O presente trabalho teve como objetivo estudar a morfologia e fisiologia reprodutiva de Lobotes surinamensis em ambiente natural, reunindo informações que permitam trabalhos aplicados na produção e conservação desta espécie. Machos e fêmeas adultos foram coletados na Baía da Ilha Grande, Rio de Janeiro durante a primavera (outubro-novembro-dezembro), verão (janeiro-fevereiro-março), outono (abril-maio-junho) e inverno (julho-agosto-setembro). Os perfis plasmáticos dos esteroides gonadais, 17β-estradiol (E2), 17-hidroxiprogesterona (17-OHP) e 11-cetotestosterona (11-KT) foram analisados em fêmeas, e a concentração de testosterona (T) e 11-KT nos machos. Análises histológicas das gônadas foram realizadas como uma ferramenta para avaliação morfológica, que foi corroborada com os dados fisiológicos, durante o ciclo reprodutivo. Foram analisadas ainda a expressão gênica hipofisária do fshβ e lhβ e a fecundidade relativa pelo número de oócitos desenvolvidos. Durante a primavera e verão, as fêmeas estavam com os ovários desenvolvidos e capazes de desovar, com oócitos vitelogênicos e desenvolvidos, e membrana radiata bem evidente. No outono e inverno, as fêmeas estavam se preparando para o período reprodutivo, com predomínio de ninhos de oogônias e oócitos perinucleolares de uma forma geral. A concentração plasmática de E2 se manteve elevada nas fêmeas durante a primavera em relação ao verão e outono/inverno. O perfil anual deste esteroide nas fêmeas de L. surinamensis pode ser relacionado com o grau de desenvolvimento do folículo ovariano, observado na histologia. Já a concentração plasmática de 11-KT foi inversa ao observado para o E2, com baixa concentração na primavera e tendência à elevação no inverno, corroborando com o papel da 11-KT no crescimento primário dos oócitos. A concentração plasmática de 17-OHP nas fêmeas não apresentou diferenças significativas entre as estações, o que sugere que este não seja o progestágeno ativo em teleósteos, mas sim o precursor do esteroide indutor da maturação final (MIS). Na primavera e no verão, o lhβ apresentou expressão maior do que no período outono/inverno em fêmeas, enquanto o fshβ se manteve com níveis de expressão constante durante todas as estações. Nos machos, a análise histológica dos testículos, mostrou que na primavera e no verão, os ductos espermáticos estavam preenchidos com espermatozoides, evidenciando o período de espermiação, já no período outono/inverno houve predominância de cistos de espermatogônias e as células em diferentes estágios de desenvolvimento, o que corresponde a uma fase de maturação inicial, ou seja, preparação para o período reprodutivo. A concentração plasmática de T nos machos se manteve estável ao longo das estações, já a concentração plasmática de 11-KT foi mais elevada na primavera quando comparada ao período outono/inverno. Na primavera e verão, a expressão de lhβ foi mais elevada que no período outono/inverno, enquanto de forma similar às fêmeas, os níveis de expressão de fshβ não se alteraram ao longo das estações. As análises de expressão destas gonadotropinas, associadas à concentração dos esteroides gonadais e à morfologia gonadal deixou evidente que o pico do período reprodutivo de L. surinamensis ocorre na primavera, estendendo-se até o verão / The present study aimed to study the morphology and reproductive physiology of Lobotes surinamensis in a natural environment, gathering information that allows applied works in the production and conservation of this species. Adult males and females were collected in the Baía da Ilha Grande, Rio de Janeiro during the spring (October-November-December), summer (January-February-March), autumn (April- May-June) and winter (July-August-September). Plasma profiles of gonadal steroids, 17β-estradiol (E2), 17-hydroxyprogesterone (17-OHP) and 11-ketotestosterone (11-KT) were analyzed in females, and the concentration of testosterone (T) and 11-KT in males. Histological analyzes of the gonads were performed as a tool for morphological evaluation, which was corroborated with the physiological data, during the reproductive cycle. The genetic expression of fshβ and lhβ and the relative fecundity by the number of developed oocytes were also analyzed. During spring and summer, the females had the ovaries developed and capable of spawning, with vitellogenic and developed oocytes, and a well evident radiata zone. In autumn and winter, females were preparing for the reproductive period, with a predominance of nest of oogonia and perinucleolar oocytes in general. The plasma concentration of E2 remained higher in females during the spring in relation to summer and autumn/winter. The annual profile of this steroid in L. surinamensis females may be related to the degree of development of the ovarian follicle observed in histology. The plasma concentration of 11-KT was inversely of that observed for E2, with a low concentration in the spring and a tendency to increase in winter/autumn, corroborating the role of 11-KT in the primary oocyte growth. The plasma concentration of 17-OHP in the females did not present significant differences between the seasons, suggesting that this is not the active progestogen in teleosts, but the precursor of the final maturation inducing steroid (MIS). In spring and summer, lhβ presented higher gene expression than in the autumn/winter period in females, while fshβ remained with constant expression levels during all seasons. In males, the histological analysis of the testicles showed that in the spring and summer, the sperm ducts were filled with spermatozoa, evidencing the period of spermiation, whereas in the autumn/winter period there was a predominance of cysts of spermatogonia and cells in different stages of. development, which corresponds to an initial maturation stage, that is, the preparation for the reproductive period. The plasma concentration of T in males remained stable throughout the seasons, whereas the plasma concentration of 11-KT was higher in the spring when compared to the autumn/winter period. In spring and summer, the expression of lhβ was higher than in the autumn/winter period, while similarly to females, fshβ expression levels did not change over the seasons. The analysis of the expression of these gonadotropin genes, associated with the concentration of gonadal steroids and gonadal morphology, made it evident that the peak of the reproductive period of L. surinamensis occurs in the spring, extending until the summer

In the past, oceans have strongly influenced atmospheric CO2 levels through organic and inorganic carbon cycling. The inorganic carbon pump relies on the formation of calcium carbonate which releases CO2 into the surface ocean and traps alkalinity in solid form which sinks to deeper ocean layers and sediments. After sinking, calcium carbonate can either then become trapped in the sediments or dissolve increasing the alkalinity of deeper ocean layers. The net effect is of acidifying surface oceans and encouraging release of CO2 to the atmosphere. The present thesis focuses on marine teleost (bony) fish in temperate areas as previously poorly understood but potentially major producers of calcium carbonate in the ocean. Fish in temperate areas may be contributing to carbonate sediment production and as such the inorganic carbon pump. Prior to this thesis only tropical fish have been investigated as major piscine sediment producers. The present thesis describes the composition and morphology of carbonates produced by many different species of temperate fish providing a basis for the understanding the fate of these carbonates in the environments and their potential contribution to sediment production and the inorganic carbon cycle. Characteristics of carbonates produced by fish in the wild were fairly consistent within a species upon examination of carbonates produced by poor cod (Trisopterus minutus) over the course of a year. However, despite the likely consistent and distinct characteristics of fish carbonates, little evidence of them was found in temperate shallow sediments beneath pens of farmed Atlantic salmon (Salmo salar) where there theoretically should be very high production rates. Reduced salinity, often a feature of temperate areas compared to tropical areas, was found to reduce production rates of carbonate from fish compared to higher salinities. However, salinity reductions below the ocean average of 35 psu (practical salinity units) had less impact on production rates than increases above 35 psu. As such it is argued that production rates in temperate environments should still be relatively high considering high fish biomasses in some temperate regions and could still mean fish in temperate areas are an important source of carbonate production and potential sediment production.

Osmoregulation is an essential process to maintain water and ionic balance and when euryhaline fish move between freshwater and seawater environments as part of their life cycle this presents additional osmoregulatory challenges. Migrating fish can be exposed in both environments to pollutants such as endocrine disrupting chemicals (EDCs) that include natural hormones (e.g. 17β-estradiol; E2), synthetic hormones (e.g. 17α-ethinylestradiol; EE2), and industrial chemicals (e.g. nonylphenol). The focus of this thesis was to study the effects of different categories of EDCs on the osmoregulatory functions of euryhaline fish such as three-spined sticklebacks (Gasterosteus aculeatus) and rainbow trout (Oncorhynchus mykiss). Osmoregulatory variables (such as osmolality, water and ionic content) were compared in plasma and tissues (white muscle and carcass) of rainbow trout. This validated the use of specific tissue parameters as a surrogate of plasma responses to various osmoregulatory challenges. Waterborne exposure to 17α-ethinylestradiol revealed differential sensitivity of vitellogenesis in the three-spined sticklebacks (no induction) and rainbow trout, but had a significant effect on calcium homeostasis in both species. Intraperitoneal implants of 17β-estradiol reduced CaCO3 production and apparent water absorption in the intestine and increased in tissue calcium stores of seawater-acclimated trout, but fish were able to compensate and showed no overall osmoregulatory disturbance. Waterborne exposure to nonylphenol in freshwater trout was also investigated, but no effects on osmoregulation were found up to 2 ng/l. Overall, estrogens can affect osmoregulation differentially in euryhaline fish species, and sometimes at EDC levels lower than the threshold for reproductive effects (i.e. vitellogenin induction).