Microhabitat distribution of metazoan parasites on gills ofSilurus asotus in Jiangkou Reservoir, Jiangxi Province, China

This paper deals with the proportional distribution, niche breadth and niche overlap of two metazoan parasites (copepods species,Ergasilus anchoratus Markewitsch, 1946 andPseudergasilus parasiluri Yamaguti, 1936) and monogeneans (in the genusSilurodiscoides Gussev, 1976) found on gills of the fish,Silurus asotus L. from Jiangkou Reservoir in Jiangxi Province, China.E. anchoratus was the common and dominant metazoan parasite on gills of the fish in this locality as indicated by the higher infection levels, and distributed almost evenly on gill arches without any observed gill-arch preference, as shown by the wide proportional distribution and broad niche breadth.P. parasiluri and monogeneans inSilurodiscoides were found also without any significant gill-arch preference although they had a rather narrow niche breadth. The observed significant overlap betweenP. parasiluri andSilurodiscoides spp. may be simply due to the lower infection levels of the parasites. The observed pattern of unrestricted distributions of the parasitic copepods on gills of the fish may be accounted for, at least in part, by the moving ability of the copepods, and may also indicate that the parasite does not exhibit any feature of gill-arch preference. However, further experimental research is needed to verify the microhabitat distribution of the parasites. Project 39370122 supported by NSFC.     

新发现的江河寄生性等足类——细角鳃虫的人工感染试验

珠江水系贺江段近年出现严重危害网箱养殖和江河鱼类资源的大型寄生虫病害,初步鉴定该虫隶属于甲壳纲,等足目,鳃虫科,细角鳃虫属,是国内新发现的淡水鱼类寄生虫。用该虫对草鱼、银鲫、麦鲮进行人工感染,结果表明:该虫具有很强的寄生能力,累积感染率为76.2%~100.0%;对寄生部位具有一定的选择性,以寄生在鳃部的比例(55.6%~72.0%)最大,胸鳍(11.7%~28.8%)次之;对试验鱼有较强的致死性;该虫吸血后体长(L)增长较大,体宽(W)基本不变;从寄主体上主动脱落的虫体,其L/W的增长率(16.32%~18.00%)较大,而一直寄生在寄主身上的虫体,其L/W的增长率则因各自摄食量的不同而存在较大的差异。     

Niches of dominant fish in the waters surrounding the Taishan Islands,China

An index of relative importance (IRI) was employed to screen for dominant fish in the waters surrounding the Taishan Islands, China, using data from four seasonal trawl surveys undertaken between 2012 and 2013. Niche breadth and niche overlap were measured using the Feinsinger and Morisita-Horn indices, respectively, and the characteristics and seasonal variations in the niches of dominant fish were assessed via non-metric multidimensional scaling (NMDS) and cluster analysis. A total of 80 fish species, including 16 dominant species, were recorded. Only Amblychaeturichthys hexanema was dominant in all seasons. According to niche breadth values and NMDS, the 16 dominant species were grouped into the following three types: (1) wide niche breadth species, including Cynoglossus macrolepidotus, A. hexanema, and Trypauchen vagina, among others; (2) medium niche breadth species, including Setipinna taty and Johnius belangerii; and (3) narrow niche breadth species, including Atrobucca nibe and Coilia mystus. Most species with a wider niche breadth were demersal fish with a lower swimming capability and even distribution. The niche breadth of migrating fish was narrower than that of settled fish. At a given spatial scale, fish with stronger swimming capabilities had a narrower niche breadth. Niche overlap, which is associated with niche specialization, ranged from 0.000 to 0.886 and had an annual mean value of 0.314. In summer and autumn, niche overlap was relatively high within species of the Sciaenidae family and within species of the Gobiidae in autumn. Differences in thermophily, feeding habits, food organism abundance/distribution and predator-prey relationships affected the niche overlap of fish in this area. Cluster analysis revealed that species with the narrowest niche breadth and lowest niche overlap values usually displayed lower aggregation and greater distribution differences compared with other species.     

Spatial distribution of Dactylogyrus wunderi Bychowsky on gills of Abramis brama orientalis Berg (Leuciscinae) in Irtysh River, China

The spatial distribution of the monogenean Dactylogyrus wunderi Bychowsky,1931 on the gill filaments of the bream Abramis brama orientalis Berg(Leuciscinae) inhabiting the Irtysh River of Xinjiang,China was investigated from June to July 2012.D.wunderi was identified by sequencing a fragment of its ITS rDNA region.Sixty-five fish were examined,with 55% testing positive for monogenean infection.The prevalence of the parasite in the left and right gill arches was 46% and 48%,respectively.In fish with a large body length,the prevalence of the parasite and the infection intensity did not significantly differ between the right and left gill arches but both were slightly higher in the former.Among the three size groups of fish(small,medium and large) the prevalence and the intensity of infection were lowest in fish with small body lengths.The distribution of the monogenean population in the host gills showed an aggregate distribution,with little change in the degree of aggregation,suggesting that most hosts were either not or only slightly infected by D.wunderi and that the parasite infected only a few hosts.In addition,differences in D.wunderi infections between gill arches of A.brama orientalis were not significant(P>0.05).     

Occurrence of Bothriocephalus acheilognathi (Cestoda, Bothriocephallidea) in grass carp Ctenopharyngodon idella in the Changjiang River drainage

Bothriocephalus acheilognathi is a potentially serious pathogen in wild or cultured fish in worldwide distribution. We examined 58-farmed grass carp from Nanchang in the Changjiang (Yangtze) River drainage, from which 20.7% were found to harbor the parasite with an infection intensity of 36.9±54.7. The parasites were identified based on morphology and rDNA ITS sequence analysis. The present report represents the first record of the parasite in grass carp Ctenopharyngodon idella in the river drainage.     

Multiple Spatial Scale Analysis of the Niche Characteristics of the Rhododendron dauricum Plant Communities in Northeast China

This study aims to verify the concept of niches at multiple spatial scales in plant communities. To this end, we analyzed the niche characteristic of Rhododendron dauricum plant communities in Northeast China at three spatial scales. At the local scale, we calculated the Importance Value(IV) of species in five communities in the north of the Da Hinggan Mountains. At the intermediate scale, we examined five communities in their entirety, calculated the niche breadth of the species, and integrated niche overlap and interspecific association to analyze interspecific relationships. Further, the generalized additive model(GAM) was used to analyze the impact of topography and soil factors on niche characteristics. At the regional scale, we analyzed the geographical distribution of dominant species of R. dauricum plant communities in Northeast China and used principal component analysis(PCA) to analyze the impact of geographical and climate factors on species distribution. The results show that at the local scale, the IV of the species in each community varies widely. At the intermediate scale, species with a wide niche breadth tend to have a high value for IV. Larix gmelinii, Betula platyphylla, R. dauricum, Ledum palustre, and Vaccinium vitis-idaea had a relatively wide niche breadth and a high niche overlap, and the interspecific associations were almost all positive. Elevation and soil nutrients were the most dominant environmental factors. At the regional scale, species with a wide niche breadth tend to have a wide range of distribution, and temperature and precipitation were the most dominant environmental factors. This study suggests that the niche characteristics at three scales are both related and different. Niche characteristics at the local scale were various and labile, and niche characteristics at the intermediate and regional scales were relatively regular. These results show some degree of consistency with previous studies from an evolutionary perspective. The action mechanisms of these communities are related to differences in the dominant environmental factors. In addition, the integration of niche overlap and interspecific association determine interspecific relationships more accurately.     

提高鳜鱼催产率受精率和苗种成活率的试验

在常规催产剂中加入适量的Ａ型添加剂，可使鳜鱼的催产率提高１０％以上，受精率提高５％以上。使用１５×１０－６的福尔马林，可有效地杀灭寄生于鳃及体表的寄生虫和细菌，从而大大提高苗种成活率。     

A niche model to predict Microcystis bloom decline in Chaohu Lake, China

Cyanobacterial blooms occur frequently in lakes due to eutrophication. Although a number of models have been proposed to forecast algal blooms, a good and applicable method is still lacking. This study explored a simple and effective mathematical-ecological model to evaluate the growth status and predict the population dynamics of Microcystis blooms. In this study, phytoplankton were collected and identified from 8 sampling sites in Chaohu Lake every month from July to October, 2010. The niche breadth and niche overlap of common species were calculated using standard equations, and the potential relative growth rates of Microcystis were calculated as a weighted-value of niche overlap. In July, the potential relative growth rate was 2.79 (a.u., arbitrary units) but then rapidly declined in the following months to -3.99 a.u. in September. A significant correlation (R=0.998, P<0.01) was found in the model between the net-increase in biomass of Microcystis in the field and the predicted values calculated by the niche model, we concluded that the niche model is suitable for forecasting the dynamics of Microcystis blooms. Redundancy analysis indicated that decreases in water temperature, dissolved oxygen and total dissolved phosphorus might be major factors underlying bloom decline. Based on the theory of community succession being caused by resource competition, the growth and decline of blooms can be predicted from a community structure. This may provide a basis for early warning and control of algal blooms.     

广西养殖拟穴青蟹携带病原体状况的初步调查

采用微生物分离培养技术和巢式PCR技术相结合方法对2011年采自广西北海南万和古城、钦州茅岭和钦州港、防城港企沙和公车的拟穴青蟹(Scylla paramamosain)携带寄生虫、细菌和病毒状况开展调查.寄生虫检测结果显示,仅钦州茅岭拟穴青蟹鳃组织中发现寄生虫茗荷(儿).细菌性病原体检测结果显示,共有11种病原性细菌存在于健康养殖拟穴青蟹体内,弧菌属细菌性病原出现频率最高,其中副溶血弧菌和溶藻弧菌在调查区域内均有分布,其他菌种则呈现一定的地域特异性.病毒性病原体检测结果显示,白斑综合症病毒仅在钦州茅岭拟穴青蟹检出,阳性率为4.94%;双顺反子病毒于北海古城和钦州茅岭拟穴青蟹检出阳性携带率为3.70%;呼肠孤病毒携带率则较高,北海、防城港以及钦州拟穴青蟹均有检出,阳性率达25.93%.由此可见,10-11月广西区内健康养殖拟穴青蟹携带弧菌和呼肠孤病毒的比例远远高于其他病原体,为拟穴青蟹携带的主要病原体.     

PROTEOCEPHALUS SINOCYCLOCHEILI N.SP.(CESTODA:PROTEOCEPHALIDAE) IN A FISH SINOCYCLOCHEILUS GRAHAMI TINGI FANG FROM YUNNAN, CHINA

mODUcrIONDuringaninvestigationofthehtrithcorTunnitiesofFishinthehighlandlakesinYunnanProvinceofChina,aastodewasfoundintheintchtinesofafish,SinocycIocheiIusgrahamitingiFangwhichoccursonlyinFuxianLake(Chuetal.,l989),oneofthesevenlakesstudied.ThecharaCteristiesoftheastodespdriobtainedassignsthemdearlytothegenusProt~alus.FurtherexathenationstalustoconsiderthisastodeasanewspedesinthegenusProteOCotalus.Thisnewspedisdescritalinthispaper.MareRIusroMErnOosFuxianLake,theserenddeepestlakeinC…     

Experimental clearance rates of Aurelia coerulea ephyrae and medusae,and the predation impact on zooplankton in Jiaozhou Bay

The population explosion of jellyfish Aurelia coerulea occurred in Jiaozhou Bay,China in 2009.The potential predation impact of A.coerulea on zooplankton was investigated.Population clearance potential and residence time(t_(1/2)) for copepods were calculated from laboratory clearance rates and measurements of jellyfish size and abundance from May to August 2009 in Jiaozhou Bay.Clearance rates varied widely with prey organisms,but they were not significantly different among various prey concentrations.Medusae captured rotifers,fish larvae and hydromedusae more efficiently than fish eggs,copepods and chaetognaths.Ephyrae captured rotifers and hydromedusae more efficiently than fish larvae and copepods.Clearance rate linearly increased with the cro s s sectional area of A.coerulea(size from 0.3 to7.1 cm).Water temperature also had a marked effect on clearance rate and this was related to the increased beat freque ncy as water temperature increased.In early May 2009,A.coerulea potentially cleared the volume of water in the Bay less than 0.001 times a day,but this value was estimated to be more than 0.3 times a day in July.The t_(1/2) for copepods was less than 6 d in June and July.Abundances of copepods,hydromedusae and chaetognaths were extremely low in 2009 compared to 2008 and 2010(jellyfish non-bloom years).Large predation pressure by the A.coerulea population occurred to control zooplankton communities in Jiaozhou Bay.A.coerulea,when present at a high population level,can be a keystone species in Jiaozhou Bay and control the trophic structure here.     

斑节对虾细菌性烂鳃病的病理组织学观察

对自然发生的斑节对虾烂鳃病进行了病理组织切片观察,发现病虾由杆状细菌感染造成鳃丝萎缩、坏死,鳃小片呼吸上皮脱落,鳃血中有菌团存在,而且病虾的肝胰脏、胃、肠、心脏等器官组织受毒素影响而发生组织变性坏死。证实斑节对虾烂鳃病由杆状细菌感染引起。本文对细菌引起虾体的损害及对虾的防御机制进行了探讨,认为斑节对虾是由于细菌感染造成鳃呼吸功能障碍和细菌毒血症造成肝胰脏功能障碍而死亡。     

大口黑鲈仔幼鱼的饵料选择和生长的研究

全长5.8—6.4mm 具卵黄和油球的仔鱼开口摄食轮虫和无节幼体。稚鱼选择枝角类为主。幼鱼对桡足类的选择明显地高于枝角类,对轮虫和无节幼体则无选择性。早期幼鱼还摄食摇蚊幼虫,虾,草鱼苗和本种小鱼。26日龄幼鱼平均日增长1.18mm,日增重22.31mg。数理统计分析确定,全长与日龄呈直线关系。体重与日龄,全长对体重均呈幂函数关系。     

Zinc and copper bioaccumulation in fish from Laizhou Bay,the Bohai Sea

Abstract Zinc （Zn） and copper （Cu） concentrations were determined in the tissues （muscle, stomach, liver, gills, skin, and gonads） of five commercial fish species （mullet Liza haematocheilus, flathead Platycephalus indicus, mackerel Scomberomorus niphonius, silver pomfret Pampus argenteus, and sea bass Lateolabrax japonicus） from Laizhou Bay in the Bohai Sea. Metal bioaccumulation was highest in the metabolically active tissues of the gonads and liver. Bioconcentration factors for Zn were higher in all tissues （gonads 44.35, stomach 7.73, gills 7.72, liver 5.61, skin 4.88, and muscle 1.63） than the corresponding values for Cu （gonads 3.50, stomach 3.00, gills 1.60, liver 5.43, skin 1.50, and muscle 0.93）. Mackerel tissues accumulated metal to higher concentrations than did other fish species, but bioaccumulation levels were not significantly correlated with the trophic levels of the fish. Zn and Cu concentrations in the tissues were generally negatively correlated with fish length, except for a few tissues of sea bass. Risk assessment based on national and international permissible limits and provisional tolerances for weekly intake of Zn and Cu revealed that the concentrations of these two metals in muscle were relatively low and would not pose hazards to human health.     

Selection of diet for culture of juvenile silver pomfret, Pampus argenteus

Juvenile silver pomfret, Pampus argenteus, was grown in culture tanks for 9 weeks on four different diets, and their effects on fish growth, digestive enzyme activity, and body composition were assessed. The feeding regime was as follows: Diet 1: fish meat; Diet 2: fish meat+artificial feed; Diet 3: fish meat+artificial feed+Agamaki clam meat; Diet 4: fish meat+artificial feed+Agamaki clam+copepods. The greatest weight gain was associated with Diet 4, while the lowest weight gain was associated with Diet 1. No significant difference was observed in weight gain between fish receiving Diet 2 and Diet 3. Specific growth rate followed similar trends as weight gain. The feed conversion ratio (FCR) of fish fed Diet 1 was significantly higher than the other fish groups, but no significant differences were observed in FCRs of fish fed Diet 2, Diet 3 or Diet 4. There was also no significant difference in the hepatosomatic index (HSI) between the four diets. For fish that received Diets 2-4, containing artificial feed, higher protease activities were detected. A higher lipid content of the experimental diets also significantly increased lipase activities and body lipid content. No significant differences in amylase activity or body protein content were found between Diets 1-4. In conclusion, a variety of food components, including copepods and artificial feed, in the diet of silver pomfret significantly increased digestive enzyme activity and could improve growth performance.     

The Toxic Mechanism of High Lethality of Herbicide Butachlor in Marine Flatfish Flounder,Paralichthys olivaceus

The toxic mechanism of herbicide butachlor to induce extremely high lethality in marine flatfish flounder,Paralichthys Olivaceus,was analyzed by histopathological examination,antioxidant enzymes activities and ATP content assay.Histopathological examination of gill,liver and kidney of exposed fishes showed that gill was a target organ of butachlor.The butachlor seriously impaired the respiration of gills by a series of lesions such as edema,lifting and detachment of lamellar epithelium,breakdown of pillar cells,and blood congestion.The dysfunction of gill respiration caused suffocation to the exposed flounder with extremely high acute lethality.Antioxidant enzyme activity assay of the in vitro cultured flounder gill(FG) cells exposed to butachlor indicated that butachlor markedly inhibited the antioxidant enzyme activities of Superoxide dismutase(SOD),catalase(CAT) and glutathione peroxidase(GPX).Furthermore,along with the decline of antioxidant enzyme activities,ATP content in the exposed FG cells decreased,too.This infers that the oxidative stress induced by butachlor can inhibit the production of cellular ATP.Similar decrease of ATP content was also observed in the exposed flounder gill tissues.Taken together,as in FG cells,butachlor possibly induced a short supply of ATP in pillar cells by inhibiting the antioxidant enzyme activities and then affecting the contractibility of the pillar cells,which in turn resulted in the blood congestion and suffocation of exposed flounder.     

Effect of Salinity on Hemolymph Osmotic Pressure, Sodium Concentration and Na^＋-K^＋-ATPase Activity of Gill of Chinese Crab, Eriocheir sinensis

The effects of salinity on hemolymph osmotic pressure, Na^＋ concentration and Na^＋-K^＋-ATPase activity of gill of Chinese crab Eriocheir sinensis were studied. The results showed that hemolymph osmotic pressure and Na^＋ concentration increased significantly （P〈0.05）, and the Na^＋-K^＋-ATPase activity of gills decreased significantly （P〈0.05） when salinity increased from 0 to 16. The hemolymph osmotic pressure and Na^＋ concentration in each treatment group rose remarkably at 0.125 d or 0.25 d, while the Na^＋-K^＋-ATPase activity of gill reduced gradually with increased experiment time in 3 d. Then the three parameters remained at a constant level after 0.25 d, 0.125 d and 3 d, respectively, and higher hemolymph osmotic pressure, higher Na^＋ concentration and lower Na^＋-K^＋-ATPase activity of gill occurred at higher salinity. The effect of salinity change on protein concentration of hemolymph was indistinct （P〉0.05）; However, the protein concentration decreased gradually with the increase of salinity from 0.25 d to 1d, and then tended to be stable from day 1 to day 15.     

The toxic mechanism of high lethality of herbicide butachlor in marine flatfish flounder, <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis>

The toxic mechanism of herbicide butachlor to induce extremely high lethality in marine flatfish flounder, Paralichthys Olivaceus, was analyzed by histopathological examination, antioxidant enzymes activities and ATP content assay. Histopathological examination of gill, liver and kidney of exposed fishes showed that gill was a target organ of butachlor. The butachlor seriously impaired the respiration of gills by a series of lesions such as edema, lifting and detachment of lamellar epithelium, breakdown of pillar cells, and blood congestion. The dysfunction of gill respiration caused suffocation to the exposed flounder with extremely high acute lethality. Antioxidant enzyme activity assay of the in vitro cultured flounder gill(FG)cells exposed to butachlor indicated that butachlor markedly inhibited the antioxidant enzyme activities of Superoxide dismutase(SOD), catalase(CAT)and glutathione peroxidase(GPX). Furthermore, along with the decline of antioxidant enzyme activities, ATP content in the exposed FG cells decreased, too. This infers that the oxidative stress induced by butachlor can inhibit the production of cellular ATP. Similar decrease of ATP content was also observed in the exposed flounder gill tissues. Taken together, as in FG cells, butachlor possibly induced a short supply of ATP in pillar cells by inhibiting the antioxidant enzyme activities and then affecting the contractibility of the pillar cells, which in turn resulted in the blood congestion and suffocation of exposed flounder.     

Relationship between niche breadth and range shifts of Rhinopoma muscatellum(Chiroptera: Rhinopomatidae) in climate change scenarios in arid and semiarid mountainous region of Iran

Rapid climate change has provided the opportunity for many species to learn to adapt fast enough to modify their range distribution. The positive and negative responses of the species in terms of distribution are related to parameters such as kind of species, degree of specialization, size and movement skills, and such factors. Moving to high elevations and transitions to higher latitudes are among the strategies proposed as a solution to the negative effects of climate change. Therefore, predicting how different species respond to climate change can help predict the conservation program for them. Species distribution models(SDMs) are widely used to predict the geographical distribution of habitat suitability and species occurrence. Rhinopoma muscatellum is one of the three mousetailed bats(Rhinopomatidae) inhabiting the southeastern, southern, and southwestern parts of Iran and its distribution range to the interior and northern parts of Iran has been limited by the Elburz and Zagros Mountain. To study the effect of climate change on this species, range shifts and coverage of protected regions, 74 presence points and environmental variables(climate, topography, anthropogenic, and vegetation) in MaxEnt software were used. Before the implementation of the model, the autocorrelation of the presence points was reduced and the selection of pseudo absent points was limited by using the bias grid. Climate variables were prepared for Mid-Holocene, Current, Climate Current, and Future scenarios in 2070(RCP2.6, RCP4.5, RCP6, and RCP8.5). In order to evaluate the overlap of ecological niche, the Schoener's D and I statistic metrics were used. Also, to measure the breadth of the niches, B1(inverse concentration) and B2(uncertainty) metrics in ENMTOOLS software were employed. TSS statistics were used as a threshold. Species distribution trend changes in climatic scenarios were performed by the Mann Kendall(MK) test. Based on the results, the AUC values for current and future climate models were calculated to be 0.89 and 0.85, respectively. The distance from settlement, soil organic carbon, and altitude variables have the greatest impact on the current distribution of the species; and among the climatic variables, Isothermality(Bio3), Temperature Seasonality(Bio4), and Max Temperature of Warmest Month(Bio5) had the greatest impact on species distribution. The results showed that in climate change scenarios by 2070, the distribution range and breadth of climatic niche of Rhinopoma muscatellum will be significantly increased(P-value 0.05), habitat fragmentation will be reduced, and in RCP8.5 scenario it will reach the maximum distribution(39.38% of total Iran). This increase will cover the Elburz and Zagros mountain ranges, and a large part of the country will be suitable for the species. In response to current climate change, migration to higher latitudes was identified in this study. Among the main different classes of protected regions in Iran(National parks, Wildlife refuges, and Protected areas), protected areas in all scenarios had the most coverage of the suitable species habitat.     

Application of hydroacoustics to investigate the distribution,diel movement,and abundance of fish on Zhubi Reef,Nansha Islands,South China Sea

A combination of traditional fish sampling methods(hand-line and gill net) and modern hydroacoustic techniques were used to study fish community structure,distribution,and diel movements of fish on Zhubi Reef to enhance understanding of the ecosystem.We collected 126 individuals from 29 species,20 genera,17 families,three orders,and two classes using traditional gear.Perciforms were the dominant group in terms of species richness and biomass.The acoustic data indicated that very small(target strength[TS],dB) -60 dB) and small(-60 dB≤TS-45 dB) fish contributed the most to abundance and species richness on the coral reef,and that the proportion of medium-sized(-45 dB≤TS-35 dB) and largesized(-35 dB≤TS) fish increased gradually as depth increased.The single-target detection method revealed two distinct size classes during the day in the 12-16 and 16-20-m layers.One group consisted of very smallsized fish(TS-60 dB) and the other consisted of medium and large-sized fish(TS-55 dB).The number of single-target detections was significantly higher during the night than during the day(P0.05).The singletarget TS frequency distribution during the day was significantly different than during the night at depths of4-8,8-12,12-16,and 16-20 m.Significant differences were observed among the 4-8,8-12,12-16,and16-20-m-depth layers during day and night.Diel vertical movement was evidenced as fish began to spread and move upward just before sunset and began to assemble and descend shortly(15 min) after sunrise.