scholarly journals Suppression of P450 aromatase gene expression in sex-reversed males produced by rearing genetically female larvae at a high water temperature during a period of sex differentiation in the Japanese flounder (Paralichthys olivaceus)

1999 ◽  
Vol 23 (2) ◽  
pp. 167-176 ◽  
Author(s):  
T Kitano ◽  
K Takamune ◽  
T Kobayashi ◽  
Y Nagahama ◽  
SI Abe
Keyword(s):  
Gene Expression ◽  
Sex Determination ◽  
Water Temperature ◽  
Sex Differentiation ◽  
High Water ◽  
Japanese Flounder ◽  
Female Group ◽  
High Water Temperature ◽  
Male Group

The phenotypic sex of many teleost fishes including flounders can be experimentally altered by treating embryos or larvae with varied temperatures or sex-steroid hormones. To analyse the sex determination mechanism, especially the role of cytochrome P450 aromatase (P450arom), an enzyme that catalyses the conversion of androgens to estrogens, in temperature-dependent gonadal sex differentiation in the Japanese flounder, we generated two populations of larvae, both having XX (genetic females) but each growing up to display all phenotypic females or males, by rearing the larvae at normal (18 degrees C) or high (27 degrees C) water temperatures from days 30 to 100 after hatching respectively. The larvae (XX) were produced artificially by mating normal females (XX) with gynogenetic diploid males (XX) which had been sex-reversed to phenotypic males by 17alpha-methyltestosterone. To study the role of P450arom in sex determination in the flounder, we first isolated a P450arom cDNA containing the complete open reading frame from the ovary. RT-PCR showed that P450arom mRNA was highly expressed in the ovary and spleen but weakly in the testis and brain. Semi-quantitative analyses of P450arom mRNA in gonads during sex differentiation showed that there was no difference in the levels of P450arom mRNA between the female and male groups when the gonad was sexually indifferent (day 50 after hatching). However, after the initiation of sex differentiation (day 60), the mRNA levels increased rapidly in the female group, whereas they decreased slightly in the male group. Similarly, estradiol-17beta levels rose remarkably in the female group, yet remained constant in the male group. These results suggest that induction of sex reversal of genetically female larvae to phenotypic males by rearing them at a high water temperature caused a suppression of P450arom gene expression. Furthermore, we suggest that the maintenance of P450arom mRNA at very low levels is a prerequisite for testicular differentiation, while the increased levels are indispensable for ovarian differentiation.

scholarly journals Cortisol Is Involved in Temperature-Dependent Sex Determination in the Japanese Flounder

Endocrinology ◽  
2010 ◽  
Vol 151 (8) ◽  
pp. 3900-3908 ◽  
Author(s):  
Toshiya Yamaguchi ◽  
Norifumi Yoshinaga ◽  
Takashi Yazawa ◽  
Koichiro Gen ◽  
Takeshi Kitano
Keyword(s):  
Sex Determination ◽  
Water Temperature ◽  
Mrna Expression ◽  
Molecular Mechanisms ◽  
Sex Differentiation ◽  
Paralichthys Olivaceus ◽  
High Water ◽  
Japanese Flounder ◽  
High Water Temperature ◽  
Temperature Dependent

In vertebrates, sex is normally determined by genotype. However, in poikilothermal vertebrates, including reptiles, amphibians, and fishes, sex determination is greatly influenced by environmental factors, such as temperature. Little is known about the molecular mechanisms underlying environmental sex determination in these species. The Japanese flounder (Paralichthys olivaceus) is a teleost fish with an XX/XY sex determination system. However, XX flounder can be induced to develop into predominantly either phenotypic females or males, by rearing at 18 or 27 C, respectively, during the sex differentiation period. Therefore, the flounder provides an excellent model to study the molecular mechanisms underlying temperature-dependent sex determination. We previously showed that an aromatase inhibitor, an antiestrogen, and 27 C treatments cause masculinization of XX flounder, as well as suppression of mRNA expression of ovary-type aromatase (cyp19a1), a steroidogenic enzyme responsible for the conversion of androgens to estrogens in the gonads. Furthermore, estrogen administration completely inhibits masculinization by these treatments, suggesting suppression of cyp19a1 mRNA expression, and the resultant estrogen biosynthesis may trigger masculinization of the XX flounder induced by high water temperature. Here, we demonstrated that cortisol causes female-to-male sex reversal by directly suppressing cyp19a1 mRNA expression via interference with cAMP-mediated activation and that metyrapone (an inhibitor of cortisol synthesis) inhibits 27 C-induced masculinization of XX flounder. Moreover, cortisol concentrations in 27 C-reared juveniles were significantly higher than in 18 C-reared fishes during sexual differentiation. These results strongly suggest that masculinization by high water temperature is ascribable to elevation of cortisol concentration during gonadal sex differentiation in the flounder.

scholarly journals Sex differentiation in grayling (Salmonidae) goes through an all-male stage and is delayed in genetic males who instead grow faster

2017 ◽  
Author(s):  
Diane Maitre ◽  
Oliver M. Selmoni ◽  
Anshu Uppal ◽  
Lucas Marques da Cunha ◽  
Laetitia G. E. Wilkins ◽  
...  
Keyword(s):  
Gene Expression ◽  
Sex Determination ◽  
Sex Differentiation ◽  
Sex Ratios ◽  
Molecular Genetic ◽  
Specific Gene ◽  
Genetic Sexing ◽  
Experimental Conditions ◽  
Two Samples

AbstractFish can be threatened by distorted sex ratios that arise during sex differentiation. It is therefore important to understand sex determination and differentiation, especially in river-dwelling fish that are often exposed to environmental factors that may interfere with sex differentiation. However, sex differentiation is not sufficiently understood in keystone taxa such as the Thymallinae, one of the three salmonid subfamilies. Here we study a wild grayling (Thymallus thymallus) population that suffers from distorted sex ratios. We found sex determination in the wild and in captivity to be genetic and linked to the sdY locus. We therefore studied sex-specific gene expression in embryos and early larvae that were bred and raised under different experimental conditions, and we studied gonadal morphology in five monthly samples taken after hatching. Significant sex-specific changes in gene expression (affecting about 25,000 genes) started around hatching. Gonads were still undifferentiated three weeks after hatching, but about half of the fish showed immature testes around seven weeks after hatching. Over the next few months, this phenotype was mostly replaced by the “testis-to-ovary” or “ovaries” phenotypes. The gonads of the remaining fish, i.e. approximately half of the fish in each sampling period, remained undifferentiated until six months after fertilization. Genetic sexing of the last two samples revealed that fish with undifferentiated gonads were all males, who, by that time, were on average larger than the genetic females (verified in 8-months old juveniles raised in another experiment). Only 12% of the genetic males showed testicular tissue six months after fertilization. We conclude that sex differentiation starts around hatching, goes through an all-male stage for both sexes (which represents a rare case of “undifferentiated” gonochoristic species that usually go through an all-female stage), and is delayed in males who, instead of developing their gonads, grow faster than females during these juvenile stages.Author contributionMRR and CW initiated the project. DM, OS, AU, LMC, LW, and CW sampled the adult fish, did the experimental in vitro fertilizations, and prepared the embryos for experimental rearing in the laboratory. All further manipulations on the embryos and the larvae were done by DM, OS, AU, LMC, and LW. The RNA-seq data were analyzed by OS, JR, and MRR, the histological analyses were done by DM, supervised by SK, and the molecular genetic sexing was performed by DM, OS, AU, and KBM. DM, OS, and CW performed the remaining statistical analyses and wrote the first version of the manuscript that was then critically revised by all other authors.

scholarly journals The Monthly Variation Process of Water Temperature in Jiaozhou Bay

2019 ◽  
Vol 136 ◽  
pp. 06015
Author(s):  
Dongfang Yang ◽  
Haoyuan Ren ◽  
Dong Yang ◽  
Longlei Zhang ◽  
Haixia Li
Keyword(s):  
Water Temperature ◽  
Jiaozhou Bay ◽  
High Water ◽  
Water Bodies ◽  
Interval Length ◽  
Monthly Variation ◽  
High Water Temperature ◽  
Water Field ◽  
Variation Process ◽  
Peak Value

According to the investigation materials in the water field of Jiaozhou Bay from May to October 1980, this paper studies the water temperature of Jiaozhou Bay and the monthly variation. The results show that in each monthfrom May to October, the water temperature varies from 10.80 to 26.53 °C in the waters of Jiaozhou Bay, and the interval length of water temperature is 15.73 °C. This paper determines the changing curve of the high or low value of the water temperature ateach month and establishes the corresponding simulation equation.The high water temperature reaches a maximum of 26.53 °C in August, and the low water temperature reaches a maximum of 24.69 °C in August. In the water bodies of Jiaozhou Bay, the high or low water temperature both reaches its highest value in August. In June, the increasing rate of peak value in water temperature is the fastest, and the increasing rate of low value in water temperature is relatively fast. In October, the decreasing rate of the peak water temperature is relatively fast, and decreasing rateof the lowest value in water temperature is the fastest. From May to August, the high (low) water temperature is on the rise in Jiaozhou Bay. The high water temperature appears in the western waters of the top of bay and the western waters inside of bay mouth. The low water temperature appears in the eastern and southern waters outside of bay mouth. In September and October, the high (low) water temperature in the Jiaozhou Bay water bodies is decreasing. The high water temperature appears in the eastern and southern waters outside of bay mouth, and the low water temperature appears in the western waters of the bayhead.

scholarly journals The breeding ecology of the pipefish Nerophis lumbriciformis and its relation to latitude and water temperature

2001 ◽  
Vol 81 (6) ◽  
pp. 1031-1033 ◽  
Author(s):  
N. Monteiro ◽  
V.C. Almada ◽  
A.M. Santos ◽  
M.N. Vieira
Keyword(s):  
Water Temperature ◽  
Breeding Season ◽  
Marked Reduction ◽  
High Water ◽  
Inhibitory Effect ◽  
Breeding Ecology ◽  
High Water Temperature ◽  
Temporal Differences ◽  
Breeding Activity ◽  
Different Temperatures

The breeding season of Nerophis lumbriciformis (Pisces: Syngnathidae), has not yet been determined for the southernmost part of its range. A total of 863 individuals was examined between March 1997 and November 1999. In Portugal, the breeding season of this species occurs throughout the year, with a marked reduction during summer and autumn, whilst in Britain it occurs from May to September. Despite these temporal differences, the water temperature at which breeding takes place is similar in the two areas (13–16°C). Together with preliminary laboratory observations with animals kept at different temperatures, these data support the hypothesis that the decrease in breeding activity during summer and autumn in Portugal is due to an inhibitory effect of high water temperature.

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