Domestication shapes morphology in rainbow trout Oncorhynchus mykiss.

In this study, clonal lines from North American resident and migratory populations of rainbow trout Oncorhynchus mykiss adapted to different geographical conditions and with different domestication histories were characterized morphologically. Lines reared in a common-garden experiment were characterized for external shape and meristic values, searching for a general pattern of morphological variation due to exposure to captive conditions. A sharp distinction was identified between wild and captive lines. The body profile was deeper in captive lines, with longer dorsal and anal fins and shorter and deeper caudal peduncles. Highly significant differences were also identified in meristic values among the lines but no consistent relation between meristic values and domestication status was detected. This morphological characterization will facilitate the selection of lines with divergent phenotypes for subsequent quantitative trait loci analysis, aimed at identifying genome regions linked with morphological adaptive response to captive conditions.

The cutthroat trout Y chromosome is conserved with that of rainbow trout.

Five genetic markers previously shown to be located on the sex chromosomes of rainbow trout (Oncorhynchus mykiss) were tested for linkage with the sex locus of Yellowstone cutthroat trout (Oncorhynchus clarki bouvieri) in a genetic cross created from a rainbow x cutthroat male hybrid. We show that the sex locus of both rainbow and cutthroat trout is on the same homologous linkage group. Fluorescence in situ hybridization (FISH) using a probe for the microsatellite marker Omm1665, which maps close to the sex locus of Yellowstone cutthroat trout, was used to identify the Y chromosome of cutthroat trout in the hybrid. The Y chromosome of cutthroat trout is sub-telocentric and lacks a DAPI band found on the short arm of the Y chromosome of some rainbow trout males.

A consolidated linkage map for rainbow trout (Oncorhynchus mykiss).

Androgenetic doubled haploid progeny produced from a cross between the Oregon State University and Arlee clonal rainbow trout (Oncorhynchus mykiss) lines, used for a previous published rainbow trout map, were used to update the map with the addition of more amplified fragment length polymorphic (AFLP) markers, microsatellites, type I and allozyme markers. We have added more than 900 markers, bringing the total number to 1359 genetic markers and the sex phenotype including 799 EcoRI AFLPs, 174 PstI AFLPs, 226 microsatellites, 72 VNTR, 38 SINE markers, 29 known genes, 12 minisatellites, five RAPDs, and four allozymes. Thirty major linkage groups were identified. Synteny of linkage groups in our map with the outcrossed microsatellite map has been established for all except one linkage group in this doubled haploid cross. Putative homeologous relationships among linkage groups, resulting from the autotetraploid nature of the salmonid genome, have been revealed based on the placement of duplicated microsatellites and type I loci.

Composite interval mapping reveals a major locus influencing embryonic development rate in rainbow trout (Oncorhynchus mykiss).

Little is known about the genetics controlling the rate of embryonic development in salmonids, despite the fact that this trait plays an important role in the life history of wild and cultured stocks. We investigated the genetics of embryonic development rate by performing an analysis of quantitative trait loci (QTL) on two families of androgenetically derived doubled haploid rainbow trout produced from a hybrid of two clonal lines with divergent embryonic development rates. A total of 170 doubled haploid individuals were genotyped at 222 marker loci [219 amplified fragment length polymorphism (AFLP) markers, 2 microsatellites, and p53]. A genetic linkage analysis resulted in a map consisting of 27 linkage groups with 21 of the markers remaining unlinked at a minimum LOD of 3.0 and maximum theta of 0.40. Eight of these linkage groups were matched to published rainbow trout linkage groups. Composite interval mapping (CIM) revealed evidence for two QTL influencing time to hatch, and suggestive evidence for a third. These QTL accounted for a total of 24.6% of the variation in time to hatch. One of these QTL had a large effect on development rate, especially in one family of doubled haploids, in which it explained 25.6% of the variance in time to hatch. QTL influencing embryonic length and weight at the commencement of exogenous feeding were also identified. The QTL with the strongest effect on embryonic length (lenR13) mapped to the same position as the QTL with the strongest effect on time to hatch (tthR13), suggesting a single QTL may have a pleiotropic effect on both these traits. These results suggest that the use of clonal lines with a doubled haploid crossing design is an effective way of analyzing the genetic basis of complex traits in salmonids.

Testis transplantation in male rainbow trout (Oncorhynchus mykiss).

The objective of the present study was to establish a procedure for the transplantation of an intact testis from one male rainbow trout (Oncorhynchus mykiss) to another individual and evaluate the reproductive function of the transplanted testis at sexual maturity. Isogenic (cloned) male rainbow trout were produced by crossing a completely homozygous male (YY) with a homozygous female (XX) to eliminate any problem of tissue rejection. Transplantation was performed on four pairs of sexually immature animals (n = 8); each served both as a donor and recipient. The left testis was removed by making a ventral midline incision to expose the body cavity and gonads. The left testis was disconnected at the anterior and posterior points of attachment and transferred to the recipient fish where it was placed in position adjacent to the pyloric cecae. The right testis was left intact. After 4 wk, the fish were injected (i.p.) twice weekly for 8 or 9 wk with salmon pituitary extract (1.5 mg/kg) to induce precocious sexual maturation. A similar number of untreated fish were maintained as controls. Following this treatment, all the fish were killed, and the right (intact) and left (transplanted) testes were removed, weighed, and sampled for sperm. Although the mean weights of the left, transplanted testes were significantly (P: < 0.05) smaller than the intact testes (transplants = 1.2 g; intact = 3.9 g), transplanted testes were present in all animals, had increased in mass, and were sexually mature containing sperm. The mean fertility, as measured by the proportion of eggs completing first cleavage, of sperm derived from transplanted testes (92%) was no different from the sperm obtained from intact testes (84%). Similarly, there was no difference in the number of embryos attaining the eyed stage of development, after 18 days of incubation, that were derived from transplanted (84%) or intact testes (85%).

Gonadal morphology of female diploid gynogenetic and triploid rainbow trout.

Chromosome sets of fishes can be manipulated; this practice includes the production of triploid and gynogenetic salmonids. Such chromosomal modifications often result in abnormal ovarian development. In rainbow trout (RBT), triploid females have string-like gonads lacking significant developing oocytes and are suggested to be sterile due to the odd set of chromosomes disrupting oogenesis. Aberrant ovarian development is reported to occur in about 30% of gynogenetic females. It has been suggested that gynogenetic fish are more prone to expressing developmental abnormalities due to either increased homozygosity or to incomplete inactivation of the paternal chromatin. This investigation was done to compare the ovarian morphology of female triploid and induced gynogenetic diploid RBT. The objective was to determine whether the presence of supernumerary chromosomal fragments, potentially generated during the process of sperm genome inactivation, would result in abnormal gonadal development in gynogens comparable to that observed in triploid females. Gonadal morphology was observed and karyotypical analysis was completed on 21 gynogenetic fish. In 90% of the fish examined, the presence of chromosomal fragments was positively correlated with irregular ovarian development. The atypical gonadal morphology observed in the gynogens resembled triploid RBT ovarian morphology. The results of this investigation support the hypothesis that disruption of the normal diploid chromosomal complement alters germ cell development in gynogenetic female RBT due to the unbalanced nature of the genome. J. Exp. Zool. 286:505-512, 2000.

A detailed linkage map of rainbow trout produced using doubled haploids.

We report the first detailed genetic linkage map of rainbow trout (Oncorhynchus mykiss). The segregation analysis was performed using 76 doubled haploid rainbow trout produced by androgenesis from a hybrid between the "OSU" and "Arlee" androgenetically derived homozygous lines. Four hundred and seventy-six markers segregated into 31 major linkage groups and 11 small groups (< 5 markers/group). The minimum genome size is estimated to be 2627.5 cM in length. The sex-determining locus segregated to a distal position on one of the linkage groups. We analyzed the chromosomal distribution of three classes of markers: (1) amplified fragment length polymorphisms, (2) variable number of tandem repeats, and (3) markers obtained using probes homologous to the 5' or 3' end of salmonid-specific small interspersed nuclear elements. Many of the first class of markers were clustered in regions that appear to correspond to centromeres. The second class of markers were more telomeric in distribution, and the third class were intermediate. Tetrasomic inheritance, apparently related to the tetraploid ancestry of salmonid fishes, was detected at one simple sequence repeat locus and suggested by the presence of one extremely large linkage group that appeared to consist of two smaller groups linked at their tips. The double haploid rainbow trout lines and linkage map present a foundation for further genomic studies.

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.

Benthic-pelagic links and rocky intertidal communities: bottom-up effects on top-down control?

Insight into the dependence of benthic communities on biological and physical processes in nearshore pelagic environments, long considered a "black box," has eluded ecologists. In rocky intertidal communities at Oregon coastal sites 80 km apart, differences in abundance of sessile invertebrates, herbivores, carnivores, and macrophytes in the low zone were not readily explained by local scale differences in hydrodynamic or physical conditions (wave forces, surge flow, or air temperature during low tide). Field experiments employing predator and herbivore manipulations and prey transplants suggested top-down (predation, grazing) processes varied positively with bottom-up processes (growth of filter-feeders, prey recruitment), but the basis for these differences was unknown. Shore-based sampling revealed that between-site differences were associated with nearshore oceanographic conditions, including phytoplankton concentration and productivity, particulates, and water temperature during upwelling. Further, samples taken at 19 sites along 380 km of coastline suggested that the differences documented between two sites reflect broader scale gradients of phytoplankton concentration. Among several alternative explanations, a coastal hydrodynamics hypothesis, reflecting mesoscale (tens to hundreds of kilometers) variation in the interaction between offshore currents and winds and continental shelf bathymetry, was inferred to be the primary underlying cause. Satellite imagery and offshore chlorophyll-a samples are consistent with the postulated mechanism. Our results suggest that benthic community dynamics can be coupled to pelagic ecosystems by both trophic and transport linkages.

Acceptance of skin grafts by isogenic rainbow trout (Oncorhynchus mykiss).

OBJECTIVE: To test the immunocompetence of isogenic families of rainbow trout by measuring their ability to accept or reject skin grafts. ANIMALS: 3 families of isogenic rainbow trout (Oncorhynchus mykiss), produced by mating homozygous females and homozygous males, plus 4 chinook salmon (O tshawytscha) were used in these experiments. PROCEDURE: Grafts (allografts, members of the same family; autografts, donor and recipient were the same fish; and xenografts, O tshawytscha as donor) were exchanged. Grafts were applied on day 0 and removed on day 21, placed in neutral-buffered formalin, and embedded in paraffin. Lymphocytes and nuclei were counted in representative stained sections in the epidermis, dermis, and hypodermis. Results were analyzed by univariate analysis, using the Shapiro-Wilk statistic. RESULTS: Autografts were retained and minimal histologic changes were apparent. Allografts were histologically similar to autografts. Xenografts were rejected. CONCLUSIONS: Results indicate that the immune system of isogenic rainbow trout is unable to distinguish between family members within isogenic families, but that a vigorous response is mounted against chinook salmon xenografts. The isogenic rainbow trout are immunocompetent with respect to the phenomenon of graft rejection.

DNA fingerprinting confirms isogenicity of androgenetically derived rainbow trout lines.

Homozygous and hybrid clonal lines of rainbow trout (Oncorhynchus mykiss) were confirmed to be isogenic using multilocus DNA fingerprinting. Homozygous clones were produced by androgenesis and gynogenesis using gametes from androgenetic male and female rainbow trout, respectively. Isogenic F1 hybrid lines were produced by crossing homozygous fish from different strains. One line of hybrid clones showed segregation for maternally inherited DNA fingerprint markers. The female from this cross, the only presumptive homozygous gynogenetic individual used in this study, was thought to have been produced by gynogenesis followed by blockage of the first cleavage division, but based on the DNA fingerprint analysis, apparently was derived by spontaneous polar body retention that maintained heterozygosity at some loci. Mutations at DNA fingerprint loci were not observed, indicating relative stability of fingerprint loci in the clonal lines. DNA fingerprinting appears to be a useful tool for identifying and genetically monitoring clonal lines of rainbow trout. Isogenic lines of rainbow trout will facilitate the production of saturated genetic maps for rainbow trout and enhance such endeavors as quantitative trait locus (QTL) analysis and loss of heterozygosity (LOH) studies in tumors.

Arlee line of rainbow trout (Oncorhynchus mykiss) exhibits a low level of nonspecific cytotoxic cell activity.

Nonspecific cytotoxic cell (NCC) activity was assessed in the peripheral blood of four isogenic lines of rainbow trout (Oncorhynchus mykiss) which were derived by the chromosome set manipulation technique of androgenesis. In these fish, whose isogenicity was previously confirmed by multilocus DNA fingerprint analysis, NCC activity was studied by the release of 51Cr from YAC-1 targets. Two groups of trout (the homozygous Arlee 12 line and the heterozygous hybrid of the Arlee 63 and Arlee 12 lines) had significantly lower levels of NCC activity in peripheral blood than either outbred rainbow trout or other lines with Hot Creek or hybrid Arlee x Hot Creek ancestry. The low NCC activity in the Arlee line appears to be inherited as a recessive trait. Peripheral blood cells of the trout mediated lectin dependent cellular cytotoxicity (LDCC) with the addition of phytohemagglutinin to co-cultures of effector cells and YAC-1 cells. The low NCC activity in the peripheral blood of these fish is not due to a condition analogous to the NCC-deficient Chediak-Higashi syndrome of man or the beige mutation of mice.

The role of chlamydial antibodies in an in vitro fertilization program.

The reported incidence of antibodies to Chlamydia trachomatis in patients attending infertility clinics is at least 30%. It has been reported that chlamydial antibodies are associated with decreased pregnancy rates following in vitro fertilization (IVF). A study was performed to investigate the significance of chlamydial antibodies in an established IVF program. The results did not show a decreased pregnancy rate in the presence of chlamydial antibodies. Of the women achieving pregnancy, 41% were seropositive compared with 38% seropositivity in women who did not become pregnant. There was no apparent benefit of the use of prophylactic antibiotics. The results also suggested that past infection with C. trachomatis in men did not adversely affect semen analysis or fertilization.

Uptake and Concentration of Alkylamines by a Marine Diatom: EFFECTS OF H AND K AND IMPLICATIONS FOR THE TRANSPORT AND ACCUMULATION OF WEAK BASES.

Methylamine, ethylamine, and dimethylamine (10 micromolar) are taken up and concentrated 600 to 6,000-fold by Cyclotella cryptica. Methylamine is concentrated most strongly, and its accumulation and retention are relatively insensitive to external pH but strongly inhibited by 30 millimolar external K(+). Accumulation and retention of ethyl- and dimethylamine, on the other hand, are strongly affected by external pH and less sensitive to external [K(+)]. Intracellular pH, as estimated from neutral red staining and quenching of 9-aminoacridine fluorescence, was between 4 and 5, with the central vacuole being the major acidic compartment. The accumulation of ethyl- and dimethylamine could result from diffusion of the uncharged amine across the membrane(s) and passive equilibration of the charged form (R-NH(3) (+)) inside and outside the cell. Differences in the accumulation ratio and the ion dependence for methylamine uptake relative to ethyl- and dimethylamine uptake suggests that a different mechanism is responsible for the concentration of the simpler amine.