Seasonal variations in carbon and nitrogen content of Acartia clausi (Copepoda,Calanoida) in the Gulf of Trieste (Northern Adriatic Sea)

A yearly study was made on total and cephalothorax lengths, dry weight, carbon and nitrogen contents and C:N ratio of the species Acartia clausi (Copepoda, Calanoida) which is always abundant, particularly in spring, in the net zooplankton community of the Gulf of Trieste (Northern Adriatic Sea). The samples of net zooplankton were carried out every month at the permanent station located 200 m offshore and preserved for about one year in 4% buffered formalin to insure weight loss stabilization. A. clausi was separated from other zooplankton specimens; washed and dried. For each monthly sample the average total and cephalothorax lengths and the average dry weight of adult organisms of A. clausi were measured. The mean carbon and nitrogen contents, as a percentage of dry weight, were determined by using a CHN analyser. Linear regression models were computed on the log-transformed data in order to check the relationships between dry weight, total and cephalothorax lengths, carbon and nitrogen contents and C:N ratio of A. clausi. The best of the various established correlations, was between dry weight and carbon content. Our study pinpointed a high seasonal variability of the C:N ratio, mainly due to seasonal fluctuations in the nitrogen content.     

Biological observations on small cyclopoid copepods in the Red Sea

The breeding activity, sex ratio and variation in body lengthof a number of cyclopoid copepod species from the upper 450mof the Red Sea were analyzed. In most species the body lengthof adult specimens was in the lower range or less than thosereported from other pelagic regions. In the central Red Seamost species had some individuals actively breeding, duringboth autumn and winter. To the north, breeding was observedin fewer species. Only two species, Paroithona sp. and Agetuslimbatus, however, seemed to find conditions for reproductionbetter in the north than in the central area. The sex ratioswere quite consistent for all species within the families Sapphirinidaeand Corycaeidae (high percentage of males) and Oithonidae (lowpercentage of males). Within the Oncaeidae, the percentage ofmales varied from a few percent to >60% of adults. Thereappears to be a relationship between sex ratio and size. Populationsof the very small Oncaea species, O.ivlevi, O.prendeli and O.zernovi,include far fewer males than those of their larger congeners.The available information on the biology of Oncaea is summarized.Peculiarities in their life histories and reproduction are discussed.     

In situ time budgets of the scyphomedusae Aurelia aurita, Cyanea sp., and Chrysaora quinquecirrha

The in situ behavior of three scyphomedusan species was videorecorded by scuba divers in natural daytime lighting with minimalinterference to the medusae. The mean percentage of time thatindividual medusae spent swimming ranged from 93 to 100%. Therewere no significant differences in the percent time spent swimmingbetween life stages of a species (ephyra, adult) or betweenspecies. The predominance of swimming activity by medusae indicatesthat swimming, and hence the creation of fluid motions responsiblefor prey entrainment and capture, plays a widespread functionalrole in feeding by scyphomedusae.     

Integrating conventional microscopy and molecular analysis to analyse the abundance and distribution of four Calanus congeners in the North Atlantic

Analysis of the demographic structure of Calanus species inthe North Atlantic presents particular difficulties due to theoverlapping spatial distributions of four main congeneric species(Calanus finmarchicus, Calanus helgolandicus, Calanus glacialisand Calanus hyperboreus). These species have similar morphologies,making microscopic discrimination only possible between someof the species at late copepodite or adult stages. However,molecular techniques now offer the possibility of screeningsignificant numbers of specimens and unambiguously identifyingthem to species, regardless of developmental stage. Unfortunately,the processing rate of specimens by molecular methods is stilltoo low to offer a realistic alternative to microscopy for analysisof samples from large field surveys. Here, we outline and testan approach involving the use of molecular methodology in conjunctionwith conventional microscopy to assess the species assignmentof developmental stage abundances of Calanus congeners. Ourstudy has highlighted many important methodological issues.First, it cannot be assumed that the species composition ishomogeneous across the development stages; applying proportionalspecies composition of adults to morphologically undistinguishableearlier development stages can result in error. The second importantconclusion is that prosome length may be a highly unreliablediscriminator of C. finmarchicus and C. glacialis.     

The relative importance of food and temperature to copepod egg production and somatic growth in the southern Benguela upwelling system

The fecundity and somatic growth rates of Calanus agulhensisand Calanoides carinatus, the dominant large calanoid copepodsin the southern Benguela upwelling system, as well as the fecundityof several other common copepods, were measured between Septemberand March of 1993/94 and 1994/95. Mean egg production of mostcopepods was low at >30 eggs female^-1 day^-1 {Calanoides carinatus23.7, Calanus agulhensis 19.0, Neocalanus tonsus 16.1 and Rhincalanusnasutus 26.1), whereas the mean fecundity of Centropages brachiatuswas significantly greater (83.6 eggs female^–1 day^-1).This study also presents the first comprehensive field estimatesof the fecundity of Nanno-calanus minor (mean: 26.1 eggs female^–1day^–1, range: 0.0–96.2 eggs female^–1 day^–1)and of somatic growth of N6 and all copepodite stages of Calanoidescarinatus (decreasing from 0.58 day^–1 for N6 to 0.04 day^–1for C5). Somatic growth rates of Calanus agulhensis also declinedwith age: from 0.57 day1 for N6 to 0.09 day1 for C5. Data ongrowth rates were used to assess the relative importance offood [as measured by total chlorophyll (Chi) a concentration],phytoplankton cell size (proportion of cells >10 µm)and temperature to the growth of copepods. Multiple regressionresults suggested that fecundity and somatic growth rates werepositively related to both Chi a concentration and phytoplanktoncell size, but not to temperature. Although it was not possibleto separate the effects of Chi a concentration and phytoplanktoncell size, data from previous laboratory experiments suggestthat copepod growth is not limited by small cells per se, butby the low Chi a concentrations that are associated with theseparticles in the field. Despite growth not being directly relatedto temperature, a dome-shaped relationship was evident in somespecies, with slower growth rates at cool (<13°C) andwarm (>18°C) temperatures. The shape of this relationshipmirrors that of Chi a versus temperature, where poor Chi a concentrationsare associated with cool and warm temperatures. It is concludedthat the effect of food limitation on growth of copepods outweighsthat of temperature in the southern Benguela region. Sourcesof variability in relationships between growth and Chi a concentrationare discussed.     

Measurements of buoyancy for some Antarctic notothenioid fishes from the South Shetland Islands

Buoyancy was measured for 258 specimens representing 13 species of adult and sub-adult nototheniids, bathydraconids, and channichthyids from the South Shetland Islands. Measurements were expressed as percentage buoyancy (%B)=W_water/W_air᎒². There were no neutrally buoyant species and mean values for %B were 3.07-6.11%, with channichthyids at the low end and benthic nototheniids and bathydraconids at the high end. All species showed an ontogenetic decrease in %B with increasing body weight. With the exception of Champsocephalus gunnari, there was no sexual dimorphism in %B within this sample. With some exceptions, values for %B were consistent with life-history information. Sub-adult Dissostichus mawsoni were not neutrally buoyant, as are large adults. Notothenia rossii had a significantly lower %B than closely related N. coriiceps. Benthic Gobionotothen gibberifrons had a lower %B than semipelagic Lepidonotothen larseni. Although they exhibit some diversification in life history, the four channichthyids in the sample were similar in %B. Neutral buoyancy is rare in notothenioids and may be confined to a single nototheniid clade.     

Zooplankton prey selection by juvenile fish in Nova Scotian Shelf basins

The stomach contents of fish <100 mm standard length (SL)and fish >100 mm SL collected during June and October intwo deep basins on the Scotian Shelf, showed that juvenile co(and silver hake fed primarily on the two most abundant speciesof zooplankton in the basins: Calanus finmarchicus and Meganyctiphanesnorvegica. These zooplankton were abundant in the basin: duringthe 2 months, forming high concentrations at depths below 200m during the day. In June fish (<100 mm SL) concentratedin the upper 50 m during both day and night. Cod and wolffislcollected between 195 and 240 m had a large percentage of C.finmarchicusin their stomachs suggesting that these fish exploited the highconcentrations of C.finmarchicus below 200 m depth There wasno evidence that Calanus hyperboreus was eaten by any juvenilefish species. Calanus finmarchicus was the most common preyof cod feeding in the top 50 m, but the percentages o C.finmarchicusstages IV and V were lower in the stomachs than in the watercolumn. Cod showed ; strong preference for M.norvegica, withthis prey species having a modified Ivlev's index of 1 indicatingthat cod were highly selective for this species. There was noevidence that C.hyperboreus. stage IV was eaten by any of thespecies offish. Silver hake and dogfish (>100 mm SL) bothfeed oi M.norvegica and C.finmarchicus in the deep regions ofthe basins. In October, silver hake was the most common juvenilefish in the basins, feeding primarily on small stages of M.norvegica.The populations of fish (>100 mm SL) in the basins were mainlyspecies known to feed heavily or euphausiids. The two basinsare unique regions of the shelf because of the large populationsof Calanus copepods and M.norvegica they contain all the yeararound, thereby providing an atrractive feeding ground for manyspecies of fish, particularly silver hake.     

突尼斯非洲跳鼠(Jaculus jaculus)和埃及跳鼠(J.orientalis)群体的等位酶多态及遗传分化(英文)

运用16种酶蛋白编码的23个遗传座位对突尼斯非洲跳鼠(Jaculus jaculus)和埃及跳鼠(J. orientalis)自然群体的遗传变异和分化进行了电泳分析。结果表明,与其他啮齿动物等哺乳动物的相关数据比较,发现这两个种群体的遗传变异水平较低。非洲跳鼠群体的观测杂合度 (H_obs) 为0.08—0.19,多态座位百分比(P)为26.2%—45.2%,每个座位的平均等位基因数(A)为1.1—1.4;埃及跳鼠的H_obs为0.10—0.15,P为29.3%—44.1%,A为1.1—1.7。两个种群体各自的遗传分化程度较低(非洲跳鼠和埃及跳鼠的F_st分别为0.0017和0.0019)。而两个种群体间的F_st为0.607（P<0.05）,表明两个种之间高度的遗传分化。本研究支持这两个种分类地位的合法性,并强调了地理因素（环境类型和生物气候阶段）对两个种遗传结构的影响。     

Prey size, prey nutrition, and food handling by shrews of different body sizes

We tested some predictions relating metabolic constraints offoraging behavior and prey selection by comparing food handlingand utilization in four sympatric shrew species: Sorex minutus(mean body mass = 3.0 g), S. araneus (8.0 g), Neomys anomalus(10.0 g), and N. fodiens (14.4 g). Live fly larvae, mealwormlarvae, and aquatic arthropods were offered to shrews as smallprey (body mass <0.1 g). Live earthworms, snails, and smallfish were offered as large prey (>0.3 g). The larvae werethe high-nutrition food (>8 kJ/g), and the other prey werethe low-nutrition food (<4 kJ/g). The smallest shrew, S.minutus, utilized (ate + hoarded) <30% of offered food,and the other species utilized >48% of food. The largerthe shrew, the more prey it ate per capita. However, highlyenergetic insect larvae composed 75% of food utilized by S.minutus and only >40% of the food utilized by the other species. Thus, inverse relationships appeared between shrewbody mass and mass-specific food mass utilization and betweenshrew body mass and mass-specific food energy utilization:the largest shrew, N. fodiens, utilized the least food massand the least energy quantity per 1 g of its body mass. Also,the proportion of food hoarded by shrews decreased with increase in size of shrew. With the exception of S. araneus, the sizeof prey hoarded by the shrews was significantly larger thanthe size of prey eaten. Tiny S. minutus hoarded and ate smallerprey items than the other shrews, and large N. fodiens hoardedlarger prey than the other shrews.     

Seasonal cycles in population abundances and egg production rates in the planktonic copepods Centropages typicus and Acartia clausi

Laboratory studies on the seasonal cycling of egg productionrates for Centropages typicus and Acartia clausi did not reflectseasonal changes in densities for these species at sea. Maximumegg production rates occurred from autumn to spring when populationabundances at sea were low. In late spring, an increment inpopulation numbers was followed by a drastic decline in eggdeposition which continued into summer. The percentage lossdue to mortality, calculated using egg data and total numberof copepodid stages CIII and CIV recorded at sea {small tilde}2weeks later, indicated greatest mortality (80–99%) fromeggs to copepodids during periods of high breeding intensity.These results suggest that high and low density phases in populationnumbers may be the outcome of variations in reproductive potentialand survival rates of eggs and immature stages rather than reproductivepotential per se.     

不同保藏处理的昆虫标本DNA提取及其随机扩增多态DNA反应

实验利用CTAB法对柳二十斑叶甲Chrysomela vigintipunctata (Scopoli)、异色瓢虫Harmonia axyridis Pollas、七星瓢虫Coccinella septempunctata Linnaeus、小地老虎Agrotis ypsilon (Rottemberg)、红蜻Crocothemis servilia Drury、无齿稻蝗Oxya abentata Willemse和中华稻蝗Oxya chinensis (Thunberg)等7种昆虫进行了基因组DNA提取。从自然干燥标本、烘干标本及酒精浸泡标本获得的DNA均可用于RAPD-PCR反应,且烘干标本、酒精浸泡标本提取效果优于自然干燥标本。这种提取方法简便易行,容易掌握,且耗资小于其它分子生物学方法。     

Post-embryonic developmental rates as a function of food type in the cyclopoid copepod, Mesocyclops thermocyclopoides Harada

We studied under laboratory conditions the post-embryonic developmentalrates (from nauplii to adult stage) of Mesocyclops thermocyclopoides,commonly found in the eutrophic and hypertrophic local ponds,in relation to different food types. Nauplii hatched from theeggs collected from laboratory-maintained mass cultures werereared at 25l.5C, using the following test diets: bacteria(Klebsiella aerogenes), cyanobacteria (Microcystis aeruginosa,as single cells and in the form of colonies), green algae (Chlorella,Scenedesmus and Chlorogonium), ciliates (Tetrahymena) and rotifers(Brachionus angularis). The developmental rates were fastest,and the proportion of nauplii reaching the copepodid stage andthat of copepodids reaching the adult stage the highest, withChlorogonium, followed by ciliates and rotifers. Developmentwas incomplete with bacteria and Microcys-tis.Ttie algae Chlorellaand Scenedesmus supported complete post-embryonic developmentonly when cultured in media enriched with beef extract, bactotryptoneand yeast extract. With rotifers as the exclusive food, >70%of the nauplii reached the copepodid stage, and >85% of thecopepodids the adult stage. The ratio (D_c/D_n) of copepodid duration(D_c) and naupliar duration (D_n) was significantly differentfrom 1.0, indicating the absence of isochronal development inM.thermocyclopoides. Our results show that post-embryonic developmentin this species is not possible with certain algal diets, probablybecause of nutritional deficiencies, and that the later stagenauplii are capable of capturing rotifers and utilizing themas food to complete their development to the adult stage.     

Factors determining the nutritive status and production of zooplankton in a humic lake

Zooplankton egg production and nutritional status as relatedto environmental factors were studied in a humic lake. Bothparameters exhibited a pronounced spring peak, a mid-summerdepression and a second, smaller autumnal peak. The overallmacrozooplankton community apparently suffered from severe foodlimitation, particularly with regard to food quality, duringthe study period. This limitation was confirmed with length/carbonregressions of well-fed and starved laboratory individuals ofDaphnia. Body carbon in the lake animals corresponded to thatof laboratory-raised, starved individuals. Regression analysisindicated that bacteria, particulate organic carbon and particulatenitrogen best explained changes in egg production, while algalbiomass was of negligible importance for all species. For Daphnia,size-specific carbon content (length/carbon regressions) andC/N ratios were computed for all sampling dates. a and b fromthe equation W=aL^b were positively correlated (P=0.001). a rangedover 1.17–4.44 and was positively correlated with size-specificcarbon content (P<0.001) and the C/N ratio (P=0.01). Whena mean time lag of 12 days was introduced, a was positivelycorrelated with egg production (P=0.04.6). b ranged over 2.05–3.54and was inversely correlated to the same parameters. Both simpleand multiple regression analysis confirmed that bacteria, particulateorganic carbon and particulate nitrogen gave the major positivecontribution to variance in size-specific C content, a and C/Nratio in Daphnia, whereas total zooplankton biomass was themain negative contributor to the same parameters.     

Developmental rates of the copepods Calanus australisand Calanoides carinatus in the laboratory, with discussion of methods used for calculation of development time

The copepods Calanus australis and Calanoides carinatus developedfrom egg to adult in 20.3 and 18.3 days respectively at 15.5?Cand 16.0 and 12.0 days at 19.5?C. For both species the durationof the first two naupliar stages was short, <1 day. The thirdnaupliar stage was prolonged in C.australis but short in C.carinatus. Isochronal development was approximated from fourthnauplius through third copepodite; fourth and fifth copepoditestages were relatively long. Only female C.australis were produced;60% of the C.carinatus were female. Equiproportional developmentwas found for C.carinatus but not for C.australis. For bothspecies the variance in stage duration was established at thethird nauplius then remained unchanged through the older stages.In calculating developmental rates several commonly used methodswere compared. The method of ‘first appearance of an individualof a given stage’ and ‘mean time of appearance ofa stage’ both yielded estimates of development time thatwere 10–15% faster than the more commonly used methodof ‘median development time’. We suggest that allfuture work on developmental rates of copepods should use astandardized method for the calculation of stage-specific developmentalrates and that ‘median development time’ be themethod of choice. ³Present address: Marine Sciences Research Center, SUNY, StonyBrook, NY 11794-5000, USA     

ON THE EXPERIMENTAL SUSCEPTIBILITY OF SOME HYGROMIINAE (MOLLUSCA, STYLOMMATOPHORA) SPECIES, AS INTERMEDIATE HOSTS OF NEOSTRONGYLUS LINEARIS(NEMATODA, PROTOSTRONGYLIDAE)

The experimental susceptibility of Portugala inchoata, Euomphalia(M.) brigantina, Ponentina ponentina, Hygromia (P.) cantabricacantabrica and Hygromia (P.) cantabrica covadongae to Neostrongyluslinearis larvae were studied for the first rime. The total numberof molluscs used in the infections was 207 and they were killedin series between day 6 and SO post-infection. In order to definethe suitability of the molluscs as intermediate hosts for thisparasite, the number of L-I that penetrated the foot and developedto L-I, L-Il and L-III has been taken into account, as wellas the first days on which the different stages were observed One way analysis of variance showed statistically significantdifferences for the penetration and development of the larvaeamong the species of molluscs examined Statistically significant differences concerning the susceptibilityof the adult and young examples of P. inchoata and E. (M.) brigantinato N. linearis were confirmed by using the chi-square test The most susceptible species of molluscs to N. linearis usingexperimental infections were in decreasing order: P. inchoata,E.(M.) brigantina, H. (P.). caniabrica covadongae, P. ponentinaand H. (P.) caniabrica cantabric ^*This work was supported, in partt, by both the C.A.I.C.Y.T.(Project number 142/83) and C.S.I.C. (211) (Received 12 March 1987;     

Motion behavior of nauplii and early copepodid stages of marine planktonic copepods

The goal of this study was to quantify periods of activity andvelocities of late naupliar and early copepodid stages of planktoniccopepods occurring regularly on the southeastern continentalshelf of the USA. We obtained quantitative information on eightspecies, including adult females of Oithona plumifera. All studieswere conducted at food concentrations near or above satiationlevels. Activities ranged from 0.85% (adult females of O.plumifera)to 100% of time (nauplii and copepodids of various calanoidspecies). Motion velocities (excluding escape motion) coveredmore than one order of magnitude: from 0.39 mm s^–1 fornauplii of Temora stylifera to 5.24 mm s^–1 for naupliiof Oncaea mediterranea. Ranges of activities of species rangefrom occasional for early juveniles to adult females of O.plumiferato 100% for the same range of T.stylifera, the latter creatinga feeding current from N III onwards, the former not at all.Of notable interest is Centropages velificatus which moves intermittentlyas a late nauplius, continuously as an early copepodid and intermittentlyas an adult. All observed calanoid late nauplii and copepodidsmove in three dimensions, excluding copepodids of the shelfbreak/oceanicParacalanus aculeatus. The results indicate not only significantdifferences in motion behavior between cyclopoids and calanoids,but also between calanoid species. Yet, some calanoid speciesshow little ontogenetic changes at all.     

Relationships between otolith and fish size from Mediterranean and north‐eastern Atlantic species to be used in predator–prey studies

Regressions between fish length and otolith size are provided for 40 species from the north‐eastern Atlantic Ocean and 142 species from the Mediterranean Sea. Regressions were also estimated at genus level. Most of the regressions (c. 84%) explained a high percentage of the deviance (>75%).     

Carbon, nitrogen and phosphorus stoichiometry of crustacean zooplankton in the Baltic Sea: implications for nutrient recycling

The carbon (C), nitrogen (N) and phosphorus (P) contents (%of dry weight) of some crustacean zooplankton were studied inthe Baltic Sea. The copepod Acartia sp. had a stable C and Ncontent (48.3 ± 0.8% C, 12.4 ± 0.2% N, C:N ratio4.5 ± 0.1). The P content was variable (1–2%),probably depending on developmental stage and season. Copepodsaccumulating fat, like Pseudocalanus minutus elongatus, hadhigher and more variable C content (50–60%), and lowerN and P content (7–12% N, 0.6–1.5% P). The highestC and lowest N and P contents were found in adult Limnocalanusmacrurus. However, the N:P ratio was apparently independentof fat content and between 14 and 27 for all copepods. The cladoceransBosmina longispina maritima and Evadne nordmanni had lower Ncontent (9.3–10.8%) and higher C:N ratio (5.1–5.7)than Acartia sp. The P content (1.2–1.4%) was similarto Acartia sp. and the N:P ratios (16–19) were in thelower range of that found for the copepods. The N:P ratio wasgenerally somewhat higher in the copepods than in seston, whichmost of the year had nearly Redfield C:N:P ratios. Potentially,nutrient recycling from crustacean zooplankton could enhanceN limitation of phytoplankton, but small stoichiometric differencessuggest that this effect is probably weak. The extent is dependenton the structure of the zooplankton community and the grossgrowth efficiencies. Acartia copepodites, which had nearly RedfieldN:P ratios, would have the opposite effect and enhance P limitationin late summer when seston N:P ratios increased.     

THE PHYSIOLOGY AND FEEDING BEHAVIOUR OF TWO MARINE SCAVENGING GASTROPODS IN HONG KONG: THE SUBTIDAL BABYLONIA LUTOSA (LAMARCK) AND THE INTERTIDAL NASSARIUS FESTIVUS (POWYS)

Aspects of the physiology and feeding behaviour of the scavengingsnails, Babylonia lutosa and Nassarius festivus have been studiedand compared. N. festivus has a wider physiological tolerancethan B. lutosa; upper lethal temperatures being 31.5°C and28.5°C respectively and lower lethal salinities 15.5 and11.5. N. festivus was also more resistant to desiccation. N.festivus is adapted to an intertidal environment that is morevariable than the subtidal habitat of B. lutosa. The metabolicrate of adult N. festivus was two to three times higher thanthat of adult B. lutosa, the specific oxygen consumption rateof the former being 7.91±0.49x10^–6 mol of O₂.g^–1wet wt.hr^–1. This correlates with estimates of consumptionobtained for the two animals, B. lutosa eating, on average,6.57% of its wet tissue weight per day, N. festivus 15.33%.Standardization of the data for 2 g animals of both species,however, reveals no significant difference in terms of oxygenconsumption and thus the enhanced consumption by N. festivussimply reflects its smaller size. Both species are opportunisticfeeders and can survive long periods of starvation (>100days). The feeding strategies of the two are also different,N. festivus eating faster than B. lutosa, possibly because ofthe more ephemeral nature of carrion in the intertidal. Starvationaffected the feeding behaviour of N. festivus more than B. lutosaand N. festivus was able to perceive carrion from greater relativedistances than B. lutosa. (Received 27 February 1989; accepted 24 July 1989)     

广东蚋属二新种记述(双翅目：蚋科)

Five speices of Simuliidae, Simulium (Eusimulium) aureohirtum Brunetti,1911, S. (Simulium ) quinquestriatum (Shiraki, 1935) S.(Gomphostilbia ) pingxiangense An & Hao, 1990, S.(S.) shangchuanense sp. Nov. , S.(S.) spoonatum sp. Nov. were collected from Shangchuan Island, Guangdong Province, China. Both adult and pupal stages of the new species are described in this paper. All the specimens are kept in the Medical Entomological Specimen Building, Institute of Microbiology and Epidemiology Academy of Military Medical Sciences, Beijing.