Adult lake sturgeon (Acipenser fulvescens Rafinesque, 1817) occurrence in the Muskegon River system,a Lake Michigan drowned river mouth,USA

Recent advancements in telemetry have allowed managers and researchers to conduct comprehensive studies on the movement ecology of lake sturgeon (Acipenser fulvescens), a species of conservation concern in most of the Laurentian Great Lakes basin. In Michigan waters of Lake Michigan, drowned river mouth systems (a protected lake-like habitat that connects a river to lake) support 4 of 11 remaining lake sturgeon populations. One of those remnant populations is supported by the Muskegon River, a drowned river mouth system consisting of both Muskegon Lake and the Muskegon River. The objectives of this 6-year telemetry study were to determine whether adult lake sturgeon occupied the Muskegon River system outside of the spawning season (defined as March to July), to quantify their use of the system annually, and to identify and characterize patterns in occurrence. A total of 21 adult lake sturgeon implanted with acoustic transmitters were passively monitored throughout the year during 2012–2017. Eighty-two percent of tagged fish at large were detected ≥1 day in the Muskegon River system annually, and tagged lake sturgeon were frequently detected during both spawning and non-spawning time periods. Residency index (i.e., no. detection days/365 days) values indicated that adult lake sturgeon were not only detected throughout the year but that they occupied the Muskegon River system for an average of 130 days each year (residency index = 0.36 ± 0.05 SE) during our most spatially intensive acoustic monitoring in 2016–2017. Additionally, 24% of tagged lake sturgeon were primary residents (i.e., residency index >0.5) of the Muskegon River system in both years. Adult lake sturgeon followed 1 of 3 patterns of occurrence based on individual detection histories, and those patterns varied temporally and by the relative amount of use (i.e., high, medium, and low). Our findings build on previous research that found drowned river mouth systems in Lake Michigan can be important nursery habitats for juvenile lake sturgeon by showing that these habitats also can be used extensively by adult lake sturgeon throughout the year.     

Periventricular and central nuclei of the pretectal area of diencephalon of the sturgeons

Cytoarchitectonics of periventricular and central nuclei of the pretectal area was studied in four species of the sturgeons: the great sturgeon Huso huso, L., the Russian sturgeon Acipenser gъldenst?dti persicus n. kurensis, Belyaeff, the starred sturgeon Ac. stellatus, Pall., and the barbel sturgeon Ac. nudiventris, Lov.; this pretectum part has a similar structure. Study of these parts of the pretectal area was carried out by methods of Nissl and Bielshowskii modified by Viktorov. In this part of the pretectal area, nine nuclear structures were described, eight of them—nuclear; these are ventral periventricular pretectal nucleus and its dorsal component, dorsal periventricular pretectal nucleus, nucleus of medial longitudinal bundle, subcomissural organ, medial and lateral intercalate nuclei, and central and posterior pretectal nuclei. The main attention has been paid to the issue of the evolutional progression of this part of the pretectal area in the sturgeons as compared with other Actinopterygii.     

A survey of bacterial infections in sturgeon farming in Italy

Sturgeon aquaculture production has increased worldwide, particularly in Italy, yet there is little information about diseases that affect sturgeons. With this study we describe the results of screening for bacterial infections during monitoring campaigns carried out from 2014 to 2017. A total of 402 sturgeons from six sturgeon farms with one or more reared sturgeon species among five species and two hybrids were analysed. Bacteriological exam was positive in 93 individuals (23%) and negative in the remaining 309 (77%). Generally, no external or internal macroscopic lesions were present, though some specimens showed skin lesions, liver anaemia or splenomegaly, which are non‐pathognomonic signs of bacterial infection. The majority of the isolated bacteria were opportunistic. This knowledge base is important to help create a bacterial profile of sturgeons reared in Italy.     

5种鲟鱼免疫球蛋白重链恒定区序列研究

为了探讨几种鲟鱼免疫球蛋白(IgM)所包含的信息与其亲缘和进化之间的关系, 分别对俄罗斯鲟(Acipenser. gueldenstaedtii)、小体鲟(A. ruthenus)、施氏鲟(A. schrenckii)、中华鲟(A. sinensis)和欧鳇(Huso huso)的IgM重链(IgH)恒定区进行了研究。采用RT-PCR的方法对IgH核酸序列进行了克隆, 通过软件获得了相应的IgH氨基酸序列。在分别对这5种鲟鱼免疫球蛋白重链恒定区4个区(CH1～CH4)进行研究后发现, 其CH4区氨基酸序列相似性最高。通过对CH4区序列氨基酸变异期望值(Kaa), 物种分化时间(T)及物种间系统进化树(Phylogenetic Tree)等参数的分析, 将克隆的5种鲟鱼IgH恒定区序列与已发表的西伯利亚鲟同源序列比对(源于NCBI序列)后发现: 西伯利亚鲟与俄罗斯鲟、施氏鲟与欧鳇、小体鲟各构成一个分支, 并与中华鲟相对。实验结果从体液免疫系统的演化这个角度, 反映了被研究的鲟鱼物种间的分类地位、地理分布及进化关系之间的联系。     

The threatened status of acipenseriform species: a summary

...increased demand has recently driven the price of black market smoked sturgeon as high as $ 26 a kilogram. With poachers standing to gain roughly a third of this price [besides the much higher price of caviar], a large fish could be worth thousands of dollars. Gary Hamilton in Canadian Geographic, July/August 1996, p. 62     

Proliferative zones in the brain of the Amur sturgeon fry. Interactions with neuromeres and migration of secondary matrix zones

Neurogenesis in the forebrain region was studied in the Amur sturgeon Acipenser schrenki fry using immunocytochemical marking of the proliferative nuclear antigen. The brain zones with high proliferative activities were located at the brain ventricle surface facing the periventricular cavity. In addition to the periventricular zone of primary proliferation, several secondary proliferative zones were found in the forebrain region of the Amur sturgeon Acipenser schrenki.     

Fertility of females of sturgeon hybrids obtained from species with different levels of ploidy (Acipenser ruthenus and A. dauricus) and their cloning

Main purpose of this work is the identification of females of artificial sturgeon hybrids capable to produce unreduced oocytes. The importance of this task is due to the ability to receive clonal all-female lines. Experiments were performed on the previously obtained reciprocal hybrids of sterlet, Acipenser ruthenus (S) with ~120 chromosomes and kaluga, Acipenser dauricus (K) with ~260 chromosomes. Karyotypes of backcross hybrids of (S × K) female (obtained by crossing sterlet female with kaluga male) and sterlet male included 180 – 190 chromosomes. This means that (S × K) female produced eggs with ~125 chromosomes and its karyotype consisted of ~250 chromosomes. This number was confirmed by a comparative analysis of erythrocyte size in this female and species with different ploidy. Karyotype with ~250 chromosomes can occur in (S x K) female only as a result of fertilization of a diploid sterlet egg (120 chromosomes) with kaluga haploid sperm (~130 chromosomes). Eggs of hybrid fertile (S × K) female, inseminated with inactivated sperm of Amur sturgeon and sterlet, developed into viable gynogenetic offspring, confirmed by the analysis of five microsatellite loci in this progeny, (S x K) female, and males used for UV-inactivated sperm. These data allow us to propose a method for obtaining fertile females of sturgeon hybrids from species with different ploidy. For this, experimentally obtained diploidized eggs from diploid 120-chromosome species must be fertilized by 250–270-chromosome male. Karyotypes of backcross hybrids of (K × S) female (obtained by crossing kaluga female with sterlet male) and sterlet male included ~250 chromosomes and hybrids of this female with kaluga male had ~320 chromosomes. These results proved an ability of hybrid (K × S) female to produce unreduced eggs, resulting in triploid backcrosses. The absence of reduction during egg development is well known in clonal forms (species) of vertebrates, which are of hybrid origin, and in artificially created fish hybrids. However, this has not been reported previously for sturgeons. Insemination of eggs of (K × S) female with UV-inactivated sperm of sterlet and Amur sturgeon led to offspring generation for which the genetic identity to their mother was proved using microsatellite analysis. That is, clonal inheritance was observed. These results suggest the possibility of developing a technology to produce all-female offspring. Artificial production of clonal lines in hybrid vertebrates can be also considered as experimental reproduction of the first stages of reticular speciation in nature.     

Effects of Cycloheximide,Aminoglutethimide, Cytochalasin B,and Colchicine on Ovulation and the Ultrastructure of the Ovarian Follicle Wall in the Stellate Sturgeon Acipenser stellatus Pall

The inhibitor of protein synthesis cycloheximide, inhibitor of steroidogenesis aminoglutethimide, and inhibitor of prostaglandin synthesis indomethacin, as well as the drugs affecting the cell cytoskeleton, such as cytochalasin B and colchicine, were used for studying the mechanisms of ovulation in the stellate sturgeon Acipenser stellatus Pall. Follicles were isolated from the body cavity within certain time intervals after the injection of pituitary suspension to a female and cultivated in media with the inhibitors. In the case of follicles isolated in the middle of the period from hormonal injection until ovulation, cycloheximide, cytochalasin B, and aminoglutethimide suppressed ovulation most effectively, while in the case of oocytes isolated during the last quarter of this period, aminoglutethimide and cytochalasin B were the most effective. It was shown using TEM and SEM that cycloheximide suppressed all processes related to the preparation for ovulation, except the initial ones: contraction of follicle cells and their processes and secondary flattening of these cells. In the presence of aminoglutethimide, the follicle cells underwent pathological changes. Incubation in the media containing indomethacin and colchicine prevented degradation of the outer theca layer at the follicle apex. In the presence of cytochalasin B affecting the cytoskeleton, the drawing of follicle cell processes from the jelly coat channels was blocked, the outer theca cells were strongly contracted, but the cell layer integrity was affected and it was divided in separate fragments. A relationship is discussed between the metabolic processes and morphological changes that lead to ovulation. It was proposed on the basis of the present and previous data that the preovulatory preparation of the follicle tissues comprises two contractile and two apoptotic processes distinctly coordinated in time and space.     

鲟致病性类志贺邻单胞菌的鉴定及药物敏感性

【目的】2012年夏季北京地区多地养殖的鲟鱼发病,主要临床症状为肛门红肿、伴有黄色分泌物,腹腔内有大量腹水,腹腔内壁有出血点,肝脏点状出血,脾脏肿大等,累计死亡率达60%。本文目的为研究其病原。【方法】从具有临床症状的濒死鱼中分离病原菌,分析病原菌的形态特征、理化特性、分类地位及药物敏感性等特性,经过人工感染及引起的组织病理确认致病性。【结果】结果显示病原菌的16S rDNA序列构建的进化树,与类志贺邻单胞菌同源性最高,在99%以上;结合其生理生化特征和API细菌鉴定系统的结果,确认为类志贺邻单胞菌。该菌对鲟鱼的半致死量LD50为1.0×105.8CFU/mL,引起肝、肾和脾组织病变。胞外产物不具有淀粉酶、蛋白酶、脂肪酶和明胶酶活性,也无溶血性,推测其毒性可能来源于内毒素。该菌对恩诺沙星、盐酸多西环素、氟苯尼考和甲枫霉素敏感,药物敏感浓度均小于2μg/mL;而对试验的其它抗菌药物不敏感。【结论】确认类志贺邻单胞菌是引起北京地区鲟鱼发生上述临床症状疾病的主要致病菌,可优选盐酸多西环素、氟苯尼考和恩诺沙星进行防治。