Acclimation trials of juvenile Italian sturgeon to different salinities: morpho-physiological descriptors

In this study the first experimental trials of acclimation to salinities of the Italian sturgeon Acipenser naccarii are described. Preliminary observations regarding some morphological features of the gut, kidney and gills following exposure to 20 and 30% salinity are reported, and compared with those displayed by many teleosts in hyper- and hypoosmoregulation. Results are discussed with regard to the osmoregulatory mechanisms and to the physiological limits of adaptability of this species in the second year of its life cycle. Within the Acipenseridae, Acipenser naccarii is generally considered a euryhaline species, but nothing is known about its mechanisms of osmotic homeostasis. This species could be a good candidate for aquaculture in fresh and brackish waters owing to the recent success obtained in artificial reproduction.     

Sex differentiation and aspects of gametogenesis in shortnose sturgeon Acipenser brevirostrum Lesueur

Shortnose sturgeon Acipenser brevirostrum gonad samples were collected from industry-reared fish and wild broodstock at various developmental stages to elucidate patterns of gonadal differentiation and maturation. Genital ridges, containing germ cells, were present in 26 day-old fish and distinct gonads were present by day 54. Sturgeon gonads are known to consist of two tissue types (adipose and gametogenic) and both were present at 72 day. Anatomical differentiation of gonads occurred by 6 months and was advanced by 15 months. Ovaries had distinct lamellae while testes remained non-lamellate. Gonial proliferation had occurred by 15 months, but the cells were not identifiable as spermatogonia or oogonia. Small white 'pinhead' oocytes were macroscopically visible in ovaries as early as 36 months. At 43 months ovaries were clearly organized, with some areas containing only immature oocytes and other containing oocytes apparently developing as cohorts. Individual fish showed considerable variation: the level of development remained unchanged at 84 months in some females, while others showed clear progression towards sexual maturation at 48 months. Sperm cells were present in males as early as 52 months. Advanced development of ovarian follicles was observed only in biopsies of re-conditioned broodstock of wild origin. In the year before spawning, the most advanced oocytes became pigmented, the chorion thickened, the nucleus (germinal vesicle) migrated towards the micropyle complex at the animal pole, and ovulation occurred in May under appropriate environmental conditions.     

Use of non‐island,shallow nearshore beach environments by Gulf Sturgeon (Acipenser oxyrinchus desotoi) within the Mississippi Sound,USA

Large sub‐adult/adult western population Gulf Sturgeon move to barrier islands in winter to feed whereas eastern fish move offshore or to nearshore non‐island environments; most small sub‐adults/juveniles remain in the estuarine system during winter. To test this, we used an acoustic data set deployed around the Port of Gulfport (hereafter Port footprint, east gate, west gate) within Mississippi Sound. We documented between three and six fish on each receiver totaling 12,285 detections for all 19 receivers between September 2012–May 2013. Only 30% of fish had both a high number of overall detections and a high number of detection days. In contrast, from October 2013–May 2014, between three and nine fish were detected on each receiver but with only 2,371 detections. Five fish (29.4%) had a high number of detections but a reduced number of detection days in the acoustic array; all fish appeared to be transients. Adults, unexpectedly, had the most prevalent occurrence and number of detection days in these shallow, non‐island beach environments contrary to our initial hypothesis. Our data suggests annually variable, regional‐scale use of beach environments not associated with barrier islands that likely serve as a travel corridor between drainages/offshore barrier islands, or as feeding zones; these movements may enhance the potential for mortality in Mississippi Sound.     

中华鲟授精过程扫描电镜观察

在扫描电镜下观察到:中华鲟的成熟卵具有一层放射膜,两层卵黄膜;卵的动物极端有9—15个受精孔,受精孔直径约为12.7—13.9μm;精子由伞状顶体、棍棒状头部、漏斗状中段及扁平细长的尾部组成;各受精孔都能接纳多个精子;卵受精5秒后,精子才开始入卵,且精子入卵速度各不相同。受精时间持续较长,可由5秒延长至5分钟;卵受梢后,受精管道内除缠绕成团的精子尾部外,未发现其他堵塞物。     

Characterization and inhibition studies of carbonic anhydrase from gill of Russian Sturgeon Fish (Acipenser gueldenstaedtii)

An α-carbonic anhydrase (CA, EC 4.2.1.1) was purified and characterized kinetically from gill of Acipenser gueldenstaedtii as an endangered sturgeon species. The carbonic anhydrase was purified 66-folds with yield 20.7% by Sepharose-4B-l-tyrosine-sulfanilamide affinity column and the specific activity was determined as 222.2?EU/mg protein. K_m and V_max kinetic values for gill carbonic anhydrase were calculated by a Lineweaver–Burk graph using p-nitrophenol acetate (p-NPA) as a substrate, and was defined as 2.5?mM and 5?×?10^6?μM/min, respectively. It was observed that CA from the sturgeon gill in the presence of the sulfanilamide and acetazolamide as an inhibitor had very low IC₅₀ values such as 13.0 and 0.1?μM, respectively. In addition, it was determined that the enzyme was inhibited by Fe^2+, Co^2+, Ni²⁺, and Zn²⁺–Ba²⁺ with the IC₅₀ values of 0.2, 1.7, 1.2, and 1.1?mM, respectively.     

A validation of intracellular pH measurements in fish exposed to hypercarbia: the effect of duration of tissue storage and efficacy of the metabolic inhibitor tissue homogenate method

This study assessed the effect of tissue storage duration and accuracy of the metabolic inhibitor tissue homogenate (MITH) method on intracellular pH (pHi) values of tissues of white sturgeon Acipenser transmontanus during hypercarbia. No effect of storage in liquid nitrogen of up to 30 days was observed and MITH appears appropriate for measurement of pH in fish exposed to up to 10% CO₂ (10000 Pa p CO₂).     

Relative Cost/Benefit Trade‐Off Between Cover‐Seeking and Escape Behaviour in an Ancestral Fish: The Importance of Structural Habitat Heterogeneity

Fleeing from predators and moving into protective habitats are two common antipredator behaviours in the animal kingdom. Surprisingly, the relative cost/benefit trade‐off of each behavioural option has rarely been examined empirically. Here, we investigate the interplay between decisions surrounding escape behaviour and rocky microhabitat occupancy in lake sturgeon, Acipenser fulvescens. In high‐risk clear‐water environments, sturgeon responded to danger by evoking an escape response and by seeking cover in rocky microhabitats. However, in low‐risk turbid environments, we found that sturgeon responded to danger by seeking cover in rocky microhabitats, but not fleeing to a significant degree. Cover‐seeking behaviour may therefore be a relatively low‐cost/high‐benefit antipredator strategy. These findings highlight the importance of structural habitat heterogeneity for prey animals in predator‐dominated landscapes.     

中华鲟铁蛋白基因cDNA全长克隆与组织表达分析(英文）

根据铁蛋白基因的保守序列,搜索GenBank数据库中华鲟的EST数据库得到一条同源序列。通过RT-PCR的方法对该序列进行扩增,修改其测序错误,获得中华鲟铁蛋白亚基cDNA全长,经过注释提交GenBank数据库,获取序列登录号EU348782。该cDNA长度为896 bp,包含531bp的完整编码区,推测编码的蛋白质为176 aa,分子量为20339.9 Mr,理论等电点为5.66。它和大西洋鲑鱼铁蛋白序列同源性最高,达到82.9%。该基因在中华鲟肝脏、胰脏、肌肉、脑、心脏、鳃和胃粘膜等多种组织表达,在胰脏和心脏中表达量较高,在肌肉组织中表达较低。根据同源模建的方法得到该蛋白质三维结构,其包括5个α螺旋和10个转角结构,和人、蛙和细菌的铁蛋白均能很好的叠合,表现了很高的相似性,表明该蛋白结构和功能在基因进化中的高度保守性。     

Na+、K+、Mg2+、Ca2+和葡萄糖溶液作为授精-激活介质对中华鲟精子受精率的影响

以不同浓度的NaCl、KCl、MgCl2、CaCl2溶液和葡萄糖溶液作为授精介质,研究了中华鲟(Acipenser sinensis)的受精效果.结果显示,适量的阳离子和葡萄糖作为激活授精介质时中华鲟卵受精率都有所提高.在实验设置浓度范围内25 mmol/L NaCI溶液、0.1 mmol/L KCl溶液、1 mmol/L MgCl2溶液、1 mmol/LCaCh溶液和50 mmol/L葡萄糖溶液浓度下,受精率分别可达到最高值,依次为87.72%、86.82%、82.24%、89.76%、80.92%.随着实验浓度继续增加,受精率反而呈下降趋势.结果显示,作为人工配制的中华鲟精子授精一激活介质,最适NaCI溶液浓度在25 mmol/L附近,最适葡萄糖溶液浓度在25 mmol/L附近,最适KCI溶液浓度≤0.1 mmol/L,最适MgCl2溶液浓度≤1 mol/L,最适CaCh溶液浓度≤1 mmol/L.     

西伯利亚鲟卵黄脂磷蛋白的分离纯化及性质

卵黄是鱼类胚胎发生期的主要营养物质,卵黄的含量和质量对于早期幼体维持生命和生长发育至关重要.本研究采用Sephacryl S-300凝胶过滤层析法和蛋白质电泳技术分离纯化西伯利亚鲟(Acipenser baerii)卵黄脂磷蛋白(lipovitellin,Lv),层析洗脱共得到7个蛋白峰.对每个峰进行SDS-PAGE电泳及油红O、甲基绿和Schiff试剂特异染色,峰b蛋白均呈阳性,表明峰b蛋白为西伯利亚鲟卵中的一种卵黄脂磷蛋白,SDS-PAGE电泳分析表明,其由3个亚基构成,相对分子质量分别为30.6 ku、40.8 ku和76.7 ku.对西伯利亚鲟Lv氨基酸组成进行分析,证明是一种含有相对较多天冬氨酸、赖氨酸、谷氨酸、丝氨酸、缬氨酸和亮氨酸的蛋白,并且所含鲜味氨基酸含量比其他鱼偏高.