of albino rainbow trout. Survival rates in egg, hatchling, fry and yearling stages, and the annual growth rate were higher than those of either parent. Reciprocal crosses with females of albino rainbow trout and males of common rainbow trout showed poor survival rate. Gonadial development of these hybrids was normal.

Fisherman Reaction to the Stocking of Albino Rainbow Trout in Utah

Fisherman Reaction to the Stocking of Albino Rainbow Trout in Utah

Precipitating Antibody AgainstAeromonas salmonicidain Serums of Inbred Albino Rainbow Trout (Salmo gairdneri)

Precipitins in albino rainbow trout serums were demonstrated by gel diffusion after a single parenteral exposure to the soluble antigens of Aeromonas salmonicida. The fraction of the serum containing antibody activity against the presented antigens was shown by immunoelectrophoresis to be in the nonmigrating region. This corresponded to the beta-2 fraction of rabbit serum. An antibody-containing component comparable with rabbit gamma globulin was not detected.