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Climate change is reshaping our planet.Warming surface waters, acidification, and deoxygenation are the most critical effects of climate change in aquatic environments. Increasing mean water temperatures modify species distribution, alters their basal metabolic rates, the occurrence and intensity of marine diseases, and the timing of pivotal biological events, among others. Ocean acidification results in physiological stress and inhibits the growth and calcification of endo- and exo-skeletons, while ocean deoxygenation, and particularly hypoxic events, may alter the distribution, aerobic scope, and survival of organisms (Reid et al., 2019). As climate change is projected to continue over this century and beyond, it is expected that the above-mentioned stressors will be intensified, further altering the structure, and functioning of marine ecosystems (Benedetti et al., 2021). Understanding and predicting the effects of climate change is one of the most pressing challenges in marine science, since this knowledge has an impact on fisheries, aquaculture, conservation, and applied ecology. Under this scenario, this Research Topic was conceived for updating and increasing the knowledge of ocean water rise on the biology and physiology of aquatic species, resulting in a Research Topic of four works on crustaceans, fish, and phytoplankton.

Gilthead seabream (Sparus aurata) tend to increase fat deposition during summer farming conditions in the Mediterranean, which may negatively affect productive performance and consumers' quality perception of the final product. Therefore, this study evaluated the impacts of protein to lipid ratios in low fishmeal/fish oil diets on growth performance, body composition, feed conversion and nutrient utilization of seabream on-grown during summer temperature conditions. The experimental diets contained low levels of fishmeal, fish oil, and crude protein (39%), differing in crude lipid content: 16% (MF diet) or 12% (LF diet). A growth trial was per-formed with seabream (initial weight: 100 & PLUSMN; 7 g) from August to October (water temperature: 23.1 & PLUSMN; 2.2 & DEG;C). A digestibility trial was also performed (at 23 & DEG;C). Key performance indicators, whole-body composition and ac-tivities of digestive enzymes were evaluated at the end of the experiment (64 days). Low dietary lipid levels negatively affected lipid, energy, and amino acid digestibility, and as a result, fish fed the LF diet presented higher nitrogen faecal losses. Still, the decrease in nutrient digestibility was not related to dietary effects on the digestive enzyme activities. The experimental diets did not compromise the activity of pancreatic, gastric, and intestinal digestive enzymes nor feed utilization, but a slight growth impairment was observed in fish fed the LF diet, probably due to the lower amino acid and lipid digestibility. However, a potential benefit of this dietary treatment towards reducing fat accumulation in seabream during summer was observed. Nevertheless, the environmental impact of the nitrogen losses during seabream on-growing should be considered when estimating the sustainability of the production. This study demonstrated that the optimisation of diet formulations should account for the environmental conditions, especially in Mediterranean aquaculture, so the economic and envi-ronmental impacts may be correctly evaluated towards a more sustainable fish production. LA/P/0101/2020 info:eu-repo/semantics/publishedVersion

A two-month feeding trial was conducted to evaluate the effect of partial replacement of fish meal (FM) by soybean protein (SP) alone or in combination with lysine (Lys) and methionine (Met) supplementation in practical diets for silvery-black porgy juveniles (16.7±0.1 g). Seven isoproteic (ca. 50% crude protein) and isoenergetic (ca. 22.4 MJ kg-1) diets were formulated in which 45% (SP45), 60% (SP60) and 75% (SP75) of FM protein were replaced by SP and the control diet (FM) was prepared with FM as the major source of protein. In SP45+, SP60+ and SP75+ diets, 45 to 75% of FM was replaced by SP with supplementing blends of Lys and Met. Growth performance, feed utilization, and protein and lipid digestibility decreased with increasing dietary SP levels (p

Human activities such as trade and transport have increased considerably in the last decades, greatly facilitating the introduction and spread of non-native species at a global level. In the Iberian Peninsula, Fundulus heteroclitus, a small euryhaline coastal fish with short dispersal, was found for the first time in the mid-1970s. Since then, F. heteroclitus has undergone range expansions, colonizing the southern region of Portugal, southwestern coast of Spain and the Ebro Delta in the Mediterranean Sea. Cytochrome b sequences were used to elucidate the species invasion pathway in Iberia. Three Iberian locations (Faro, Cádiz and Ebro Delta) and 13 other locations along the native range of F. heteroclitus in North America were sampled. Results revealed a single haplotype, common to all invasive populations, which can be traced to the northern region of the species’ native range. We posit that the origin of the founder individuals is between New York and Nova Scotia. Additionally, the lack of genetic structure within Iberia is consistent with a recent invasion scenario and a strong founder effect. We suggest the most probable introduction vector is associated with the aquarium trade. We further discuss the hypothesis of a second human-mediated introduction responsible for the establishment of individuals in the Ebro Delta supported by the absence of adequate muddy habitats linking Cádiz and the Ebro Delta. Although the species has a high tolerance to salinity and temperature, ecological niche modelling indicates that benthic habitat constraints prevent along-shore colonisation suggesting that such expansions would need to be aided by human release.

Pseudoplatystoma punctifer posee un gran potencial para la acuicultura, pero la alta tasa de canibalismo existente durante su etapa temprana de vida dificulta por ahora su cultivo a gran escala. Una nutrición adecuada reduce significativamente la incidencia de canibalismo y el conocimiento de la ontogenia funcional del sistema digestivo es esencial para adaptar el protocolo de alimentación a las capacidades digestivas de esta especie y así aumentar la producción de semilla. Por tanto, el objetivo del presente estudio fue analizar la expresión de los principales genes implicados en la digestión (amilasa, tripsina, quimotripsina, pepsinógeno, fosfolipasa, lipoproteína lipasa y neuropéptido Y) durante el desarrollo larvario y juvenil temprano de P. punctifer. Los resultados mostraron que esta especie cuenta con la maquinaria enzimática necesaria para digerir el alimento exógeno antes de la primera alimentación (4 dpf). La expresión de los genes siguió el perfil común de una especie carnívora con un aumento significativo en la expresión de pepsinógeno a partir de los 10 dpf para pasar de una digestión proteica básica en el intestino (tripsina, quimotripsina) a una digestión proteica ácida más eficiente en el estómago (pepsina). Por tanto, P. punctifer está preparada para ser destetada con dietas complejas a partir de 10 dpf. Los resultados también mostraron que el cambio de dieta durante la etapa juvenil moduló la actividad enzimática a nivel transcripcional, por lo que el análisis de la expresión de los precursores enzimáticos digestivos será de utilidad en estudios nutricionales dirigidos a establecer la composición nutricional óptima para esta especie.

The effect of dietary partial replacement of fish meal (FM) by soybean protein (SP) alone or in combination with lysine (Lys) and methionine (Met) supplementation were tested in a 60-days feeding trial for silvery-black porgy (Sparidentex hasta) juveniles. Seven isoproteic (ca. 50% crude protein) and isoenergetic (ca. 22.4 MJ/kg) diets were formulated in which 45% (SP45), 60% (SP60) and 75% (SP75) of FM protein were replaced by SP and the control diet (FM) was prepared with FM as the major source of protein. In SP45+, SP60+ and SP75+ diets, 45 to 75% of FM was replaced by SP with supplementing blends of Lys and Met (98% of purity). The activities of the trypsin, lipase and α-amylase were higher in fish fed SP diets with crystalline amino acids supplementation than in the other groups (P < 0.05). Fish fed SP75 and SP75+ diets had the lowest red blood cell count and hematocrit level (P < 0.05). The results of the current study indicated that anti-nutritional factors in a soy-protein based diet rather than lysine and methionine deficiencies may have adverse effects on digestive enzymes activities and health condition in silvery-black porgy juveniles. info:eu-repo/semantics/publishedVersion

Farmed Senegalese sole (Solea senegalensis) still show a high incidence of vertebral anomalies that limit its intensive production and hamper its economic profitability. A great effort towards understanding how fish species develops and grows in captivity has been undertaken in the last decade, with particular emphasis to how different biotic and abiotic factors affect its skeletal development. Although some work has been performed on its skeletal development and expression patterns of key genes in developmental signaling pathways, a detailed description of the above-mentioned processes is still lacking. Here, the progression of skeletal development of cranial, appendicular and axial skeleton has been described through the implementation of an acid free double staining protocol; while the gene expression pattern of vitamin A (VA) and thyroid hormones (THs) signaling pathways were assessed through quantitative PCR (qPCR) during larval fish development under a standard larval rearing protocol and in Senegalese sole larvae fed with increased dietary VA levels (8-fold increase) during the Anemia feeding phase (from 6 to 27 dph). The ontogenetic study allowed us to identify the onset and follow-up the development of most skeletal structures in this fish species, and to gather some insights on the potential onset of deformities originated at the larval to juvenile transition affecting Senegalese sole rearing. The pro-meta-morphosis stage is when the caudal fin vertebrae are formed, where the most common skeletal deformities are found in Senegalese sole. A highly coordinated expression of VA- and TH-related genes has been revealed during larval to juvenile transition, while a comparative gene expression analysis in larvae fed control and high dietary VA content identified the specific timing of VA and THs signaling disruption through which VA and THs directly or indirectly might increase the incidence of skeletal deformities in this species. The present research work represents an important step forward towards the proper identification of the onset of some skeletal deformities and urge the investigation of nutritional and rearing conditions during the switch of larval behavior - from pelagic to benthonic - in order to overcome them in this important species for southwestern European aquaculture.

The present study describes morphological development of the skeleton in the Persian sturgeon Acipenser persicus and discusses the hypothesis that expression of genes encoding vitamin K‐dependent proteins (VKDP) might be correlated with the mineralization of skeletal tissues during early development in sturgeons. Results showed that development of cartilage started just after hatching (mean ± S.D., 10·9 ± 0·7 mm in total length, LT) in the head and notochord, whereas the first signs of mineralization occurred in the dentary and in the dermopalatine and palatopterygoid elements of the upper jaw, coinciding with the onset of exogenous feeding (20·1 ± 1·5 mm LT). All branchial arch elements developed between 19·3 and 22·3 mm LT, whereas mineralization was only observed in tooth plates associated with the hypobranchial 1 and gill rakers at 20·8 ± 1·5 mm LT and 48·4 ± 6·4 mm LT, respectively. Quantitative real‐time PCR showed that transcripts of VKDP genes including bone Gla protein (bgp), matrix Gla protein (mgp) and Gla rich protein (grp) genes were significantly up‐regulated during the transition to exogenous feeding, supporting hypotheses about relevance of the above‐mentioned genes in chondrogenesis at early developmental stages. The strong mineralization of skeletal elements from 21·5 to 27·3 mm LT (20 days post hatch) was in accordance with the maximal levels of bgp, mgp and grp expression indicating a correlation between development of the skeleton and the expression of VKDP genes. These data are important for evaluating A. persicus larval quality, understanding the influence of rearing biotic and abiotic factors on skeletogenesis and recognizing the occurrence of skeletal deformities in this species. info:eu-repo/semantics/acceptedVersion

Terrestrial animal byproduct meals, including nonruminant blood meal and blood products, represent the largest and largely untapped safe source of animal protein available within the international market for the aquafeed industry. Spray-dried blood and spray-dried plasma (SDP) proteins have long been recognized as high-quality feed ingredients for farmed animals. In this study, we evaluated the inclusion of SDP from porcine blood (SDPP) in growing diets for gilthead sea bream. Three isonitrogenous (CP = 51.2%) and isolipidic (fat = 12.4%) diets manufactured by cold extrusion (0.8 to 1.5 mm pellet size) were prepared by substituting high-quality fish meal with 0, 3, and 6% SDPP. The diets were tested for a period of 60 d at 22°C with 4 replicates each (400-L cylindroconical tanks, 150 fish per tank, and initial density = 0.5 kg/ m3). The SDPP inclusion in diets for gilthead sea bream fingerlings were evaluated in terms of growth performance, feed utilization, histological organization of the intestinal mucosa, activity of oxidative stress enzymes (catalase, glutathione S-transferase, glutathione peroxidase, and glutathione reductase) in the intestine, and nonspecific serum immune parameters (lysozyme and bactericidal activity). Results from this study indicated that dietary SDPP promoted fish growth in terms of BW and length; fish fed 3% SDPP were 10.5% heavier (P < 0.05) than those fed the control diet. Spray-dried plasma from porcine blood modulated the activity of the antioxidative defenses in the intestine (P < 0.05) and increased the density of goblet cells in the intestine (P < 0.05) and benefited the host by providing an effective immune barrier against gut pathogenic microbiota. The nonspecific serum immune response in fish fed diets with SDPP was greater (P < 0.05) than in fish fed the control diet. These results indicated that the inclusion of SDPP in gilthead sea bream feed could be beneficial for the fish by enhancing intestinal and serum innate immune function and the activity of antioxidative stress enzymes of the intestine and promoting growth performance. info:eu-repo/semantics/publishedVersion

The aim of the study was to evaluate the influence of different dietary protein and lipid levels and their ratios on larval growth, survival and the incidence of cannibalism in Pseudoplatystoma punctifer. Larvae were raised in a recirculation system from 3 to 26days post-fertilization (dpf) (2-25days post hatching, dph) at an initial density of 40 larvae L-1, 27.8 +/- 0.65 degrees C and 0L:24D photoperiod. Larvae were fed from 4 to 12 dpf with Artemia nauplii and weaned onto four different compound diets from 13 dpf within 3days, then fed exclusively with these diets until 26 dpf. These diets contained 30:15, 30:10, 45:15 or 45:10 protein:lipid (P:L) (in % of dry matter) levels. A control group was fed Artemia nauplii until 17 dpf and weaned thereafter with the 45P:10L compound diet. The experiment was carried out in triplicate. Results showed higher growth and survival rates and lower incidence of cannibalism in the group fed the 45P:15L diet than in the other treatments. Differences in larval survival and growth performance were associated with the higher protein and lipid content rather than the protein:lipid ratio of this diet. When comparing diets with the same protein level, the increase in dietary lipid led to an improvement in growth, suggesting that energy from lipids spares protein for growth in P.punctifer fingerlings. An Artemia feeding period longer than 12 dpf did not improve larval growth or survival.