Rudã Fernandes Brandão Santos

Coral reefs are among the most productive marine ecosystems, sustained by the tight coupling between physiological processes and environmental conditions, in which nutrition plays a central regulatory role. This review synthesizes the multifactorial nutritional ecology of tropical scleractinian corals, emphasizing how autotrophic and heterotrophic pathways are dynamically integrated to support metabolic performance, calcification, and stress resilience. Particular attention is given to the acquisition, assimilation, and functional roles of key—macronutrients (nitrogen-containing compounds and lipids) and micronutrients (essential minerals and trace elements)—in regulating symbiotic stability and holobiont homeostasis, while explicitly distinguishing a coral’s carbon budget—which tracks the sources and sinks of carbon-containing molecules—from its energy budget, which additionally requires conversion of these molecules into caloric equivalents relative to metabolic demand. We further examine trophic plasticity as a central adaptive mechanism, enabling corals to adjust energy acquisition strategies under environmental stressors such as thermal anomalies, ocean acidification, and eutrophication. This includes shifts in feeding rates, prey selectivity, and reliance on dissolved and particulate organic matter, which collectively determine the capacity for metabolic compensation during periods of reduced autotrophic input. In addition, we evaluate emerging approaches in coral nutrition research, including artificial diets, probiotic-based interventions, and biochemical and isotopic markers. By integrating experimental and biogeochemical evidence, we demonstrate that nutrient availability, stoichiometric balance, and environmental drivers jointly regulate coral performance through tightly coupled metabolic feedbacks, positioning a species’ “nutritional niche”—its capacity for compensatory heterotrophy relative to its dependence on symbiont-derived carbon—as a primary determinant of resilience under global change. Overall, this review advances a mechanistic framework in which coral nutrition is understood as an integrated, dynamic system, linking resource acquisition, metabolic allocation, and environmental variability, with direct implications for predicting coral resilience under ongoing climate change.

Zinc is an essential metal to living organisms, including corals and their symbiotic microalgae (Symbiodiniaceae). Both Zn(II) deprivation and overload are capable of leading to dysfunctional metabolism, coral bleaching, and even organism death. The present work investigated the effects of chemically defined Zn species (free Zn, ZnO nanoparticles, and the complexes Zn-histidinate and Zn-EDTA) over the growth of the dinoflagellates Symbiodinium microadriaticum, Breviolum minutum, and Effrenium voratum, and on the trypsin-like proteolytic activity of the hydrocoral Millepora alcicornis. B. minutum was the most sensitive strain to any form of added Zn. For the other strains, the complex [Zn(His)₂] better translated metal load into growth. This complex was the only tested compound that did not interfere with the trypsin-like activity of Millepora alcicornis extracts. Also, histidine was able to recover the activity of the enzyme inhibited by zinc. [Zn(His)₂] is a potential biocarrier of zinc for microalgae or coral cultivation. These findings suggest that the control of chemical speciation of an essential metal could lead to useful compounds that assist autotrophy, while not affecting heterotrophy, in the coral holobiont.

The objective of this study was to evaluate the effects of three levels of lipids in the diet on growth, metabolism, and intestinal and hepatic histopathology in discus fish (Symphysodon aequifasciatus). Fish were stocked in quadruplicate in aquarium (50L) and were fed experimental diets containing three levels (3%, 10%, and 14%) of dietary lipids (LP). At the end of the trial, no significant differences in growth performance were observed. Fish fed diets with 3% and 10% LP exhibited significantly higher protein efficiency rates compared to those fed the 14% LP diet. A significant increase in lipase and alkaline phosphatase activity was observed in fish fed 14% LP diets. The inclusion of 14% lipids in the diet led to a decrease in albumin activity and an increase in the height of the intestinal villi. Although no significant differences were observed in aspartate aminotransferase, alanine aminotransferase activities, and size of hepatocytes. The histopathology of the liver indicated reduced hepatocyte size, lipid vacuoles, and sinusoidal space in the group fed the 3% LP diet. In conclusion, the use of 10% LP diet was found to be more favorable for liver health and growth performance.

This study evaluated the growth performance and parasite load of angelfish juveniles Pterophyllum scalare kept at different stocking densities using two rearing systems. The experiment was conducted in a factorial design (4x2) with four stocking densities (0.1, 0.4, 0.7, and 1.0 g/L), two type of aquarium tanks (glass and ceramic aquariums), and four replicates. The experiment lasted 60 days using 148 juvenile fish (3.05 ± 0.09 g) randomly placed in 32 aquariums (50 L) equipped with filters and aeration. All fish received two meals a day ad libitum (8:00 and 16:00). Water quality parameters such as temperature, dissolved oxygen, pH, and total ammonia were measured. At the end of the experiment, all fish were measured and weighed to determine growth performance and then subjected to parasitological analysis. The data were analyzed with a two-way ANOVA with post-hoc Tukey test (pCapillaria pterophylli infestation in the high stocking density within ceramic aquariums. Thus, this study recommends the use of 1.0 g/L for the intensive aquaculture system of freshwater angelfish, and applying cleaning management to avoid parasite infestation, particularly in ceramic aquariums.

The selection of ingredients is an important aspect for diets formulation for fish in captivity. The use of fruit industry by-products can be an alternative for inclusion in diets for ornamental fish, as discus fish case, to improve health and reduction of production costs, further to reducing the environmental impacts of fruits industries residues. The objective the studies was to evaluate the bioavailability of fruit industry by-products in the diet for discus fish by coefficients of digestibility. The digestibility of three by-products: pineapple by-product, mango by-product, and passion fruit by-product were evaluated. Thirty-two discus fish (106 ± 26.6 g) were distributed in 4 tanks for feeding and fecal collection, constituting an experimental design in Latin square (4 diets test- x 4 periods of fecal collection x 4 replicates). The three by-products had digestibility coefficients above 80%, 70%, and 69% for dry matter, protein, and fat, respectively, being possible to use them as a source of these nutrients in diets for the discus fish. However, it was observed that the mango and passion fruit by-product had the lowest energy digestibility coefficient, with bioavailabilities less than 50% of utilization. The co-products of the fruit processing industry tested in this work have nutritional conditions to be used as food for root discs. The use of these co-products as food for ornamental fish can be an alternative use and value.

The aim of this study was to evaluate the chronic salinity tolerance of Carassius auratus and the effects on blood parameters, gill morphology, and survival. In the first test, nine different concentrations (0.0, 0.5, 1.0, 2.5, 5.0, 10, 15, 20, and 25 g L-1) of NaCl were used with nine repetitions for 96 h. The survival of fish subjected to 15 g L-1 NaCl was 4 h, and 5 min at a concentration of 25 g L-1. The mortality of fish with 15 g L-1 NaCl was 100%. Morphological analyses of the gills showed hyperplasia of the coated cells in the interlamellar space and hypersecretion of mucus in fish exposed to 10 g L-1 of NaCl. At concentrations of 20 and 25 g L-1, necrosis of the support collagen caused the cells to detach from the lamellar structure mucosa. In the chronic test, two concentrations were used, with four replications containing nine fish in each aquarium for a period of 21 days. Blood samples and gills from the fish were collected, and it was observed that the fish showed a decrease in the concentration of bicarbonate (NaHCO3) in the blood, indicating hypernatremia. Acute exposure of C. auratus to sodium chloride (NaCl) should be at a maximum of 10 g L-1 of NaCl, after which level there would be a loss in animal performance and/or mortality. Chronic exposure to 5 g L-1 of NaCl promotes acidemia, ionic imbalance, and pathological changes in the gills; therefore, it is not recommended.

Symphysodon aequifasciatus is a fish with a disk-shaped body and bright colors, important characteristics of ornamental fish. We evaluated amino acid supplementation strategies to reduce crude protein in the diet for evaluation of performance, the content of digestive enzymes, liver metabolism, and intestinal histopathology. A total of 180 fish were randomly distributed in 12 separate 50 L glass aquariums, consisting of a completely randomized design with four treatments (DC - Control diet with 34.4% crude protein; DL - Control diet plus 1% of lysine; DEAA - Control diet plus 1% free essential amino acids (threonine, phenylalanine, leucine, valine, arginine, and tryptophan); and DHP - Diet with a high level of crude protein 48.4%), three repetitions, lasting 60 days. The use of DL and DEAA diets resulted in higher intestinal villus height and higher zootechnical performance. The use of DL diet increased alkaline phosphatase and digestive amylase activity. The use of DHP diets promotes severe liver changes due to increased activity of Alanine aminotraserase. Therefore, it was possible to observe that the use of amino acids can supply the nutritional need of blue discus. Supplementation of diets with AAs allows the reduction of dietary protein, which is a strategy for feeding management.

The objective of this work was to evaluate the effect of dietary arginine concentrations on the health status of Nile tilapia (Oreochromis niloticus) cultivated in cages. The experiment was carried out in a completely randomized design with four treatments (2.3, 2.9, 3.5, and 4.1% arginine in dry matter) and three replicates, in 12 net cages of 8 m³, containing 4,000 sexually reverted tilapia (63±20 g, at 500 fish m^-3). Fish productive performance and health were evaluated. Biochemical, hematological, and immunological parameters, as well as the morphological aspects of gills and liver, were evaluated. Arginine inclusion did not cause significant differences in fish growth performance. However, arginine supplementation at 3.5% concentration improved the biochemical parameters and leucocyte counts, consequently improving the immune system. The arginine concentration of 4.1% caused lipid degeneration, shown by the increase of alanine aminotransferase and the decrease of albumin, urea, lactate, and glucose. Arginine supplementation above 2.3% and below 3.5%, in the diets of tilapia reared in cages, improves fish immune system, without adverse morphological and physiological effects.

A espécie Symphysodon aequifasciatus é uma das espécies de peixe ornamental de grande importância econômica no comércio nacional e internacional, no entanto, pouco se sabe sobre seus aspectos fisiológicos e sanitários dessa espécie em cativeiro. Nesse sentido, o objetivo do presente estudo foi determinar o perfil hematológico basal do acará disco mantido em cativeiro. Para isso, 14 animais adultos selvagens foram aclimatados em condições laboratoriais semelhantes às condições ambientais. O sangue dos peixes foi retirado por punção da veia caudal para as análises eritrocitárias, trombocitárias e leucocitárias. O resultado do hemograma mostrou maior frequência de linfócitos e ausência de eosinófilos, basófilos e LG-PAS, semelhante a resultados obtidos por outras espécies da família Cichlidae descritos na literatura. Não foi observada mortalidade indicando adaptação às condições de cativeiro refletido pelo exame sanguíneo normal.