Food and feeding habits of juvenile flounder Platichthys flesus (L.), abd turbot Scophthalmus maximus L. in the åland archipelago, northern Baltic Sea

The food choice of juvenile flounder (Platichthys flesus) and turbot (Scophthalmus maximus) was studied in the northern Baltic Sea during the years 1988, 1989, 1994 and 1995. The diet included organisms from 30 species/taxa in flounder (n = 306) and 10 species/taxa in turbot (n = 41). Flounder 45 mm mainly consumed meiofauna (dominating taxon: Harpacticoida, Copepoda) and larger fish (46–101 mm) consumed macrofauna (dominating taxa: Oligochaeta, Amphipoda and Chironomidae). In terms of biomass, macrofauna dominated for all sizes of flounders, and meiofauna was important only for the smallest fish. A strong seasonal variation could be detected in the diet. In spring, macrofauna dominated for all size classes of fish (only fish > 30 mm were caught in spring), while in summer and autumn meiofauna dominated the diets for fish 45 mm in size. Juvenile turbot (22–88 mm) consumed macrofauna and small fish. Turbot 30 mm consumed mainly amphipods, while > 30 mm turbot consumed mysid shrimps, amphipods and fish.The ontogenetic shift from meio- to macrofauna-sized prey in flounders occurs at a larger fish size in the northern Baltic Sea than reported in other areas, possibly depending on the increased relative importance of meiofauna in the northern Baltic. The seasonal variation in the diet could be due to seasonally changing abundances in the zoobenthos, or for the small fish (1-group, spring), to switching from meio- to macrofauna in order to optimize their energy gain. The 0-group flounders consumed meiofauna for a long period, possibly due to a learning-process or simply due to easy availability of meiofauna. Turbot has a much larger mouth gap than flounders, thus allowing them to consume macrofauna from the beginning of their benthic life.     

Burrow Structure and Burrowing Activity of the Funnel-feeding Enteropneust Balanoglossus aurantiacus in Bogue Sound, North Carolina, USA

Abstract. This study of the enteropneust, Balanoglossus aurantiacus , in Bogue Sound, NC, provides information on the general structure and variability in geometry of its burrow, B. aurantiacus employs a funnel at the anterior end of its burrow to cave in surface sediments. It ingests, processes, then deposits these sediments back on the surface as fecal castings. Measurements made on resin casts of burrows and on photographs of surface features (burrow openings and funnels) revealed a new and consistent pattern of burrow construction. This pattern distinguishes B. aurantiacus burrows from those reported for other funnel feeders and enteropneusts (except, perhaps, for B. clavigerus). Laboratory and field observations revealed that, within its burrow, B. aurantiacus is elongated, can double-back on itself, and can use anterior burrow openings for subsequent fecal castings. Tests for significant changes in location of surface features gave estimates of how frequently individuals in aquaria and field populations abandon old burrow locations and construct new burrows. Field observations showed that B. aurantiacus will reopen a blocked burrow opening.     

Characterization,tissue distribution,and expression of neuropeptide Y in olive flounder Paralichthys olivaceus

Neuropeptide Y(NPY) is a 36-amino acid peptide of the neuropeptide Y family that plays key roles in the regulation of food intake. In this study,we focused on NPY m RNA expression changes around feeding time and during food deprivation in olive flounder. The olive flounder NPY m RNA levels were analyzed in different tissues and a high level of expression was detected in the brain. We also demonstrated a correlation between NPY expression levels in the brain and feeding schedule. NPY expression levels in olive flounder maintained on a daily scheduled feeding regimen increased shortly before feeding and decreased after the scheduled feeding time. Compared with the-1 h group before feeding,NPY expression in the 3 h group after feeding decreased significantly( P <0.05). Food deprivation led to an 81.7% decrease in NPY m RNA levels in the 24 h fasted group(P <0.05) and a 91.7% decrease in the 48 h fasted group(P <0.05). Therefore,our study demonstrates that NPY expression is associated with food intake in olive flounder. This result reveals the function of NPY in regulating food intake and its potential importance in olive flounder aquaculture.     

Effects of salinity on survival,feeding behavior and growth of the juvenile swimming crab,Portunus trituberculatus (Miers, 1876)

Effect of salinity on survival,feeding behavior and growth of juvenile swimming crab P ortunus trituberculatus was investigated under 5 salinity levels of 5,10,20,30 and 40. The results show that the crab juveniles fed 2 or 3 times at the salinity 20 and 30,each lasted for about 25 minutes,for a total feeding time of 73.2±22.65 minutes per day. At these salinities,there were significantly higher in the frequency of feeding and in total feeding time than those at lower salinities of 5 and 10. All crab juveniles moulted when reared at a salinity of 20 during the 5 days duration of the experiment,which is significantly higher than those at other salinities. All juveniles survived at salinity 20,and the survivorship was not significantly different from that at 30,but was signif icantly higher than those at other salinities. The crab juveniles reared at a salinity of 20 had the highest value of food ration of 0.190 8±0.011 3 g/g BW,average body weight gain of 0.796±0.128 g,gain rate of 87%–96%,and food conversion ratio of 1.20±0.09. There was no significant difference in the values found between 20 and 30 but these values were significantly lower than that at the other salinities( P 0.05). Highest activities of digestive enzymes(Amylase,Protease,Lipase) and lowest activities of protective enzymes(SOD,PO,CAT) were also obtained on crab juveniles reared at salinity of 20.     

Infant feeding in North East England: contested spaces of reproduction

Decisions about infant feeding are commonly viewed as an issue of personal choice made in the light of information about the benefits of breastfeeding. A pilot study of first-time parents' decisions and experiences in Newcastle upon Tyne, England, suggests that local cultural contexts, in particular how men and women are seen to be parenting in different spaces, have a profound influence on infant feeding.     

Effect of the selective feeding ofGalaxias maculatus (Salmoniformes,Galaxiidae) on zooplankton of a South Andes lake

The effect of larval and juvenile predation ofGalaxias maculatus on a natural small-sized zooplankton was studied in a South Andes lake. Field data of zooplankton density and composition were combined with fish gut content analysis during a spring-summer season. Results showed thatGalaxias early stages ingested mostly planktonic preys. A shift was observed in prey electivity: larvae preferred copepod nauplii whereas juveniles preferred cladocerans. Larval predation provokes the failure of the summer cohort of the calanoid copepodBoeckella gracilipes. The effect of juveniles is more undefined, but seems to prevent the reappearance ofCeriodaphnia in the summer plankton.     

Hydrodynamics of Copepods: A Review

This paper reviews the hydrodynamics of copepods, guided by results obtained from recent theoretical and numerical studies of this topic to highlight the key concepts. First, we briefly summarize observational studies of the water flows (e.g., the feeding currents) created by copepods at their body scale. It is noticed that the water flows at individual copepod scale not only determine the net currents going around and through a copepods hair-bearing appendages but also set up a laminar flow field around the copepod. This laminar flow field interacts constantly with environmental background flows. Theoretically, we explain the creation of the laminar flow field in terms of the fact that a free-swimming copepod is a self-propelled body. This explanation is able to relate the various flow fields created by copepods to their complex swimming behaviors, and relevant results obtained from numerical simulations are summarized. Finally, we review the role of hydrodynamics in facilitating chemoreception and mechanoreception in copepods. As a conclusion, both past and current research suggests that the fluid mechanical phenomena occurring at copepod body scale play an important role in copepod feeding, sensing, swarming, mating, and predator avoidance.     

MZ-150型锚杆钻机变角机构的力学分析

锚杆钻机是基础工程施工中的一种十分重要的钻孔设备。其变角机构关系到钻机的整体性能。对ＭＺ－１５０型锚杆钻机的变角机构进行了运动学和力学分析,提出了合理的设计参数,为钻机设计提供了理论依据。     

新疆塔里木河下游应急输水的生态效益

2000年5月中旬至7月中旬向塔里木河下游断流河段应急输水，历时60天，输水2亿m^3，其后对进水河段分5个断面考察了沿岸植被的生长发育、恢复状况、草本植物地表生物量，根系的分布与数量、植被的分布特点、土壤状况及地下水分布等，通过比较分析，初步结论如下：1、断流河道应急输水对沿岸植被恢复作用显著，其中草本植物效果明显，灌木次之，乔木较差；2、非风积土壤效果更佳；3、应急输水加人工保护与更新则效果更好。     

南海大眼金枪鱼(Thunnus obesus)摄食生态研究

根据2011年12月—2013年2月于我国南海海域采用金枪鱼延绳钓以及灯光罩网调查捕获的大眼金枪鱼(Thunnusobesus)的各项基础生物学以及胃含物的数据,对其摄食生态进行了分析研究。结果表明:(1)南海海域大眼金枪鱼的食物组成包括鸢乌贼、帆蜥鱼、金色小沙丁鱼、飞鱼、竹荚鱼、鲐鱼、小公鱼属、圆鲹属以及不可辨别的鱼类与虾类,其主要饵料生物为鸢乌贼(%IRI=45.21),其次为金色小沙丁鱼(%IRI=21.36)和帆蜥鱼(%IRI=13.72);(2)空胃率与平均饱满指数随季节变化明显,空胃率在春季时会达到顶峰(37.9%),秋季时最低(16.7%),呈先下降后上升趋势,同时平均饱满指数也在春季达到最高值(0.33),随季节下降并稳定于0.1,空胃率随性腺成熟度的提高有明显上升趋势,平均饱满度指数在性成熟度Ⅰ期与Ⅵ期均呈现高值(1.18、1.04);(3) Shannon-Weiner多样性指数H′和Pielou均匀度指数J随季节变化呈现出明显的变化,Shannon-Weiner多样性指数H′随叉长组基本在1.52—1.72之间变化, Pielou均匀度指数J随性腺成熟度的提高有逐步下降的趋势;(4)营养长度(NR)较高,说明其摄食的饵料成分多、氮来源较复杂,基础食物来源(CR)和生态位总空间(TA)的冬季指标值近乎夏季指标的两倍;通过δ15N稳定同位素法计算大眼金枪鱼的平均营养级为4.73。总体上,南海海域大眼金枪鱼主要以头足类和鱼类为食,其摄食习性与季节和个体发育相关,在食物链中处于较高营养位置。