Weaning European glass eels (Anguilla anguilla) with plant protein-based diets and its effects on intestinal maturation

Weaning glass eels with compound diets (36% proteins, 16% lipids) differing in their fishmeal (FM) level (50, 75 and 100% FM replaced by a blend of plant proteins, PP) was compared to a group fed cod roe. Weaning lasted for 20 days and then, eels were fed compound diets for 70 days, whereas the other group was only fed cod roe (90 days). Diets were tested with four replicates and evaluated in terms of growth, survival, glass eels metamorphosis into elvers, oxidative stress status and activity of digestive enzymes. Although glass eels are traditionally fed with fish roe and progressively weaned onto compound diets, results revealed that this strategy should not be prolonged for a long time, since feeding glass eels with cod roe for 90 days negatively affected their growth (2 times lower than fish fed compound diets), delayed their metamorphosis, as well as the maturation of their digestive function as the ratio of alkaline phosphatase and leucine-alanine peptidase indicated. Weaning glass eels onto compound diets differing in their FM levels did not affect their growth, metamorphic stage nor the activity of pancreatic enzymes (total alkaline proteases, trypsin, bile salt-activated lipase and α-amylase), although 75% FM replacement by PP sources delayed the level of intestinal maturation in eels. In comparison to glass eels fed the 100% FM diet, survival was negatively affected in groups fed diets with 50 and 75% FM replacement by PP ingredients, which indicated that further improvement is needed in diet formulation for this stage of development.info:eu-repo/semantics/acceptedVersio

Towards the standardization of brush border purification and intestinal alkaline phosphatase quantification in fish with notes on other digestive enzymes

Assessing the activity of digestive enzymes is a common procedure in many biological, physiological and nutritional studies. After reviewing the available literature on fish digestive tract maturation and enzymatic activity (pancreatic and intestinal enzymes) published between 1994 and 2017, authors detected some possible methodological and/or interpretative inconsistencies in this kind of studies, and concluded that special attention should be paid on: i) the time of conservation of frozen samples prior their analysis, ii) the proper purification of the brush border of enterocytes by a double centrifugation step (Crane et al., 1979) when authors want to evaluate the activity of intestinal brush border enzymes in order to avoid the overestimation, particularly of alkaline phosphatase (AP), because it is present in other tissues; iii) the use of the proper reaction conditions at the normal range of values in terms of ions, temperature and intestinal alkalinity for the species of interest, and AP unit calculation. The implementation of these recommendations will promote the standardization of actual analytical procedures, as well as improve the reliability of comparative studies between different fish species or rearing procedures.info:eu-repo/semantics/acceptedVersio

Editorial: Animal welfare, Volume I: Animal welfare in aquaculture - Physiological basis and recent findings

Since animal welfare is a multidisciplinary scientific discipline, the papers published in this special issue are based on diverse subjects, such as feeding and nutrition, behavior, immunology, reproduction, pathology, endocrinology, and neuroendocrinology. The studies targeting fish species have been the most frequent, being salmonids the main group. Nevertheless, only one out of the thirteen published articles deals with an invertebrate species, the lobster (Homarus americanus), which highlights the recent interest for crustaceans’ welfare. The results derived from these works state objectively the importance of animal welfare in both physiological and behavioral traits and responses, as well as in zootechnical parameters of interest for farmers.info:eu-repo/semantics/publishedVersio

Demographic structure of the exploited stock of European eel (Anguilla anguilla (Linnaeus, 1758)) from Albufera d'es Grau (Minorca)

Abstract not availabl

Utilization of grape seed oil as a dietary lipid source in rainbow trout (Oncorhynchus mykiss) diets

A 60-day feeding trial was conducted to determine the effects of different levels of grape seed oil (GO) on growth performance, digestive enzyme activity, fillet proximate and fatty acid composition of rainbow trout (Oncorhynchus mykiss) juveniles (40.17 ± 0.04 g). Five experimental diets were formulated where fish oil (FO) was replaced with 0 (D1), 25 (D2), 50 (D3), 75 (D4) and 100 (D5) % GO. The growth performance was significantly improved with increasing GO levels up to 50% after which fish growth declined (P < .05). Fillet fatty acid composition was showed significantly highest n-6 PUFA levels with increasing GO in diets, while n-3 HUFA levels especially EPA and DHA were significantly decreased (P < .05). Fish fed on diets containing higher levels of GO revealed a decrease in α-amylase activity, whereas trypsin, total alkaline protease, and lipase activities increased significantly with increasing GO levels up to 50% and then decreased. Based on the findings of the present study, it could be concluded that GO could be included in diets up to 50% where it had the best performance over the other diets tested in the present experiment.info:eu-repo/semantics/acceptedVersio

Editorial: Rising stars in aquatic physiology: 2022

Promoting and visualizing cutting-edge research from young generations is the cornerstone of our academic environment. Under this scenario, this Research Topic aims gathering innovative research studies on aquatic physiology, studies that range from ecological field studies focused on how ocean acidification might affect cleaning fish services in reefs (Paula et al.) to molecular biology studies dedicated to the characterization of genes involved in longevity in two molluscan species (Xu et al.) and cortisol receptors expression in a teleostean fish (Vallejos-Vidal et al.). Additionally, a fourth manuscript has been published in this Research Topic, a very interesting study describing how parental metabolite provisioning is directed to offspring (both spermatozoa and developing embryos) in an elasmobranch lecithotrophic viviparous species (Wosnick et al.).info:eu-repo/semantics/publishedVersio

Coordinated regulation of chromatophore differentiation and melanogenesis during the ontogeny of skin pigmentation of Solea senegalensis (Kaup, 1858)

Abnormal pigmentation of Senegalese sole has been described as one problem facing the full exploitation of its commercial production. To improve our understanding of flatfish pigmentation of this commercially important species we have evaluated eleven genes related to two different processes of pigmentation: melanophore differentiation, and melanin production. The temporal distribution of gene expression peaks corresponds well with changes in pigmentation patterns and the intensity of skin melanization. Several gene ratios were also examined to put in perspective possible genetic markers for the different stages of normal pigmentation development. Further, the phenotypic changes that occur during morphogenesis correspond well with the main transitions in gene expression that occur. Given the dramatic phenotypic alterations which flatfish undergo, including the asymmetric coloration that occurs between the ocular and the blind side, and the synchrony of the two processes of morphogenesis and pigmentation ontogenesis, these species constitute an interesting model for the study of pigmentation. In this study we present a first approximation towards explaining the genetic mechanisms for regulating pigmentation ontogeny in Senegalese sole, Solea senegalensis.Ministry of Science and Innovation (MICIIN) of the Spanish Government [AGL2008-03897-C04-01/ACU]; European Community [FP7/2007-2013-222719-LIFECYCLE]; Spanish Governmentinfo:eu-repo/semantics/publishedVersio

The importance of pepsin‐like acid protease quantification in aquaculture studies: a revision of available procedures and presentation of a new protocol for its assessment

Assessing the activity of acid pepsin‐like protease is a common procedure in many biological, physiological and nutritional studies in gastric fish species. After reviewing the available literature on fish digestive acid proteases (stomach acid pepsin‐like proteases), especially those species of relevance for aquaculture purposes, published during a time span of ten years (2008–2018), authors detected some possible methodological and/or interpretative inconsistencies in this kind of studies when quantifying pepsin‐like enzymes. Thus, we concluded that special attention should be paid on the following issues when assessing digestive acid protease activity: (i) the proper preparation of stomach extracts, (ii) the use of the proper reaction conditions at the normal range of physiological pH and temperature values, and (iii) the proper quantification of the number of peptide bonds hydrolyzed for acid protease unit calculation. The implementation of these recommendations, and the proposal of more suitable (previously tested) methodological steps, will promote the standardization of acid pepsin‐like protease analytical procedures, as well as improve the reliability of comparative studies dealing with this proteolytic enzyme between different fish species of aquacultural importance.info:eu-repo/semantics/acceptedVersio

Evaluation of a bacterial single-cell protein in compound diets for rainbow trout (Oncorhynchus mykiss) fry as an alternative protein source

A 60-day trial was conducted in rainbow trout (Oncorhynchus mykiss) fry (initial weight = 2.5 ± 0.6 g) to evaluate the potential use of a bacterial single-cell protein (SCP) as an alternative protein source. Five experimental diets with different levels of fishmeal replacement (0, 25, 50, 75 and 100%) and no amino acid supplementation were tested. At the end of the trial, we found that fry fed diets, replacing 25 and 50% of fishmeal with bacterial SCP, were 9.1 and 21.8% heavier, respectively, than those fed the control diet (p 50%), which was associated to feed palatability. High levels of bacterial SCP (>50%) affected the muscular amino acid and fatty acid profiles, imbalances that were associated to their dietary content. The broken-line regression analysis using muscle DHA content and weight gain data showed that the maximum levels of fishmeal replacement by bacterial SCP were 46.9 and 52%, respectively.info:eu-repo/semantics/publishedVersio