Molecular cloning and functional analysis of Chinese sturgeon (Acipenser sinensis) growth hormone receptor

A full length cDNA encoding the growth hormone receptor (GHR) of Chinese sturgeon was cloned in order to investigate the mechanism of growth hormone in regulating the growth of Chinese sturgeon. The open reading frame of the cloned Chinese sturgeon growth hormone receptor (csGHR) cDNA encodes a trans-membrane protein of 611 amino acids containing all the characteristic motifs of GHR. By sequence alignment, substitutions of amino acid residues highly conserved in other species were identified. Using the CHO cell culture system, the function of csGHR and the biological significance of the amino acid substitution in csGHR were examined. The promoter of serine protease inhibitor 2.1 (Spi2.1) was trans-activated upon stimulation of seabream GH (sbGH) in the csGHR-expressing CHO cells. Furthermore, CHO cells stably expressing csGHR were stimulated to proliferate by sbGH. In agreement with our previous report, Chinese sturgeon growth hormone-binding protein (csGHBP) was detected in the culture medium of CHO cells stably expressing csGHR. Mutation of Asp residue in the ligand binding motif in csGHR to Glu significantly enhanced csGHR’s biological function, whereas mutation of Asp residue to Ala decreased its biological function. The results demonstrated that the cloned csGHR was of full biological function and the csGHBP could be generated through proteolysis of csGHR. These findings might provide new insights into thoroughly understanding the regulatory mechanism of Chinese sturgeon growth.     

Microsatellite and mtDNA analysis of the population structure of grey seals (Halichoerus grypus) from three breeding areas in the Baltic Sea

The growing number of grey seals in the Baltic Sea has led to a dramatic increase in interactions between seals and fisheries. The conflict has become such a problem that hunting was introduced in Finland in 1998 and the Swedish Environment Protection Agency recommended a cull of grey seals starting in 2001. Culling has been implemented despite the lack of data on population structure. Low levels of migration between regions would mean that intensive culling in specific geographic areas would have disproportionate effects on local population structure and genetic diversity. We used eight microsatellite loci and a 489 bp section of the mtDNA control region to examine the genetic variability and differentiation between three breeding sites in the Baltic Sea and two in the UK. We found high levels of genetic variability in all sampled Baltic groups for both the microsatellites and the control region. There were highly significant differences in microsatellite allele frequencies between all three Baltic breeding sites and between the Baltic sites and the UK sites. However, there were no significant differences in mtDNA control region haplotypes between the Baltic sites. This genetic substructure of the Baltic grey seal populations should be taken into consideration when managing the seal population to prevent the hunting regime from having an adverse effect on genetic diversity by setting hunting quotas separately for the different subpopulations. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Long‐term temporal and spatial trends in eutrophication status of the Baltic Sea

Much of the Baltic Sea is currently classified as ‘affected by eutrophication’. The causes for this are twofold. First, current levels of nutrient inputs (nitrogen and phosphorus) from human activities exceed the natural processing capacity with an accumulation of nutrients in the Baltic Sea over the last 50–100 years. Secondly, the Baltic Sea is naturally susceptible to nutrient enrichment due to a combination of long retention times and stratification restricting ventilation of deep waters. Here, based on a unique data set collated from research activities and long‐term monitoring programs, we report on the temporal and spatial trends of eutrophication status for the open Baltic Sea over a 112‐year period using the HELCOM Eutrophication Assessment Tool (HEAT 3.0). Further, we analyse variation in the confidence of the eutrophication status assessment based on a systematic quantitative approach using coefficients of variation in the observations. The classifications in our assessment indicate that the first signs of eutrophication emerged in the mid‐1950s and the central parts of the Baltic Sea changed from being unaffected by eutrophication to being affected. We document improvements in eutrophication status that are direct consequences of long‐term efforts to reduce the inputs of nutrients. The reductions in both nitrogen and phosphorus loads have led to large‐scale alleviation of eutrophication and to a healthier Baltic Sea. Reduced confidence in our assessment is seen more recently due to reductions in the scope of monitoring programs. Our study sets a baseline for implementation of the ecosystem‐based management strategies and policies currently in place including the EU Marine Strategy Framework Directives and the HELCOM Baltic Sea Action Plan.     

Assessing nature and dynamics of POM in transitional environment (the Curonian Lagoon,SE Baltic Sea) using a stable isotope approach

The nature of the particulate organic matter (POM) as well as its temporal and spatial distribution and dynamics in the Curonian Lagoon (south-eastern part of the Baltic Sea) were investigated. The organic matter was characterized by the organic carbon and nitrogen content, δ¹³C and δ¹⁵N signatures as well as POC/Chl-a and C/N ratios. Additionally, data on hydrological, chemical and biological parameters were used for better understanding the POM distribution and dynamics. The sampling was performed at 13 stations in the Curonian Lagoon and its outflow in the Baltic Sea during the 2012–2013 period. Samples were also collected at the Nemunas River mouth in order to test the riverine impact. Obtained results showed that isotopic values of carbon and nitrogen ranged from −36.1‰ to −25.2‰ and from −0.9‰ to 15.5‰, respectively. The isotopic composition, together with the low C/N molar (∼7) and POC/Chl-a ratios (<100) of the POM, suggested the dominance of living phytoplankton in POM throughout the year with the higher input of detrital material (C/N >10, POC/Chl-a ratios >100) in late autumn − winter.The results of multivariate analysis evidenced a spatial distinction of POM distribution in the northern-transitional and central confined areas and allowed us to distinguish the main driving factors. The seasonal variation of the δ¹³C and δ¹⁵N values in POM (towards higher δ¹³C and lower δ¹⁵N values in the summer − early autumn period and lower δ¹³C and higher δ¹⁵N values in the late autumn − spring period) was determined by combination of factors such as availability of inorganic carbon and nitrogen, the riverine discharge, seasonal phytoplankton succession and by the short-term saline water intrusion to the northern-transitional part of the lagoon.     

Indexing serum and mucous biochemical parameters of endangered Chinese sturgeon Acipenser sinensis with implications for health assessment

The Chinese sturgeon (Acipenser sinensis) is a critically endangered aquatic fish. Health monitoring and welfare assessments are critical for the conservation of Chinese sturgeon. In this study, biochemical parameters of serum and skin mucus in Chinese sturgeon were examined to evaluate the potential biomarkers. Serum and mucous samples were obtained from Chinese sturgeon, and the levels of total protein (TP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), creatine kinase (CK), lactic acid (LD), acid phosphatase (ACP), lysozyme (LYZ), glucose (GLU), and cortisol were determined. The concentrations of ALT, AST, cortisol, and LYZ were significantly higher in the mucous group than those in the serum group (p < 0.05). In addition, the concentrations of ALP, ACP, LD, LDH, CK, and TP were significantly higher level in the serum group than those in the mucous group (p < 0.05). Moreover, the correlations between serum and mucous biochemical parameters were established. Statistical analysis showed a positive correlation between serum and skin mucous markers (ACP, cortisol, and LYZ). AST versus ALT in serum and mucus showed a significant positive correlation (p < 0.01). A significant positive correlation was found between cortisol and CK in mucus (p < 0.01). Moreover, LD versus LDH in serum showed a significant but weak positive correlation (p < 0.01). Principal component analysis revealed a complete separation between the serum and mucous groups, with the biomarkers that contributed the most being ALP, TP, ALT, and AST. This study provides baseline data and reference intervals for serum and mucous biochemical parameters in presumably healthy Chinese sturgeons. The current study has important implications for the development of conservation strategies and the conservation status of critically endangered species.     

Water velocity shapes fish movement behavior

Stream and river ecosystems present fluvial fishes with a dynamic energy landscape because moving water generates heterogeneous flow fields that are rarely static in space and time. Fish movement behavior should be consistent with conserving energy in these dynamic flowing environments, but little evidence supporting this hypothesis exists. Here, we tested experimentally whether three general movement behaviors—against the current, with the current, or holding position (i.e., staying in one position and location)—were performed in a way consistent with minimizing the cost of swimming in a heterogeneous flow field. We tested the effects of water velocity on movement behavior across three age classes (0, 1, and 5 years) of two different fluvial specialist fishes, the pallid sturgeon (Scaphirhynchus albus) and shovelnose sturgeon (Scaphirhynchus platorynchus). Individuals from the three age classes were exposed to a continuous and dynamic velocity field ranging from 0.02 to 0.53 m s⁻¹, which represented natural benthic flow regimes occupied by these species in rivers. Both sturgeon species exhibited the same pattern with regard to their tendency to hold position, move upstream, or move downstream. Moving downstream was positively associated with velocity for all age groups. Moving upstream was inversely related to velocity for young fish, but as the fish aged, moving upstream was not related to water velocity. The oldest fish (age 5) moved upstream more frequently compared to the younger age classes. Holding position within a water current was the most frequent behavior and occurred with similar probability across the range of experimental velocity for youngest fish (age 0), but was inversely related to velocity in older fish. Our experiment across age classes suggests that the suite of swimming behaviors exhibited by fluvial specialists might have evolved to mitigate the energetic costs of complex energy landscapes generated by moving water to ultimately maximize net energy gain.     

Heydenius araneus n.sp. (Nematoda: Mermithidae), a parasite of a fossil spider, with an examination of helminths from extant spiders (Arachnida: Araneae)

Abstract. A mermithid, a parasite of a spider (Araneae: Thomisidae) in Baltic amber (40 mya), is described as Heydenius araneus n.sp. (Nematoda: Mermithidae) and represents the first fossil record of a nematode parasite of an arachnid. After a critical examination of reports of naturally occurring helminths of extant spiders, I conclude that although mermithid parasitism is well established in this host group, previous reports of hairworm parasites of spiders are "nomina dubia," putative records, or refer to mermithid nematodes.     

Further expansion of the genus Cercopagis (Crustacea,Branchiopoda, Onychopoda) in the Baltic Sea,with notes on the taxa present and their ecology

The onychopod cladoceran Cercopagis that recently invaded the Baltic Sea is reported from new zones of the northern Baltic proper. Because of successful survival and an expanding distribution range, the addition of Cercopagis to the Baltic fauna is considered to be permanent. What has previously been cited as Cercopagis pengoi encompasses the morphology of several other species, subspecies and forms. Either a number of morphologically similar species is present, or there is a number of spurious species in Cercopagis. The last hypothesis is favoured. The spatial distribution pattern of Cercopagis, as well as that of total zooplankton, was correlated with depth. Deep (>100 m) and shallow (<10 m) stations had significantly lower abundance than stations of intermediate depth (<100 m). An overview of the distribution of C. pengoi group in fresh and brackish waters suggests a high tolerance to environmental factors, but with differences among taxa. Due to this ecological flexibility, the colonization of the Baltic is not unexpected. Increasing salinity may restrict dispersal of cercopagids to the southern areas of the Baltic and to the North Sea, but inland lakes (e.g. in Sweden) present an ecological profile suitable for colonization.     

中华鲟产卵场平面平均涡量计算与分析

采用Delft3D-Flow模型对葛洲坝下游中华鲟产卵场河段进行流场模拟,用实测资料对模型进行验证和参数率定,模拟结果和实测资料基本吻合.在此基础上,阐述了平面平均涡量计算方法,利用模拟所得流速场,通过计算得到中华鲟产卵场河段区域平面平均涡量强度分布.计算结果表明,鱼卵密集区的平面平均涡量为1.38×10-3～1.64×10-3s-1,说明中华鲟产卵对区域平面涡量强度有偏好选择,这种选择具有生物学意义.可为今后保护中华鲟产卵场水力学环境提供理论支持和参考.     

A dynamic mass balance model for phosphorus fluxes and concentrations in coastal areas

This paper presents a general, process-based mass balance model (CoastMab) for total phosphorus (TP) in defined coastal areas (at the ecosystem scale). The model is based on ordinary differential equations and calculates inflow, outflow and internal fluxes on a monthly basis. It consists of four compartments: surface water, deep water, erosion/transportation areas for fine sediments and accumulation areas for fine sediments. The separation between surface water and deep water is not done based on water temperature, but on sedimentological criteria instead (from the theoretical wave base). There are algorithms for all major internal TP fluxes (sedimentation, resuspension, diffusion, mixing and burial). Validations were performed using data from 21 different Baltic coastal areas. The results show that the model predicts monthly TP in water and chlorophyll a very well (generally within the uncertainty bands of the empirical data). The model has also been put through sensitivity tests, which show that the most important factor regulating the predictions of the model is generally the TP concentration in the sea beyond the coast. The model is simple to apply, since all driving variables may be accessed from maps or monitoring programs. The driving variables include coastal area, section area (between the defined coastal area and the adjacent sea), mean and maximum depths, latitude (used to predict water temperatures, stratification and mixing), salinity and TP concentration in the sea. Many of the model structures are general and could be used for areas other than those included in this study, e.g., for open coasts, estuaries or tidal coasts, as well as for other substances than phosphorus.