Variations of Some Physiological and Immunological Parameters in Siberian Sturgeon (Acipenser baerii,Brandt, 1869) Subjected to an Acute Stressor

This study was carried out to investigate the effect of an acute stressor on the variation of some physiological and immunological parameters of Siberian sturgeon (Acipenser baerii) juveniles. Fish, reared in 3 tanks for 10 weeks, were used for this study. The acute stress of fish consisted of 2 min of air exposure stress. Plasma levels of cortisol, glucose, and lactate as well as lysozyme activity in plasma were measured before stress and 1 hr, 3 hr, 6 hr, 9 hr, 12 hr, and 24 hr after stress. The plasma cortisol significantly increased in the highest level 1 hr after stress, yet it gradually declined after 3 hr. The glucose significantly increased only 1 hr after stress. There was no significant difference between plasma lactate prestress and poststress. Moreover, lysozyme activity was enhanced by stress, thus reaching the highest level 9 hr after stress. The results of this study indicate that Siberian sturgeon not only have a rapid response to acute stress, but also a great capacity for recovery from stress, thus returning physiological parameters to prestress levels after 6 hr.     

Comparative coelomic fluid composition of sterlet sturgeon Acipenser ruthenus Linnaeus, 1758, Siberian sturgeon Acipenser baerii Brandt, 1869, and Russian sturgeon Acipenser gueldenstaedtii Brandt & Ratzeburg, 1833

The objectives of this study were to compare the physicochemical properties of coelomic fluid (CF) in three sturgeon species, sterlet sturgeon Acipenser ruthenus (age 5–8 years), Siberian sturgeon Acipenser baerii (age 15–20 years), and Russian sturgeon Acipenser gueldenstaedtii (age 13–18 years). For the study, CF was collected by plastic pipette from the eggs of mature female sterlet sturgeon (N = 10), Siberian sturgeon (N = 7) and Russian sturgeon (N = 4); osmolality, pH, ionic composition (Na⁺, K⁺, Ca²⁺, Mg²⁺, Cl^?), glucose, cholesterol and total protein of the CF were then analyzed. Mean concentration of K⁺ (4.4–6.11 mmol/L), Cl^? (89.8–98.0 mmol/L), Ca²⁺ (0.87–0.96 mmol/L), Mg²⁺ (0.57–0.67 mmol/L), cholesterol (0.13–0.16 mmol/L), total protein (2.41–3.57 g/L), pH (7.92–7.98), and osmolality (190–213 mOsm/kg) of CF were not significantly different among these three species. However, the mean concentration of Na⁺ was significantly lower in sterlet sturgeon (104.6 ± 7.7 mmol/L; p < .05) than in the Siberian (126.4 ± 6.2) and Russian (123.0 ± 5.9) sturgeon. For these three species, Na⁺, K⁺, Cl^?, and Mg²⁺ were the dominating ions; several significant correlations were observed among these ions and other physiochemical properties of CF. This is the first report on the ionic and biochemical composition of the CF of sterlet, Siberian and Russian sturgeon, which can be used as a reference point for further development of artificial media for the short‐term storage of unfertilized sturgeon eggs as well as for the standardization of the fertilization protocol for these species in controlled reproduction.     

Behavioural modifications in the early life stages of Siberian sturgeon (Acipenser baerii, Brandt)

Behavioural modifications of Acipenser baeri were studied during early ontogeny at 18 °C by means of specific tests and general observations. During A. baeri ontogeny, several different periods could be clearly distinguished by behavioural patterns. From hatching to 3 days post hatch (p.h.), specimens exhibited swimming-up and drift behaviour. A transition from a pelagic to benthic behaviour occurred between 4–5 days p.h. and specimens were positively rheotactic. At 7–8 days p.h., prelarvae aggregated into schools of different shapes. During prelarval development, specimens were positively phototactic, preferred white bottoms and did not show any preference for bottom concealment. Between 9–10 days p.h. coinciding with the onset of the exogenous feeding, larvae were active bottom swimmers, schooling behaviour disappeared and larvae dispersed. During early ontogeny, changes in body coloration were observed among those specimens who swam over bottoms of different brightness and during the day/night cycle. From 9 to 12 days p.h., larvae were positively phototactic, denied bottom cover and showed preference for white substrates. At 13 days p.h., the percentage of fish exhibiting positive phototactism, preferring open to concealed bottom habitats and white bottoms started to decrease, while at 20 days p.h. specimens showed a clear preference for bottom concealment and black and greyish bottoms. The significance, use and evolution of the former behavioural patterns is deeply discussed.     

Intraperitoneal injection urocortin-3 reduces the food intake of Siberian sturgeon (Acipenser baerii)

Urocortin-3 (UCN3), one of the corticotropin releasing factor (CRF) family peptides, which was discovered in 2001, has a variety of biological functions. However, the researches of UCN3 in fish were scarce. In order to understand whether UCN3 play a role in regulating food intake in fish, we first cloned the ucn3 cDNAs sequence of Siberian sturgeon (Acipenser baerii Brandt), and investigated the ucn3 mRNA levels in 11 tissues. The Siberian sturgeon ucn3 cDNA sequence was 1044 bp, including an open reading frame (ORF) of 447 bp that encoded 148 amino acids with a mature peptide of 40 amino acids, a 5ʹ-terminal untranslated region (5ʹ-UTR) of 162 bp and a 3ʹ-terminal untranslated region (3ʹ-UTR) of 435 bp. The result of tissue distribution showed that ucn3 widely distributed in 11 tissues with highest expression in brain. We also assessed the effects of periprandial (pre- and post-feeding), fasting and re-feeding on ucn3 mRNAs abundance in brain. The results showed the expression of ucn3 mRNA in brain was significantly elevated after feeding, decreased after fasting 17 days and increased after re-feeding. To further investigate the food intake role of UCN3 in Siberian sturgeon, we performed intraperitoneal (i.p.) injection of Siberian sturgeon UCN3 (SsUCN3) with three doses (60, 120 or 240 ng/g) and recorded the food intake. Acute and chronic i.p. injection SsUCN3 reduced the food intake in a dose-dependent pattern. In conclusion, this study indicates that SsUCN3 acts as a satiety factor to inhibit the food intake of Siberian sturgeon.     

The effect of feeding strategies and body weight on growth performance and hematological parameters of Siberian sturgeon (Acipenser baerii,Brandt 1869): Preliminary results

The purpose of present study was to investigate the growth performance and hematological parameters of Siberian sturgeon Acipenser baerii in three feeding strategies (satiation feeding, restricted feeding and starvation). We considered two body weights 465.75 ± 11.18 g and 250.40 ± 12 g for large fish and small fish, respectively. In a 45‐day experiment, eighteen fiberglass tanks were used for six triplicate treatments. In restricted feeding strategy, the fish were fed to 50% of satiation and starved treatments were an absolute feed deprivation throughout the experiment. At the end of 45‐day period, the hematological parameters were measured. The reduction of weight, condition factor and daily growth rate in the smaller fish was dramatically higher than the larger fish. Feed deprivation increased the rate of weight loss. Specific growth rate were negative in the large and small fish of starved treatments. The hematological results revealed no significant differences in except for the number of monocytes in larger fish. Large satiated fish showed the highest number of monocytes. In general, these strategies (restriction and deprivation) did not have any negative impacts on the hematological parameter in both sizes but respect to fish body weight, difference in total feed input between satiated and restricted treatments changed growth performance. It seems that restricted feeding (50% of satiation) in large fish was enough to achieve optimal growth while the amount of feed provided for small fish was not enough. Therefore; we can conclude that the restricted feeding is an effective strategy in rearing sturgeon at higher weight when the rearing condition is unsuitable.     

Phylogenetic relationships of Amur sturgeon Acipenser schrenckii Brandt, 1869 based on 18S rDNA sequencing

The phylogenetic relationships of Amur sturgeon A. schrenckii Brandt, 1869 with related species have been analyzed based on sequencing of the 18S rDNA small subunit. The complete sequence (1746 bp) of 18S rDNA has been estimated in seven individual A. schrenckii clones. The results show that the rDNA mutation profile of A. schrenckii 18S is very similar to that of A. fulvescens (Genbank data). Structural-functional and phylogenetic analyses allowed us to identify a presumably expressed variant, as well as taxon-specific mutation (adenine insertion after position 658 bp), for A. schrenckii 18S rDNA. Phylogenetic reconstructions performed with various approaches (NJ, MP, ML and Bayesian) support the monophyly of the genus Acipenser and point (1), based on which, in accordance with the classification based on ecological and morphological data (Artyukhin, 2006), the Amur sturgeon is closer to the sterlet than the Baltic sturgeon and (2) to substantial differentiation between North American (A. fulvescens) and Eurasian (A. schrenckii, A. ruthenus, and A. sturio) species of Acipenseridae.     

The evidence of apelin has the bidirectional effects on feeding regulation in Siberian sturgeon (Acipenser baerii)

Apelin is a peptide, mainly produced in the brain, which participates in several physiologic effects. However, knowledge about the mechanism of appetite regulation in teleosts, including the role of apelin is not well understood. The aim of this study is to explore the effect of feeding status on the expression of apelin mRNA in the whole brain and the effects of injection of apelin on food intake in Siberian sturgeon (Acipenser baerii). In this study, we first cloned the apelin cDNA sequence of the Siberian sturgeon. We obtained a 1046-bp cDNA fragment, including a 237-bp open reading frame (ORF) that encoded 78 amino acids. Apelin was widely distributed in 11 tissues related to feeding regulation, with the highest expression in thewhole brain, followed by the spleen and trunk kidney. In addition, we measured the effects of periprandial (preprandial and postprandial) change, fasting and re-feeding on apelin mRNA expression in whole brain. The level of apelin mRNA was significantly decreased 1 h after feeding. The results of the fasting experiment showed that the expression of apelin mRNA in the brain was significantly reduced after 1 day of fasting but consistently increased throughout the 15-day food deprivation period. When the 15-day fasted fish were re-fed, apelin mRNA expression in the brain was significantly increased as compared to that of the control. These results suggest that apelin may play a bidirectional role in the regulation of food intake in the Siberian sturgeon. In order to further examine the effect of apelin on feeding regulation in Siberian sturgeons, acute and chronic intraperitoneal (i.p.) injection experiments were performed and food intakes were recorded. Results showed that acute i.p. injection of apelin-13 reduced food intake, however, chronic i.p. injection apelin-13 increased the food intake for 7 days in Siberian sturgeons. In conclusion, our results show that apelin has a bidirectional effect on feeding regulation in Siberian sturgeons by acting as a satiety factor in short-term feeding regulation and a starvation factor in long-term feeding regulation.     

Morphology and ultrastructure of Siberian sturgeon (Acipenser baerii) spermatozoa using scanning and transmission electron microscopy

BACKGROUND INFORMATION: Available data concerning the sperm morphology of teleost fishes demonstrate wide variation. In the present study, the spermatozoa of Siberian sturgeon (Acipenser baerii Brandt, 1869), a chondrostean fish, was investigated. In contrast with teleost fish, chondrostean spermatozoa have a head with a distinct acrosome, whereas other structures, such as a midpiece and a single flagellum, are present in spermatozoa of most species. RESULTS: The average length of the head including the acrosome and the midpiece was 7.01+/-0.83 microm. Ten posterolateral projections derived from the acrosome were present on a subacrosomal region, with mean lengths of 0.94+/-0.15 microm and widths of 0.93+/-0.11 microm. The nucleus consisted of electrodense homogeneous nuclear chromatin. Three intertwining endonuclear canals, bound by membranes, traversed the nucleus longitudinally from the acrosomal end to the basal nuclear fossa region. There were between three and six mitochondria, two types of centrioles (proximal and distal) in the midpiece and two vacuoles composed of lipid droplets. The flagellum (44.75+/-4.93 microm in length), originating from the centriolar apparatus, had a typical 9+2 eukaryotic flagellar organization. In addition, there was an extracellular cytoplasm canal between the cytoplasmic sheath and the flagellum. CONCLUSIONS: A principal components analysis explained the individual morphological variation fairly well. Of the total accumulated variance, 41.45% was accounted for by parameters related to the head and midpiece of the sperm and the length of the flagellum. Comparing the present study with previous studies of morphology of sturgeon spermatozoa, there were large inter- or intra-specific differences that could be valuable taxonomically.     

Verification of meiotic gynogenesis in Siberian sturgeon (Acipenser baeri Brandt) using microsatellite DNA and cytogenetical markers

Diploid gynogenesis was induced in Siberian sturgeon Acipenser baeri using ultra violet (UV)-irradiated bester ( Huso huso × Acipenser ruthenus ) sperm. The higher survival rate of meiotic diploids was noted after 1350 ergs mm⁻² UV irradiation. A total of 80 meiotic diploids of known parentage from two different experimental treatments were screened using microsatellite DNA and cytogenetical analysis, and uniparental transmission in meiotic diploids was confirmed.     

西伯利亚鲟(Acipenser baerii)致病性维氏气单胞菌的分离鉴定

摘要：【目的】本研究旨在寻找引起养殖西伯利亚鲟鱼(Acipenser baerii)病害的致病因子。【方法】从北京地区自然患病的西伯利亚鲟鱼体内分离到致病菌株X-1-06909,采用生理生化鉴定结合16S rRNA基因序列的系统发育学分析确定该菌株的系统发育地位。同时采用琼脂扩散法对抗菌类药物的敏感性进行测定。【结果】菌株X-1-06909与Aeromonas veronii ATCC 35624T的16S rRNA基因序列相似性达99.6％;结合形态特征与生理生化测定结果,革兰氏阴性杆菌,具极生单鞭毛     

Compensatory growth in sub‐yearling Siberian sturgeon,Acipenser baerii Brandt, 1869: Effects of starvation and refeeding on growth,feed utilization and body composition

The capacity of sub‐yearling Siberian sturgeon (Acipenser baerii Brandt, 1869) (19.7 ± 0.8 g) to show compensatory growth was assessed for a 40‐day period for the effects of short‐term starvation and refeeding on growth, feeding performance and body composition. After acclimation, 25 experimental fish were randomly distributed among twelve 500‐L cylindrical fiberglass tanks with a flow‐through system. The fish were subjected to four different feeding regimes: control, which was fed four times daily to apparent satiation; T₁: four periods of 2 days starvation alternating with 8 days re‐feeding; T₂: two periods of 4 days starvation alternating with 16 days refeeding; T₃: an 8 days starvation period followed by 32 days refeeding. At the end of the experiment, the deprived fish attained body weights comparable to those attained by the control fish. There were no differences in growth and feeding performances between the deprived and the control fish. Total protein and lipid contents of the control fish were significantly higher than that of T₁ and T₂ fish at the end of the experiment (P < 0.05). A significant difference in the energy content was observed between T₂ and the control. Siberian sturgeon exhibited complete compensation, indicating a high ability of the deprived fish to grow sufficiently to fully compensate for weight loss during starvation. The results suggested that the feeding schedule involving starvation–refeeding cycles could be a promising feed management option for the culture of this species.     

Characterization,tissue distribution of resistin gene and the effect of fasting and refeeding on resistin mRNA expression in Siberian sturgeon (Acipenser baerii)

Resistin as an adipokine identified from rodents in 2001 is involved in many biological processes. However, little is known about this gene in fish. We cloned Siberian sturgeon (Acipenser baerii) resistin cDNA of 795 base pairs, encoding 107 amino acids, which showed 38–40% identity to human and rodents. Real-time quantitative PCR showed that the resistin gene was widely distributed in tissues of Siberian sturgeon, with the highest expression in liver. After fasting for 1, 3, 6 and 10 days, the expression of the resistin gene in the liver of Siberian sturgeon decreased significantly, and after refeeding on the 10 days of fasting the resistin mRNA expression increased rapidly, suggesting that resistin may play an important role in liver in response to starvation. Taken together, these results suggest that resistin may be involved in the regulation of energy homeostasis in liver.     

Ovarian nests in cultured females of the Siberian sturgeon Acipenser baerii (Chondrostei,Acipenseriformes)

Ovaries of Acipenser baerii are of an alimentary type and probably are meroistic. They contain ovarian nests, individual follicles, inner germinal ovarian epithelium, and fat tissue. Nests comprise cystoblasts, germline cysts, numerous early previtellogenic oocytes, and somatic cells. Cysts are composed of cystocytes, which are connected by intercellular bridges and are in the pachytene stage of the first meiotic prophase. They contain bivalents, finely granular, medium electron dense material, and nucleoli in the nucleoplasm. Many cystocytes degenerate. Oocytes differ in size and structure. Most oocytes are in the pachytene and early diplotene stages and are referred to as the PACH oocytes. Oocytes in more advanced diplotene stage are referred to as the DIP oocytes. Nuclei in the PACH oocytes contain bivalents and irregularly shaped accumulation of DNA (DNA‐body), most probably corresponding to the rDNA‐body. The DNA‐body is composed of loose, fine granular material, and comprises multiple nucleoli. At peripheries, it is fragmented into blocks that remain in contact with the inner nuclear membrane. In the ooplasm, there is the rough endoplasmic reticulum, Golgi complexes, free ribosomes, complexes of mitochondria with cement, fine fibrillar material containing granules, and lipid droplets. The organelles and material of nuclear origin form a distinct accumulation (a granular ooplasm) in the vicinity of the nucleus. Some of the PACH oocytes are surrounded by flat somatic cells. There are lampbrush chromosomes and multiple nucleoli present (early diplotene stage) in the nucleoplasm. These PACH oocytes and neighboring somatic cells have initiated the formation of ovarian follicles. The remaining PACH oocytes transform to the DIP oocytes. The DIP oocytes contain lampbrush chromosomes and a DNA‐body is absent in nuclei. Multiple nucleoli are numerous in the nucleoplasm and granular ooplasm is present at the vegetal region of the oocyte.     

Ontogenetic behavior of Siberian sturgeon, Acipenser baerii: A synthesis between laboratory tests and field data

We have reviewed field data and studies on the behavior and development of Siberian sturgeon at early-life intervals and related them to different ecologically relevant environmental factors that may play a role in the distribution, recruitment, and survival of young fish. Four behavioral phases (swimming-up, rheotactism, shoaling, and foraging) are observed from hatching to the juvenile phase. Each behavior is associated with an early-life interval and might allow fish to occupy different river habitats, directly influencing their distribution, survival, and recruitment. River current intensity, substrate typology, food resources, and predation pressure seem to be the most important factors affecting the distribution of Siberian sturgeon free embryos and larvae, while juveniles and adult fish disperse and migrate according to food abundance and reproduction. Mechanisms involved in regulating downstream migration during Siberian sturgeon early life stages are different than those observed in anadromous sturgeon species. In all large Siberian rivers, with the exception of the Lake Baikal, the Siberian sturgeon is represented by population continuums, and in many cases the foraging range also includes the spawning areas. Ontogenetic changes in Siberian sturgeon behavior could be interpreted as a species-specific mechanism to maintain the population continuums described in this species without significant mixture of local populations within the river.     

Development of the skull and pectoral girdle in Siberian sturgeon,Acipenser baerii,and Russian sturgeon,Acipenser gueldenstaedtii (Acipenseriformes: Acipenseridae)

The head is considered the major novelty of the vertebrates and directly linked to their evolutionary success. Its form and development as well as its function, for example in feeding, is of major interest for evolutionary biologists. In this study, we describe the skeletal development of the cranium and pectoral girdle in Siberian (Acipenser baerii ) and Russian sturgeon (A. gueldenstaedtii ), two species that are commonly farmed in aquaculture and increasingly important in developmental studies. This study comprises the development of the neuro‐, viscero‐ and dermatocranium and the dermal and chondral components of the pectoral girdle, from first condensation of chondrocytes in prehatchlings to the early juvenile stage and reveals a clear pattern in formation. The otic capsules, the parachordal cartilages, and the trabeculae cranii are the first centers of chondrification, at 8.4mm TL. These are followed by the mandibular, then the hyoid, and later the branchial arches. Teeth form early on the dentary, dermopalatine, and palatopterygoid, and then appear later in the buccal cavity as dorsal and ventral toothplates. With ongoing chondrification in the neurocranium a capsule around the brain and a strong rostrum are formed. Dermal ossifications start to form before closure of the dorsal neurocranial fenestrae. Perichondral ossification of cartilage bones occurs much later in ontogeny. Our results contribute data bearing on the homology of elements such as the lateral rostral canal bone that we regard homologous to the antorbital of other actinopterygians based on its sequence of formation, position and form. We further raise doubts on the homology of the posterior ceratobranchial among Actinopteri based on the formation of the hyoid arch elements. We also investigate the basibranchials and the closely associated unidentified gill‐arch elements and show that they are not homologous. J. Morphol. 278:418–442, 2017. © 2017 Wiley Periodicals, Inc.     

Growth performance,antioxidant and immune status of Siberian sturgeon (Acipenser baeri) fed diets containing green tea extract and oxidized fish oil

The present study was conducted to determine the effects of dietary oxidized fish oil (OFO) and green tea extract (GTE) on growth performance, antioxidant status and immunological parameters in Siberian sturgeon (Acipenser baeri). Fish weighing about 108 g were randomly assigned to one of nine dietary treatments (control diet without OFO and GTE; diets containing only 25 or 50 mg/kg of GTE; diets containing 50 mg/kg of OFO combined with 0, 25 or 50 mg/kg of GTE; diets containing 100 mg/kg of OFO combined with 0, 25 or 50 mg/kg of GTE) with three replicates of 15 fish stocked in fiberglass tanks using a completely randomized design. Growth performance indices, immunological parameters and antioxidant status of all treatment groups were determined using appropriate assays and compared. Results showed that GTE could enhance growth performance. Feeding GTE alone or combined with the OFO could decrease the hepatosomatic index (HSI) and viscerosomatic index (VSI). Serum lysozyme activity and antibody level were increased significantly by GTE alone or combined with OFO compared to the oxidized diets (p < 0.05). Conversely, lipid peroxidation products and antioxidant enzyme activity were significantly lower in GTE treatment groups and those that received combination of GTE and OFO compared to the oxidized diets. Low‐density lipoprotein (LDL) level in GTE groups was lower than other treatment groups (p < 0.05) however, in OFO treatment groups the LDL level in fish serum was significantly increased in comparison with the other treatment groups (p < 0.05). GTE and OFO alone or combined together significantly decreased the levels of triglyceride and cholesterol compared to the control group (p < 0.05). In conclusion, immunological and biochemical parameters were improved by inclusion of GTE into Siberian sturgeon rancid diets which can protect fish from the oxidative damage challenged by dietary oil oxidation.     

Effect of temperature on fatty acid composition and development of unfed Siberian sturgeon (A. baerii) larvae

The fatty acid metabolism in fish is influenced by various factors, including fish species, water temperature, water environment and diet supply. The aim of present work is to investigate the fatty acid composition of yolk‐stage Siberian sturgeon larvae reared at three different temperatures. Fertilized Siberian sturgeon eggs were transferred to the Lodi Aquaculture Research Center of the University of Milan, divided in three aquaria, each containing three incubators and incubated at 16°C. After hatching the temperature was switched to 16, 19 and 22°C. Larvae sampling was performed at the end of yolk sac reabsorption. No feed was dispensed during the trial. Eggs and larvae were weighed and fatty acid profile was determined by GC‐FID analysis after lipid extraction by chloroform/methanol mixture and fatty acid transesterification by methanolic hydrogen chloride. The fertilized eggs had a weight of 23.27 mg and a lipid content of 2.67 mg/egg. At hatching, the weight was 12.2 (0.17 SD) mg and lipid content 1.9 (0.6 SD) mg/larva. At the end of the trial, larvae mean weight was 33.6 (3.6 SD), 34.7 (1.8 SD) and 36.9 (1.1 SD) mg, while lipid content was 2.0 (0.3 SD), 2.1 (0.3 SD) and 2.0 (0.2 SD) mg for larvae reared at 16, 19 and 22°C respectively, without statistically significant difference. Larvae subjected to the highest water temperature showed a faster yolk‐sac absorption. No differences were found across temperatures regarding survival rates and regarding ontogenic development. The fatty acid composition of larvae was affected by the temperature. Larvae reared at 16°C had the lowest amount of saturated fatty acids, mainly due to a lower palmitic acid content, that was offset by a higher level of linolenic and linoleic acid, if compared with larvae reared at 19°C and 22°C. The study suggests that at a lower temperature sturgeon spare unsaturated fatty acid consuming preferably saturated fatty acids, increasing our knowledge of the fatty acid metabolism in this species.     

Morphometric comparison of the cephalic region of cultured Acipenser baerii (Brandt, 1869), Acipenser naccarii (Bonaparte, 1836) and their hybrid*

Geometric morphometric techniques were used in the characterization of morphological differences of the cranial region in cultured Acipenser baerii and A. naccarii and their hybrid. Species identification in sturgeons sometimes is difficult, because of the morphological plasticity of individual variability and the small differences between taxa. Identification is also complicated by human intervention and manipulation (e.g. aquaculture, hybridization, pollution). This study indicates how the differences between two species and their hybrids can be quantified and accurately visualized via geometric morphometrics. This technique may serve as a useful methodology to supplement analytical studies on morphometrics and systematics in Acipenseridae.