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

 – Among the species in the family Salmonidae, those represented by the genera Salmo, Salvelinus, and Oncorhynchus (subfamily Salmoninae) are the most studied. Here, various aspects of phenotypic and life-history variation of Atlantic salmon Salmo salar L., brown trout Salmo trutta L., and Arctic charr Salvelinus alpinus (L.) are reviewed. While many strategies and tactics are commonly used by these species, there are also differences in their ecology and population dynamics that result in a variety of interesting and diverse topics that are challenging for future research. Atlantic salmon display considerable phenotypic plasticity and variability in life-history characters ranging from fully freshwater resident forms, where females can mature at approximately 10 cm in length, to anadromous populations characterised by 3–5 sea-winter (5SW) salmon. Even within simple 1SW populations, 20 or more spawning life-history types can be identified. Juveniles in freshwater can use both fluvial and lacustrine habitats for rearing, and while most smolts migrate to sea during the spring, fall migrations occur in some populations. At sea, some salmon undertake extensive oceanic migrations while other populations stay within the geographical confines of areas such as the Baltic Sea. At the other extreme are those that reside in estuaries and return to freshwater to spawn after spending only a few months at sea. The review of information on the diversity of life-history forms is related to conservation aspects associated with Atlantic salmon populations and current trends in abundance and survival. Brown trout is indigenous to Europe, North Africa and western Asia, but was introduced into at least 24 countries outside Europe and now has a world-wide distribution. It exploits both fresh and salt waters for feeding and spawning (brackish), and populations are often partially migratory. One part of the population leaves and feeds elsewhere, while another part stays as residents. In large, complex systems, the species is polymorphic with different size morphs in the various parts of the habitat. Brown trout feed close to the surface and near shore, but large individuals may move far offshore. The species exhibits ontogenetic niche shifts partly related to size and partly to developmental rate. They switch when the amount of surplus energy available for growth becomes small with fast growers being younger and smaller fish than slow growers. Brown trout is an opportunistic carnivore, but individuals specialise at least temporarily on particular food items; insect larvae are important for the young in streams, while littoral epibenthos in lakes and fish are most important for large trout. The sexes differ in resource use and size. Females are more inclined than males to become migratory and feed in pelagic waters. Males exploit running water, near-shore and surface waters more than females. Therefore, females feed more on zooplankton and exhibit a more uniform phenotype than males. The Arctic charr is the northernmost freshwater fish on earth, with a circumpolar distribution in the Holarctic that matches the last glaciation. Recent mtDNA studies indicate that there are five phylogeographic lineages (Atlantic, Arctic, Bering, Siberian and Acadian) that may be of Pleistocene origin. Phenotypic expression and ecology are more variable in charr than in most fish. Weights at maturation range from 3 g to 12 kg. Population differences in morphology and coloration are large and can have some genetic basis. Charr live in streams, at sea and in all habitats of oligotrophic lakes, including very deep areas. Ontogenetic habitat shifts between lacustrine habitats are common. The charr feed on all major prey types of streams, lakes and near-shore marine habitats, but has high niche flexibility in competition. Cannibalism is expressed in several cases, and can be important for developing and maintaining bimodal size distributions. Anadromy is found in the northern part of its range and involves about 40, but sometimes more days in the sea. All charr overwinter in freshwater. Partial migration is common, but the degree of anadromy varies greatly among populations. The food at sea includes zooplankton and pelagic fish, but also epibenthos. Polymorphism and sympatric morphs are much studied. As a prominent fish of glaciated lakes, charr is an important species for studying ecological speciation by the combination of field studies and experiments, particularly in the fields of morphometric heterochrony and comparative behaviour.

https://onlinelibrary.wiley.com/doi/pdf/10.1034/j.1600-0633.2003.00010.x

Atlantic salmon Salmo salar L., brown trout Salmo trutta L. and Arctic charr Salvelinus alpinus (L.): a review of aspects of their life histories

Spermatogenesis in fish.

Androgens in teleost fishes

Interaction between growth and reproduction occurs in many vertebrates and is particularly obvious at certain stages of the life cycle in fish. Endocrine interactions between the gonadotropic axis and the somatotropic axis are described, the potential role of GH being emphasised. A comparative analysis of these phenomena in mammals, amphibians and fish, suggests a specific role of GH in the physiology of puberty, gametogenesis and fertility. It also shows the original contribution made by studies on the fish model in this field of investigations.

/pdf/growth-hormone-gh-and-reproduction-a-review-16wafhysuq.pdf

Growth hormone (GH) and reproduction: a review

Changes in plasma and gonadal steroid hormones in relation to the reproductive cycle and the sex inversion process in the protandrous seabass, Lates calcarifer.

/pdf/the-modulatory-effect-in-vitro-of-oestradiol-17b-wa5ivddw1v.pdf

The modulatory effect in vitro of oestradiol-17β, testosterone or cortisol on the output of 17α-hydroxy-20β-dihydroprogesterone by rainbow trout (Salmo gairdneri) ovarian follicles stimulated by the maturational gonadotropin s-GtH

Changes of growth hormone receptivity in the ovary during the reproductive cycle were studied in rainbow trout (Oncorhynchus mykiss). A method for characterizing growth hormone receptors in crude ovary homogenate was required for this. Binding of radiolabelled recombinant rainbow trout growth hormone ( 125 I-labelled rtGH) to crude ovary preparation was dependent on ovarian tissue concentration. The sites were specific to growth hormone, with no affinity for prolactins and gonadotrophins. Similar high affinities for 125 I-labelled rtGH were obtained with crude ovary (4.2 × 10 9 ± 0.3 mol l -1 ) and crude liver preparations (4.9 × 10 9 ± 0.1 mol l -1 ) at all stages of ovogenesis, and with ovarian membrane preparations (8.2 × 10 9 mol l -1 ) tested at the beginning of vitellogenesis. Ovarian growth hormone receptor concentration was highest during the early phases of follicular development (endogenous vitellogenesis: 315-310 fmol g -1 ovary) and decreased regularly during oocyte and follicular growth (exogenous vitellogenesis) to reach a minimal value at oocyte maturation (42 fmol g -1 ovary). In postovulated fish, binding was at a similar level (297 fmol g -1 ovary) to that found in endogenous vitellogenesis. Conversely, the absolute binding capacity of the whole ovary was low from immaturity to early exogenous vitellogenesis (0.1-0.6 pmol per pair of gonads), increased slowly during vitellogenesis and more markedly during rapid oocyte growth and at the time of final maturation (10.8 pmol per pair of gonads). In postovulated fish, the absolute binding capacity decreased partially (4.4 pmol per pair of gonads). Mean hepatic growth hormone receptor concentration did not vary with the reproductive stage for most of the cycle (3.0-4.5 pmol g -1 liver) except in endogenous vitellogenesis where significantly higher concentrations were observed (6.7 pmol g -1 liver). Individual ovarian growth hormone receptor concentrations were correlated with hepatic growth hormone receptor concentrations, indicating that they are regulated in a similar way. We conclude that growth hormone receptors are present in the ovary during the entire ovarian cycle in rainbow trout, probably mainly in somatic cells as indicated by the same concentration of binding sites in immature and in postovulated fish. Growth hormone is potentially important during oocyte recruitment in vitellogenesis and initiation of growth and during final follicular maturation.

/pdf/growth-hormone-receptors-in-ovary-and-liver-during-3ir3e7m1br.pdf

Growth hormone receptors in ovary and liver during gametogenesis in female rainbow trout (Oncorhynchus mykiss).

The reproductive cycle and sex inversion of the protandrous, tropical seabass, Lates calcarifer, reared in seacages in French Polynesia, were studied. In Tahiti, this species exhibits a single annual reproductive period from October to February beginning with the warm and wet season. Sex inversion begins at the end of this reproductive period in post-spawning males. The main histological features of this process were: degeneration of testicular tissue, appearance of peripheral female germinal cells, and centripetal proliferation of ovarian tissue. Completion of sex inversion required profound morphological changes in the gonads because of the strong dimorphism that exists between testis and ovary. All transitional gonads appeared morphologically smaller than testes and typically had a red-pink colour. About 45% of the three-year-old male stock underwent sex inversion, and males averaged smaller in size than did females and transitional fish.

Reproductive cycle and sex inversion of the seabass, Lates calcarifer, reared in sea cages in French Polynesia: histological and morphometric description.

A. Fostier

Papers

Growth hormone (GH) and reproduction: a review

Changes in plasma and gonadal steroid hormones in relation to the reproductive cycle and the sex inversion process in the protandrous seabass, Lates calcarifer.

The modulatory effect in vitro of oestradiol-17β, testosterone or cortisol on the output of 17α-hydroxy-20β-dihydroprogesterone by rainbow trout (Salmo gairdneri) ovarian follicles stimulated by the maturational gonadotropin s-GtH

Growth hormone receptors in ovary and liver during gametogenesis in female rainbow trout (Oncorhynchus mykiss).

Reproductive cycle and sex inversion of the seabass, Lates calcarifer, reared in sea cages in French Polynesia: histological and morphometric description.