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1.
The gut fluorescence method was used to study algal grazingby Penilia avirostris in a semiestuarine embayment. Grazingimpact estimated from ingestion rate and animal abundance revealedthat only {small tilde}1% of the algal biomass was grazed perday by the cladocerans. 相似文献
2.
Ingestion and clearance rates, feeding behaviors and life historyvariables of the marine cladoceran Penilia avirostris were evaluatedover a range of food concentrations encountered in nature (0.013.0mm3 11 of Isochrysis galbana). Ingestion rates increasedand clearance rates decreased with increasing food concentration.No maximum feeding thresholds were observed over the range ofalgal concentrations offered. Weight-specific ingestion ratesdecreased with increasing body weight. Feeding behaviors suchas mandibular activity, abdominal claw rejections of cloggedfeeding structures and feeding appendage activity decreasedat a food level of 0.3 mm3 l1 of l. galbana. Peniliaavirostris had very poor survivorship at extremely low (0.01mm3 l1 and high (3.00 mm3 l1) food levels. Mortalitywas hardly affected at food levels of 0.031.0 mm3 l1Reproduction did not occur at food levels of 相似文献
3.
Development time of embryos in the brood pouch of the cladoceran Penilia avirostris Dana, 1852, was estimated by collecting zooplankton daily for 15 days in surface water of Guanabara Bay, Brazil. Each day the maturity stage of embryos of 90 parthenogenic females was noted. Total development time (egg to birth) varied from 2 to 3 days, the immature phase (stages I to IV) being generally longer (2 days) than intermediate and mature phases (1 day, stages V to XII). Similar results were obtained from Bottrell's equation, which takes water temperature into account. 相似文献
4.
The herbivory of the marine cladoceran Peniliaavirostris was studied in the Gulf of Trieste(Northern Adriatic) from June 1993 to December1994 using the gut fluorescence method. P. avirostrisoccurred from June to December, butreached its greatest abundance in the summer months.A significant correlation between the gut pigmentcontent and chlorophyll a concentration in thesurface layer was established. Observations with anepifluorescence microscope revealed that the guts werefilled with fluorescing nanoplankton and picoplankton(cyanobacteria). Quantitative estimates indicated thatP. avirostris grazed less than 5% of theavailable chlorophyll a in more than half of allmeasurements, but removed most of the availablechlorophyll a in the surface layer during someperiods in September. It can therefore be concludedthat P. avirostris, together with planktonicprotists, plays an important role within the microbialloop. 相似文献
5.
An ecological model for the simulation of the population dynamics of the cladoceran Penilia avirostris in Guanabara Bay, a tropical Brazilian bay, was developed. The simulated curve gave a good fit, in time and intensity, to the exponential increase and decrease in densities of P. avirostris during the March-July 2000 period. The densities of embryos, young individuals, males, and parthenogenic and gamogenic females were the state variables. Parameters of the model were varied within the range of field and literature data. Predation was considered as the main factor affecting mortality, the death rate being a function of the density of chaetognaths, the dominant invertebrate predator in Guanabara Bay. Input of resting eggs into the model as a “seed” source of embryos provided a good fit to the exponential increase of Penilia density. The observed sharp decreases and collapses of the population could not be explained by mortality or a shift from parthenogenic to gamogenic reproduction only. To provide an explanation, it was necessary to introduce an output forcing function, which probably represents physical factors such as water mass exchanges by tide- and wind-driven currents. 相似文献
6.
The invasive garden ant, Lasius neglectus, is a dominant species due to its capacity to form large supercolonies. This species was assumed to possess a wide thermal niche since it is able to adapt to cold climates, which is a factor that boosted its rapid expansion from south to many central-northern European Countries. However, the effect of variations in environmental temperatures on its competitive ability against other species has still not been investigated. In this paper, we analyzed the change in survival ability of Lasius neglectus during encounters with two Mediterranean dominant ants (Crematogaster scutellaris and Tapinoma nigerrimum) at four different temperatures (15, 20, 25 and 30 °C). Firstly, control tests were performed to provide the baseline survival ability of the three species at different temperatures. Secondly, competition tests were carried out at the same temperatures. Lasius neglectus survival was negatively affected by high temperature (30 °C) in control tests, and this impairment was much more pronounced in competition tests. On the contrary, the two opponent species were only marginally affected by temperatures in control tests. Crematogaster scutellaris was a better competitor than L. neglectus, particularly at high temperatures. Tapinoma nigerrimum was a weaker competitor and was always outcompeted by L. neglectus, particularly at low temperatures. This result could suggest that L. neglectus is at a disadvantage during interspecific encounters when temperatures are high and that the predicted future increase in environmental temperatures may potentially enhance this handicap. 相似文献
7.
A number of explanations have been advanced to account for the increased frequency and intensity at which jellyfish (pelagic
cnidarians and ctenophores) blooms are being observed, most of which have been locally directed. Here, we investigate seasonal
and inter-annual patterns in abundance and distribution of jellyfish in the North Atlantic Ocean to determine if there have
been any system-wide changes over the period 1946–2005, by analysing records of the presence of coelenterates from the Continuous
Plankton Recorder (CPR) survey. Peaks in jellyfish abundance are strongly seasonal in both oceanic and shelf areas: oceanic
populations have a mid-year peak that is more closely related to peaks in phyto- and zooplankton, whilst the later peak of
shelf populations mirrors changes in SST and reflects processes of advection and aggregation. There have been large amplitude
cycles in the abundance of oceanic and shelf jellyfish (although not synchronous) over the last 60 years, with a pronounced
synchronous increase in abundance in both areas over the last 10 years. Inter-annual variations in jellyfish abundance in
oceanic areas are related to zooplankton abundance and temperature changes, but not to the North Atlantic Oscillation or to
a chlorophyll index. The long-term inter-annual abundance of jellyfish on the shelf could not be explained by any environmental
variables investigated. As multi-decadal cycles and more recent increase in jellyfish were obvious in both oceanic and shelf
areas, we conclude that these are likely to reflect an underlying climatic signal (and bottom-up control) rather than any
change in fishing pressure (top-down control). Our results also highlight the role of the CPR data in investigating long-term
changes in jellyfish, and suggest that the cnidarians sampled by the CPR are more likely to be holoplanktic hydrozoans and
not the much larger meroplanktic scyphozoans as has been suggested previously.
Guest editors: K. A. Pitt & J. E. Purcell
Jellyfish Blooms: Causes, Consequences, and Recent Advances 相似文献
8.
Evadne tergestina and Penilia avirostris were sampled duringseveral diel cycles in the well-mixed, turbid Inland Sea ofJapan and the more stratified, less turbid Gulf of Mexico shelf.Parthenogenetic female Evadne contained embryos with pigmentedeyes only at night, and apparently released neonates near dawnor in the morning. There was no significant diel vertical migrationin the Gulf of Mexico, and a reverse migrationin the Inland Sea. Female Penilia could contain mature embryosat any time, but were most likely to do so at night. Peniliadid not migrate dielly, and in the Gulf of Mexico was concentratedin a nepheloid layer near the bottom. 相似文献
9.
Sommer U Aberle N Engel A Hansen T Lengfellner K Sandow M Wohlers J Zöllner E Riebesell U 《Oecologia》2007,150(4):655-667
An indoor mesocosm system was set up to study the response of phytoplankton and zooplankton spring succession to winter and
spring warming of sea surface temperatures. The experimental temperature regimes consisted of the decadal average of the Kiel
Bight, Baltic Sea, and three elevated regimes with 2°C, 4°C, and 6°C temperature difference from that at baseline. While the
peak of the phytoplankton spring bloom was accelerated only weakly by increasing temperatures (1.4 days per degree Celsius),
the subsequent biomass minimum of phytoplankton was accelerated more strongly (4.25 days per degree Celsius). Phytoplankton
size structure showed a pronounced response to warming, with large phytoplankton being more dominant in the cooler mesocosms.
The first seasonal ciliate peak was accelerated by 2.1 days per degree Celsius and the second one by 2.0 days per degree Celsius.
The over-wintering copepod populations declined faster in the warmer mesocosm, and the appearance of nauplii was strongly
accelerated by temperature (9.2 days per degree Celsius). The strong difference between the acceleration of the phytoplankton
peak and the acceleration of the nauplii could be one of the “Achilles heels” of pelagic systems subject to climate change,
because nauplii are the most starvation-sensitive life cycle stage of copepods and the most important food item of first-feeding
fish larvae.
Priority programme of the German Research Foundation—contribution 3. 相似文献
10.
We analysed monthly samples collected in Guanabara Bay, with a conical net of 200 m mesh during 1985. The bay was divided into three areas: an outer region (area A), influenced by oceanic waters; an inner region (area C), influenced by fluvial inflow; and a transition region (area B) with intermediate features. Penilia avirostris and Evadne tergestina were observed in the three areas, with greatest densities, however, in the outermost region, which had the highest salinities and lowest temperatures. Penilia avirostris was more abundant in summer (March), a period with the greatest relative densities of nanoplankton. Evadne tergestina was also abundant in summer, but its peak fell in November, a period with a relative increase in microphytoplankton density in the bay. The two species disappeared in winter: Penilia avirostris was absent from May to August, whereas Evadne tergestina disappeared in August and September. 相似文献
11.
The first documented occurrence of a silvery John dory, Zenopsis conchifera , in the Mediterranean Sea is reported. A female (645 mm total length, 3296 g body mass) of Z. conchifera was caught in July 2006 by a commercial bottom trawler off the northern Tunisian coast (central Mediterranean Sea). 相似文献
12.
Climate change is a major threat to biodiversity and distributions shifts are one of the most significant threats to global warming, but the extent to which these shifts keep pace with a changing climate is yet uncertain. Understanding the factors governing range shifts is crucial for conservation management to anticipate patterns of biodiversity distribution under future anthropogenic climate change. Soft‐sediment invertebrates are a key faunal group because of their role in marine biogeochemistry and as a food source for commercial fish species. However, little information exists on their response to climate change. Here, we evaluate changes in the distribution of 65 North Sea benthic invertebrate species between 1986 and 2000 by examining their geographic, bathymetric and thermal niche shifts and test whether species are tracking their thermal niche as defined by minimum, mean or maximum sea bottom (SBT) and surface (SST) temperatures. Temperatures increased in the whole North Sea with many benthic invertebrates showing north‐westerly range shifts (leading/trailing edges as well as distribution centroids) and deepening. Nevertheless, distribution shifts for most species (3.8–7.3 km yr?1 interquantile range) lagged behind shifts in both SBT and SST (mean 8.1 km yr?1), resulting in many species experiencing increasing temperatures. The velocity of climate change (VoCC) of mean SST accurately predicted both the direction and magnitude of distribution centroid shifts, while maximum SST did the same for contraction of the trailing edge. The VoCC of SBT was not a good predictor of range shifts. No good predictor of expansions of the leading edge was found. Our results show that invertebrates need to shift at different rates and directions to track the climate velocities of different temperature measures, and are therefore lagging behind most temperature measures. If these species cannot withstand a change in thermal habitat, this could ultimately lead to a drop in benthic biodiversity. 相似文献
13.
Katechakis Alexis; Stibor Herwig; Sommer Ulrich; Hansen Thomas 《Journal of plankton research》2004,26(6):589-603
Selectivity-size spectra, clearance and ingestion rates andassimilation efficiencies of Acartia clausi (Copepoda), Peniliaavirostris (Cladocera) and Doliolum denticulatum (Doliolida)from Blanes Bay (Catalan Sea, NW Mediterranean) were evaluatedin grazing experiments over a wide range of food concentrations(0.028.8 mm3 L1 plankton assemblages from BlanesBay, grown in mesocosms at different nutrient levels). Acartiaclausi reached the highest grazing coefficients for large algae>70 µm (longest linear extension), P. avirostris forintermediate food sizes between 15 and 70 µm, and D. denticulatumfor small sizes from 2.5 to 15 µm. Penilia avirostrisand D. denticulatum acted as passive filter-feeders. Acartiaclausi gave some evidence for a supplementary raptorial feedingmode. Effective food concentration (EFC) decreased linearlywith increasing nutrient enrichment for D. denticulatum andfollowed domed curves for A. clausi and for P. avirostris withmaximum values at intermediate and high enrichment levels, respectively.Clearance rates of crustacean species showed curvilinear responseswith narrow modal ranges to increasing food concentration. Clearancerates of D. denticulatum increased abruptly and levelled intoa plateau at low food concentrations. Mean clearance rates were13.9, 25.5 and 64.1 mL ind.1 day1, respectively.No clearance could be detected for A. clausi at food concentrations<0.1 mm3 L1 and for P. avirostris at food concentrations 相似文献
14.
15.
A mature male pelagic stingray Pteroplatytrygon violacea (99 cm total length, 33·5 cm disc length and 42 cm disc width; 2·5 kg) was caught by commercial Nephrops trawl in the North Sea (at c . 54º49' N; 0º57' W) on 14 November 2005. Records of P. violacea in the north-east Atlantic are reviewed, with only two vagrant specimens known from the North Sea, representing the most northerly records of this species in the Atlantic Ocean. 相似文献
16.
The present study provides first comprehensive and up-to-date results on alien plant taxa in Iceland since 1967. We evidenced the presence of 336 alien vascular plant taxa, including 277 casuals and 59 naturalised taxa, two being invasive. The distribution of the alien flora exhibits a clear spatial pattern showing hotspots of occurrence and diversity within areas of major settlement centres. Altitude above sea level and temperature-related variables proved to be the most important factors shaping alien plant distribution in Iceland. Predictive modelling evidenced that arctic areas of Iceland and the Central Highlands are under serious risk of alien plant invasion due to climate change. The results provide crucial information for alien and invasive plant management and contribute data for meta-analyses of invasion processes worldwide. 相似文献
17.
Marine mussels illustrate a stunning variability in shape and color. Such variability, added to the scarcity of reliable morphological characters for their identification, can mislead recognition prompting the assignation of specimens of a single species to different ones or incorporate specimens belonging to different taxa into a single one. DNA barcoding is widely used for species identification; however, as this method relies on the previous morphological identification of the specimens, some of the DNA sequences stored in DNA databases are incorrectly assigned to a given species. In view of this uncertainty, further criteria beyond morphological characters and DNA sequences in databases are required to more reliably and accurately identify marine mussels. In this work we mapped ribosomal RNA and histone gene clusters to chromosomes of four species of marine mussels and compared them with those from another eight marine mussel taxa. Specimens of these twelve taxa were also DNA barcoded. Our results clearly demonstrated that the chromosomal analysis of marine mussels could shed light on their identification and, therefore, solve contradictions posed by morphological and molecular data. 相似文献
18.
Carlo Andreoli Claudio Tolomio Laura Scarabel Isabella Moro Sabrina Bellato Marta Moretto 《Plant biosystems》2013,147(6):1007-1027
Abstract During research directed towards the employment of the biological resources of the North Adriatic lagoons, from January 1991 to December 1992, in both tidal phases, a survey was carried out on the phytoplankton and the chemico-physical parameters of the Scardovari lagoon. Data analyses allowed two different areas to be distinguished: one inner, which was generally characterized by high phytoplanktonic densities (St. 3–4), the other outer, which was more influced by marine load (St. 1–2). Photosynthetic picoplankton was dominant in terms of cell number in most samples. Phytoplanktonic fraction >2 μm was represented mainly by diatoms, which showed the higher species number. During the sample observation, some dinoflagellates, considered toxic or potentially toxic, were found. Their presence was important because of their effect on the bivalve mollusc cultures. 相似文献
19.
Paratanais rosadi
sp. n. described from Puerto Rican coastal waters represents the first species of the genus from the northwestern Atlantic. It is distinguished from the other Paratanais species by a combination of characters, including article-2 of the maxilliped palp with a geniculate, finely-serrulate seta on inner margin; chela with stiff, geniculate, seta arising from propodus between fixed finger and dactylus and with short, stout, finely serrulate, seta on inner distal face of propodus adjacent to base of dactylus; carpus of pereopods 4−6 having three, instead of four stout modified spiniform setae distally, uropodal exopod distinctly shorter than endopodal article-1; and uropodal endopod with articles of about of equal in length. A key for the separation of Paratanais species from the Atlantic Ocean is presented. 相似文献
20.
Nicolas Djeghri Aurélien Boyé Clare Ostle Pierre Hélaouët 《Global Ecology and Biogeography》2023,32(6):962-975