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  • 1
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    Fine Mapping and Evolution of the Major Sex Determining Region in Turbot (Scophthalmus maximus) (2014)
    Genetics Society of America (GSA)
    Details
    Publication Date: 2014-10-17
    Description: Fish sex determination (SD) systems are varied, suggesting evolutionary changes including either multiple evolution origins of genetic SD from nongenetic systems (such as environmental SD) and/or turnover events replacing one genetic system by another. When genetic SD is found, cytological differentiation between the two members of the sex chromosome pair is often minor or undetectable. The turbot ( Scophthalmus maximus ), a valuable commercial flatfish, has a ZZ/ZW system and a major SD region on linkage group 5 (LG5), but there are also other minor genetic and environmental influences. We here report refined mapping of the turbot SD region, supported by comparative mapping with model fish species, to identify the turbot master SD gene. Six genes were located to the SD region, two of them associated with gonad development ( sox2 and dnajc19 ). All showed a high association with sex within families ( P = 0), but not at the population level, so they are probably partially sex-linked genes, but not SD gene itself. Analysis of crossovers in LG5 using two families confirmed a ZZ/ZW system in turbot and suggested a revised map position for the master gene. Genetic diversity and differentiation for 25 LG5 genetic markers showed no differences between males and females sampled from a wild population, suggesting a recent origin of the SD region in turbot. We also analyzed associations with markers of the most relevant sex-related linkage groups in brill ( S. rhombus ), a closely related species to turbot; the data suggest that an ancient XX/XY system in brill changed to a ZZ/ZW mechanism in turbot.
    Electronic ISSN: 2160-1836
    Topics: Biology
    Published by Genetics Society of America (GSA)
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  • 2
    Electronic Resource
    Electronic Resource
    Gonadal morphology of normal and sex-reversed triploid and gynogenetic diploid coho salmon (Oncorhynchus kisutch) (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 45 (1994), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In this study, the gonadal morphology of untreated and sex-reversed juvenile triploid and gynogenetic diploid coho salmon was compared with that of diploids. Testes of triploids were of the same size as those of diploids. Spermatogonia, however, were significantly bigger than those of diptoids in both diameter (P〈0·001) and volume (P〈0·01), suggesting that this characteristic can be a useful indicator of ploidy in the early stages of gonadal development. In females, induction of triploidy did not affect the lamellar structure of the ovaries but reduced their size considerably. Further, these ovaries had no oocytes. Treatment of triploids with oestrogen resulted in the feminization of genotypic males, which had ovaries similar to those found in tripioid females. However, gonads of triploid males partially sex-re versed into females were identified by their enlargement, the presence of remnants of the male vascular system, and by the appearance of ovarian lacunae and germinal and somatic cells typical of triploid females, Induction of gynogenesis resulted in 100% females, of which 34% had ovaries of reduced size with areas devoid of oocytes. However, and contrary to what has been found in cyprinids, no male germ cells were observed in these ovaries. This discrepancy may reflect differences, in the mechanisms of sex determination between salmonids and cyprinids. Treatment of gynogenetics with androgen increased the number of fish with abnormal ovaries but also resulted in the production of phenotypic-male gynogenetic diploids, of which 11% had testes indistinguishable from those of untreated control diploids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1994.tb00923.x
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of rearing temperature during the larval and nursery periods on growth and sex differentiation in two Mediterranean strains of Dicentrarchus labrax (2005)
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 67 (2005), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: European sea bass Dicentrarchus labrax of the north-western (NW) and south-eastern (SE) Mediterranean Sea strains were exposed to different temperatures (13, 17 or 21° C) during the larval rearing (11–51 days post hatching, dph) or nursery periods (55–95 dph), in order to examine the effects of temperature on sex differentiation and subsequent growth during the first year of life. Higher growth was observed during exposure to higher temperatures, but fish of the NW strain exposed to 13 or 17° C during larval rearing exhibited compensatory growth once exposure to the lower temperatures finished, and as a result their final size at 300 dph was similar or greater to the group exposed to 21° C. Fish exposed to 17° C during the nursery period also had similar size to fish exposed to 21° C after 300 days of rearing, but the fish exposed to 13° C remained significantly smaller (ANOVA, n = 55–100, P 〈 0·05). There were significant differences in the sex ratio among the fish exposed to different temperatures during the two periods of rearing, with high temperature (21° C) resulting in a significantly higher percentage of males in the population, both in the NW (ANOVA, n = 2, P 〈 0·04) and SE populations (ANOVA, n = 2, P 〈 0·01). The masculinization effect of high temperature was significantly stronger during the larval rearing stage, both in the NW (ANOVA, n = 2, P 〈 0·005) and SE populations (ANOVA, n = 2, P 〈 0·01). None of the temperature manipulations could produce 100% females, suggesting that there is a part of the genetic component in sex differentiation which is not labile to environmental influence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.0022-1112.2005.00766.x
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  • 4
    Electronic Resource
    Electronic Resource
    Comparative growth performance of diploid and triploid European sea bass over the first four spawning seasons (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 58 (2001), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: During their 3–4 first years of life, triploid sea bass Dicentrarchus labrax grew in a similar fashion to diploids in fork length but more slowly than diploids (P〈0·05) in body weight, even when the diploids reached full sexual maturity. However, from 48–53 months of age triploids exhibited non-significantly higher instantaneous growth rates, and thus when fish were 4 years or older, differences in weight with diploids were no longer apparent, suggesting that triploidy could be of benefit in the culture of large (〉1 kg) sea bass. The condition factor was reduced in both ploidies during the spawning season which took place in winter when the temperature was low. These observations suggest that any growth advantage in triploids, which were functionally sterile, may be offset by unfavourable environmental conditions. Thus, the potential gain of triploid fish, because they do not direct energy to gonadal growth, could not overcome the effects of low temperature on somatic growth, which coincided with the spawning season. This suggests that the low growth of this species during winter is more a consequence of low temperature than of the energetic cost associated with reproduction. On the other hand, the lower hepatosomatic index in triploid females in contrast to diploid females might be indicative of the lack of gonadal oestradiol-mediated hepatic synthesis of vitellogenin. Also, erythrocyte and haematocrit measurements showed an increased nuclear and cellular volume in triploids, but with similar cell numbers to those of diploids, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.2001.tb00500.x
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of Natural, Synthetic, Aromatizable, and Nonaromatizable Androgens in Inducing Male Sex Differentiation in Genotypic Female Chinook Salmon (Oncorhynchus tshawytscha)
    Amsterdam : Elsevier
    General and Comparative Endocrinology 91 (1993), S. 59-65 
    Details
    ISSN: 0016-6480
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1006/gcen.1993.1104
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  • 6
    Electronic Resource
    Electronic Resource
    Induction of sterility in coho salmon (Oncorhynchus kisutch) by androgen immersion before first feeding
    Amsterdam : Elsevier
    Aquaculture 119 (1994), S. 409-423 
    Details
    ISSN: 0044-8486
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0044-8486(94)90304-2
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  • 7
    Electronic Resource
    Electronic Resource
    The comparative effectiveness of the natural and a synthetic estrogen for the direct feminization of chinook salmon (Oncorhynchus tshawytscha)
    Amsterdam : Elsevier
    Aquaculture 106 (1992), S. 183-193 
    Details
    ISSN: 0044-8486
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0044-8486(92)90202-V
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  • 8
    Electronic Resource
    Electronic Resource
    Gonadal differentiation in coho salmon, Oncorhynchus kisutch, after a single treatment with androgen or estrogen at different stages during ontogenesis
    Amsterdam : Elsevier
    Aquaculture 77 (1989), S. 251-262 
    Details
    ISSN: 0044-8486
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0044-8486(89)90207-X
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  • 9
    Electronic Resource
    Electronic Resource
    Growth, sex differentiation and gonad and plasma levels of sex steroids in male- and female-dominant populations of Dicentrarchus labrax obtained through repeated size grading (2005)
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 66 (2005), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Starting from 66 days post hatching (dph), European sea bass Dicentrarchus labrax were graded successively to create a fast growing (L-extreme) and a slow growing (S-extreme) population. The L-extreme population grew significantly larger (ANOVA, n = 89–101, P 〈 0·01) attaining twice the wet mass of the S-extreme population at 300 dph (130·9 ± 1·8 v. 66·7 ± 0·9 g, mean ± s.e.). When the two populations were sexed, the L-extreme consisted of 96·5% and the S-extreme of 30·2% females, while the ungraded control had 59·2% females. Sex differentiation began first in females at a total length (LT) of 97 ± 4 mm and wet mass of 9·4 ± 1·2 g (150 dph), and was completed when fish reached 166 ± 6 mm and 53·4 ± 6·4 g (250 dph) in both sexes. Precocious maturation in males was positively correlated to growth. Gonad oestradiol (E2) was significantly higher in the female-dominant population at the onset of ovarian differentiation (ANOVA, n = 10, P 〈 0·05) and in the plasma after the appearance of the first primary oocytes (P 〈 0·01). Gonad testosterone (T) increased in both populations after sex differentiation (ANOVA, n = 10, P 〈 0·05), while plasma levels were significantly higher in the male-dominant population (P 〈 0·001). Both gonad and plasma 11-keto testosterone (11-KT) were significantly higher in the male-dominant population (ANOVA, n = 10, P 〈 0·01) reaching maximal values at spermiation. The results suggest that E2 is closely related with ovarian differentiation and the onset of oogenesis, while T and 11-KT is more related to spermatogenesis and precocious maturation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.0022-1112.2005.00639.x
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  • 10
    Electronic Resource
    Electronic Resource
    Growth, gonadal development and sex ratios of meiogynogenetic diploid sea bass (2002)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 61 (2002), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Gynogenesis showed little effect on general physiology and gonadal development in sea bass Dicentrarchus labrax. Meiogynogenetic fish showed well-developed gonads indicating low occurrence of developmental imbalances even after gynogenesis induction in this species. In addition, the proportion of sexes of meiogynogenetic sea bass was similar to the diploid controls in two independent trials, which did not deviate significantly from a 1:1 male: female sex ratio. Even considering some environmental influence on sex differentiation, as has been previously demonstrated, the fact that the proportion of sexes was similar between gynogenetic and control diploids essentially eliminates the possibility that in the sea bass the females are the homogametic sex. Although the mechanism of sex determination of this species still remains unknown, even after gynogenesis induction, the genetic mechanism of the ZW/ZZ type could probably operate in the sea bass.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.2002.tb01570.x
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