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The sequence and timing of the embryonic development of Adriatic sturgeon (Acipenser naccarii) are described at a constant temperature (17±1 °C), from fertilisation to hatch in a hatchery. Fertilised eggs, obtained from one female and two males, were held in a flow-through system. On the first day, embryos were sampled every 20 min during the first 12 h, and every 40 min in the following 12 h. Embryos were sampled hourly on the second day. On the third and fourth days, embryos were sampled every 2 h, and every 3 h on the fifth and sixth days. The first cleavage furrow appeared at 1 h 40 min postfertilisation. Blastulation concluded at 12 HPF (hours postfertilisation), when the dorsal blastopore lip formed. The completion of gastrulation was at 18 HPF, closing of the neural tube at 23 HPF and formation of the s-shape heart at 31 HPF. The mass hatch occurred at 120 HPF. A. naccarii is a relatively common sturgeon species in aquaculture and possesses similar developmental patterns to those of other sturgeons; hence, we can use this species as a model for further studies about sturgeon species which are more difficult to breed artificially. Information about the embryonic development of the Adriatic sturgeon could assist restocking programmes. [ABSTRACT FROM AUTHOR]

The main objective of this study was to analyse differences and a similarities in morphometric characteristics among specimens of the same year class of Acipenser naccarii (Bonaparte, 1836), comparing fish raised either in Italy or Spain. All specimens were F1 of captive broodstock in Italy. Fifteen biometric variables were measured, and three derived indices were calculated, on 30 individuals of 3+ year class from Lombardy (Italy) and 90 individuals of 1+, 2+ and 3+ year class from Riofrío (Granada, Spain). A stepwise discriminate analysis (SDA) was carried out, and the results were contrasted using a non-hierarchical cluster analysis. The two groups proved to be similar, so a principal component analysis and a simple regression analysis were performed on all individuals, taking total length (Tl) as the independent variable and all the biometric variables as dependent. The study revealed that although the Soljan index (i.e. ratio of mouth width to snout length) is related to T1, and is a valid taxonomic characteristic, the CA index (i.e. relative position of the barbels) and FB index (i.e. ratio of snout length to width) are also valid characteristics for individuals longer than 57 cm, being independent of T1. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Summary The present work examines the temporal appearance and degree of activity of digestive enzymes of pancreatic and intestinal origin (amylase as well as neutral and alkaline proteases) together with the evolution of the ontogenic development of the intestine and pancreas during the first month of free-living (30 days post-hatch-[dph]) of the sturgeon Acipenser naccarii. In addition, the influence of exogenous live feeding with Artemia salina on the detection of digestive enzymes was studied. Shown are that in the first life stages of the A. naccarii, from the time of fertilisation to the juvenile stage, the following events related to its digestive physiology occurred: digestive enzymes were detected in the embryo stage within the egg, presumably related to the hatching gland; in the free-living embryo stage, opening of the mouth was at 10 dpf and protease and amylase digestive activities occurred due to an early differentiation of the pancreas and intestine (12-13 dpf). At this stage, digestive enzymatic activities are partly owing to the live feed offered before disappearance of the yolk reserves (14 dpf); the expulsion of the melanin plug and the appearance of a continuity of the digestion tract (16 dpf) together with the disappearance of the yolk reserves (17 dpf) mark the passage from the free-living embryo phase to the juvenile stage; finally, from the first month after hatching in this sturgeon species, there is a stabilisation in digestive amylase and protease activities together with a fully developed digestive structure. The contribution of enzymes from prey in the detection of enzymatic activities determined in the fish was beyond doubt; therefore these exogenous enzymes must also have a certain physiological importance. Subsequent work will be needed to clarify the importance of digestive processes of the exogenous enzyme pool from live feed as well as to assess the possibility of shortening the weaning period. [ABSTRACT FROM AUTHOR]

This paper presents a sequential analysis of the development of the sturgeon (Acipenser naccarii) heart from the end of gastrulation to the early juvenile stages. At late neurulation, the heart appears as a straight, short tube located over the endoderm that forms the wall of the yolk sac, in front of the developing head. The heart axis is aligned with the axis of the developing head. Subsequently, the heart elongates and adopts a C-shape, and its axis becomes perpendicular to that of the head. Around the time of hatching, the heart loses the loop and appears as a mostly straight tube with the chambers arranged in a craniocaudal sequence: outflow tract, ventricle, atrium, and a small sinus venosus. During the first 4 days post-hatching (dph), the heart starts looping again, adopts a C-shape, and undergoes a counterclockwise movement that brings the atrium to the left of the outflow tract and the ventricle to a caudal position. Thus, a primary and a secondary cardiac loop occur in the sturgeon. Later, the atria come to occupy a middle position behind the outflow tract, and the sinus venosus shifts from a caudal to a dorsal position. A morphological arrangement similar to that found in adult sturgeons is attained in all specimens at days 7-9 dph. The external changes are accompanied by a series of internal modifications that include trabeculation (3-4 dph), development of endocardial cushions in the atrioventricular canal (4 dph) and in the conus arteriosus (3-4 dph), conus (22-24 dph) and atrioventricular (18-20 dph) valve formation, and development of the epicardium (4 dph) and the coronary vessels (10 dph). The main developmental features of the heart have been registered, and a basic body of information, which should be very useful in future developmental studies, has been established. Similarities and dissimilarities between the development of the sturgeon heart and that of other vertebrates are underscored. [ABSTRACT FROM AUTHOR]

The possible repercussions of osmoregulatory processes on some indicators of classical and oxidative stress were examined during gradual acclimation of sturgeons (Acipenser naccarii) to full seawater (35‰ salinity) and after a period of 20∼days at this salinity. Erythrocyte constants and levels of cortisol, protein and glucose in the plasma were determined. In addition, plasma osmolality and muscle-hydration values, as well as liver and heart protein, were determined. Catalase, glutathione peroxidase and superoxide dismutase activities and lipidperoxidation levels were measured in blood (plasma and red blood cells) and tissue (liver and heart). A number of physiological responses, such as disturbance in body fluid, activation of osmoregulatory mechanisms, augmented antioxidant defences in blood and alteration of energy metabolites, were detected with increasing environmental salinity. After 20 days at 35‰ salinity, plasma osmolality, erythrocyte constants and muscle water content all returned to values usual for low environmental salinity, indicating that osmoregulatory processes have achieved their objective. However, cortisol values, antioxidant enzyme activities in the blood (plasma and red blood cells), lipid peroxidation in plasma, and hepatic proteins did not return to initial values, showing that osmoregulatory processes cause major physiological changes in the fish. [ABSTRACT FROM AUTHOR]

One approach into the lipid requirements and the quality evaluation of the sturgeon Acipenser naccarii is the study of the fatty acid composition of lipids in several tissues. Four different ages of this new target species for freshwater culture were sampled from a fish farm. Oleic and palmitic acids were the most abundant fatty acids in all age groups and tissues sampled. High quantities of 16:1n7, 20:1n9, 22:1n9, 20:5n3 and 22:6n3 were also detected. The overall pattern closely resembles that of other freshwater fish species. No important differences were found in muscle age. The high lipid level and the relatively high proportion of HUFAn3 fatty acids renders this species as a highly desirable food for human consumption. [ABSTRACT FROM AUTHOR]

Abstract: In order to assess the metabolic organization of Acipenser naccarii, a representative species of the ancient ancipenserid chondrosteans, the activity of key enzymes of the main metabolic pathways in the liver, white muscle, and heart, as well as the levels of plasma and tissue metabolites of this sturgeon species have been evaluated and compared to those of the advanced teleost Oncorhynchus mykiss. In general, the epibenthic character of A. naccarii is reflected in the lower specific activity of most enzymes evaluated, in comparison to those of the more active O. mykiss. However, the metabolic organization of this sturgeon species shows some particularities that clearly differed from that of teleosts. Whereas the liver is the main gluconeogenic organ in rainbow trout, both the liver and white muscle of sturgeon possess the same capacity for glucose synthesis, with glycerol being the more suitable glucose precursor. Unlike teleosts, the liver is the main site for lipid storage in sturgeon which would be related to its lower capacity to transport metabolites involved in lipid metabolism. Although the capacity to transport free fatty acids (FFA) is lower in sturgeon than in trout, HOAD activity shows that this acipenserid is able to oxidize fatty acids in extrahepatic tissues such as the heart. Also, both sturgeon and trout showed the same hepatic capacity to oxidize fatty acids. The liver of sturgeon possesses a higher capacity to synthesize ketone bodies than trout which would be a primitive trait to export these compounds as fuels for peripheral tissues in order to offset the low ability to transport FFA in the blood. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]