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Early development of the Adriatic sturgeon Acipenser naccarii from its free embryo after hatching (stage 36), until late embryo stage, when the transition to exogenous feeding starts (stage 45) is described. Special emphasis is given to morphological development and description of the different structures that are formed at each life stage. After hatching, free embryos still present embryonic characteristics, little pigmentation and an ovoid yolk sac. The mouth begins to open on the second day post hatch (dph) and is fully open at 3 dph. The head begins to separate from the body at 4 dph and straightens at 6 dph. The first fins to appear are the pectoral fins on the yolk sac and an embryological fin fold that extends from behind the head to the posterior part of the yolk sac. All other fins will develop from this fold. At 7 dph the caudal fin begins to take a heterocercal form and dorsal scutes are observed. This study provides information that will assist aquaculturists by establishing a reference for the normal development of A. naccarii, which may be useful for evaluating the suitability and quality of fish produced for restocking. [ABSTRACT FROM AUTHOR]

This work analyses the changes in the redox balance in two fish species: Adriatic sturgeon ( Acipenser naccarii) and rainbow trout ( Oncorhynchus mykiss) during starvation and refeeding period. The starvation period raised the lipid peroxidation (thiobarbituric-acid-reacting substances) levels in liver and blood, while a decline occurred in the antioxidant enzymatic activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) and glutathione reductase (GR) in both fish species. In liver, after the refeeding period, SOD activity recovered in both species, whereas CAT activity recovered only in trout. Furthermore, in both tissues of the two species, the lipid peroxidation levels remained high after 2 months of refeeding. In white muscle and heart, the lipid peroxidation levels indicate that these tissues did not undergo oxidative stress during the 72-day period. During starvation, in the muscle of both fish the fall in the lipid peroxidation level coincided with a rise in CAT, GPX and GR. The refeeding period in this tissue raised the lipid peroxidation level, and the enzymatic activities reached the values of the first point of starvation. In heart, no oxidative damage was detected during starvation in either species. The CAT and SOD activities increased during the starvation period only in trout. [ABSTRACT FROM AUTHOR]

Summary The objective of these experiments was to determine juvenile sturgeon (Acipenser naccarii ) ability to capture live prey as well as to determine their feeding preferences when born and raised in captivity and fed on manufactured feeds until the commencement of the experiment. The purpose was to improve their nutrition and to aid in the development of restocking programmes. For the experiment, one non-adapted group (A) and one group (C, control) previously adapted for 10 days to live feed were used; each group comprised eight similar-age sturgeon (16 fish in total). The experiment was repeated four times for each specimen in group A (A1 to A4) and twice for each in group C (C1 and C2). Using aquaria of 40-L capacity in each experiment, each fish, in isolation, was provided with three individuals of each of the 12 prey categories tested. The number of attacks, differentiating between successful and unsuccessful, were counted, and the elapsed times until the first and third successes were measured together with the type of prey taken. During the course of the experiment, there was a significant reduction in the number of times required to achieve both the first and third successes, as well as a significant increase in the number of successes with time. Preferred prey were those of the worm type (Tubificidae and Lumbricidae). [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]

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]

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]

Summary Ray-finned fishes display a spectacular range of evolutionary diversification, which is also reflected in their brain structure. Chondrosteans can be considered the most closely related extant taxa to the primitive actinopterygian fishes. However, current anatomical knowledge of the ontogenesis of the central nervous system of chondrosteans is scarce. In the present work, we studied the cytoarchitecture and gross morphology of the brain of the southern Europe autochthonous sturgeon Acipenser naccarii during ontogenesis. Nissl-stained serial paraffin sections of the brain of A. naccarii pre-larvae from day 1 after hatching to the transition stage to exogenous feeding to 90 days after hatching, were obtained. The five main brain divisions can be readily distinguished in 1-day-old specimens. The telencephalon of Acipenser develops by a process of eversion that can first be observed in 4-day-old larvae, although morphological changes in the telencephalon extend to very late in the development. With regard to the diencephalon, the epiphysis differentiates during the first days of development, but the outgrowth of the hypothalamic lobes occurs relatively late. During ontogenesis the mesencephalon maintains the embryonic tube-like shape, the tegmental portion differentiating much earlier than the dorsal or tectal portion. The cerebellum originates from two bilateral primordia; due to the fusion thereof, the medial portion of this area is transformed into a solid body which expands into the ventricular cavity of the brainstem. Finally, the rhombencephalon basal plate is strongly curved during the first days of development; later this curvature disappears and the dorsal walls of the rhombencephalon diverge, leading to the roof-plate transformation into a wide tela ependymalis. [ABSTRACT FROM AUTHOR]

Summary The present study maps the activity patterns of cytochrome oxidase (CO), a mitochondrial enzyme essential for oxidative phosphorylation, throughout the brain of the southern Europe autochthonous sturgeon Acipenser naccarii . The objective was to obtain detailed topographic knowledge on CO activity in the sturgeon brain at the light microscope level, which may reveal patterns of normal brain function, while serving as a baseline for subsequent comparison in studies on neural systems function, brain diseases, its development, plasticity, or aging. The CO histochemical staining intensity was quantified in 2-year-old specimens by optical densitometry of stained sections using a computer-assisted image analysis system; the standards were used to convert optical density into enzymatic activity. The CO activity was distributed in characteristic patterns and amounts that differed among various neural pathways, brain nuclei, cerebral layers, and neuron types. As in mammals, CO activity was relatively high in sensory and motor systems, but relatively low in the autonomic and visceral regulatory systems. [ABSTRACT FROM AUTHOR]

Abstract: A study has been made of the activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), and glutathione reductase (GR), as well as of lipid peroxidation and of glutathione, during the first stages of ontogenic development of the sturgeon Acipenser naccarii: the embryo within the egg, the free embryo (with vitellin reserves), and the juvenile. Also, the same determinations were made in Artemia nauplii to determine the possible influence of the presence of live food in the quantification of the antioxidant-enzyme pool of the sturgeon. Activity was found for the antioxidant enzymes SOD, CAT, and GPX in all the stages of ontogenic development corresponding to the first month of life of the sturgeon A. naccarii. Notable activity of these enzymes was found during the embryonic phase. On the contrary, the GR activity was not detected in this phase, coinciding with a greater proportion of oxidized glutathione. In the sturgeon A. naccarii, after the embryo phase of free life, the activity of all the antioxidant enzymes tended to increase with age as did the glutathione levels. The results are compared with those previously determined in the different organs of the adult. The marked activity of the antioxidant enzymes found in the sturgeon A. naccarii during the first month of life provides the sturgeon effective protection against oxidative damage. [ABSTRACT FROM AUTHOR]