Comparative morphology of the pectoral fin spine of the Persian sturgeon Acipenser persicus,the Russian sturgeon Acipenser gueldenstaedtii,and the Starry sturgeon Acipenser stellatus in Iranian waters of the Caspian Sea

The morphological characteristics of the pectoral fin spine were compared in three species of sturgeon, the Persian sturgeon (Acipenser persicus), the Russian sturgeon (Acipenser gueldenstaedtii), and the Starry sturgeon (Acipenser stellatus), all sampled from the Caspian Sea. On the basis of morphological characters of the pectoral fin spine, 62.2% of the individuals were correctly classified into separate groups. The cluster analysis also divided the three species into two major subgroups. Acipenser persicus and A. gueldenstaedtii were grouped together, suggesting a similar evolutionary basis. Significant morphological heterogeneity in pectoral fin spine characteristics was observed among the three sturgeon species. Principal component analysis identified the largest differences were in the pectoral fin spine size and the angle between distal pectoral fin spine and the horizontal line (A°). The first and second principal components (PC1 and PC2) of all observations accounted for 64.19% and 14.33% of the total variation, respectively. The combination of all analyses showed the relevance of applying pectoral fin spine shape for interspecific distinction of the three species of sturgeons.     

Polyphyly of mtDNA lineages in the Russian sturgeon, Acipenser gueldenstaedtii: forensic and evolutionary implications

Molecular species identification methods are an important component of CITES monitoring programs for trade in sturgeon and caviar. To date, obtaining molecular evidence for distinguishing caviar from four closely related Eurasian sturgeon species Acipenser baerii (Siberian sturgeon), A. gueldenstaedtii (osetra), A. persicus (Persian sturgeon), A. naccarii (Italian sturgeon) remains problematic. Using approximately 2.3 kb of mtDNA sequence data (cytochrome b, NADH5, control region), we find this to be attributable to the polyphyletic nature of these mitochondrial DNA markers in the Russian sturgeon, A. gueldenstaedtii. Two mitochondrial lineages are present within this species: one is phylogenetically affiliated with A. persicus and A. naccarii, while the other clusters with A. baerii. These findings have a direct impact on molecular testing of commercial caviar and demonstrate the necessity of using large sample sizes when constructing forensic databases. Furthermore, the results affect current taxonomic designations for these species as well as hypotheses concerning their evolutionary origins.     

High‐throughput SNP‐genotyping analysis of the relationships among Ponto‐Caspian sturgeon species

Legally certified sturgeon fisheries require population protection and conservation methods, including DNA tests to identify the source of valuable sturgeon roe. However, the available genetic data are insufficient to distinguish between different sturgeon populations, and are even unable to distinguish between some species. We performed high‐throughput single‐nucleotide polymorphism (SNP)‐genotyping analysis on different populations of Russian (Acipenser gueldenstaedtii), Persian (A. persicus), and Siberian (A. baerii) sturgeon species from the Caspian Sea region (Volga and Ural Rivers), the Azov Sea, and two Siberian rivers. We found that Russian sturgeons from the Volga and Ural Rivers were essentially indistinguishable, but they differed from Russian sturgeons in the Azov Sea, and from Persian and Siberian sturgeons. We identified eight SNPs that were sufficient to distinguish these sturgeon populations with 80% confidence, and allowed the development of markers to distinguish sturgeon species. Finally, on the basis of our SNP data, we propose that the A. baerii‐like mitochondrial DNA found in some Russian sturgeons from the Caspian Sea arose via an introgression event during the Pleistocene glaciation.     

Diet composition of the Persian sturgeon <Emphasis Type="Italic">Acipenser persicus</Emphasis> at the coast of the Guilan Province,Caspian Sea

Sturgeons are one of the most important and valuable species in the Caspian Sea. This investigation (2000–2002) was aimed at determining the feeding habits and the main and secondary prey organisms consumed by the Persian sturgeon (Acipenser persicus Borodin, 1897) living at depths less than 10 m in the Caspian Sea (Guilan Province). The food spectrum of immature A. persicus was comprised of benthic invertebrates of seven genera and fishes of three genera. The main prey items of immature A. persicus were polychaete worms and the secondary prey were crustaceans. The study of stomach contents showed that polychaetes were the most important component of the diet of immature A. persicus of the length class up to 25 cm.     

Morphological and molecular genetic study of the Persian sturgeon <Emphasis Type="Italic">Acipenser persicus</Emphasis> Borodin (Acipenseridae) taxonomic status

Morphological and molecular genetic analyses of the Russian sturgeon sensu Berg (1934) were accomplished using the sample of individuals collected in the southern part of the Caspian Sea. The distribution of specimens in the space of principal components calculated using 28 morphometric characters demonstrates the absence of separate clusters. Frequency distributions of six studied meristic characters are unimodal and do not demonstrate the existence of morphologically distinguishable forms within the analyzed sample. The results of molecular genetic study, based on the cytochrome b polymorphism analysis of the same sample of fish, demonstrate its homogeneity. The joined results of morphological and molecular genetic analyses of the Russian sturgeon sensu Berg (1934) do not support the validity of the Persian sturgeon as a separate species Acipenser persicus. The text was submitted by the authors in English     

Behavioral response of mature males of acipenseridae to female sex pheromone

It was established that, as in many other representatives of Teleostei, there is a pheromonal regulation of reproductive behavior in Acipenseridae. The postovulatory releasing sex pheromone in Russian sturgeon Acipenser gueldenstaedtii, Persian sturgeon A. persicus, and starred sturgeon A. stellatus is in the ovarian fluid of females, whose odor has an interspecific efficiency and causes manifestation of typical spawning behavior (increase in locomotor activity, attraction to the site of solution presentation, circular swimming, and slightly convulsive movements) in mature males of its own and closely related species. A relationship was found between the ability of males injected with suspension of acetonized hypotheses of acipenserids to respond to odor of ovarian fluid and by both quality and quantity of sperm obtained from them. Data obtained extend our concepts of the role of chemical reception in biology of acipenserids and the range of their chemocommunications.     

Phylogeny and biogeography of Arabian populations of the Persian Horned Viper Pseudocerastes persicus (Duméril,Bibron & Duméril, 1854)

The Persian Horned Viper (Pseudocerastes persicus) is distributed from northeast Iraq through the Iranian Plateau to western Pakistan with isolated populations in the Hajar Mountains of south-eastern Arabia. Like the other members of the genus Pseudocerastes, P. persicus is a sit-and-wait ambush feeder with low vagility, a characteristic that often results in high levels of population differentiation. In order to clarify the level of genetic variability, phylogenetic relationships, and biogeography of the Arabian populations of P. persicus we sequenced 597 base pairs of the mitochondrial cytochrome b of four individuals from the Hajar Mountains in south-eastern Arabia and inferred their phylogenetic relationships including 10 samples of P. persicus from Iran and Pakistan, four P. urarachnoides and one P. fieldi downloaded from GenBank. The four Arabian samples are genetically very similar in the gene fragment analysed and are phylogenetically very closely related to populations of P. persicus from coastal south Iran. Biogeographically, it appears that colonisation of the Hajar Mountains by P. persicus took place from Iran very recently, most probably during the last glaciation, when most of the Persian Gulf was above sea level and did not represent a barrier for dispersal.     

Genetic diversity of lactic acid bacteria in the intestine of Persian sturgeon fingerlings

Lactic acid bacteria (LAB) are often found as sub‐dominant microbial components in the gastrointestinal (GI) tract of fish and have positive effects on the host. They are generally promising candidates for probiotics and can act as substances to improving both native immune responses and growth performance of animals including fish. In the present study the Persian sturgeon Acipenser persicus autochthonous intestinal LAB were investigated. A total of 90 sturgeon fingerlings were sampled and LAB were isolated and enumerated on MRS agar. Initial identification of 47 LAB isolates using standard biochemical and phenotypic tests revealed five dominant phenotypes. Twenty‐one isolates, representatives from each of these phenotypes, were subsequently identified by 16S rRNA sequence analysis. The results showed that cultivable authochthonous LAB ranged from log 2.93 to 5.61 CFU g^?1 intestine, with a mean of 4.38 ± 0.58 CFU g^?1. 16S rRNA sequence analysis revealed that the LAB community was dominated by Lactococcus spp., with Lactococcus garvieae and Lactococcus lactis accounting for 42.55 and 36.17% of the LAB population, respectively. Pediococcus pentosaceus (14.90%), Weissella cibaria (4.25%) and Enterococcus faecalis (2.13%) were identified as minor components of the LAB community. This is the first report of these LAB as members of the microbial community in the intestine of Acipenser persicus. The results show that both potentially pathogenic (i.e. Lactococcus garvieae) and probiotic (i.e. Lactococcus lactis and Weissella cibaria) LAB inhabit the Persian sturgeon GI tract. Future studies should seek to elucidate the relevance of these species to the host.     

Polymorphism of the mitochondrial DNA control region in eight sturgeon species and development of a system for DNA-based species identification

Intraspecific and interspecific nucleotide sequence variations of the mtDNA control region (D-loop) were studied with mtDNAs isolated from tissue specimens of more than 1400 sturgeons of nine species: Russian sturgeon Acipenser gueldenstaedtii, Persian sturgeon A. persicus, Siberian sturgeon A. baerii, Amur sturgeon A. schrenkii, Fringebarbel sturgeon A. nudiventris, sterlet A. ruthenus, stellate sturgeon A. stellatus, beluga Huso huso, and kaluga H. dauricus. The results were used to analyze the interspecific variation of the mtDNA control region in the given set of species and to develop a test system of ten species-specific primers, which allowed species identification from noninvasive tissue samples, spawn, and food products of eight species. The system proved suitable for multiplex PCR. A method was developed for the first time to reliably differentiate the A. baerii mitotype and the baerii-like mitotype of A. gueldenstaedtii. It was found that, although genetically separate, A. gueldenstaedtii and A. persicus are relatively young species and have common mitochondrial haplotypes, precluding their identification via mtDNA analysis alone. To develop a system for species identification of A. gueldenstaedtii and A. persicus, it is necessary to study the polymorphism of nuclear markers.     

Application of enriched <Superscript>137</Superscript>Ba tracer to mark juvenile Persian sturgeon (<Emphasis Type="Italic">Acipenser persicus</Emphasis>)

The present study evaluates the variations of ¹³⁷Ba abundance in pectoral fin spine of 1-month-old juvenile Persian sturgeon (Acipenser persicus) upon marking using the stable isotope approach. The marking of the fish was achieved by incorporation of ¹³⁷Ba²⁺ in the calcified lattice of the pectoral fin spine through substitution with structural Ca²⁺. This process was carried out by rearing juveniles in treatment tanks containing elevated concentrations of ¹³⁷Ba for 1, 3 and 5 days. The marked fish were then retained in natural abundance fresh and brackish waters, to evaluate the trend of exchange of ¹³⁷Ba from the fin spines. The abundance of ¹³⁷Ba in fin spines during marking and post-marking experiments were detected by inductively coupled plasma mass spectrometry (ICP-MS). The results showed that a significant isotope mark can be obtained with no mortality and 100% marking rate on the first day of exposure to the isotope. The marked juveniles maintained their isotopic signature for at least 25 days. Statistical analysis of the obtained ¹³⁸Ba/¹³⁷Ba ratios demonstrated that the successful incorporation of ¹³⁷Ba²⁺ in pectoral fin spines provides an effective marking method for Persian sturgeon restocking programs.     

The use of microsatellite loci for identification of sturgeon species (Acipenseridae) and hybrid forms

The genetic polymorphism of ten sturgeon species that inhabit the territory of the Russian Federation (Russian sturgeon, Siberian sturgeon, Amur sturgeon, Sakhalin sturgeon, Persian sturgeon, ship sturgeon, sterlet, stellate sturgeon, beluga, and kaluga) was examined at five microsatellite loci (Afug41, Afug51, An20, AoxD161, AoxD165) (in total, 3821 individuals). The examined loci were successfully amplified with the same primer set in all species tested and demonstrated a high level of variation. Alleles specific to different species have been identified, which allows them to be used to identify species of sturgeon and their food products. In addition, the possibility of identifying hybrid forms was demonstrated. The assignment test performed in the STRUCTURE software program showed a high probability of correctly assigning each individual to its species based on genotyping with five microsatellite loci examined (96–98%, on average). However, for Russian and Persian sturgeon, the rate of proper species assignment was considerably lower (75 and 84%, respectively).

     

Evolutionary history of the Persian Jird,Meriones persicus,based on genetics,species distribution modelling and morphometric data

The Persian Jird, Meriones persicus, is distributed from Eastern Anatolia to Afghanistan and western Pakistan. Six subspecies were described based on skull features and coat colours, but the validity of these subspecies is uncertain, and no molecular work has ever been conducted on this species. Iran appears to be a key geographical region in which to revise the systematic and evolutionary history of this species, because five of the six subspecies are present in this country. To evaluate the phylogeographical history and taxonomy of this species in Iran, we used a combination of genetic (cytochrome b gene sequences of 70 specimens) and geometric morphometric (2D landmarks on the ventral side of skull of 258 specimens) analyses. We also used ecological niche modelling to make inferences about the evolutionary history of these lineages. Our molecular data highlight the existence of four genetic lineages, but they only partly correspond to the previously described subspecies. Our molecular and morphometric data confirm the validity of M. p. rossicus and show that it has a wider geographical range than previously thought. M. p. gurganensis and M. p. baptistae are genetically very close. The skull of M. p. gurganensis is morphologically distinguishable from other subspecies. The subspecies M. p. persicus and M. p. baptistae are genetically distinct, but morphologically close. Meriones p. ambrosius is genetically close to M. p. persicus, and additional analyses with more specimens are needed to validate its subspecific status. The genetic structure observed in Iran seems to fit the topography and biogeography of the country and emphasize the role of the Abarkooh, Central and Lut deserts as barriers to gene flow. All intraspecific divergent events within the Persian Jird occurred during the last 1.4 My, suggesting that climatic changes probably trigger diversification within this species. Our genetic and species niche modelling results suggest that potential refugial areas persisted during glacial periods for this species in north‐western Zagros Mountains, north‐eastern Alborz Mountains and Kohrud Mountains.     

A review of the past and present status of anadromous fish species in the Netherlands: is restocking the Rhine feasible?

The paper reviews the past, present and future of eight anadromous fish species inhabiting the Lower Rhine (The Netherlands), viz. -sturgeon (Acipenser sturio), whitefish and houting (Coregonus lavaretus, C. oxyrinchus), smelt (Osmerus eperlanus), allis and twaite shad (Alosa alosa, A. fallax), sea trout (Salmo trutta) and salmon (Salmo salar). All species are under threat or became extinct (e.g. sturgeon, allis shad). It is not possible to single out a specific factor for the decline or disappearance. A combination of factors is responsible, as the degradation of the spawning and nursery areas, river correction for shipping, building of sluices and hydropower dams, extraction of sand and gravel and river pollution. The likelihood that a species will return via natural recovery, or restocking is assessed. The return of the sturgeon is unlikely. Present observations of sturgeon can be attributed to releases of unwanted sturgeon hybrids. A natural stock of coregonids in Dutch waters seems not feasible any more due to irreversible habitat degradation. Present day catches originate from German releases. The anadromous smelt, heavily reduced in numbers, still inhabits some of our waters, the non-migratory smelt is still very common. The allis shad is extinct and unlikely to recover. The species never spawned in the Dutch part of the Rhine. Twaite shad, declining in numbers, are still observed in the lower reaches of Rhine and Meuse. Sea trout is presumably still present in the same varying numbers as before. Spawning in our waters has not been documented. The salmon, once fished in large numbers, is now the subject of restocking programmes in Germany. Observations of individuals can partly be attributed to these programmes but also to straying salmon. Restocking programmes should be considerably improved before noticeable success is to be met.     

Growth performance and body composition of sub-yearling Persian sturgeon, (Acipenser persicus, Borodin, 1897), fed different dietary protein and lipid levels

In order to evaluate the protein and energy requirement of Persian sturgeon (Acipenser persicus) sub‐yearlings, eight experimental diets containing two protein levels (40% and 45%) and four lipid levels (10%, 15%, 20% and 25%) were tested. Sturgeons (W₀ = 136.8 g) were fed the experimental diets to satiation four times daily for 150 days, resulting in a final mean weight of 375.8 g. Growth was significantly affected by lipid content of the diets. At 40% protein level, weight gain and specific growth rate (% per day) were significantly improved (P < 0.05) by increasing the dietary lipid (energy) content. Protein efficiency ratio (PER) was significantly affected by different dietary treatments for each dietary protein level tested, reaching a mean value of 3.58 in fish fed high lipid diets and a PER of 2.77 in low lipid diets. Results obtained in the present study suggest that the optimum dietary protein content for Persian sturgeon is 40%, with an estimated optimum protein‐to‐energy ratio of 18–20 mg kJ⁻¹.     

Comparative larval ontogeny of two fish species (Characiformes and Siluriformes) endemic to the São Francisco River in Brazil

The aim of the present study was to perform comparative histological analyses of the ontogenetic development of two fish species endemic to the São Francisco River in Brazil: Prochilodus argenteus and Lophiosilurus alexandri. Histological analyses were performed every 24 h from the moment of hatching until 14 days post-hatching (dph) for the observation of larval development and until 39 dph for the observation of gonadal development. Whole larvae were fixed in Bouin's solution and the histological slides were stained with haematoxylin–eosin. Lophiosilurus alexandri larvae had a larger body size compared with P. argenteus larvae since hatching. Lophiosilurus alexandri larvae had mouth opening and pigmentation of the eyes upon hatching, whereas these events were observed at 1 dph in P. argenteus larvae. The visualisation and the inflation of the swim bladder occurred at 1 and 3 dph, respectively, in the P. argenteus, whereas these events occurred at 2 and 8 dph, respectively, in L. alexandri. Yolk granules were absorbed at 4 dph in P. argenteus and the 10 dph in L. alexandri. At 7 dph, the digestive tube was more differentiated in L. alexandri than P. argenteus and at 14 dph, the digestive system of both species had features of their eating habits: broad stomach and short intestine in L. alexandri, typical of carnivorous habits; stomach with a mechanical function and long intestine in P. argenteus, typical of detritivorous habits. The epithelial lining tissue, formed by a single layer of cells in the newly hatched larvae (0 dph), differentiated throughout the study, exhibiting scales in P. argenteus and numerous club cells in the middle epithelial region of L. alexandri at 39 dph. Undifferentiated gonads with somatic cells and primordial germ cells were observed at 39 dph, with caudal-cranial migration since 1 dph in both species. The anatomic changes during the ontogeny of P. argenteus and L. alexandri larvae are directly associated with the evolutionary history of each species, which explains their feeding habits, behaviour and distribution in the environment: Prochilodus argenteus is detritivorous and actively swims in the water column, whereas L. alexandri is carnivorous and inhabits bottom regions. At 39 dph neither species exhibited sexual differentiation.     

Taste attractiveness of free amino acids for juveniles of Persian sturgeon <Emphasis Type="Italic">Acipenser persicus</Emphasis>

Taste preferences towards 20 free amino acids (L-isomers, 0.1–0.0001 M) were determined in juveniles of Persian sturgeon Acipenser persicus. It was found that most amino acids (16) had a positive effect on extraoral gustatory reception (increased the frequency of catching artificial pellets by fishes). The most efficient amino acids were the following: threonine, histidine, arginine, asparagine, phenylalanine, cysteine, glutamine, and glycine. Fifteen amino acids were efficient for intraoral gustatory receptors: serine, arginine, cysteine, histidine, alanine, and some others. The presence of these amino acids in pellets increased the consumption. Amino acids decreasing the frequency of catching or consumption of pellets were not found. Highly significant positive correlation was found between the amino acid ranges mediated by the extraoral and intraoral gustatory reception. The fishes demonstrated maximum sensitivity to aspartic acid, 0.01 and 0.001 M, respectively, for intraoral and extraoral gustatory systems. The threshold concentrations of arginine and glycine were higher for the intraoral gustatory system (0.01 M) than for the extraoral one (0.1 M). The comparison of Persian sturgeon with sturgeon fishes (Russian sturgeon A. gueldenstaedtii, Siberian sturgeon A, baerii, and starred sturgeon A. stellatus) studied earlier confirmed high species specificity of intraoral taste preferences in representatives of Acipenser genus. Species specificity of extraoral taste ranges was less pronounced.     

Interspecific hybridization in natural sturgeon populations of the Eastern Black Sea: the consequence of drastic population decline?

The eastern part of the Black Sea and its tributaries are suitable habitats for several sturgeon species, among which Acipenser gueldenstaedtii, A. stellatus, A. nudiventris, A. persicus, A. sturio, and H. huso are well documented. However, different threats have led these species to a dramatic decline, all of them are currently listed as Critically Endangered, and some Locally Extinct, in that area. We tested 94 wild sturgeon samples from the Black Sea and Rioni River by analyzing the mitochondrial Control Region and nuclear markers for hybrid identification. The data analyses (1) assessed mitochondrial diversity among samples, (2) identified their species, as well as (3) indicated instances of hybridization. The data collected, besides confirming a sharp decrease of catches of Beluga and Stellate sturgeon in recent years, also revealed four juvenile hybrids between Russian and Stellate sturgeon, providing the first evidence of natural interspecific hybridization in the Rioni. The present communication raises concerns about the status of sturgeon species in this area and underlines the urgent need for conservation programs to restore self-sustaining populations.

     

Comparative enzymologic study of catalytical properties of liver monoamine oxidases of sturgeon fish

We carried out the comparative study of the substrate and inhibitory specificity of liver monoamine oxidases (MAO) of the giant sturgeon Huso huso, the starred sturgeon Acipenser stellatus, the Persian sturgeon Acipenser persicus, and the Russian sturgeon Acipenser gueldenstaedtii. Results of the substrate-inhibitor analysis with use of inhibitors chlorgilin and deprenil, as well as five specific substrates indicate homogeneity of these enzymes. All studied MAO have the several orders higher sensitivity to chlorgilin than to deprenil, with essential interspecies differences being observed. There are determined kinetic parameters of enzymatic deamination (K _M and V) of tyramine, serotonin, noradrenalin, benzylamine, β-phenylethylamine, and N-methylhistamine. All studied enzymes have been established to have the higher activity toward serotonin and noradrenalin-substrates of the MAO A form as compared with benzylamine, β-phenylethylamine, and N-methylhistamine-substrate of the mammalian MAO B form, the maximal activity being characteristic of the giant sturgeon.     

Evolution,biogeography and systematics of the western Palaearctic Zamenis ratsnakes

The phylogenetic relationships between western Palaearctic Zamenis and Rhinechis ratsnakes have been troubled, with recent estimates based on the supermatrix approach questioning their monophyly and providing contradictory results. In this study, we generated a comprehensive molecular data set for Zamenis and closely related ratsnakes to assess their phylogenetic and systematic relationships and infer their spatial and temporal modes of diversification. We obtained a fully resolved and well‐supported phylogeny, which is consistent across markers, taxon‐sets and phylogenetic methods. The close phylogenetic relationship between Rhinechis and Zamenis is well‐established. However, the early branching pattern within this clade, and the position of R. scalaris and Z. hohenackeri, remains poorly supported. The Persian ratsnake Z. persicus is sister to the Mediterranean species Z. situla, Z. longissimus and Z. lineatus, of which Z. situla is sister to a clade containing the latter two species. These results are consistent with a recent phylogenomic study on ratsnakes based on hundreds of loci. Whereas, topological tests based on our data and evidence from such phylogenomic study strongly rejected previous phylogenetic estimates based on the supermatrix approach and demonstrate that these “mega‐phylogenies”, with hundreds of taxa and high levels of missing data, have recovered inconsistent relationships with spurious nodal support. Biogeographical and molecular dating analyses suggest an origin of the ancestor of Rhinechis and Zamenis in the Aegean region with early cladogenesis during the Late Miocene associated with the Aegean arch formation and support a scenario of east‐to‐west diversification. Finally, while we have little morphological and phylogenetic evidence for the distinctiveness between Rhinechis and Zamenis, a classification of them in a single genus, and the designation of Zamenis scalaris (Schinz, 1822), reflects better their evolutionary relationships.