http://aerg.canberra.edu.au/library/sex_general/2002_Devlin_Nagahama_sex_determination_in_fish_review.pdf

Sex determination and sex differentiation in fish: an overview of genetic, physiological, and environmental influences

Physiological changes in fish from stress in aquaculture with emphasis on the response and effects of corticosteroids

The lipid composition and biochemistry of freshwater fish.

Spermatogenesis in fish.

Oogenesis in teleosts: How fish eggs are formed

Publisher Summary This chapter discusses that the gonads potentiality to produce steroids, and the regulation of the syntheses. The nature, shape, and intensity of a hormonal signal, ready to be received by a target cell, is the result of an intricate series of positive and negative regulations. In the case of hormonal steroids in fish, only some aspects of this complex have been considered. Once a steroid is secreted, several mechanisms may inactivate it before it reaches its target. Little is known of catabolism of sexual steroids in teleosts. Most available data are concerned with the total radioactivity found in tissues after fish are fed labeled steroid. The biological significance of glucuronidation or sulfonation remains to be explored. Although the conjugated steroids are usually considered to be inactive, recent studies attribute a pheromonal role to glucuronides. In other respects, the binding to plasma proteins may lead to a reversible inactivation, although, in mammals, it has been suggested that steroid secretion may be enhanced by the presence of serum steroid-binding proteins. Finally, the conversion of plasma steroids into biologically active metabolites can occur in some target tissues. The actual physiological role of gonadal steroids in fish is discussed with emphasis on gametogenesis.

7 The Gonadal Steroids

Up to now, temperature sex differentiation has been demonstrated in a single fish species, #Menidia menidia# This study analyzes this hypothesis in #Oreochromis niloticus# Treatments at 36 °C, covering the hormone sensitive period, increased the proportion of males (33% to 81%)The male proportion was affected by treatments starting not later than 13 days after fertilization and lasting 10 days or more Survival rates were not affected by treatments Functional masculinization of genetic females was demonstrated by the sex-ratio analysis of 10 temperature-treated males Sex reversal by temperature treatment was also confirmed on a genotypic female population The response to temperature strongly depends upon the breeding pairs Hight temperatures override sex chromosome influence in #Oreochromis niloticus# Therefore, #Oreochromis niloticus# sex is determined by genetic factors, temperature level, and genotype-temperature interactions Temperature-dependent sex differentiation may occur more frequently in fish than previously thought, despite the presence of functional sex chromosomes (Resume d'auteur)

Temperature and sex chromosomes govern sex ratios of the mouthbrooding Cichlid fish Oreochromis niloticus

Compared to mammals, teleost reproduction presents many original features. Reproductive strategies of species are diversified into numerous adaptations to a large variety of aquatic environments. This diversity may concern sexuality, spawning and parental behaviour, sensitivity to environmental factors, and specific features of gametogenesis such as the duration of vitellogenesis, and egg morphology. Sexuality presents a variety of natural modalities, from gonochorism to hermaphrodism. The absence of definitive arrest of body growth in the adult of most species gives a particular interest to the practical control of growth-reproduction interactions. Vitellogenesis, which represents an important metabolic effort for the maternal organism, involves the synthesis of vitellogenin, a specific glycolipo-phosphoprotein produced in the liver under estradiol stimulation, and its incorporation into oocytes by a receptor mediated process. Both estradiol synthesis in follicle cells and vtg uptake by vitellogenic follicles appear to be mainly controlled by FSH. Oocyte maturation is directly triggered by a progestin, or MIS (maturation inducing steroid) synthesised in follicle cells mainly under LH control, and acting through the non-genomic activation of a membrane receptor. Practical applications of some of these particularities result mainly from the external character of the fertilisation process and of embryonic development, which allows manipulating respectively egg chromosome stocks and sex differentiation. Moreover, the sensitivity of sex differentiation to exogenous factors favours the development of practical methods to control the sex of farmed populations. Finally, the sensitivity of reproductive mechanisms to xenobiotics has led to various kinds of bioassays for putative pollutants.

/pdf/particularities-of-reproduction-and-oogenesis-in-teleost-3gl1u4hoek.pdf

Particularities of reproduction and oogenesis in teleost fish compared to mammals.

Effects of post-ovulatory oocyte ageing and temperature on egg quality and on the occurrence of triploid fry in rainbow trout, Oncorhynchus mykiss.

The mRNA levels of 39 target genes were monitored in unfertilized eggs of 14 rainbow trout sampled the day of ovulation and again 5, 14, and 21 days later. For all 56 collected egg batches, an egg sample was fertilized to estimate egg quality by monitoring embryonic development. Remaining eggs were used for RNA extraction and subsequent real-time PCR analysis. A significant drop of egg quality was observed when eggs were held in the body cavity for 14 or 21 days post-ovulation (dpo). During the same period, eight transcripts (nucleoplasmin or Npm2, ferritin H, tubulin β, JNK1, cyclin A1, cyclin A2, cathepsin Z, and IGF2) exhibited a differential abundance at one or several collection time(s). Interestingly, we observed higher levels of cyclins A1 and A2 mRNAs in eggs taken 5 days post-ovulation than in eggs taken, from the same females, at the time of ovulation. In addition, seven transcripts exhibited a differential abundance between low quality and high quality eggs. Low quality eggs were characterized by lower levels of Npm2, tubulin β, and IGF1 transcripts. In contrast, keratins 8 and 18, cathepsin Z, and prostaglandin synthase 2 were more abundant in low quality eggs than in high quality eggs. In this study, we have demonstrated differences in mRNA levels in the rainbow trout egg that are reflective of developmental competence differences induced by post-ovulatory ageing. The putative role of these transcripts in post-ovulatory ageing-induced egg quality defects is discussed with special attention for corresponding cellular functions. Mol. Reprod. Dev. © 2005 Wiley-Liss, Inc.

Bernard Jalabert

Papers

7 The Gonadal Steroids

Temperature and sex chromosomes govern sex ratios of the mouthbrooding Cichlid fish Oreochromis niloticus

Particularities of reproduction and oogenesis in teleost fish compared to mammals.

Effects of post-ovulatory oocyte ageing and temperature on egg quality and on the occurrence of triploid fry in rainbow trout, Oncorhynchus mykiss.

Large scale real-time PCR analysis of mRNA abundance in rainbow trout eggs in relationship with egg quality and post-ovulatory ageing.