Distribution of dominant calanoid copepod species in the Greenland sea during late fall

Summary Between 6 November and 12 December 1988, vertical distributions of Calanus finmarchicus, C. hyperboreus, C. glacialis and Metridia longa were studied at three stations in the Arctic water of the Greenland Sea Gyre (GSG) and compared with two stations in the Atlantic water (AW) of the Westspitsbergen Current. Nine depth strata down to 3,000 m were sampled. C.finmarchicus was most abundant in AW, C. hyperboreus in GSG, M. longa showed no preference and C. glacialis was rare everywhere. Stage composition differed with species and water mass. Vertical distribution varied also with water mass in all species but C. hyperboreus, which was always centered between 1,000 and 1,500 m. The other species were concentrated in the upper 300 m in AW and between 1,000 and 1,500 m in GSG, although not all stages followed this trend. Ontogenetic vertical migration leads to significant dislocations of organic matter from the euphotic zone to great depth in the Greenland Sea. In egg production experiments, C. hyperboreus spawned up to 149 eggs female^–1 day^–1. Implications of stage composition, sex ratio, and gonad maturation on copepod life cycles are discussed.     

Seasonal variability and inter-specific differences in hatching of calanoid copepod resting eggs from sediments of the German Bight (North Sea)

Hatching experiments were conducted on sediment samples collectedon seven cruises between March 2002 and February 2003, at fourstations near Helgoland (54°11'N, 7°53'E). Samples wereincubated for up to 12 months and examined weekly for calanoidcopepod nauplii. 12807 nauplii hatched in total. Of these 36.43%were stage N1 (pooled), 44.08% were Temora longicornis (stageN2 and older), and 17.96% were Centropages hamatus (stage N2and older). Some Acartia spp. and an unidentified species werefound, too. Hatching varied significantly between sampling dates.At three stations, counts of all nauplii peaked in samples takenin April, while at one station the maximum was recorded in thesample collected in October. The seasonal pattern of hatchingwas similar in T. longicornis and C. hamatus. In March, April,October and February numbers of all nauplii were initially low,but increased over the following 2–3 weeks. In June, Augustand December, however, average numbers were comparatively highat first, but declined thereafter. In three of the four samplesthat were incubated for 12 months nauplii hatched from the sedimentfor the entire experimental period. Temora longicornis and C.hamatus displayed clearly distinct patterns of hatching in theselong-term incubations.     

Reproduction of Calanus glacialis in the Laptev Sea, Arctic Ocean

Abundance and reproductive biology (gonad maturation and egg production) of the Arctic copepod Calanus glacialis were studied in the Laptev Sea and adjacent Arctic Ocean in September 1993 and from July to September 1995. Both abundance and reproductive activity were subject to strong spatial and seasonal variability, which was related to the ice cover, feeding conditions and circulation pattern. Maximum abundance of the C. glacialis population was generally confined to the outer shelf and slope with depths between 50 and 1000 m. During both cruises, highest egg production rates and largest number of young copepodite stages were observed in the eastern Laptev Sea, where the development of the C. glacialis population seems to follow the opening of the “Siberian Polynya”. In the western part, which is usually covered by pack ice, females were all immature, and no young stages were found. However, females responded quickly to a temporary opening of the ice there in 1995 and spawned. Starvation experiments showed that food-independent reproduction fuelled by internal energy resources was at least partly responsible for relatively high egg production rates at low ambient food concentrations. Egg production rates in starved females were considerably higher than those previously reported. Accepted: 14 June 2000     

Rhythm Patterns Interaction - Synchronization Behavior for Human-Robot Joint Action

Interactive behavior among humans is governed by the dynamics of movement synchronization in a variety of repetitive tasks. This requires the interaction partners to perform for example rhythmic limb swinging or even goal-directed arm movements. Inspired by that essential feature of human interaction, we present a novel concept and design methodology to synthesize goal-directed synchronization behavior for robotic agents in repetitive joint action tasks. The agents’ tasks are described by closed movement trajectories and interpreted as limit cycles, for which instantaneous phase variables are derived based on oscillator theory. Events segmenting the trajectories into multiple primitives are introduced as anchoring points for enhanced synchronization modes. Utilizing both continuous phases and discrete events in a unifying view, we design a continuous dynamical process synchronizing the derived modes. Inverse to the derivation of phases, we also address the generation of goal-directed movements from the behavioral dynamics. The developed concept is implemented to an anthropomorphic robot. For evaluation of the concept an experiment is designed and conducted in which the robot performs a prototypical pick-and-place task jointly with human partners. The effectiveness of the designed behavior is successfully evidenced by objective measures of phase and event synchronization. Feedback gathered from the participants of our exploratory study suggests a subjectively pleasant sense of interaction created by the interactive behavior. The results highlight potential applications of the synchronization concept both in motor coordination among robotic agents and in enhanced social interaction between humanoid agents and humans.     

Transesterification of alkylphosphate esters by phospolipase D

Phospholipase D from cabbage or Streptomyces chromofuscus catalyses the transesterification of alkylphosphate esters, which are potent antitumor agents. The exchange of choline in octadecylphosphosphocholine by N-(2-hydroxy-ethyl)-N-methylpiperidine with phospholipase D from cabbage is kinetically controlled and amounts to maximum 60% in buffer, 43% in buffer/n-hexane, and 82% in buffer/n-hexane/1-octanol.     

Biomarkers of toxicity in Clarias gariepinus exposed to sublethal concentrations of polycyclic aromatic hydrocarbons

Physiological, biochemical and histological indices in Clarias gariepinus broodstock, and teratogenic indices in embryos exposed to sublethal concentrations of naphthalene, phenanthrene and pyrene were investigated in 2014 using a static-renewal bioassay protocol. Phenanthrene (1.41 mg l^?1) was the most toxic, followed by pyrene (1.53 mg l^?1) and naphthalene (7.21 mg l^?1), based on 96 h LC50 values. Hepatosomatic indices were significantly higher in naphthalene- and pyrene-treated males compared with solvent controls, whereas fecundity in females was significantly lower by factors of 2.4 (naphthalene), 2.8 (phenanthrene) and 2.4 (pyrene), compared with controls. Catalase levels were lower in female phenanthrene-treated fish compared with controls. Histological alterations observed in PAH-treated fish include oedema, inflammatory cells, epithelial lifting and hyperplasia in the gills, vacuolation, haemosiderin pigments and sinusoidal congestion in the liver, and degenerated zona radiata in the ovary. Teratogenic effects were not observed, as evidenced by the lack of histological alterations in embryos spawned from pre-exposed broodstock. Sex-specific responses and the utility of biomarkers at cellular and individual levels of organisation are therefore demonstrated for holistic evaluations of polycyclic aromatic hydrocarbons in ecotoxicological studies.     

Composition and distribution of zooplankton in the Laptev Sea and adjacent Nansen Basin during summer, 1993

Zooplankton composition and distribution were investigated on the Laptev Sea shelf, over the continental slope and in the adjacent deep Nansen Basin during the joint German-Russian expedition “Arctic 93” with RV Polarstern and Ivan Kireyev in August/September 1993. In the shelf area biomass decreased from west to east with the lowest values in the area influenced by the Lena river runoff. A gradual increase of biomass from the shallow to the deep area correlated with water depth. Total biomass ranged between 0.1 and 1.5 g m⁻² on the shelf and 4.7 and 7.9 g m⁻² in the adjacent Nansen Basin. On the shelf Calanus glacialis/finmarchicus dominated overall. The contribution of brackish-water taxa was low in the west, where high salinity and southward currents from the Arctic Basin supported a marine neritic community, but on the southern and eastern Laptev shelf, in the areas of freshwater influence, brackish-water taxa contributed up to 27% of the total biomass. On the slope and in deep areas a few large Arctic copepod species, Calanus glacialis, C. hyperboreus and Metridia longa, composed the bulk of biomass and determined the pattern of its vertical distribution. The export of Calanus species from the Nansen Basin onto the Laptev shelf appears to be of great importance for the shelf communities. In turn, the eastern outer shelf and slope area of the Laptev Sea are thought to have a pronounced effect on the deep basin, modifying the populations entering the central Arctic. Received: 25 March 1997 / Accepted: 18 July 1997     

Seasonal Cycles of Egg Production of Two Planktonic Copepods, Centropages typicus and Temora stylifera, in the North-western Mediterranean Sea

Reproduction of the dominant copepods Centropages typicus andTemora stylifera was studied at a permanent station in the LigurianSea (north-western Mediterranean). Seasonal patterns of eggproduction, clutch size, egg size and female prosome lengthwere followed from January 1998 to December 1999. Female carboncontent and weight-specific egg production were compared inautumn 1998 and spring 1999. Reproductive patterns of C. typicusand T. stylifera were very similar, indicating that reproductionwas affected by the same environmental factors. Reproductiveactivity was highest in autumn in both species and years. Asecond peak of egg production was observed in early summer,which was less intense in 1999 after a bloom of salps. Egg productionrates reached maximal values of 33.5 and 33.3 eggs female^–1day^–1 and annual means of 10.8 and 11.7 eggs female^–1day^–1 in Centropages and Temora, respectively. Maximalweight-specific egg production was 0.21 day^–1 in bothspecies in November 1998, when female carbon contents were 6.7(C. typicus) and 12.0 µg (T. stylifera). No statisticalrelationship between egg production and food availability ortemperature was detected. Reproductive activity did not reflectthe seasonal abundance patterns, with C. typicus dominatingin spring and T. stylifera in autumn.     

Herpetomonas roitmani (Fiorini et al., 1989) N. Comb.: A Trypanosomatid with a Bacterium-like Endosymbiont in the Cytoplasm

The trypanosomatid previously described as Crithidia roitmani is characterized here at the ultrastructural and biochemical levels. The data indicates that the parasite belongs to the Herpetomonas genus, and we therefore suggest the flagellate to be denominated as Herpetomonas roitmani n. comb. Cladistic analysis of isoenzyme data generated by eight different enzymes showed that the parasite presented a distinct banding pattern and could be grouped with some Herpetomonas spp., but not with Crithidia spp., used as reference strains. Accordingly, when the parasites were grown for longer periods in Roitman's defined medium, expontaneous differentiation from promastigotes to opisthomastigotes (typical of the Herpetomonas genus) occurred. Transmission electron microscopy revealed the presence of bacterium-like endosymbionts in the cytoplasm of all evolutive forms of the parasite. All morphological alterations characteristic of endosymbiont-bearing trypanosomatids could be observed.