Comparison of methods to quantify metabolic rate and its relationship with activity in larval lake sturgeon Acipenser fulvescens

Until recently most studies have focussed on method development for metabolic rate assessment in adult and/or juvenile fish with less focus on measurement of oxygen consumption (ṀO₂) during early life history stages, including fast-growing larval fish and even less focus on nonteleostean species. In the present study we evaluated measurement techniques for standard metabolic rate (SMR), maximum metabolic rate (MMR) and aerobic scope in an Acipenseriform, the lake sturgeon Acipenser fulvescens, throughout the first year of life. Standardized forced exercise protocols to assess MMR were conducted for 5 or 15 min before or after measurement of SMR. We used different levels of oxygen decline during the measurement period of MMR post forced exercise to understand the influence these may have on the calculation of MMR. Opercular rate and tail beat frequencies were recorded by video as measures of behaviours and compared to metabolic rate recorded over a 24 h period. Results indicate that calculated values for aerobic scope were lower in younger fish. Neither exercise sequence nor exercise duration influenced metabolic rate measurements in the younger fish, but exercise duration did affect measurement of MMR in older fish. Finally, there was no strong correlation between metabolic rate and the measured behaviours in the lake sturgeon at either age. Based on the results, we recommend that a minimum of 6 h of acclimation to the respirometry chamber should be given prior to measuring SMR, a chasing protocol to elicit MMR should ideally be performed at the end of experiment, a short chasing time should be avoided to minimize variation and assessment of MMR should balance measurement limitations of the probes along with when and for how long oxygen consumption is measured.     

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.     

Experimental assessment of predation risk for juvenile green sturgeon,Acipenser medirostris,by two predatory fishes

Predation is a common cause of early life stage mortality in fishes, with reduced risk as individuals grow and become too large to be consumed by gape-limited predatory fishes. Large-bodied species, such as sturgeon, may reach this size-refuge within the first year. However, there is limited understanding of what this size threshold is despite the value of this information for conservation management. We conducted laboratory-based predation experiments on juvenile green sturgeon, Acipenser medirostris, to estimate vulnerability to predation during outmigration from their natal reaches in California to the Pacific Ocean. Two highly abundant and non-native predatory fish species (largemouth bass, Micropterus salmoides, and striped bass, Morone saxatilis) were captured in the wild to be tested with developing juvenile green sturgeon from the UC Davis Green Sturgeon Broodstock Program. Experimental tanks, each containing five predators, received thirty prey for 24-hr exposures. Between sturgeon prey trials, predators were exposed to alternative prey species to confirm predators were exhibiting normal feeding behaviors. In addition to green sturgeon mortality data, trials were video recorded and predatory behaviors were quantified. Overall, these predator species displayed much lower rates of predation on juvenile green sturgeon than alternate prey. Predation decreased with green sturgeon size, and predation risk diminished to zero once sturgeon reached a length threshold of roughly 20–22 cm total length, or between 38% and 58% of predator total length. Behavioral analyses showed low motivation to feed on green sturgeon, with both predators attempting predation less frequently as sturgeon grew. Results of this study imply that optimizing growth rates for larval and juvenile sturgeon would shorten the time in which they are vulnerable to predation. Future experiments should assess predation risk of juvenile green sturgeon by additional predator species common to the Sacramento-San Joaquin watershed.     

黑龙江省东完达山地区东北虎猎物种群现状及动态趋势

猎物种群丰度是限制虎分布和数量的关键因子,因此猎物种群密度监测和估算是虎保护的重要内容之一。应用采用大样方法,地理信息系统技术和多元统计分析,研究了黑龙江东完达山东部地区东北虎猎物种群(马鹿、狍子和野猪)现状及动态变化趋势。结果表明:研究地区马鹿的种群平均密度为(0.2010±0.0270)只/km²、狍子的平均种群密度为(0.4980±0.0436)只/km²、野猪的平均种群密度为(0.3423±0.0275)只/km²。单因素方差分析表明,在相同生境下,3种有蹄类密度在在阔叶混交林中和杂木林中差异极为显著;不同的生境,3种猎物的猎物的密度也存在着显著差异。相关分析表明马鹿密度和野猪密度程正相关,而马鹿密度和狍子密度、狍子密度和野猪密度则不相关。 同1989年该地区东北虎猎物种群相比:1989-2002年的13 a时间内马鹿的年平均递减率为13.48%、狍子的年平均递减率为12.69%、野猪的年平均递减率为1.89%。     

A new species of the genus <Emphasis Type="Italic">Platimeliphyllum</Emphasis> N. Maslova from the Paleocene of the Amur Region,Russia

A new species, Platimeliphyllum valentinii, is described from the Paleocene of the Amur Region on the basis of macromorphological and epidermal characters. It was shown that leaves of Platimeliphyllum N. Maslova associate with two fundamentally different types of reproductive structures: platanaceous Archaranthus N. Maslova et Kodrul and Bogutchanthus N. Maslova, Kodrul et Tekleva, which combines characters of the Platanaceae and Hamamelidaceae. The higher evolutionary stability of leaf structures in comparison with reproductive organs is discussed.     

Population Status of North American Green Sturgeon, Acipenser medirostris

North American green sturgeon, Acipenser medirostris, was petitioned for listing under the Endangered Species Act (ESA). The two questions that need to be answered when considering an ESA listing are; (1) Is the entity a species under the ESA and if so (2) is the “species” in danger of extinction or likely to become an endangered species in the foreseeable future throughout all or a significant portion of its range? Green sturgeon genetic analyses showed strong differentiation between northern and southern populations, and therefore, the species was divided into Northern and Southern Distinct Population Segments (DPSs). The Northern DPS includes populations in the Rogue, Klamath-Trinity, and Eel rivers, while the Southern DPS only includes a single population in the Sacramento River. The principal risk factors for green sturgeon include loss of spawning habitat, harvest, and entrainment. The Northern DPS is not considered to be in danger of extinction or likely to become an endangered species in the foreseeable future. The loss of spawning habitat is not large enough to threaten this DPS, although the Eel River has been severely impacted by sedimentation due to poor land use practices and floods. The two main spawning populations in the Rogue and Klamath-Trinity rivers occupy separate basins reducing the potential for loss of the DPS through catastrophic events. Harvest has been substantially reduced and green sturgeon in this DPS do not face substantial entrainment loss. However there are significant concerns due to lack of information, flow and temperature issues, and habitat degradation. The Southern DPS is considered likely to become an endangered species in the foreseeable future. Green sturgeon in this DPS are concentrated into one spawning area outside of their natural habitat in the Sacramento River, making them vulnerable to catastrophic extinction. Green sturgeon spawning areas have been lost from the area above Shasta Dam on the Sacramento River and Oroville Dam on the Feather River. Entrainment of individuals into water diversion projects is an additional source of risk, and the large decline in numbers of green sturgeon entrained since 1986 causes additional concern.     

The Effect of Temperature Stress on Development and Heat-shock Protein Expression in Larval Green Sturgeon (Acipenser mirostris)

Water temperature is an important environmental variable influencing the distribution and health of coldwater fishes such as the green sturgeon, Acipenser medirostris. In this study, we investigated if larval sturgeon were able to tolerate or recover from acute, non-lethal temperature stress that commonly causes deformed notochords, and sought to identify the role of heat-shock proteins (hsp) in stress tolerance. The hsp response is one of the most important cellular mechanisms to prevent the damaging effects of thermal cellular stress, and differences in the ability to over-express hsps during stressful conditions may be associated with an organism’s vulnerability and the extent of thermal injury. In this study, newly hatched larvae were maintained at 17°C (control), or exposed to (a) 26°C for 3 d then maintained at 17°C until yolk-sac absorption or (b) 26°C until yolk-sac absorption. Individuals with deformed notochords were counted, and hsp60, 72, 78 and 89 were analyzed in both normal and deformed larvae by western blotting. Approximately 33% of fish developed curved notochords within the first 3 d of exposure to 26°C. After transfer to cool water 16.5% showed deformities at stage 45, suggesting a significant number of larvae had recovered. Hsp levels remained elevated for at least 9 days after termination of heat-exposure. Overall, percentage of deformed larvae, and hsp72/hsp78 levels were highest in fish continuously exposed to 26°C until yolk-sac absorption. Deformed individuals had significantly higher expression levels of hsp72 and hsp78, and lower hsp60 levels than normal larvae. We conclude that expression of hsp72 and hsp78 and potentially hsp60 are linked to phenotypic variation in the response and vulnerability of green sturgeon larvae to thermal stress.     

葛洲坝下游中华鲟(Acipenser sinensis)产卵场地形分析

根据1981年葛洲坝截流至1998年对葛洲坝坝下河床研究的历史资料,结合1999~2006年间获得的中华鲟产卵场所在江段河床的5次地形数据,采用ArcGIS9.0软件,对中华鲟产卵场河床的高程、坡度、坡向等地形因子进行了详细分析。结果表明:葛洲坝至磨基山江段中华鲟产卵场与历史产卵场相比具有极其相似的特征,临江溪至虎牙滩江段中华鲟自然繁殖频率不高可能主要是因为地形不符合要求,从而造成相关的水文因子也不能满足需要。中华鲟自然繁殖前期的迁徙分布和产卵后受精卵的散播与河床地形都有一定的关系,葛洲坝水利枢纽下游河势调整工程较大地改变了葛洲坝至庙咀江段河床的地形,地形复杂度的增加可能对中华鲟自然繁殖前期的栖息有利,而河床坡度、底质的改变则可能会对中华鲟受精卵的散播和发育产生不利影响。有必要结合中华鲟历史产卵场精确的地形数据,对"中华鲟产卵场功能分区模型假说"进行验证,并针对产卵场地形对中华鲟自然繁殖的影响,做出进一步探讨。     

Bioinformatic analysis of antivirus‐related TRIM genes in Dabry’s sturgeon Acipenser dabryanus

TRIM proteins are a group of highly conserved proteins that participate in a variety of biological processes in innate immunity. However, the roles of the Acipenseridae trim genes in the anti‐bacterial immune response remained uncertain. In the present study, the Dabry’s sturgeon (Acipenser dabryanus) TRIM2, TRIM8, and TRIM59 protein sequences were found to be similar to Chicken (Gallus gallus), with identities 92.8%, 89.1%, and 79.4%, respectively. Meanwhile, the TRIM23, TRIM37, and TRIM82 proteins shared 95.8%, 81.7%, and 78.1% similarity with Zebrafish (Danio rerio) homologs, respectively. Sequence alignment indicated that these six adTRIMs contained incomplete domains at their N‐termini, including a RING‐finger domain and one or two B‐boxes domains. The six adtrim genes were constitutively expressed in immune related tissues, such as the head kidney, and were also expressed in non‐immune related tissues, like the blood, brain, muscle, and liver. After challenge with Aeromonas hydrophila, the expression levels of adtrims changed during the early stage of infection. Stimulation by A. hydrophila upregulated the expression levels of adtrim8 and adtrim59 in the spleen and caudal kidney, while the expression of adtrim82 in the spleen and caudal kidney was inhibited at 12 hr post‐infection. A. hydrophila challenge led to significant upregulation of adtrim2 and downregulation of adtrim23 in the spleen. In addition, adtrim37 was only weakly affected by A. hydrophila stimulation. These results suggested that adtrims were related to the immune response to bacterial infection, which provides the fundamental basis for protecting Dabry’s sturgeon against pathogen attack.     

Site heteroplasmy in the mitochondrial cytochrome b gene of the sterlet sturgeon Acipenser ruthenus

Sturgeons are fish species with a complex biology. They are also characterized by complex aspects including polyploidization and easiness of hybridization. As with most of the Ponto-Caspian sturgeons, the populations of Acipenser ruthenus from the Danube have declined drastically during the last decades. This is the first report on mitochondrial point heteroplasmy in the cytochrome b gene of this species. The 1141 bp sequence of the cytb gene in wild sterlet sturgeon individuals from the Lower Danube was determined, and site heteroplasmy evidenced in three of the 30 specimens collected. Two nucleotide sequences were identified in these heteroplasmic individuals. The majority of the heteroplasmic sites are synonymous and do not modify the sequence of amino acids in cytochrome B protein. To date, several cases of point heteroplasmy have been reported in animals, mostly due to paternal leakage of mtDNA. The presence of specific point heteroplasmic sites might be interesting for a possible correlation with genetically distinct groups in the Danube River.