Androgens in teleost fishes

Publisher Summary This chapter discusses the functional morphology of teleost gonads. Information presented in this chapter indicates that there are several processes of germ cell development, which are closely associated with changes in cellular activities of somatic cell elements. Recent studies on biochemical aspects of vitellogenesis in teleosts have shown that the hepatic and ovarian yolk proteins are similar to those of amphibian species. An in vitro method involving the separation of the follicular components has facilitated investigations of the detailed mechanism of the production of two major follicular steroid hormones. As a result of the usage of this technique, a two cell-type model involving thecal and granulosa cell layers has been proposed for the production of these two steroids for the first time in lower vertebrates. With further refinements this well characterized incubation procedure should provide an excellent system for studying the molecular basis of the mechanism of gonadotropin action on follicular steroidogenesis.

6 The Functional Morphology of Teleost Gonads

http://digital.csic.es/bitstream/10261/44729/1/Taranger%20et%20al_%2c%20GCE.pdf

Control of puberty in farmed fish

Summary The great diversity of life-history patterns in the salmonids has stimulated many theoretical studies However, virtually all studies are based on ultimate considerations, in which predictions are made by comparing the expected reproductive success of diAerent developmental or life-history pathways and choosing the one (or ones) with the highest fitness Such models are post hoc because they attribute fitness to individuals at the completion of the particular phase of the life cycle and do not attempt to characterize the mechanisms that animals use to achieve the life-history pattern We describe a model, based on proximate considerations, for salmonid life histories, focused on Atlantic salmon Salmo salar L The model involves identification of the times at which developmental conversions are initiated or inhibited and the connection between physiological states and the thresholds for such conversions Developmental paths are based on the comparison of the current physiological status of the fish (and its change of state) with a genetic threshold The state of the fish and rate of change of state are determined by environmental opportunity, but the threshold is genetic This approach therefore immediately generates a genotype‐environment interaction We use expected reproductive success to determine the fitness of individuals with diAerent genetically determined thresholds Instead of finding an optimal life history, our theory generates fitness surfaces for diAerent life histories, so that variation is inherent in this approach We describe and explain the structure of the model and present evidence on which this structure is based, thus providing a framework within which one can understand how ecology relates to the physiological mechanisms leading to the developmental changes of smolt metamorphosis and maturation

Modelling the proximate basis of salmonid life-history variation, with application to Atlantic salmon, Salmo salar L.

We provide evidence that in male Atlantic salmon (Salmo salar) parr, maturation is suppressed when mesenteric fat fails to exceed an undefined level by May. In nonmaturing parr the postwinter incre...

Role of Fat Stores in the Maturation of Male Atlantic Salmon (Salmo salar) Parr

Levels of 11-oxotestosterone (17 β-hydroxyandrost-4-ene-3, 11-dione) and testosterone in the blood serum of individually marked adult male Atlantic salmon held in captivity, were measured by radioimmunoassay at approximately monthly intervals for periods of up to 18 months. In addition to peak concentrations of both hormones shown by all the maturing fish at the time to full sexual maturation during October and November, a majority of maturing fish also showed a significant elevation of 11-oxotestosterone during the early months of the year. The possible involvement of this early elevation of 11-oxotestosterone in controlling the mitotic multiplication of spermatogonia is discussed. Weight and length increases expressed as specific values GW and GL and weight to length relationships for the maturing males for each sampling period are presented and compared with those of non-maturing fish.

Seasonal changes in the levels of 11‐oxotestosterone and testosterone in the serum of male salmon, Salmo salar L., and their relationship to growth and maturation cycle

S. V. Hunt

Papers

Seasonal changes in the levels of 11‐oxotestosterone and testosterone in the serum of male salmon, Salmo salar L., and their relationship to growth and maturation cycle

Steroid biosynthesis in the testis of dogfish (squalus acanthias).

Sex hormones in fish. The oestrogens of cod (Gadus callarias).

Sex hormones in fish. ii. the oestrogens of scyliorhinus caniculus.

Steroid biosynthesis in vitro by the component tissues of the ovary of dogfish (Scyliorhinus caniculus L.).