Variability of blood proteins in sturgeon ontogenesis and possible aspects of evolution in the family Acipenseridae

The developmental changes in blood proteins of three sturgeons genera Acipenser, Huso, and Pseudoscaphirhynchus (fam. Acipenseridae), have been studied using immunological methods. Heterochronicity and staging of protein development are revealed. Initially, proteins defining the specificity of immunoelectrophoregrams and subject to inconsiderable changes with fish growth are formed. The formation of transferrins is completed in the latest turn. Patterns of development do not depend on the ecology of anadromous and potamodromous forms of sturgeons. This results in the monotypic immunoelectrophoregrams of blood proteins in adult individuals of ten fish species. It is suggested that the variability of blood proteins in the ontogenesis of sturgeons reflects the evolution of this fish through consecutive adaptation to sea waters of different salinities and transition of ancient ancestors to the anadromous mode of life under conditions of oceanic salinity. The modern potamodromous sturgeons may have originated as a result of the return of anadromous forms to life in fresh waters.     

Research Tools to Investigate Movements,Migrations, and Life History of Sturgeons (Acipenseridae), with an Emphasis on Marine-Oriented Populations

Worldwide, sturgeons (Acipenseridae) are among the most endangered fishes due to habitat degradation, overfishing, and inherent life history characteristics (long life span, late maturation, and infrequent spawning). As most sturgeons are anadromous, a considerable portion of their life history occurs in estuarine and marine environments where they may encounter unique threats (e.g., interception in non-target fisheries). Of the 16 marine-oriented species, 12 are designated as Critically Endangered by the IUCN, and these include species commercially harvested. We review important research tools and techniques (tagging, electronic tagging, genetics, microchemistry, observatory) and discuss the comparative utility of these techniques to investigate movements, migrations, and life-history characteristics of sturgeons. Examples are provided regarding what the applications have revealed regarding movement and migration and how this information can be used for conservation and management. Through studies that include Gulf (Acipenser oxyrinchus desotoi) and Green Sturgeon (A. medirostris), we illustrate what is known about well-studied species and then explore lesser-studied species. A more complete picture of migration is available for North American sturgeon species, while European and Asian species, which are among the most endangered sturgeons, are less understood. We put forth recommendations that encourage the support of stewardship initiatives to build awareness and provide key information for population assessment and monitoring.     

Formation of populations of Acipenseridae sturgeons in the Volga-Caspian basin

Analysis of dynamics of commercial catches and the state of populations of Russian sturgeon Acipenser gueldenstaedtii, starred sturgeon A. stellatus, and great sturgeon A. huso (Huso huso) in the Caspian Sea is presented. In the retrospective, the role of natural and artificial reproduction in formation of populations of Acipenseridae sturgeons is considered. The main principles of rational organization of practical activity for preservation and restoration of populations of Acipenseridae sturgeons are formulated.     

Sex steroids in the serum of Caspian sturgeons and their specific cytosol binding in brain and gonads during the migratory cycle

Testosterone (T) and estradiol 17β (E2) concentrations were measured in the serum of Russian, stellate and beluga sturgeons. Hormone concentrations were comparatively low during the feeding period at sea and did not differ between seasons or species. At the beginning of the spring spawning migration into freshwater, both of the spring and winter races of Russian sturgeon ( Acipenser gueldenstaedtii ) and beluga sturgeon ( Huso huso ), as well as the spring-summer race of stellate sturgeon ( Acipenser stellatus ), exhibited a marked elevation of serum T, despite differences in their degrees of gonadal development. There were no differences in specific cytosol binding of androgens and estrogens in the forebrain of either migratory form of Russian sturgeon, while the specific binding of sex steroids was higher in the hypothalamus of the spring form. The data indicate that T and its receptors may control aspects of anadromous migration in sturgeons.     

Olfactory metamorphosis in the coastal tailed frog Ascaphus truei (Amphibia,Anura, Leiopelmatidae)

The structure of the olfactory organ in larvae and adults of the basal anuran Ascaphus truei was examined using light micrography, electron micrography, and resin casts of the nasal cavity. The larval olfactory organ consists of nonsensory anterior and posterior nasal tubes connected to a large, main olfactory cavity containing olfactory epithelium; the vomeronasal organ is a ventrolateral diverticulum of this cavity. A small patch of olfactory epithelium (the “epithelial band”) also is present in the preoral buccal cavity, anterolateral to the choana. The main olfactory epithelium and epithelial band have both microvillar and ciliated receptor cells, and both microvillar and ciliated supporting cells. The epithelial band also contains secretory ciliated supporting cells. The vomeronasal epithelium contains only microvillar receptor cells. After metamorphosis, the adult olfactory organ is divided into the three typical anuran olfactory chambers: the principal, middle, and inferior cavities. The anterior part of the principal cavity contains a “larval type” epithelium that has both microvillar and ciliated receptor cells and both microvillar and ciliated supporting cells, whereas the posterior part is lined with an “adult‐type” epithelium that has only ciliated receptor cells and microvillar supporting cells. The middle cavity is nonsensory. The vomeronasal epithelium of the inferior cavity resembles that of larvae but is distinguished by a novel type of microvillar cell. The presence of two distinct types of olfactory epithelium in the principal cavity of adult A. truei is unique among previously described anuran olfactory organs. A comparative review suggests that the anterior olfactory epithelium is homologous with the “recessus olfactorius” of other anurans and with the accessory nasal cavity of pipids and functions to detect water‐borne odorants. J. Morphol. 2011. © 2011 Wiley Periodicals, Inc.     

基于线粒体基因组全序列的鲟形目鱼类(Pisces: Acipenseriformes)的分子系统发育重建

为厘清鲟形目鱼类的系统发育, 研究新测定了中华鲟(Acipenser sinensis)、长江鲟(A. dabryanus)、短吻鲟(A. brevirostrum)、纳氏鲟(A. naccarii)、鳇(Huso dauricus)和匙吻鲟(Polyodon spathula)共6种鲟类的线粒体全基因组序列。联合已测的17种鲟类的线粒体基因组数据, 利用最大似然法和贝叶斯法重建了鲟形目鱼类的分子系统发育关系, 并采用似然值检验对不同的树拓扑结构进行了评价。结果表明, 6种新测鲟类的线粒体基因组大小为16521—16766 bp, 编码13个蛋白质编码基因、22个转运RNA基因和2个核糖体基因, 与大多数已测的鲟类的线粒体基因组结构高度相似。基于23种鲟形目鱼类线粒体基因组数据, 系统发育分析的结果表明: (1)鲟形目的两个科, 匙吻鲟科(Polyodontidae)和鲟科(Acipenseridae)均为单系; (2)鲟科的内部亲缘关系复杂, 鲟属和鳇属的物种均不构成单系群。鲟科鱼类按分子系统发育重建结果可以分为3个类群: 尖吻鲟类(A. sturio - A. oxyrinchus clade)、大西洋鲟类(Atlantic clade)和太平洋鲟类(Pacific clade)。树拓扑结构的检验结果表明, 鲟科的系统发育关系为(尖吻鲟类(太平洋鲟类, 大西洋鲟类))。铲鲟属(Scaphirhynchus)是大西洋鲟类的基部类群。研究也说明线粒体基因组数据在鲟形目鱼类系统与进化研究方面具有重要应用价值。     

Historical reconstruction of sturgeon (Acipenser spp.) spatiotemporal distribution and causes for their decline in North-Western Europe

Biodiversity and Conservation - This study aims to reconstruct the historical spatiotemporal distribution of the anadromous sturgeons, Acipenser sturio and A. oxyrinchus, in NW-Europe (especially...     

Screening and identification of female-specific DNA sequences in octaploid sturgeon using comparative genomics with high-throughput sequencing

In this study, six candidate female-specific DNA sequences of octaploid Amur sturgeon (Acipenser schrenckii) were identified using comparative genomic approaches with high-throughput sequencing data. Their specificity was confirmed by traditional PCR. Two of these sex-specific sequences were also validated as female-specific in other eight sturgeon species and two hybrid sturgeons. The identified female-specific DNA fragments suggest that the family Acipenseridae has a ZZ/ZW sex-determining system. However, one of the two DNA sequences has been deleted in some sturgeons such as Sterlet sturgeon (Acipenser ruthenus), Beluga (Huso huso) and Kaluga (H. dauricus). The difference of sex-specific sequences among sturgeons indicates that there are different sex-specific regions among species of sturgeon. This study not only provided the sex-specific DNA sequences for management, conservation and studies of sex-determination mechanisms in sturgeons, but also confirmed the capability of the workflow to identify sex-specific DNA sequences in the polyploid species with complex genomes.     

Past and current status of sturgeons in the upper and middle Danube River

Of the six species of sturgeons native to the Danube basin, five occurred in the upper and middle Danube. Among anadromous sturgeons were the large winter races of beluga, Huso huso, Russian sturgeon, Acipenser gueldenstaedtii, and stellate sturgeon, A. stellatus, which ascended the middle, and sometimes also the upper Danube, to spawn. Due to overfishing, followed by severe habitat alteration including damming and pollution, these anadromous sturgeons are critically endangered or extirpated from the upper and middle Danube. Acipenser gueldenstaedtii and A. nudiventris are represented only as resident non-migratory races with very small populations. The most abundant and widely distributed species is the sterlet, A. ruthenus, although it is presently limited to the middle Danube. Its population increased in some sections of the middle Danube during the past 15 years, presumably because of improving water quality, but this species remains at risk because of continuing habitat degradation.     

Disturbances in the ploidy level in the gynogenetic sterlet <Emphasis Type="Italic">Acipenser ruthenus</Emphasis>

Artificial mitotic gynogenesis, a chromosome set manipulation, is applied to provide the homozygous progeny with only maternal inheritance. Here, gynogenetic development was induced in the sterlet Acipenser ruthenus L. (Acipenseridae) by activation of the eggs originating from albino females with the UV-irradiated spermatozoa from wild-coloured males, followed by the heat shock applied to suppress the first mitotic division in the haploid zygotes. All experimentally obtained gynogenetic offspring possessed recessive albino coloration. Moreover, the genetic verification, based on three microsatellite DNA markers, confirmed the only maternal inheritance in the albino progeny. Cytogenetic screening enabled identification of the aneuploids, haploids, diploids, triploids, tetraploids and mosaic individuals among the gynogenetic larvae that hatched from the eggs subjected to the heat shock. Furthermore, 40% of the larvae from the haploid variants of the research that were not exposed to the temperature shock showed the diploid chromosome number. A variation of the ploidy level observed in the gynogenetic sterlets may be the consequence of the spontaneous polyploidisation that occurred in the haploid zygotes. Moreover, observation during embryogenesis showed varied stages of eggs development and the asynchronous cell cleavages that may have resulted in the chromosomal disturbances observed in the gynogenetic sterlets here.     

Localization of Phosphatase Responsible for Hydrolysis of Inositol 1,4,5-Triphosphate in the Olfactory Lining of True Sturgeons

The paper presents results of a cytochemical study of localization of phosphatase responsible for hydrolysis of inositol 1,4,5-triphosphate (ITP) in the olfactory lining of true sturgeons (the sturgeon, starred sturgeon, and sterlet). Reaction products as a dark discrete granules are localized in the apical parts of epithelium, practically in the same manner in all the species studied. The precipitate is found on the plasma membranes of cilia, microvilli, and clava of the olfactory cells. Occasionally, the precipitate is also found in the cilia, basal bodies, and rootlets of microvillar cells. The ITP-hydrolyzing phosphatase is supposed to restrict development of transduction process by removing excess messengers from the operating system. The data obtained indicate that in the true sturgeons, the phospholipase cascade of olfactory transduction is concentrated predominantly in the cilia and microvilli of olfactory cells.     

Cytoskeletal F-actin patterns in whole-mounted larval and adult salivary glands of the fleshfly, Sarcophaga bullata.

The patterns of filamentous actin were analysed in different larval, pupal and adult stages in the salivary glands of the fleshfly Sarcophaga bullata. Using the rhodamine labelled phalloidin staining method in combination with detergent extraction specific actin filament distribution was detected. The salivary glands which are histolysed during the process of metamorphosis show distinct cellular morphology and actin filament patterns in larvae and adults. The large third instar larval salivary gland cells contain a well developed apicolateral microvillar zone. In third instar larvae this microvillar zone invaginates and expands in the basal part of the lateral membranes. Larval salivary gland cells also contain numerous parallel basal actin bundles. The larval glands are histolysed during metamorphosis and adult glands are formed out of the imaginal cell group. At the onset of metamorphosis these basal actin bundles form a network of crossing bundles. The filamentous actin patterns of the proximal part of adult gland cells is confined to the apicolateral microvillar membranes. The cells in the distal, tubular part of the adult salivary glands show intense staining of their folded lateral membranes.     

Intravital Sex Identification of Adult Sterlets <Emphasis Type="Italic">Acipenser ruthenus</Emphasis> (Acipenseridae) Based on the Morphological Structure of Dorsal Scutes

We studied the morphological structure of dorsal scutes in adult individuals of Acipenser ruthenus. We determined the morphometric indices of scutes, the values of which are different in males and females. We created a system for sex identification in sterlets based on indices and criteria indicative of the shape of the first five scutes. The results can be used for developing a method for intravital sex identification in sturgeons at earlier stages of development.     

First evidence of hybridization between endangered sterlets (Acipenser ruthenus) and exotic Siberian sturgeons (Acipenser baerii) in the Danube River

Most natural populations of Eurasian sturgeons have declined dramatically during recent decades, reaching historic low levels today. During the same period, sturgeon has become very popular in European aquaculture. Because many hatcheries are located near rivers, their unintentional escape is often documented, especially during floods. Until now, no cases of successful hybridization of these escaped fish with wild stocks have been reported. In this study, the genetic structure of a highly threatened population of sterlets (Acipenser ruthenus) from the Upper Danube was analysed as a requirement for their conservation. Surprisingly, we observed genotypes and morphotypes of Siberian sturgeon (Acipenser baerii), as well as hybrids between this species and native sterlets. This hybridization poses a serious threat for the survival of this isolated sterlet population in the upper part of the Danube. For the first time, natural reproduction is documented for Siberian sturgeon outside their natural range in Europe. This finding demonstrates the risk of extinction by hybridisation of endangered populations. We would like to stress that taking into consideration the risks for native sturgeon populations, farmed sturgeon should not be released into the wild, and all measures should be taken to prevent their accidental escape.     

Osteology and phylogenetic interrelationships of sturgeons (Acipenseridae)

Sturgeons (Acipenseridae) are an ancient and unique assemblage of fishes historically important to discussions of actinopterygian evolution. Despite their basal position within Actinopterygii, rigorous comparative morphological studies of acipenserids have never been made, and most ideas about acipenserid evolution hinge on an untested impression that shovelnose sturgeons (Scaphirhynchini) are phylogenetically primitive. This impression promoted ideas that: (1) the earliest acipenserids were highly benthic and evolved secondarily into pelagic predators, and (2) paedomorphosis has dominated mechanisms affecting their morphological change. Using cladistic methods, this study examines generic level interrelationships within Acipenseridae. Representatives of the four acipenserid genera Huso, Acipenser, Pseudoscaphirhynchus, and Scaphirhynchus, as well as their acipenseriform outgroups Polyodontidae, Peipiaosteidae, and Chondrosteidae, were surveyed for skeletal characters. Sixty-nine characters are identified and described to support the first generic level cladogram of Acipenseridae. Huso is phylogenetically primitive within Acipenseridae and the sister group to a redefined subfamily Acipenserinae. Acipenser is not supported by any characters identified in this study, but the tribe Scaphirhynchini comprising Scaphirhynchus and Pseudoscaphirhynchus is found to be monophyletic. The cladogram contradicts historical ideas about acipenserid evolution because Huso defines an outgroup morphology and life history founded on pelagic habitats and piscivory. In contrast, acipenserines, and more markedly scaphirhynchines, are benthic predators possessing character complexes for benthic feeding, respiration, locomotion, and protection. Also, the pattern of character acquisition within Acipenseridae suggests that peramorphosis played a central role in acipenserid evolution. Peramorphic addition and enlargement of the skeleton and scalation defines most characters at all nodes within Acipenseridae, and repudiates paedomorphosis as a major trend in evolution within the family Acipenseridae.     

Olfactory metamorphosis in the Coastal Giant Salamander (Dicamptodon tenebrosus)

This study examined the gross morphology and ultrastructure of the olfactory organ of larvae, neotenic adults, and terrestrial adults of the Coastal Giant Salamander (Dicamptodon tenebrosus). The olfactory organ of all aquatic animals (larvae and neotenes) is similar in structure, forming a tube extending from the external naris to the choana. A nonsensory vestibule leads into the main olfactory cavity. The epithelium of the main olfactory cavity is thrown into a series of transverse valleys and ridges, with at least six dorsal and nine ventral valleys lined with olfactory epithelium, and separated by ridges of respiratory epithelium. The ridges enlarge with growth, forming large flaps extending into the lumen in neotenes. The vomeronasal organ is a diverticulum off the ventrolateral side of the main olfactory cavity. In terrestrial animals, by contrast, the vestibule has been lost. The main olfactory cavity has become much broader and dorsoventrally compressed. The prominent transverse ridges are lost, although small diagonal ridges of respiratory epithelium are found in the lateral region of the ventral olfactory epithelium. The posterior and posteromedial wall of the main olfactory cavity is composed of respiratory epithelium, in contrast to the olfactory epithelium found here in aquatic forms. The vomeronasal organ remains similar to that in large larvae, but is now connected to the mouth by a groove that extends back through the choana onto the palate. Bowman's glands are present in the main olfactory cavity at all stages, but are most abundant and best developed in terrestrial adults. They are lacking in the lateral olfactory epithelium of the main olfactory cavity. At the ultrastructural level, in aquatic animals receptor cells of the main olfactory cavity can have cilia, short microvilli, a mix of the two, or long microvilli. Supporting cells are of two types: secretory supporting cells with small, electron-dense secretory granules, and ciliated supporting cells. Receptor cells of the vomeronasal organ are exclusively microvillar, but supporting cells are secretory or ciliated, as in the main olfactory cavity. After metamorphosis two distinct types of sensory epithelium occur in the main olfactory cavity. The predominant epithelium, covering most of the roof and the medial part of the floor, is characterized by supporting cells with large, electron-lucent vesicles. The epithelium on the lateral floor of the main olfactory cavity, by contrast, resembles that of aquatic animals. Both types have both microvillar and ciliated receptor cells. No important changes are noted in cell types of the vomeronasal organ after metamorphosis. A literature survey suggests that some features of the metamorphic changes described here are characteristic of all salamanders, while others appear unique to D. tenebrosus.     

The skull of the Chinese sturgeon,Acipenser sinensis (Acipenseridae)

The Chinese sturgeon, Acipenser sinensis, is a large member of Acipenseridae now found only in the Yangtze River and the Yellow and East China seas. The goal of this paper was to describe the skull of A. sinensis in the context of recent anatomical and systematic studies of sturgeons. Five specimens (354–670 mm standard length) were prepared as skeletons. The left and right parietals and frontals are broadly separated by a median fontanelle. The lateral‐most lateral extrascapular variably supports the confluence of the supratemporal, occipital and trunk lateral lines. There is no distinct ventral supraorbital process as found in other sturgeons. The anterodorsal portion of the snout is unique among Acipenseridae by having a single large anamestic dorsal rostral bone instead of a series of separate dorsal rostral bones. There are 0–2 lateral rostral bones on each side positioned anterior to but not in contact with the horizontal arm of the jugal. The dorsal surface of the neurocranium lacks a pineal opening, and its anterior tip is sharply pointed in the smaller specimens examined and gently curved in larger specimens. The anteromedial arm of the palatopterygoid is broad relative to other acipenserids. These new morphological data are discussed and compared among Acipenseridae.     

Impact of the Alien Species <Emphasis Type="Italic">Mnemiopsis leidyi</Emphasis> A. Agassiz, 1865 on Fish of the Caspian Sea

The data of long-term ecological studies (1999–2014) are used for assessing the impact of a new Caspian invader Mnemiopsis leidyi A. Agassiz, 1865 on marine and anadromous fish species. The introduction of the ctenophore and its massive development in the Caspian Sea have mainly affected planktophagous fish, especially the most abundant species anchovy sprat (Clupeonella engrauliformis Borodin, 1904) and sturgeons (Family Acipenseridae). Mnemiopsis leidyi is one of the main negative factors preventing the restoration of the populations of Caspian fishes, especially anchovy tyulka. The critical state of the resources of the spawning parts of sturgeon populations (Family Acipenseridae) has been reinforced as a result of the massive development of M. leidyi.     

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.     

Expression of olfactory receptors in different life stages and life histories of wild Atlantic salmon (Salmo salar)

It has been hypothesized that salmonids use olfactory cues to return to their natal rivers and streams. However, the key components of the molecular pathway involved in imprinting and homing are still unknown. If odorants are involved in salmon homing migration, then olfactory receptors should play a critical role in the dissipation of information from the environment to the fish. Therefore, we examined the expression profiles of a suite of genes encoding olfactory receptors and other olfactory-related genes in the olfactory rosettes of different life stages in two anadromous and one non-anadromous wild Atlantic salmon populations from Newfoundland, Canada. We identified seven differentially expressed OlfC genes in juvenile anadromous salmon compared to returning adults in both populations of anadromous Atlantic salmon. The salmon from the Campbellton River had an additional 10 genes that were differentially expressed in juveniles compared to returning adults. There was no statistically significant difference in gene expression of any of the genes in the non-anadromous population (P < 0.01). The function of the OlfC gene products is not clear, but they are predicted to be amino acid receptors. Other studies have suggested that salmon use amino acids for imprinting and homing. This study, the first to examine the expression of olfactory-related genes in wild North American Atlantic salmon, has identified seven OlfC genes that may be involved in the imprinting and homeward migration of anadromous Atlantic salmon.