Nelson Colihueque

Diploid chromosome number variations and sex chromosome polymorphism in five cultured strains of rainbow trout (Oncorhynchus mykiss)

Abstract This work reveals the chromosomal characteristics of the five cultured strains of rainbow trout, Oncorhynchus mykiss. The five strains—Americana, Donaldson, Cofradex, Steelhead, and Kamloops—are those commonly used in the Chilean salmon farming industry. Chromosome characterization involved the determination of diploid chromosome number (2n), chromosome arm number (NF) and sex chromosome of individuals by Hoechst 33258/Actinomicyn D (H/AmD) fluorescent stain. Considering all of the strains studied, the 2n ranged from 58 to 63 chromosomes. All of the karyotypes had NF=104. Within this range of variation, the strains exhibited low (Americana, 2n=59–60; Steelhead and Kamloops, 2n=58–61), intermediate (Cofradex, 2n=59–62) or high chromosome numbers (Donaldson, 2n=61–63). In strains with the most extreme diploid chromosome numbers, the most frequent 2n corresponded to 59 and 61 chromosomes. Sex chromosome determination revealed that 24.5% of specimens of both sexes, presented an unexpected sex chromosome. In males, “XX” specimens were observed, whereas in females, “XY” or “XXX” individuals were recorded. The subtelocentric (st) morphology and centromeric H/AmD banding pattern of the additional “X” chromosome in “XX males” and “XXX females” is similar to that observed in the regular X chromosome. The chromosome number variation in the strains studied is consistent with the Robertsonian-type polymorphism described for rainbow trout. The presence of different chromosome numbers among strains, could reflect the chromosome differences existing within ancestral trout populations, or the presence of a certain degree of mixing with other populations of different geographical origin. The discovery of specimens with an unexpected sex chromosome is suggestive of an incomplete differentiation of the sex chromosome pair in the rainbow trout.

Physiological factors affecting triploid production in rainbow trout, Oncorhynchus mykiss

The influence of three physiological factors related to triploid production was examined for rainbow trout. Individual spawnings of 46 females were used to perform triploid production experiments from 1989 to 1991, with various water temperatures (6–13.8°C) at stripping and egg incubation. The percentage of triploids was similar for a heat shock of 26.5°C for 15 min applied 15 or 25 min after fertilization (73.4±5.6% vs 78.6±4.5%). A tendency to a higher percentage of triploids (85.9±5.7%) was observed for water temperatures of 6–8.0°C at stripping and incubation, compared to at higher water temperatures of 12.1–14°C (63.0±8.4%). Analysis of variance indicated an effect of four categories of water temperature (6–8, 8.1–10, 10.1–12, 12.1–14°C) on triploid product at P = 0.14. Regression analysis confirmed these as significant (r = −0.36; P < 0.02). A significant increase in percentage of triploids was observed when eggs remained 2, 6 and 10 days in the body cavity. The mean % triploidy was 46.1, 54.7 and 76.8, respectively. Similar results were observed for survival of the eggs.

Analysis of the association between spawning time QTL markers and the biannual spawning behavior in rainbow trout (Oncorhynchus mykiss)

The rainbow trout is a salmonid fish that occasionally exhibits broodstocks with biannual spawning behavior, a phenomenon known as a double annual reproductive cycle (DARC). Spawning time quantitative trait loci (SPT-QTLs) affect the time of the year that female rainbow trout spawn and may influence expression of the DARC trait. In this study, microsatellite markers linked and unlinked to SPT-QTLs were genotyped to investigate the underlying genetics of this trait. SPT-QTLs influenced the DARC trait since in two case-control comparisons three linked markers (OmyFGT12TUF, One3ASC and One19ASC) had significant levels of allelic frequency differentiation and marker-character association. Furthermore, alleles of One3ASC and One19ASC had significantly higher frequencies in populations that carried the DARC trait.

Appearance traits in fish farming: progress from classical genetics to genomics, providing insight into current and potential genetic improvement

Appearance traits in fish, those external body characteristics that influence consumer acceptance at point of sale, have come to the forefront of commercial fish farming, as culture profitability is closely linked to management of these traits. Appearance traits comprise mainly body shape and skin pigmentation. Analysis of the genetic basis of these traits in different fish reveals significant genetic variation within populations, indicating potential for their genetic improvement. Work into ascertaining the minor or major genes underlying appearance traits for commercial fish is emerging, with substantial progress in model fish in terms of identifying genes that control body shape and skin colors. In this review, we describe research progress to date, especially with regard to commercial fish, and discuss genomic findings in model fish in order to better address the genetic basis of the traits. Given that appearance traits are important in commercial fish, the genomic information related to this issue promises to accelerate the selection process in coming years.

Comparison of Oogenesis and Sex Steroid Profiles between Twice and Once Annually Spawning of Rainbow Trout Females (Oncorhynchus mykiss)

This study compares the gonadosomatic index (GSI), oocyte growth (OG), gonadal histology, and plasma level concentrations of sex hormones (estradiol-17β (E2) and vitellogenin (V)) of twice-spawning (T-SP) and once-spawning (O-SP) females of rainbow trout throughout the additional and the normal reproductive cycle, respectively. In T-SP, the GSI values rapidly increase from May to November, in contrast to O-SP, which showed low and constant GSI values (1.19 to 14.5 and 1.19 to 0.63, resp.). T-SP exhibited a marked increase of OG in the same period, reaching a maximum diameter of 4,900 ± 141.42 μm, in contrast to O-SP, which presented a slow OG. The gonadal histology of T-SP agreed with the general pattern of ovogenesis observed for O-SP (vitellogenesis, ovulation, and recrudescence); however, this process was nonsynchronous between the two breeder groups. Plasma steroid levels showed significant variation during oogenesis, which agreed with the GSI, OG, and gonadal histology patterns. The level of E2 increased to a maximum value of 26.2 ng/mL and 36.0 ng/mL in O-SP and T-SP, respectively, one or two months before the spawning event where vitellogenesis was fully active. The V concentrations followed a pattern similar to those of E2.

Skin Color Characterization in Rainbow Trout by Use of Computer-Based Image Analysis

Abstract Back, flank (reddish band along the lateral line and below the lateral line), and belly regions of cultured rainbow trout Oncorhynchus mykiss were characterized in terms of skin coloration, spottiness, and darkness by using computer-based image analysis as an approach to separate fish into desirable back color categories for market and export. Three highly represented colors were observed on the back (mean ± SE percentage of area covered by the given color): blue or sky-blue, 18.0 ± 1.8%; yellow, 13.4 ± 1.5%; and green, 66.1 ± 2.0%. Individuals with a high frequency of these colors on the back (at least 50% of area covered by a given color) were reclassified into groups exhibiting a yellowish back color (YB), a bluish back color (BB), or a greenish back color (GB) to determine whether the BB group presented differences in various skin color variables when compared with the other back color groups; an undefined back color (UB) group (fish for which all colors had less than 50% coverage) was also u...

Genetic divergence analysis of the Common Barn Owl Tyto alba (Scopoli, 1769) and the Short-eared Owl Asio flammeus (Pontoppidan, 1763) from southern Chile using COI sequence

Abstract In this paper new mitochondrial COI sequences of Common Barn Owl Tyto alba (Scopoli, 1769) and Short-eared Owl Asio flammeus (Pontoppidan, 1763) from southern Chile are reported and compared with sequences from other parts of the World. The intraspecific genetic divergence (mean p-distance) was 4.6 to 5.5% for the Common Barn Owl in comparison with specimens from northern Europe and Australasia and 3.1% for the Short-eared Owl with respect to samples from north America, northern Europe and northern Asia. Phylogenetic analyses revealed three distinctive groups for the Common Barn Owl: (i) South America (Chile and Argentina) plus Central and North America, (ii) northern Europe and (iii) Australasia, and two distinctive groups for the Short-eared Owl: (i) South America (Chile and Argentina) and (ii) north America plus northern Europe and northern Asia. The level of genetic divergence observed in both species exceeds the upper limit of intraspecific comparisons reported previously for Strigiformes. Therefore, this suggests that further research is needed to assess the taxonomic status, particularly for the Chilean populations that, to date, have been identified as belonging to these species through traditional taxonomy.

Skin Spotting Variation Associated with Biometric and Reproductive Parameters in Naturalized Populations of Rainbow Trout, Oncorhynchus mykiss, from Southern Chile

RESEARCH ARTICLE Skin Spotting Variation Associated with Biometric and Reproductive Parameters in Naturalized Populations of Rainbow Trout, Oncorhynchus mykiss, from Southern Chile Nelson Colihueque, Francisco Javier Estay and Miguel Yáñez Departamento de Ciencias Biológicas y Biodiversidad, Universidad de Los Lagos, Osorno, Chile Piscícola Huililco Ltda., Pucón, Chile Departamento de Estadística, Universidad del Bío-Bío, Concepción, Chile

Morphological analysis of Trichomycterus areolatus Valenciennes, 1846 from southern Chilean rivers using a truss-based system (Siluriformes, Trichomycteridae)

Abstract Trichomycterus areolatus Valenciennes, 1846 is a small endemic catfish inhabiting the Andean river basins of Chile. In this study, the morphological variability of three T. areolatus populations, collected in two river basins from southern Chile, was assessed with multivariate analyses, including principal component analysis (PCA) and discriminant function analysis (DFA). It is hypothesized that populations must segregate morphologically from each other based on the river basin that they were sampled from, since each basin presents relatively particular hydrological characteristics. Significant morphological differences among the three populations were found with PCA (ANOSIM test, r = 0.552, p < 0.0001) and DFA (Wilks’s λ = 0.036, p < 0.01). PCA accounted for a total variation of 56.16% by the first two principal components. The first Principal Component (PC1) and PC2 explained 34.72 and 21.44% of the total variation, respectively. The scatter-plot of the first two discriminant functions (DF1 on DF2) also validated the existence of three different populations. In group classification using DFA, 93.3% of the specimens were correctly-classified into their original populations. Of the total of 22 transformed truss measurements, 17 exhibited highly significant (p < 0.01) differences among populations. The data support the existence of T. areolatus morphological variation across different rivers in southern Chile, likely reflecting the geographic isolation underlying population structure of the species.