Seasonal variation of Caligus rotundigenitalis infestation on the host fish Etroplus suratensis from the Cochin Backwaters,southwest coast of India

Investigation of four edible fishes(Etroplus suratensis, Oreochromis mossambicus, Lates calcarifer, Chanos chanos)collected from a fish landing center along Cochin Backwaters has done for caligid infestation. Of these, caligids were detected only from Etroplus suratensis and was identified to be Caligus rotundigenitalis. Parasites were attached to the inner side of operculum of host which indicates strong site preference. The annual observation of prevalence, mean intensity and abundance were fo...     

Lethality of increasing CO2 levels on deep-sea copepods in the western North Pacific

The first CO₂ exposure experiments on several species of pelagic copepods inhabiting surface and deep layers in the western North Pacific were conducted. Living organisms were collected from two layers between the surface and 1,500 m between latitudes of 11 and 44°N, and they were exposed aboard ship to various pCO₂ up to about 98,000 μatm. Mortality of copepods from both shallow and deep layers in subarctic to subtropical regions increased with increasing pCO₂ and exposure time. Deep-living copepods showed higher tolerance to pCO₂ than shallow-living copepods. Furthermore, deep-living copepods from subarctic and transitional regions had higher tolerances than the subtropical copepods. The higher tolerances of the deep-living copepods from subarctic and transitional regions may be due to the adaptation to the natural pCO₂ conditions in the subarctic ocean.     

南极夏季南设得兰群岛周边海域浮游动物优势种群的分布、丰度及种群结构分析

根据2013/2014年夏季在南极南设得兰群岛周边海域使用北太平洋网采样品及同步环境调查资料,分析了南极大磷虾(Euphausia superba)、拟长臂樱磷虾(Thysanoessa macrura)、尖角似哲水蚤(Calanoides acutus)和近缘哲水蚤(Calanus propinquus)这四种优势浮游动物的丰度和分布特征。结果表明,南极大磷虾和拟长臂樱磷虾在南设得兰海域均有较为广泛的分布,其中南极大磷虾丰度较高,且它们的水平分布存在一定程度的空间分离。在研究海域东部的南奥克尼群岛(South Orkneys)邻近海域发现了大量的南极大磷虾原蚤状C期幼体,表明大磷虾曾于1月中上旬左右产卵繁殖。研究海域的东部南极大磷虾种群结构以幼体前期为主,而西部的种群结构则以幼体后期、未成体和成体为主。尖角似哲水蚤和近缘哲水蚤的空间分布也较为广泛,且两者分布基本一致。东部南奥克尼群岛临近海域的浮游植物浓度较低,这可能是大量南极大磷虾幼体和桡足类摄食活动的结果。     

Seasonal distribution of Calanus sinicus (Copepoda, Crustacea) in the East China Sea

On the basis of the four-season investigation in 23°30′~33°N and 118°30′~128°E of the East China Sea from 1997 to 2000, the seasonal distribution of Calanus sinicus was studied with aggregation intensity, regression contribution and other statistical methods. It was inferred that C. sinicus’s predominance presented from winter to summer, especially in spring and summer, because its dominance amounted to 0.62 and 0.29 respectively. The percent of its abundance in copepod abundance was 76.71% in summer, greater than 66.60% in spring, greater than 19.02% in winter, greater than 4.02% in autumn. The occurrence frequency in winter and spring was 83.08% and 93.89%, higher than that in summer and autumn, 76.71% and 73.87%. Compared with other dominant species of copepods, C. sinicus’s contribution to the copepod abundance was obviously greater than that of the other species in winter, summer and spring, but smaller in autumn. C. sinicus tended to have an aggregated distribution. The clumping index peaked in summer (50.19), followed in spring (19.60), declined in autumn (13.18) and was the lowest in winter (3.04). The abundance changed in different seasons and areas, relating to temperature but not salinity in spring and autumn, to salinity but not temperature in summer; to neither temperature nor salinity in winter. In spring and summer, its high abundance area was often located in the mixed water mass formed by the Taiwan Warm Current, the Huanghai Sea Cold Water Mass, the coastal water masses and the Changjiang Dilute Water. In spring and autumn, its abundance was affected by the warm current, as well as the runoff from continental rivers affected it in summer. It can be inferred that C. sinicus was adapted to wide salinity and temperature, as a euryhalinous and eurythermous species in the East China Sea.     

Impacts of solar UV radiation on grazing, lipids oxidation and survival of Acartia pacifica Steuer (Copepod)

UV radiation is known to affect aquatic primary producers and their grazers. However, little has been documented on its effects on zooplankton grazing. In this study, the authors investigated the effects of photosynthetically active radiation (PAR, 400-700 nm), ultraviolet-A (UV-A, 320-400 nm) and ultraviolet-B (UV-B, 280-320 nm) radiation on grazing, mortality and lipids oxidation of the copepod Acartia pacifica collected from the Xiamen Bay. After 30 min of the exposures, the copepod was fed in darkness with the diatom Phaeodactylum tricornutum at two cell concentrations (2.5 × 10 4 and 2.5 × 10 5 cells/ml). At the low cell concentration, the individuals pre-exposed to PAR (218.0 W/m 2 )+UV-A (48.2 W/m 2 ) or PAR+UV-A+UV-B (2.1 W/m 2 ) showed suppressed clearance and grazing activities compared with those receiving PAR alone, by 22.7% and 17.1% for clearance and by 22.6% and 5.5% for grazing rates, respectively. However, the suppression on clearance and grazing became indistinctive at the high food concentration. Exposures to UV-A and UV-B led to increased lipid oxidation and higher mortality, furthermore, the mortality linearly increased with enhanced oxidation of lipid.     

Temporal variation in abundance and fecundity of the invading copepod Eurytemora americana in Bahía Blanca Estuary during an unusual year

Eurytemora americana has been only reported as invader in Bahía Blanca Estuary, Argentina within the South Hemisphere. There are a few experimental researches under laboratory conditions done with this species and its reproductive behaviour around the world is very scarce. Consequently, it is still not possible to completely understand its population dynamics. In the present study, E. americana reproductive temporal behaviour and relationships among abundance, female size, egg production and hatching success were examined in the Bahía Blanca Estuary, during 2007 pulse. In order to determine the potential relationships between these variables and the environmental variables, experimental incubations were conducted in the laboratory simulating natural conditions. Spearman’s rank correlation was used to analyze the relationships among all variables. Temporal change of biotic and environmental variables was corroborated by a Mann–Whitney/Kruskal–Wallis non-parametric tests, with significant differences (p ? 0.01) in all variables throughout the study. Abundance population results showed very high values in relation to those recorded in recent years in Bahía Blanca Estuary. This response could be due to the unusual combination of environmental factors (polar wave with temperatures ≤6 °C and a drought period with high salinities, 32.7–36.6) recorded during the studied winter period. Significant positive correlations between abundance and salinity (p < 0.01, n = 226), and hatching success (p < 0.01, n = 25) as well as a significant negative correlation between abundance and chlorophyll a (p < 0.01, n = 226) were found. Although E. americana shows a k-strategy within its annual pulse, it presented two markedly distinct behaviours depending on temporal environmental variability. From July to early september, when the estuary evidenced high salinity, low temperature and high food availability, E. Americana showed large females, large clutch size and high hatching success. When environmental conditions became unfavorable from September to October, small females, small clutch size and very low hatching success were observed. The latter is associated with diapause egg laying which ensures population recruitment. According to our findings the particular combination of low temperatures, high salinities and high available food (i.e. variables which each year modulate its pulse) during 2007 winter–spring, favored the great development of E. americana. This invading species in its opportunistic role has managed to exploit a vacant niche in the estuary, developing two different behaviours within the k-strategy depending on change in environmental conditions.     

核酸指标对桡足类安氏伪镖水蚤摄食率、生长率及产卵率的指示作用

核酸指标可表征桡足类营养及生长状态, 然而多物种和多指标比较研究的相对缺乏却限制了现场海区调查中对核酸标志物的广泛应用。本研究测定了系列饵料浓度(0.2~2.0μg C·mL^-1)喂食的安氏伪镖水蚤Pseudodiaptomus annandalei的桡足幼体Ⅱ期个体的摄食率、生长率及成体产卵率, 并就生化组成, 包括RNA含量、DNA含量、蛋白含量(以下简写为PRO)、RNA:DNA、RNA:PRO、DNA:PRO及元素组成(N含量、P含量、C:N 和C:P比值)进行定量分析和计算。摄食率、生长率、产卵率及桡足幼体的RNA相关的核酸指标随饵料浓度的变化趋势均符合双曲线模型, 而雌性成体中仅RNA:DNA比值符合此模型。对RNA相关指标与各生理参数的相关性分析显示, 桡足幼体的RNA相关指标均与摄食率及生长率呈显著线性相关性, 显著程度的顺序为RNA:DNA>RNA:PRO>RNA含量; 雌性成体中RNA:DNA及RNA:PRO比值与产卵率显著相关, 前者的相关性远较后者显著。此结果表明, 在常用的现场浮游桡足类调查的标志比值(RNA:DNA比值或RNA含量)之外, RNA:PRO比值亦可作为指示桡足类生长状态的标志比值, 但是当指示体生长时, 桡足类必须处于同一生长阶段。RNA相关指标与饵料浓度之间稳固的双曲线相关性提示我们, RNA相关指标可帮助评估桡足类的饵料环境。     

Effects of some environmental parameters on the reproduction and development of a tropical marine harpacticoid copepod Nitocra affinis f. californica Lang

The effects of salinity, temperature, and light conditions on the reproduction and development of harpacticoid copepod, Nitocra affinis f. californica under controlled laboratory conditions were determined. Seven different salinity levels (5, 10, 15, 20, 25, 30, 35 ppt), four temperatures (20, 25, 30, 35 °C), three different light intensities (25, 56, 130 μmol m⁻² s⁻¹) and photoperiods (24 h:0 h, 1 h:23 h, 12 h:12 h LD cycle) were employed in this study. The highest (p < 0.05) overall reproduction and fastest development time were achieved by copepods reared under 30–35 ppt salinity. The optimum temperature required for the maximum reproduction was 30 °C while under 30 °C and 35 °C the copepod development time was shortest (p < 0.05) compared to other temperature levels. The overall reproduction was highest (p < 0.05) and development rate of N. affinis was shortest (p < 0.05) under lowest light intensity (25 μmol m⁻² s⁻¹). Continuous light (24 h:0 h LD) inhibited the egg production while, continuous darkness (1 h:23 h LD) and 12 h:12 h LD significantly favoured the overall reproductive activity of the female. Photoperiods 1 h:23 h and 12 h:12 h LD yielded highest total (p < 0.05) offspring female⁻¹ coupled with highest (p < 0.05) survival percentage. This study illustrated that although N. affinis can tolerate wide range of environmental conditions, prolonged exposure to subnormal environments affect its reproduction and development. This study showed that this species can be mass cultured for commercial purposes and has a potential to be used for toxicity studies due to its high reproductive performance fast development and a wide range of tolerance to environmental conditions.