883 resultados para Acanthocyclops americanus, copepodites


Relevância:

100.00% 100.00%

Publicador:

Relevância:

100.00% 100.00%

Publicador:

Relevância:

100.00% 100.00%

Publicador:

Resumo:

At present time, there is a lack of knowledge on the interannual climate-related variability of zooplankton communities of the tropical Atlantic, central Mediterranean Sea, Caspian Sea, and Aral Sea, due to the absence of appropriate databases. In the mid latitudes, the North Atlantic Oscillation (NAO) is the dominant mode of atmospheric fluctuations over eastern North America, the northern Atlantic Ocean and Europe. Therefore, one of the issues that need to be addressed through data synthesis is the evaluation of interannual patterns in species abundance and species diversity over these regions in regard to the NAO. The database has been used to investigate the ecological role of the NAO in interannual variations of mesozooplankton abundance and biomass along the zonal array of the NAO influence. Basic approach to the proposed research involved: (1) development of co-operation between experts and data holders in Ukraine, Russia, Kazakhstan, Azerbaijan, UK, and USA to rescue and compile the oceanographic data sets and release them on CD-ROM, (2) organization and compilation of a database based on FSU cruises to the above regions, (3) analysis of the basin-scale interannual variability of the zooplankton species abundance, biomass, and species diversity.

Relevância:

100.00% 100.00%

Publicador:

Relevância:

100.00% 100.00%

Publicador:

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The population structure, reproductive period, and juvenile recruitment of Panopeus americanus were studied in order to enhance knowledge of its life cycle and reproductive strategy and promote the maintenance of its natural stocks in an impacted region. Specimens were collected in the remnant human-impacted mangrove at Araca, state of Sao Paulo, Brazil, at two-month intervals from January to November 2005, at low tide, with a capture effort by three people. The crabs were measured (carapace width, CW) and sexed. The total catch was 275 animals, including 132 males (48.0%); 127 females (46.2%), of which 39 were ovigerous (14.2% of total catch); and 16 individuals whose sex could not be identified (5.8%). No correlation was observed between water temperature and the number of collected individuals; however, there was a significant, positive correlation with salinity. Males were significantly larger than females. The size-frequency distribution was bimodal, reflecting the occurrende of more than one recruitment pulse and the differential abundance of adults during the period of study. The overall sex ratio was 1:0.97 favoring males, and was not significantly different from the expected value, i.e., this population fits the anomalous pattern of sex occurrence in size classes. Ovigerous females were captured in all sampled months, which explain the continuous recruitment observed. Expected low levels of individuals of different size classes in the population were not confirmed. All population aspects found here allowed us to infer that this population of P. americanus is well established in the impacted mangrove by virtue of its reproductive strategy.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The distribution and density of a population of the narrowback mud crab Panopeus americanus were evaluated, with emphasis on the different developmental stages (juveniles and adults) and sexes. Specimens were collected in a remnant human-impacted mangrove at Araca on the northern coast of Sao Paulo, Brazil, at two-month intervals from January through July 2006, using 1m x 1m sample plots randomly distributed in the intertidal zone. The population was abundant, with a mean density of 14.3 +/- 9.3 individuals/m(2). Larger individuals were more abundant in the upper and middle intertidal zones, whereas smaller crabs were predominant in the lower intertidal and thus remained submerged longer. Males and juveniles were homogeneously distributed. Females preferred regions farther from the waterline. A clustered distribution pattern suggested gregarious behaviour and settling of juveniles in the vicinity of the adults` habitats, in an adaptive process as a function of tidal rhythms.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Rhamnocercus stichospinus Seamster and Monaco, 1956 (Diplectanidae) parasitic on the sciaenid fish Menticirrhus americanus from the coastal zone of the State of Rio de Janeiro, is redescribed and recorded for the first time in the South American Atlantic Ocean. The generic diagnosis of Rhamnocercus is emended to accommodate the presence of confluent intestinal ceca in R. stichospinus.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Feeding of the different developmental stages of Calanipeda aquaedulcis on natural particles (bacterio-, phyto- and microzooplankton) was measured in a Mediterranean salt marsh (Empordà wetlands, NE Iberian Peninsula). Bottle incubations were performed in the field both in autumn and spring. The results showed differences in the diet of the different developmental stages due to both prey type and size. In general, the size of the ingested prey increased with increasing size of the C. aquaedulcis stage. While C. aquaedulcis adults had high ingestion rates and selection coefficients for large prey (micro- and nanoplankton), nauplii preferentially consumed smaller prey items (picoplankton). Copepodites showed the widest prey size range, including pico-, nano- and microplankton. Nevertheless, the lower size limit for particle capture was similar for all stages, i.e. between 1.7 and 2.1 μm. Omnivory was observed in all stages of C. aquaedulcis. Heterotrophic prey (picoplankton, dinoflagellates and ciliates) were the most ingested items. The ability to partition the available food among the different developmental stages could represent an advantage in times of ood scarcity because it may reduce intraspecific competition. This may explain how C. aquaedulcis is able to predominate in the zooplankton community for several weeks during spring and summer ven in situations of low food availability

Relevância:

20.00% 20.00%

Publicador:

Resumo:

The a-globin major genes from diploid and tetraploid Odontophrynus americanus were studied using PCR-based technology. The cloned and sequenced amplified fragments were shown to contain most of the exon II sequences as well as the whole exon III sequence of the a-globin gene. Unexpectedly, intron 2 was entirely absent in the amplified fragments of both 2n and 4n origin. High conservation was observed among the obtained sequences when compared to corresponding sequences from human and Xenopus laevis origin. The possibility that these sequences might be pseudogenes is raised

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Tesis (Maestro en Ciencias Forestales) U.A.N.L.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Tesis (Doctor en Ciencias con acentuación en Manejo de Vida Silvestre y Desarrollo Sustentable) UANL, 2014.

Relevância:

20.00% 20.00%

Publicador:

Resumo:

Gills are the first site of impact by metal ions in contaminated waters. Work on whole gill cells and metal uptake has not been reported before in crustaceans. In this study, gill filaments of the American lobster, Homarus americanus, were dissociated in physiological saline and separated into several cell types on a 30, 40, 50, and 80% sucrose gradient. Cells from each sucrose solution were separately resuspended in physiological saline and incubated in (65)Zn(2+) in order to assess the nature of metal uptake by each cell type. Characteristics of zinc accumulation by each kind of cell were investigated in the presence and absence of 10 mM calcium, variable NaCl concentrations and pH values, and 100 mu M verapamil, nifedipine, and the calcium ionophore A23187. (65)Zn(2+) influxes were hyperbolic functions of zinc concentration (1-1,000 mu M) and followed Michaelis-Menten kinetics. Calcium reduced both apparent zinc binding affinity (K (m)) and maximal transport velocity (J (max)) for 30% sucrose cells, but doubled the apparent maximal transport velocity for 80% sucrose cells. Results suggest that calcium, sodium, and protons enter gill epithelial cells by an endogenous broad-specificity cation channel and trans-stimulate metal uptake by a plasma membrane carrier system. Differences in zinc transport observed between gill epithelial cell types appear related to apparent affinity differences of the transporters in each kind of cell. Low affinity cells from 30% sucrose were inhibited by calcium, while high affinity cells from 80% sucrose were stimulated. (65)Zn(2+) transport was also studied by isolated, intact, gill filament tips. These intact gill fragments generally displayed the same transport properties as did cells from 80% sucrose and provided support for metal uptake processes being an apical phenomenon. A working model for zinc transport by lobster gill cells is presented.