Physiological and behavioral responses of Bathynerita naticoidea (Gastropoda: Neritidae) and Methanoaricia dendrobranchiata (Polychaeta: Orbiniidae) to hypersaline conditions at a brine pool cold seep

Bathynerita naticoidea (Gastropoda: Neritidae) and Methanoaricia dendrobranchiata (Polychaeta: Orbiniidae) are two of the most abundant invertebrates associated with cold‐seep mussel beds in the Gulf of Mexico. At the methane seep known as Brine Pool NR‐1 (27 °43.415 N, 91 °16.756 W; 650 m depth), which is surrounded by a broad band of mussels (Bathymodiolus childressi), these species have distinctly different patterns of abundance, with the gastropod being found mostly at the outer edge of the mussel bed (average density in November 2003: 817 individuals·m⁻² in outer zone, 20·m⁻² in inner zone) and the polychaete being found almost exclusively near the inner edge (average density in November 2003: 3155 individuals·m⁻² in inner zone, 0·m⁻² in outer zone), adjacent to the brine pool itself. The salinity of the brine pool exceeds 120, so we hypothesized that M. dendrobranchiata should be more tolerant of high salinities than B. naticoidea. The opposite proved to be true. The gastropods were capable of withstanding salinities at least as high as 85, whereas the polychaetes died at salinities higher than 75. Both species were osmoconformers over the range of salinities (35–75) tested. Behavioral responses of B. naticoidea to salinities of 50, 60, and 70 were investigated in inverted vertical haloclines. Gastropods generally did not enter water of salinity greater than 60, but tolerated short periods at 60. Behavioral avoidance of brine should limit the vertical distribution of B. naticoidea in the inner zone to the top 2.5–5 cm of the mussel bed. Behavior is also a likely (though unproven) mechanism for controlling horizontal distribution of this species across the mussel bed. Methanoaricia dendrobranchiata can tolerate short excursions into the brine, but probably avoids hypersaline conditions by aggregating on the tops of the mussels.     

高温对褐藻羊栖菜逆境生理的影响

分别在27℃和32℃高温条件下培养羊栖菜(Sargassum fusiforme), 以在22℃培养条件下生长的羊栖菜作为对照, 在培养的第0、1、3、5和7天分别取气囊样品, 采用植物生理学试验方法探讨高温胁迫对羊栖菜细胞膜损伤、渗透调节和抗氧化保护的影响。结果表明: 1) 高温胁迫导致羊栖菜细胞的相对电导率提高和丙二醛(MDA)质量摩尔浓度增加, 膜系统受到了损伤, 造成体内离子外渗、细胞膜脂发生过氧化; 2) 细胞内积累了可溶性蛋白、可溶性糖和脯氨酸等渗透调节物质并且胁迫组始终高于对照组, 其中可溶性蛋白在胁迫第7天时达到最大值(11.4μg·mg^-1), 而可溶性糖和脯氨酸均呈现先升高后降低的趋势, 分别在高温培养的第3天和第5天时达到最大值; 3) 受到高温胁迫后, 羊栖菜超氧化物歧化酶(SOD)比活性增强, 而过氧化物酶(POD)和过氧化氢酶(CAT)比活性在高温胁迫过程中呈现下降的趋势, 说明羊栖菜主要通过抗氧化酶SOD比活性增强来降低胁迫对藻体带来的伤害。总之, 羊栖菜对高温胁迫比较敏感, 温度越高, 培养时间越长, 羊栖菜受到的伤害越大。     

Osmoregulation in Six Sympatric Fiddler Crabs (genus Uca) from the Northwestern Gulf of Mexico

Abstract. As problems in taxonomy and systematic relationships among the Uca species are resolved, a definition of how each fiddler crab species partitions and utilizes habitat resources is needed. To this end, the osmoregulatory capabilities were studied in six species of fiddler crabs from the western Gulf of Mexico. Specimens were placed in 50  ml of artificial seawater ranging in osmolality from 50 to 3450  mOsm (2 to 109  ‰) for five days. Survivorship was recorded for each species. Uca rapax, U. panacea and U. subcylindrica are hardy from 200 to 3200  mOsm (6 to 101  ‰). Uca spinicarpa and U. minax survive only below 1400  mOsm (44  ‰). U. longisignalis is intermediate, with limited survival above 2500  mOsm (79  ‰). Hemolymph osmolality was determined for crabs surviving the osmotic regimen. Uca panacea, U. subcylindrica and U. rapax are equivalent in their regulation between 50 and 3200  mOsm (2 – 101  ‰). Uca longisignalis lost its ability to control hemolymph osmolality above 2200  mOsm (69  ‰). On the other hand , U. spinicarpa and U. minax become less effective hyporegulators in media above 1200 (38  ‰) and 1500  mOsm (47  ‰), respectively. Only U. longisignalis appears to exhibit clear differences in osmoregulatory capacity between populations. Population data for U. panacea and laboratory experiments with U. subcylindrica also support the notion of capacitative acclimation in Uca . These physiological capabilities correlate well with the known habitat characteristics for each fiddler crab species in the northwestern Gulf of Mexico.     

降海鲑渗透生理及入海窗口期的研究进展

在过去30年中,降海鲑的发育得到了大量关注,研究降海鲑的发育,特别是如何调控降海鲑发育的时间和品质,以便幼鲑移入海水网箱。洄游型鲑科鱼类幼鲑向降海鲑的转变包含了一系列的行为、形态、生理的改变,这都为降海洄游进入河口做准备。降海鲑发育受几种激素的促进,包括生长激素、胰岛素样生长因子-I、皮质醇、甲状腺素,而催乳素通常会抑制发育。鳃氯细胞中特殊的离子转运蛋白(NKA、Na+/K+/Cl-协同转运蛋白和Cl-通道)丰度的增加引起盐分泌能力的提高,从而有利于降海鲑在海水中生长、游泳和存活。具银化期的鲑科鱼类(如大西洋鲑(Salmo salar)、硬头鳟(Oncorhyunchus mykiss)、银大麻哈鱼(Oncorhynchus kisutch)至少在淡水中生活一年,达到临界最小规格之后才可改变其对光周期的响应。如果在银化前未达到这个最小规格,则需等到下一年(或更长)。鲑科鱼类如何在一年中合适的时间确定其规格或生长率,并增加对光周期的响应性,这一重要的领域还未得到大量的关注。因此,了解降海鲑渗透生理及入海窗口期,查明不同鱼类适宜生长盐度,入海时间和方式非常重要,可为鲑科鱼类(如虹鳟(Oncorhynchus mykiss)、硬头鳟等)在黄海冷水团规模化养殖提供理论支持。     

不同盐度下鲈鱼稚鱼鳃的显微结构观察

采用石蜡切片和显微摄影技术,研究了不同盐度下鲈鱼(Lateolabrax japonicus)稚鱼鳃的显微结构.结果显示,在15.00盐度组,稚鱼鳃的鳃丝和鳃小片上泌氯细胞数量较多,泌氯细胞集中分布在鳃小片基部,且黏液细胞较多.与15.00盐度组和淡水组相比,7.50盐度组稚鱼鳃的鳃小片较窄,泌氯细胞的分布、结构及数量变化均不明显.在0.00盐度组,稚鱼鳃中鳃小片较宽,排列紧密,泌氯细胞数量较少,且主要分布在近鳃小片基部.鲈鱼稚鱼鳃的结构能够适应外界水体盐度的变化,其中泌氯细胞的结构和数量变化是与鲈鱼稚鱼所处的环境相适应的.     

电场处理对毛乌素沙地油蒿抗寒性影响的研究

不同强度的电场处理沙生植物油蒿（Artemisia ordosica Krash）种子,在毛乌素沙地自然环境下研究电场作用后其根系碳水化合物,叶片水分和渗透调节物随气温下降的变化。结果表明:电场强度为2.0 kV.cm-1、3.5 kV.cm-1和4.5 kV.cm-1时,地温降到零下摄氏度时,其根系碳水化合物和可溶性蛋白质含量增加;气温降到零下10℃左右时,叶片相对含水量、自由水和淀粉含量下降,束缚水、可溶性糖、可溶性蛋白质和脯氨酸含量增加。     

Effect of Dietary Potassium on Growth,Nitrogen Metabolism,Osmoregulation and Immunity of Pacific White Shrimp （Litopenaeus vannamel） Reared in Low Salinity Seawater

An 8 weeks feeding experiment was conducted to determine the effect of dietary potassium on the growth and physio-logical acclimation of Pacific white shrimp （Litopenaeus vannamei） reared in diluted seawater （salinity 4）. Six semi-purified practical diets containing 0.59, 0.96, 1.26, 1.48, 1.74, and 2.17 g potassium K＋ per 100 g diet were formulated, respectively. The survival and feed conversion rate did not show significant difference among groups of shrimps given these diets （P〉0.05）. The shrimps fed the diets containing 0.96-1.48 g K＋ per 100g diet gained the highest weight, specific growth rate, and protein efficiency ratio. Their ammonium-N excretion rate as well as hemolymph concentration of Na＋ and C1- were significantly lower than those of the control （P〈0.05）, but a reverse trend was observed for their gill Na＋/K＋-ATPase. Moreover, the shrimps fed with 1.48 g K＋ per 100 g diet were the highest in hemolymph urea level, and the phenoloxidase and lysozyme activities were significantly higher than those of the control （P〈0.05）. The growth and physiological response of the test shrimps suggested that diet containing 1.48 g K＋ per 100 g diet improved the growth of L. vannamei in low-salinity seawater, and enhanced the physiological acclimation of the organism.     

Effect of dietary potassium on growth,nitrogen metabolism,osmoregulation and immunity of pacific white shrimp (Litopenaeus vannamei) reared in low salinity seawater

An 8 weeks feeding experiment was conducted to determine the effect of dietary potassium on the growth and physiological acclimation of Pacific white shrimp(Litopenaeus vannamei) reared in diluted seawater(salinity 4). Six semi-purified practical diets containing 0.59, 0.96, 1.26, 1.48, 1.74, and 2.17+ g potassium K per 100 g diet were formulated, respectively. The survival and feed conversion rate did not show significant difference among groups of shrimps given these diets(P0.05). The shrimps fed the diets containing 0.96-1.48 g K+ per 100 g diet gained the highest weight, specific growth rate, and protein efficiency ratio. Their ammonium-N excretion rate as well as hemolymph concentration of Na+ and Cl- were significantly lower than those of the control(P0.05), but a reverse trend was observed for their gill Na+/K+-ATPase. Moreover, the shrimps fed with 1.48 g K+ per 100 g diet were the highest in hemolymph urea level, and the phenoloxidase and lysozyme activities were significantly higher than those of the control(P0.05). The growth and physiological response of the test shrimps suggested that diet containing 1.48 g K+ per 100 g diet improved the growth of L. vannamei in low-salinity seawater, and enhanced the physiological acclimation of the organism.     

马氏珠母贝水通道蛋白基因AQP4 cDNA克隆和表达分析

水通道蛋白4(aquaporin4, AQP4)是一类被动运输水的通道蛋白。本研究根据转录组测序获得的马氏珠母贝AQP4片段, 采用RACE技术获得了AQP4的全长cDNA, 命名为PfAQP4, 其5′非翻译区(untranslated region, UTR)为114bp, 3′UTR为839bp, 开放阅读框(open reading frame, ORF)为858bp, 编码285个氨基酸。PfAQP4含有6个α螺旋跨膜区、5个环、1个主要内嵌蛋白(major intrinsic protein, MIP)结构域、2个NPA(Asn-Pro-Ala)基序, 属于AQP1-like型。利用qPCR技术分析PfAQP4在不同组织、不同发育时期以及盐度胁迫条件下的mRNA表达模式。结果显示: (1) PfAQP4在所有被检测组织中均表达, 其中在闭壳肌、足和鳃中表达量较高; (2) PfAQP4在不同的发育时期均有表达, 其表达量整体呈现先升高后降低的趋势, 其中在2—4细胞期表达量最高, 在眼点幼虫期表达量最低; (3) 在高盐度组(36‰)盐度胁迫24、72、120h后, PfAQP4表达量显著上升, 在168h降至对照组水平; 在低盐(16‰)组, PfAQP4表达量在24h显著上调, 在72h恢复至对照组水平, 说明盐度影响鳃组织中PfAQP4的表达量, 也表明PfAQP4在马氏珠母贝渗透压调节中起着非常重要的作用。