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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Anatomia, histologia, embryologia 24 (1995), S. 0 
    ISSN: 1439-0264
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The teratogenic effect of alcohol on chick embryos has been confirmed by many investigators. However, how this occurs is unknown.The aim of this study was to establish a teratogenic pattern of alcohol effects, on the first stages of development in avians.Fertilized eggs were infused through the air space of the shell on day 0, with ethanol in concentrations of 20%, 40% and 60%. The control group was infused with 0.1 ml of NaCl at 0.9%. At a second stage, the eggs were treated on the 4th day of incubation, using the same method. In both groups the eggs were removed on the 11th day of incubation.The teratological manifestations that appeared more frequently were evisceration, haemorrhagic embryos, oedema, cranial deformities, lack of eyes, and umbilical hernia, showing every embryo a clear reduction in size and body weight.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Anatomia, histologia, embryologia 25 (1996), S. 0 
    ISSN: 1439-0264
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: HGCs were found in the head epidermis, yolk sac and pharynx epithelium of trout embryos. These cells usually appear in clusters, closely related positionally to neighbouring cells. The differentiation and specialization of HGCs seem to be mainly dependent on cell-cell interactions, which provides, in part, the positional information necessary for the cells to differentiate and localize in the appropriate place. The final secretory process is the result of a sequence of events by which the maturation of enzymatic granules occurs. The electron-density of the granules varies according to the proximity of the secretory stage. Exocytosis of the secretory granules were observed. After secretion, each HGC undergoes cellular death by apoptosis (programmed cell death).
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Anatomia, histologia, embryologia 24 (1995), S. 0 
    ISSN: 1439-0264
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The development of the cephalic region of rainbow trout in the 24th, 30th and 36th stages, corresponding to the table of development by Vernier (1969), was studied using light microscopy and SEM.The 24th stage shows a voluminous cephalic region as a principal feature. At this time, most components of this region have started their differentiation. The 30th stage can be considered as an intermediary phase in the embryonic formation, and it is characterized by the high degree of differentiation between the nervous system and the sense organs. In the 36th stage, the basic final shape of the embryo has been reached.The results of this study show that the differentiation of gill lamellae and the opening of the mouth takes place later than that moment described by other authors. This suggests that development between 30th and 36th stages is a critical survival period for rainbow trout, in which respiratory and digestive functions start.
    Type of Medium: Electronic Resource
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  • 4
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    Unknown
    Pamplona : Periodicals Archive Online (PAO)
    Ius canonicum. 31:62 (1991) 683-707 
    ISSN: 0021-325X
    Topics: Law , Theology and Religious Studies
    Notes: OTROS ESTUDIOS
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 424 (2000), S. 141-146 
    ISSN: 1573-5117
    Keywords: phytoplankton ecology ; eutrophication ; associations ; time series ; assembly rules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When looking for a pattern of phytoplankton behaviour across trophic gradients, we need to cross the boundaries between different disciplinary areas, from autoecology to systems ecology, because eutrophication is a complex process which involves different time scales and different levels of community structure. Thus, we submit our observations to the muddled conceptual world of assemblage ecology. These inaccuracies arise, for example, from both species and community arguments; eutrophication as a fertilization or a metabolic phenomenon; and the notions frequently interwoven of pattern, process and rules. We suggest that it is advantageous to tackle this issue from the perspective of general ecology, rather than from a specifically planktonic orientation. In this way, useful general ecological tools, for example, time series and assembly-rule studies, can be used. Time-series study allows the dynamics of any variable to be described or to show that long term variable fluctuations may sometimes be unregulated, in response to some exogenous factor. Rules of assembly help us to resolve which traits are selectively involved during the eutrophication process. In this context, we advocate (1) the use of traits instead of morphospecies in phytoplankton studies, (2) looking for the dynamic patterns of phytoplankton with eutrophication, (3) the use of time series techniques to study phytoplankton trajectories, (4) the use of assembly rules to discern patterns in the formation of multispecies assemblages, (5) the consideration of the pelagic food-web in studies of phytoplankton dynamics and, as an overall suggestion, to borrow knowledge and inspiration from general ecology.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-5117
    Keywords: Data reduction ; principal component analysis ; phytoplankton ; short-term dynamics ; stable states ; production ; losses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Weekly studies of phytoplankton biomass and environmental variables were made over one year in a shallow stratifying, hypertrophic El Porcal lake near Madrid (Spain). Data were collected on abiotic factors, primary production, biomass and phytoplankton losses and subjected to reduction by means of several principal component analyses. Furthermore, weekly data on the same variables were gathered from published studies on Überlinger See, an embayment of the much deeper, mesotrophic Lake Constance (Central Europe), and treated in the same way. The two first principal components of PCAs on biological variables explained more than 60% of overall variance in both lakes. They could be ascribed to phytoplankton production + biomass and photosynthetic physiology + phytoplankton losses, respectively. The ordination of the biological trajectories in the data space of the two first principal components revealed six stable states of phytoplankton biomass in the shallow lake and seven in the deep lake. The breakpoints between stable states could be due to environmental, abiotic variables in some cases but biological interactions were suspected to be the cause of the other breakpoints. The abiotic effects on phytoplankton biomass took longer to occur in the deep lake. Also, short-term dynamics (one-three weeks) were demonstrated for both phytoplankton communities. A preliminary comparison between phytoplankton biomass dynamics in stratifying, shallow and deep lakes suggests that differences may be attributed partly to differences in depth.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-5117
    Keywords: Cyanobacteria ; population dynamics ; hypertrophic lakes ; phytoplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Populations of Limnothrix redekei, Oscillatoria lanceaeformis, Planktothrix agardhii and Pseudanabaena limnetica were found in a hypertrophic, gravel-pit lake near Madrid (Spain), throughout a one year sampling at weekly intervals. Physico-chemical factors, phytoplankton biomass and net growth rates were measured. Oscillatoria lanceaeformis was only observed a few weeks, probably being related to phosphorus limitation. Planktothrix agardhii biomass was related to PhAR irradiances, light attenuation coefficient in the water, Brunt-Väisäla frequency and decrease of soluble reactive phosphorus. Limnothrix redekei and Pseudanabaena limnetica biomass values were related to a decrease of inorganic nitrogen and temperature. A different lag response of populations was observed in relation to the environmental features.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 289 (1994), S. 43-55 
    ISSN: 1573-5117
    Keywords: river phytoplankton ; structure ; species richness ; biomass ; diversity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A structural analysis of river phytoplankton has been carried out based upon published studies on 67 rivers. When available on a yearly basis to account for seasonal variability, five structural features have been chosen: species composition, species richness, species dominance, diversity and biomass (total and per taxonomic groups). Despite the high number of reported studies, most of them cover only some of the aforementioned features. As a result of the low amount of studies, tropical rivers are underepresented. No size distribution studies have been carried out on river phytoplankton. The average species richness amounts to 126, being higher in temperate rivers. Roughly one half of each flora is comprised of sporadic species. No statistically significant relationship between species richness and latitude has been found despite the fact that tropical rivers appear to house fewer species than temperate rivers. Also, one half of the support in the floras are either benthic or tychoplanktonic. Diatoms comprise the majority of species numbers in the whole data set but are substituted by desmids in tropical rivers and by green algae when benthic species are not taken into account. There appears to be lower biomass in river phytoplankton than in lakes. Diatoms are also the major taxonomic group comprising total biomass in rivers but they share clearly a lower fraction in tropical rivers. On an average basis, diatoms appear to be more dominant in rivers than in lakes. The time course of diatom dominance occurs close to the summer solstice in tropical rivers whereas is much more lagged in temperate sites. The diversity of river phytoplankton is highly scattered (0.40–4.40 bits ind−1).
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 249 (1993), S. 43-57 
    ISSN: 1573-5117
    Keywords: disturbance ; diversity ; equilibrium ; phytoplankton ; succession rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The provisions of Connell's Intermediate Disturbance Hypothesis (IDH) were investigated in relation to the behaviour of freshwater phytoplankton in a hypertrophic lagoon, paying special attention to the link between species-diversity and environmental disturbances. Phytoplankton diversity yielded different indices depending on the basic unit of calculations (cells, particles, phytoplankton units, biomass). Although their ranges were approximately equal, they did not covary so could not be considered mutually substitutable. For the purpose of IDH testing, biomass diversity was chosen. Equilibrium states were considered to obtain in those periods with a very high fraction of total phytoplankton biomass, shared by no more than three phytoplankton species. Disturbances were considered as counterparts of equilibrium states. Disturbance factors were mostly abiotic, environmental features of the lake operating on the phytoplankton community at different time scales (co-occurring and with 1- and 2-weeks' lags). These scales may relate to the time required to establish phytoplankton community structure. IDH could be suspected not to hold for the phytoplankton of this hypertrophic lake, which experienced seven near-equilibrium phases and six disturbance periods throughout the study. As a rule, equilibrium states lasted longer than disturbance periods. The expected relationships between both disturbance intensity or frequency were not shown. Furthermore, no relationship was demonstrated between diversity (and hence IDH) and the phytoplankton community change rate. Wind stress probably played a minor role in triggering disturbance events. Disturbances were shown partly to promote small-sized phytoplankton communities. Finally, a plea for studying hypertrophic phytoplankton in greater detail is stressed if its responses to disturbances are to be fully understood.
    Type of Medium: Electronic Resource
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