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This study describes the stomach development in the sturgeon Acipenser naccarii, focusing on its histoenzymatic and ultrastructural characteristics from hatching until the end of the juvenile phase, 1 month later. The study aims to assist the aquaculturist in identifying the best timing for the start of feeding and to select the appropriate food for each stage of A. naccarii development. At hatching, the anterior portion of the digestive system consists of a yolk sac with a large central yolk mass. The yolk mass is enclosed by differentiating endodermal epithelium. The most significant ultrastructural characteristics of the epithelium are the numerous supranuclear vacuoles containing protein and lipid yolk granules, dilated intercellular spaces, and filiform cytoplasmic projections related to the uptake of reserve material on the apical surface. Newly hatched eleuthero-embryos show optimal enzymatic activities at a pH of 1.5 and 3, which is probably related to the presence of hatching glands and the digestion of yolk components. During the free-embryo phase, the yolk sac epithelium undergoes a series of histological, ultrastructural, and functional modifications to form a cecal stomach with anatomical characteristics similar to those of juvenile specimens. Gastric glands emerge between 6 and 7 days post-hatching (PH), although the absence of secretion granules in their oxyntic-peptic cells indicates that the stomach is not yet functional. During the following days (the exotrophic period), development of the tubular-vesicular network is observed, and secreting granules occur in the cytoplasm of oxyntic-peptic cells until around day 35 after fertilization (day 27 PH), when acid protease enzymatic activity is again detected. These histological and enzymatic changes and the greater number and size of oxyntic-peptic cell secretion granules appear to be related to the gastric compartment ontogeny reaching functionality at this developmental stage. [ABSTRACT FROM AUTHOR]

Modifications in the chloride (mitochondria-rich) and pavement cells of the gill epithelia of the Adriatic sturgeon Acipenser naccarii after their transfer under hypertonic environmental conditions (salinity 35) were examined by light and electron microscopy. In contrast to freshwater specimens, seawater-acclimated fish showed a marked increase in the number and size of chloride cells. Ultrastructural modifications included: presence of a slightly invaginated apical crypt, a darker cytoplasm, a more compact tubular system, a major increase in cisternae from Golgi apparatus stacks and flattened-out sacs with dilated ends that produced an increase in lateral and basal cell surfaces. All these changes indicated enhanced cellular activity. Pavement cells, which largely covered the chloride cells on the gill filament and lamella, exhibited a complex system of microridges on their apical surface. Typical features included numerous desmosomes that characterized the intercellular junction, and the presence in the apical cytoplasm of bundles of filaments and of electro-dense vesicles in freshwater fish or clear vesicles in seawater-acclimated animals. [ABSTRACT FROM AUTHOR]

Juvenile meagre were sampled at intervals during their first 500 days in a cage-based fish farm. Fish muscle showed a relatively low fat content (0.65-2.0%) when compared with other species of farmed fish, corroborating the consideration of meagre as a lean fish. At the beginning of the assay, saturated and mono- unsaturated fatty acids were in a similar proportion (approximately 30%), while polyunsaturated were close to 39% of total FAs, the n-3:n-6 ratio being of 3.8. Throughout the experiment a notable reduction in the sum of PUFA n-3 and an increase of linoleic (18:2n-6) and oleic acid (18:1n-9) was found. These changes led to a fall of n-3:n-6 ratio to values close to or lower than 1.0. Most probably, these changes reflect variations in the feeding regime applied during farming. In any case, fish offered good indices of lipid quality for human consumption. [ABSTRACT FROM AUTHOR]

Antarctic benthic ecosystems support a unique fauna characterized by high levels of diversity and endemism. However, our knowledge of the macrofauna communities across the Antarctic intertidal sedimentary shore is limited, and their fundamental ecological features, including spatial variability, remain poorly understood. This study aimed to investigate the abundance, community structure (i.e. taxa-specific abundance), and biodiversity patterns (α-, β-, and λ-diversity) of benthic macrofauna communities on intertidal sedimentary shores of two Antarctic islands (South Shetland archipelago, N of Antarctic Peninsula): Livingston and Deception. We conducted a quantitative sampling during two Austral summer campaigns (2004 and 2005), studying eleven intertidal sites, with five sites located on Livingston and six on Deception. Our results demonstrated a significantly higher abundance of intertidal benthic macrofauna communities on Livingston than on Deception. Furthermore, significant differences in community structure were observed between the two islands. In terms of biodiversity patterns, there were no significant differences in the number of taxa within communities (α-diversity) between the two islands. However, significant differences in the variation of community composition (determined by the number and identity of taxa) between intertidal sites (β-diversity) were observed, shedding light on the higher total taxa count (λ-diversity) on Livingston compared to Deception. We suggest that the island-specific characteristics (e.g., granulometric characteristics, ice disturbance, sedimentation rates, and geothermal activity) determine the differences observed in macrofauna communities. However, other ecological processes and factors are operating on different spatial and temporal scales (e.g., population dynamics, biotic interactions, oceanographic conditions, and climate change) that influence the occurrence and abundance of macrofaunal taxa. Our findings contribute to the fundamental understanding of the spatial variability of these communities and provide essential information for better management decisions and conservation practices in Antarctic coastal ecosystems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

Background: This paper deals with the consequences of dietary restriction or complete starvation before slaughtering on the biochemical and textural characteristics of sea bass muscle., Results: Results showed that only severe feed restriction influenced negatively total body and individual organ weights, and these animals showed lower condition factor as well. Neither moderate feed restriction (up to 50% of the standard ration) kept for 30 days nor total starvation up to 12 days caused significant effects on fish weight and fillet yield. Muscle lipid content was lower in feed-restricted fish, although this parameter was not altered by starvation time. Differences between the two feeding strategies studied were observed in muscle textural and biochemical parameters, and the results point to an influence of the nutritional status on the post-mortem evolution of collagen and myofibrillar proteins, although firmness was not modified., Conclusions: Moderate feed restriction prior to slaughtering could be advisable in sea bass culture, given that no detrimental effects on fish quality or fish performance were noticed, whereas substantial amounts of feed can be saved., (© 2013 Society of Chemical Industry.)

The present study examines the particular metabolic strategies of the sturgeon Acipenser naccarii in facing a period of prolonged starvation (72 days) and subsequent refeeding (60 days) compared to the trout Oncorhynchus mykiss response under similar conditions. Plasma metabolites, endogenous reserves, and the activity of intermediate enzymes in liver and white muscle were evaluated. This study shows the mobilization of tissue reserves during a starvation period in both species with an associated enzymatic response. The sturgeon displayed an early increase in hepatic glycolysis during starvation. The trout preferentially used lactate for gluconeogenesis in liver and white muscle. The sturgeon had higher lipid-degradation capacity and greater synthesis of hepatic ketone bodies than the trout, although this latter species also showed strong synthesis of ketone bodies during starvation. During refeeding, the metabolic activity present before starvation was recovered in both fish, with a reestablishment of tissue reserves, plasmatic parameters (glucemia and cholesterol), and enzymatic activities in the liver and muscle. A compensatory effect in enzymes regarding lipids, ketone bodies, and oxidative metabolism was displayed in the liver of both species. There are metabolic differences between sturgeon and trout that support the contention that the sturgeon has common characteristics with elasmobranchs and teleosts.

The digestive enzyme activities were determined in Adriatic sturgeon and rainbow trout during starvation and refeeding period. Overall, the digestive enzyme activities are affected in the same sense in both species. The protease and lipase activities were decreased later than amylase activity. Even after 1 month of starvation, both species would be prepared to digest protein and lipids in an effective way. After 72 days of starvation, the digestive machinery of the sturgeon and of the trout shows an altered capacity to digest macronutrients. The capacity to digest proteins and lipids, after 60 days of refeeding, begins to become re-established in sturgeon and trout. In contrast, in this period, the capacity to digest carbohydrates remains depressed in both species.

Variations of Na(+)/K(+)-ATPase activity and fatty-acid composition in the gills of the sturgeon Acipenser naccarii subjected to progressive acclimation to full seawater (35 ppt) were determined in relation to the hypo-osmoregulatory capacity of this species in the hyperosmotic medium. Blood samples were taken and gills arches were removed at intermediate salinity levels between 0 and 35 ppt and after 20 days at constant salinity (35 ppt). Plasma osmolality and Na(+)/K(+)-ATPase activity increased significantly with growing environmental salinity. Total saturated fatty acids (SFAs) decreased, while total polyunsaturated fatty acids (PUFAs) increased significantly with increasing salinity due mainly to changes in n-3 PUFAs (20:5n-3 and 22:6n-3). The n-3/n-6 ratio increased significantly during the acclimation process. The results show a direct relationship between salinity, increased gill Na(+)/K(+)-ATPase activity and ultrastructural changes of the gill chloride cells. Changes in the fatty-acid composition in gills of A. naccarii during progressive acclimation to full seawater suggest that variations of gill fatty acids may also have a role in osmoregulatory mechanisms.