排序方式: 共有45条查询结果,搜索用时 359 毫秒
21.
Paulina Anastasiu Gavril Negrean Ciprian Samoilă Daniyar Memedemin Dan Cogălniceanu 《Journal of Coastal Conservation》2011,15(4):595-606
Previous studies have found a higher proportion of alien plant species along the coastal area of the Black Sea. The goals
of the present study were to assess the role of two harbours as gateways and reservoirs for alien plant species, to compare
the structure and invasion pattern of the alien plants recorded there, and test methods useful for effective monitoring programs.
We inventoried 12 sites along the western Black Sea coast from the harbour of Sulina in the north to Cape Kaliakra in the
south. Each site was visited at least three times each. A more intensive survey was done in the two harbours targeted by our
study: Constanţa and Sulina. The proportion of neophytes was higher in the harbours (representing about one third of the total
plant species) and lower in coastal protected areas (with an average proportion of 6.7%). Species accumulation curves and
estimators of species richness indicated that while the plant inventory was not complete, invasive alien species (IAS) were
adequately inventoried. Harbours act not only as gateways for IAS but also as reservoirs, facilitating their acclimatization
and naturalization. The use of species accumulation curves and estimators of species richness are useful tools in designing
and evaluating simple monitoring programs based on repeated inventories. Our study has stressed the importance of monitoring
not only coastal waters but also green areas in harbours for the early detection of IAS. 相似文献
22.
In the shrimp Crangon crangon, an important fishery resource and key species in the southern North Sea, we studied temporal variations in size, biomass
(dry weight, W) and chemical composition (C, N, protein and lipid) of eggs in an initial embryonic stage. Data from 2 years, 1996 and 2009,
consistently revealed that egg size and biomass varied seasonally, with maxima at the beginning of the reproductive season
(January), decreasing values throughout spring, minima in June–July, and a slight increase thereafter. This cyclic pattern
explains why “Winter eggs” are on average larger and heavier than “summer eggs”. Using a modelling approach, we estimated
the duration of oogenesis in relation to seasonally changing seawater temperatures. According to an additive model of multiple
explanatory variables, the C content per newly laid egg showed in both years a highly significant negative relationship with
day length (r2 = 0.38 and 0.40, respectively; P < 0.0001), a weak positive relationship with temperature (r2 = 0.08 and 0.09; P < 0.05), and a weak negative relationship with phytoplankton biomass (r2 = 0.11 and 0.12; P < 0.05) at the estimated time of beginning oogenesis. Phenotypic plasticity in initial egg size and biomass is interpreted
as an adaptive reproductive trait that has evolved in regions with strong seasonality in plankton production and periods of
larval food limitation. In contrast to biomass per egg, the percentage chemical composition remained similar throughout the
reproductive period. Both the absolute and percentage values also showed significant interannual variations, which caution
against generalizations based on short-term studies of reproductive traits of C. crangon and other species of shrimp. 相似文献
23.
Maria Byrne Natalie A. Soars Melanie A. Ho Eunice Wong David McElroy Paulina Selvakumaraswamy Symon A. Dworjanyn Andrew R. Davis 《Marine Biology》2010,157(9):2061-2069
Climate change driven ocean acidification and hypercapnia may have a negative impact on fertilization in marine organisms
because of the narcotic effect these stressors exert on sperm. In contrast, warmer, less viscous water may have a positive
influence on sperm swimming speed and so ocean warming may enhance fertilization. To address questions on future vulnerabilities
we examined the interactive effects of near-future ocean warming and ocean acidification/hypercapnia on fertilization in intertidal
and shallow subtidal echinoids (Heliocidaris erythrogramma, H. tuberculata, Tripneustes gratilla, Centrostephanus rodgersii), an asteroid (Patiriella regularis) and an abalone (Haliotis coccoradiata). Batches of eggs from multiple females were fertilized by sperm from multiple males in all combinations of three temperature
and three
\textpH/P\textCO2 {\text{pH}}/P_{{{\text{CO}}_{2} }} treatments. Experiments were placed in the setting of projected near-future conditions for southeast Australia, an ocean
change hot spot. There was no significant effect of warming and acidification on the percentage of fertilization. These results
indicate that fertilization in these species is robust to temperature and
\textpH/P\textCO2 {\text{pH}}/P_{{{\text{CO}}_{2} }} fluctuation. This may reflect adaptation to the marked fluctuation in temperature and pH that characterises their shallow
water coastal habitats. Efforts to identify potential impacts of ocean change to the life histories of coastal marine invertebrates
are best to focus on more vulnerable embryonic and larval stages because of their long time in the water column where seawater
chemistry and temperature have a major impact on development. 相似文献
24.
Kurt Paschke Juan Pablo Cumillaf Sergio Loyola Paulina Gebauer Mauricio Urbina María Eugenia Chimal Cristina Pascual Carlos Rosas 《Marine Biology》2010,157(1):7-18
Episodes of hypoxia are common in the marine environment, and their ecological effects depend, in part, on their severity
and duration. Many species of decapod crustaceans reside in areas with fluctuating oxygen regimens. Physiological mechanisms
enhance the ability of these crustaceans to cope with acute episodes of hypoxia. Southern king crab, Lithodes santolla, fishery is important in the south of South America, and some data describe fishing zones with low dissolved oxygen (DO) levels
(3.5 mgO2 l−1, i.e., 8.3 kPa). Our main objective was to evaluate the effect of dissolved oxygen level on respiratory metabolism, nutritional
physiology, and immunological condition of L. santolla juveniles. Individual animals were exposed for 10 days to different oxygen tensions (2.1, 4.2, 8.5, 12.7, and 21.1 kPa) to
quantify the oxygen consumption rate; thereafter, blood oxyhemocyanin (Hc), protein concentration, as well as hemocytes, were
sampled. Freeze-dried animals were dissected, and digestive gland metabolites (glycogen, protein, glucose, cholesterol, acylglycerol,
and lactate) and digestive enzyme activity (general protease, trypsin, and chymotrypsin), as well as gill lactate dehydrogenase
(LDH) activity, were quantified. In the present study, Lithodes santolla showed a critical oxygen tension between 4 and 9 kPa, indicating that this crab species is more sensitive to DO than other
crustacean species. Protein and Hc concentrations followed a similar pattern to that of oxygen consumption. Digestive gland
glycogen and protein concentration did not change after 10 days at different oxygen exposures, but glucose, cholesterol, and
acylglycerol concentrations decreased linearly and proportionally to the available oxygen in the water. As in other decapods,
chymotrypsin showed over 90% of the total quantified proteases activity. Chymotrypsin activity together with total proteases
and trypsin was not affected by the environmental oxygen tension. Gill LDH and digestive gland lactate followed a similar
increase at lower environmental oxygen tension but dropped sharply at the lowest tension (2.1 kPa). Dissolved oxygen affected
also the immune system through reduction of hemocytes. This could provide a critical window for opportunistic pathogens to
become established when crabs are exposed to hypoxic conditions. L. santolla juveniles show a moderate tolerance to low oxygen availability by modifying the concentration of hemolymph proteins, mainly
OxyHc, some digestive gland metabolites, and by activating the anaerobic metabolism. This allows L. santolla juveniles to inhabit temporarily low oxygen zones in the deep ocean and suggests an advantage for culture conditions. 相似文献
25.
Summary. The plant apparency hypothesis predicts that apparent plants invest in broadly effective defences such as tannins while unapparent
plants invest in specific toxins such as alkaloids. The stress hypothesis states that plants invest in cheaper defences if
they have evolved in habitats that impose abiotic limitations to plant fitness. We tested these hypotheses by determining
the concentrations of alkaloids and tannins in a representative sample of the vascular plants of continental Chile (with exclusion
of Pteridophyta, Cactaceae, and Poaceae) consisting of 396 species. In a subsample of 166 species which contained both alkaloids
and tannins, we constructed the A/T index (A/T = [alkaloids]/ [tannins]). We discarded the presumed effect of phylogeny (as
estimated by taxonomy) on the variation observed in the data because no correlation of A/T with taxonomic relationships among
species either at family or genus levels was found in a nested ANOVA with genera nested in families. Concentration of alkaloids
was negatively correlated with that of tannins. We compared the value of A/T among species differing in life form (herbs,
shrubs or trees), herb longevity (annual or perennial), leaf-shedding manner of woody plants (deciduous or evergreen), latitudinal
range, and level of water stress typical in their natural habitat. Unapparent plants (herbs, annual) exhibited higher mean
A/T index than apparent plants (shrubs and trees, perennial). A/T did not correlate with latitudinal range. Mean A/T values
decreased from deserts to deciduous forests. The comparisons were not always significant due to the inevitable unbalance of
the data set which lowers the power of the statistical tests employed. The results suggest that chemical defences are indeed
distributed in a non-random manner among plants, and that to a large extent the predictions derived from the apparency and
stress hypotheses are sustained. 相似文献
26.
Pedro Daleo Juan Alberti Maria Soledad Avaca Maite Narvarte Paulina Martinetto Oscar Iribarne 《Marine Biology》2012,159(10):2359-2365
Feeding decisions under predation risk can be a key in the life of scavenger organisms, and tuned recognition of predation alarm cues and flexibility in the response are fundamental. The effect of injured conspecifics on the response behavior of the whelk Buccinanops globulosum to feeding opportunities was experimentally evaluated in a Patagonian Bay (40°45′S, 64°56′W, Argentina) in September 2010. The effect of sex, size, body condition, or starvation on anti-predatory behavior was assessed. The number of B. globulosum feeding on carrion was reduced by half when damaged conspecifics were present. Smaller, lighter, and starved individuals responded less to the presence of damaged conspecifics. These results indicate that, under natural conditions, feeding avoidance after detecting damaged conspecifics is a common and important anti-predatory strategy of B. globulosum and show that morphology and starvation are significant factors in the context of the trade-off between feeding and avoiding predation risk. 相似文献
27.
Paulina L. González-Gómez Natalia Ricote-Martinez Pablo Razeto-Barry Ivania S. Cotorás Francisco Bozinovic 《Behavioral ecology and sociobiology》2011,65(11):2141-2148
A common assumption in behavioral ecology is that the valuation of a resource by consumers depends on the energetic value
of the resource itself. Nevertheless, the value of a resource may be relative to the condition of the organism, which is in
turn related to the abiotic conditions such as ambient temperature. We developed a theoretical model—incorporating these untested
assumptions—to predict a functional relationship between territorial aggression and ambient temperature for individuals sensitive
to daily variations in energy availability. We evaluated our theoretical predictions against a field experiment carried out
with the hummingbird Sephanoides sephaniodes. The model predicted a quadratic relation between aggression intensity and ambient temperature. Field data were better explained
by a quadratic equation than a linear function, suggesting the existence of lower and upper thresholds of temperature which
determine the intensity of territorial defense. Ambient temperature affects energy expenditure for thermoregulation, and therefore,
it fixes the benefit level that must be produced by the territory to pay the costs of its defense. Our findings strongly suggest
that abiotic conditions can change an animal evaluation of the yield of a resource and in turn influence the behavioral strategy
which it adopts. 相似文献
28.
Carabid beetles, like Pterostichus oblongopunctatus, living in metal contaminated areas may be exposed to elevated levels of metals within their diets. However, when compared to other second order consumers, they have one of the lowest observed levels of metals, indicating methods of detoxification to deal with such toxicants. In this study, we investigated if chronic, multigenerational exposure to metals leads to resistance to toxic metal concentrations, and if so, what are the costs associated with them. Adult organisms were collected from two sites, a polluted and a reference site near Olkusz, in southern Poland. These adults were immediately mated, and eggs were collected twice weekly to assess the effects in the larvae of the F(1) generation. Larvae were randomly exposed to one of four artificial mediums: control, 50 mg kg(-1) Cd, 500 mg kg(-1) Zn, and a combined treatment of 50 mg kg(-1) Cd and 500 mg kg(-1) Zn to investigate possible interactions. Individuals were sacrificed at 10, 30, and 40 days. Although metals were not accumulated in larvae (p>0.05), larvae fed the Cd or the Zn treatment grew significantly slower, and had the lowest survival rate (p<0.05) in respect to control. Out of metal treated animals, those on the combined treatment of CdZn grew the quickest and had the highest observed survival (p<0.05). Although previous studies have demonstrated changes in adult population parameters under chronic, multigeneration exposure to toxic metal concentrations, our study did not reveal any changes in the larval stage. 相似文献
29.
Jaszczur Marek Teneta Janusz Styszko Katarzyna Hassan Qusay Burzyńska Paulina Marcinek Ewelina Łopian Natalia 《Environmental science and pollution research international》2019,26(9):8402-8417
Environmental Science and Pollution Research - The maximisation of the efficiency of the photovoltaic system is crucial in order to increase the competitiveness of this technology. Unfortunately,... 相似文献
30.