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1.
Habitat choice in relation to environmental factors of two coexisting calanoid copepod species, Eudiaptomus gracilis and E. graciloides, was studied in a mesotrophic lake and in large indoor mesocosms. Both species and sexes showed pronounced diel vertical
migration (DVM) in the field. In 12 m deep mesocosms with free ranging fish DVM was observed and species increased day depth
over time. No changes were observed in copepod day depth over time in experiments with fish kairomone. It is hypothesized
that fish kairomone acts as an early warning system to copepods which respond by moving deeper, but only as far as the thermocline.
For full DVM, a nearby mechanical stimulus is necessary. Thus, as fish go deeper to feed, copepods retreat. The response of
copepods to fish predation, in the presence of low and high numbers of Daphnia,shows that copepods effectively use Daphniaas living shields to avoid predation. The two species adopt different vertical migration strategies depending on whether there
are high or low numbers of Daphniapresent. A dominant feature of mesocosm experiments was the night time aggregating (lekking) of E. gracilis males at the surface. When the spring and autumn percentages of risk takers in the epilimnion were compared, E. gracilis, particularly males, suffered the greatest cost. 相似文献
2.
Daphnia hyalina × galeata (Dhg) and D. pulicaria (Dp) are ready to pay greater costs in terms of predation risk avoidance at high rather than at low food levels. Such costs are
easier to assess in Daphnia than in large long-lived and difficult-to-handle herbivores, since they can be precisely determined in a few-day experiment
as the reduced growth (P=A−R) resulting from diminished assimilation (A) and/or increased respiration (R). In experiments with Daphnia grown for six days from the neonate to the first clutch of eggs, which were given different levels of algal food (Scenedesmus at concentrations from 0.05 to 1.60 mg C l−1), individual growth was lower in the presence of fish kairomone (chemical information on fish predation; present at a concentration
that induces antipredator defensive behavior and life histories) than in the absence of kairomone (control). The difference
from the control was negligible at the lowest food levels, and gradually increased with increasing food concentration. At
a food concentration of 1.6 mg C l−1, growth was reduced by 9–32 and 0–8% in Dhg and Dp, respectively, compared to the controls. A similar reduction was observed in the body length of six-day-old animals (Dhg 6–19%, Dp 0–14%), but not in the first clutch reproductive effort (clutch volume). Daphnia had a greater number of eggs per clutch in the presence of the kairomone, but smaller eggs, so that the total volume of eggs
in a clutch was the same with and without kairomone. The amplification of the effect of the kairomone due to high food levels
was weaker in Dp, a species that rarely coexists with planktivorous fish in natural habitats. 相似文献
3.
Meryem Beklioglu Ayse Gul Gozen Feriha Yıldırım Pelin Zorlu Sertac Onde 《Hydrobiologia》2008,614(1):321-327
Vertical migration of Daphnia represents the best-studied predator-avoidance behaviour known; yet the mechanisms underlying the choice to migrate require
further investigation to understand the role of environmental context. To investigate the optimal habitat choice of Daphnia under fish predation pressure, first, we selected the individuals exhibiting strong migration behaviour. The animals collected
from the hypolimnion during the daytime were significantly larger, being more conspicuous, and in turn performed stronger
diel vertical migration (DVM) when exposed to fish cue. We called them strong migrants. Second, we provided the strong migrant
D. pulex with food at high and intermediate (1 and 0.4 mg C l−1, respectively) levels, which were well above the incipient limiting level and of high quality. They traded the benefits of
staying in the warm water layer and moved down to the cold water in response to fish cue indicating fish predation. The availability
of food allowed the animals to stay in the cold hypolimnion. However, at the low food level (0.1 mg C l−1), which is an additional constraint on fitness, Daphnia moved away from the cold hypolimnion. Poor food condition resulted in strong migrant Daphnia to cease migration and remain in the upper warmer water layer. Although temperature is known to be a more important cost
factor of DVM than food, our results clearly show that this is only true as long as food is available. It becomes clear that
food availability is controlling the direction of vertical positioning when daphnids experience a dilemma between optimising
temperature and food condition while being exposed to fish cue. Then they overlook the predation risk. Thus, the optimal habitat
choice of Daphnia appears to be a function of several variables including temperature, food levels and fish predation.
Handling editor: S. I. Dodson 相似文献
4.
Helen Michels Susanne Lildal Amsinck Erik Jeppesen Luc De Meester 《Hydrobiologia》2007,594(1):117-129
In shallow temperate lakes, zooplankton populations may exhibit diel horizontal migration (DHM) and move towards macrophytes
during the day to avoid fish. Using a natural Daphnia magna population, we undertook an experimental investigation aimed to describe the genetic variation for DHM and to study whether
an adaptive micro-evolutionary response occurred to changes in macrophyte coverage and fish predation pressure through time.
Twenty-seven D. magna clones were hatched from ephippia in the sediment of shallow Lake Ring, Denmark. This lake was eutrophied during the 20th
century and was subject to restoration measures in the 1970s. The DHM behaviour of the clones was observed both in the presence
and absence of fish kairomone. Significant interclonal variation in DHM behaviour occurred in both treatments. To study the
micro-evolutionary response of the Lake Ring D. magna population, two approaches were used. First, we compared the DHM behaviour of clones derived from ephippia collected at different
depths. A comparison was conducted between clones resurrected from the period of eutrophication (1960–1980) and from the period
of recovery (1986–2000). A significant treatment (presence and absence of fish kairomone) × period interaction effect was
identified, suggesting a significant micro-evolutionary response for DHM behaviour. The D. magna clones exhibited a significantly stronger horizontal migration response during the period of eutrophication than in the recovery
phase. Second, clonal means, representing the influence of the genotype on the trait, were correlated with environmental conditions
(macrophyte cover, fish predation pressure and Secchi depth). The results of this analysis also suggest that a micro-evolutionary
response by Daphnia has occurred in reaction to changes in fish predation pressure. In periods with high fish predation pressure, Daphnia migrated more strongly towards the plants.
Guest editor: Piet Spaak
Cladocera: Proceedings of the 7th International Symposium on Cladocera 相似文献
5.
Takayuki Hanazato 《Hydrobiologia》1995,310(2):95-100
The cladoceran Daphnia ambigua was exposed to both the insecticide carbaryl and the kairomone released from the predator Chaoborus simultaneously, and its morphological changes were analyzed. Daphnia developed helmets in response to the kairomone, but not in response to carbaryl at low (sublethal) concentrations (1–3 µg 1–1). However, the carbaryl enhanced the development of high helmets and prolonged the maintenance period of the helmets over instars in the presence of the kairomone. These results suggest that sublethal concentrations of the insecticide alter predator-prey interactions by inducing helmet formation in Daphnia, which may reduce vulnerability of the Daphnia to predation. 相似文献
6.
Mirosław Ślusarczyk 《Oecologia》1999,119(2):159-165
The production of diapausing eggs by Daphnia magna stimulated by fish exudates can be explained as an anti-predator defence ensuring genome protection in periods of high risk
from fish predation. The combined effects on the induction of D. magna diapause of an “alarm” chemical originating from injured conspecific prey and fish kairomones were tested. The results of
the experiment showed that the cues when present together promote both the production of ephippial eggs and male formation,
indicating their role in the synchronization of the entire mode of Daphnia sexual reproduction. Ephippial eggs were only produced in the presence of both fish kairomone and conspecific alarm chemicals,
while male offspring occurred in the treatments where both, one or none of the cues were present. However, production of males
was the highest when both cues were provided. D. magna responded similarly to the tested cues whether or not the hypothetical alarm substance associated with predator odour came
from Daphnia specimens actually eaten by fish or from crushed conspecific individuals. However, chemicals from crushed chironomid larvae
combined with fish kairomones did not induce a similar response in D. magna. The relative advantage of utilization of alarm cues or predator kairomones in the induction of defence responses in prey
organisms is discussed.
Received: 8 June 1998 / Accepted: 11 January 1999 相似文献
7.
The life history of Daphnia exposed to fish kairomone at different developmental stages was examined in a laboratory experiment. The strongest life history
response to the applied predation threat was observed in females exposed during the 4th instar. Compared to Daphnia experiencing the presence of fish at earlier or later instars, these individuals reached maturity at a smaller size and released
fewer neonates. Moreover, their offspring also demonstrated the strongest reaction to predation threat, exhibiting the broadest
phenotypic plasticity in the life history response to predation. The breadth of their reaction norm was, on average, two times
larger comparing with individuals from other treatments. Broader phenotypic plasticity may offer clear selective advantages
under the unpredictable predation regime. This finding highlights the adaptive role of maternal effect in shaping life history
of cladocerans. 相似文献
8.
To assess the potential production of hybrids and backcrosses in a semi-natural environment, we studied the combined effect of fish kairomone, and food level on the production of males and ephippial females in different clones of five Daphnia taxa from the D. galeata species complex. We also studied the diel vertical migration (DVM) of these sexual daphnids under the same varying conditions. This was done to test the hypothesis that males and ephippial females have different migrating strategies, which would increase their mating probability. The study was carried out in two large-scale indoor mesocosms, the so-called `plankton towers' in the Max-Planck Institute in Plön, Germany.Although all of the Daphnia taxa produced ephippial females in the course of the experiment, only D. galeata produced a significant number of males. Fish kairomones had a significant negative influence on the production of ephippial females. We found no DVM in the D. galeata males. They stayed at a depth between 5 and 6 m both day and night, 1 or 2 m above the thermocline. The ephippial females of D. cucullata x hyalina migrated, whereas ephippial females of the other taxa showed no DVM but came significantly closer to the surface in the presence of fish kairomones. We conclude that males and sexual females co-occur in this species complex both in time and space. Therefore, a regular production of hybrids and backcrosses in this species complex seems likely. Fish kairomones do not seem to significantly influence this process. 相似文献
9.
1. In a laboratory batch culture experiment, a diapause response of Daphnia magna to a simulated threat of fish predation was tested at various light intensities, which under natural conditions determine potential vulnerability of Daphnia to visual planktivorous fish. 2. Under moderate light intensity (1.4 μmol m?2 s?1) that allows effective predation by fish, the proportion of females producing dormant eggs was significantly higher than under dim light conditions (0.001 μmol m?2 s?1) that are not favourable for visual detection of prey. Production of dormant eggs was not observed in complete darkness or in treatments missing fish kairomones, irrespective of tested light conditions. 3. The observed phenomenon is interpreted as a flexible response of prey to the conditional risk of predation assessed by Daphnia according to the presence of fish‐derived cues on the one hand and the presence of dark refugia on the other. Irrespective of the presence of fish kairomones, Daphnia may not produce resting eggs as long as a safe, dark, bottom zone is accessible. 相似文献
10.
Abstract
Freshwater ecosystems derive organic carbon from both allochthonous and autochthonous sources. We studied the relative contributions
of different carbon sources to zooplankton in a small, polyhumic, steeply stratified lake, using six replicate surface-to-sediment
enclosures established during summer and autumn 2004. We added 13C-enriched bicarbonate to the epilimnion of half the enclosures for three weeks during each season and monitored carbon stable
isotope ratios of DIC, DOC, POC and Daphnia, along with physical, chemical and biological variables. During summer, 13C-enriched DIC (δ13C up to 44 ± 7.2‰) was soon taken up by phytoplankton (δ13C up to −5.1 ± 13.6‰) and was transmitted to Daphnia (δ13C up to −1.7 ± 7.2‰), demonstrating consumption of phytoplankton. In contrast, during autumn, 13C-enriched DIC (δ13C up to 56.3 ± 9.8‰) was not transmitted to Daphnia, whose δ13C became progressively lower (δ13C down to −45.6 ± 3.3‰) concomitant with decreasing methane concentration. Outputs from a model suggested phytoplankton contributed
64–84% of Daphnia diet during summer, whereas a calculated pelagic carbon mass balance indicated only 30–40% could have come from phytoplankton.
Although autumn primary production was negligible, zooplankton biomass persisted at the summer level. The model suggested
methanotrophic bacteria contributed 64–87% of Daphnia diet during autumn, although the calculated carbon mass balance indicated a contribution of 37–112%. Thus methanotrophic
bacteria could supply virtually all the carbon requirement of Daphnia during autumn in this lake. The strongly 13C-depleted Daphnia values, together with the outputs from the models and the calculated carbon mass balance showed that methanotrophic bacteria
can be a greater carbon source for Daphnia in lakes than previously suspected. 相似文献
11.
Lass Sandra Boersma Maarten Wiltshire Karen Helen Spaak Piet Boriss Hinnerk 《Hydrobiologia》2001,442(1-3):199-206
Laboratory experiments were carried out to investigate life-history reactions of Daphnia to trimethylamine (TMA), a substance, which has recently been found to induce a similar phototactic reaction in Daphnia as fish kairomones. The effects of different treatments (control, fish kairomone and TMA) on the life-history traits of five clones of D. magna and one clone of D. galeata and D. hyalina, respectively, were studied. Only D. magna exhibited significant reactions to TMA and to fish kairomone. D. galeata showed no significant responses to either TMA or to fish kairomone. D. hyalina reacted to the fish treatment with two traits (size and number of eggs at maturity). The comparison of the reaction norms to TMA and fish kairomone demonstrated that the directions of some responses to both factors were similar but were different for others such as for size at maturity. TMA resulted in a larger size at maturity in D. magna, whereas fish kairomone had no significant influence on this trait. We, therefore, conclude that trimethylamine is not the primary causative chemical agent in fish induced life-history adaptations in Daphnia. 相似文献
12.
Laboratory populations of cloned Daphnia magna were exposed at different population phases (growing phase, density peak, stable phase) to the insecticide carbaryl at 15
μg 1−1, which was harmful to juveniles but not to adults, and their population dynamics were analyzed. The population declined most
at the density peak, when not only juveniles but also many adult individuals died. To analyze the factors affecting population
vulnerability to carbaryl, acute toxicity tests were conducted using Daphnia individuals of different body sizes under different food conditions. The test revealed that daphnid sensitivity to carbaryl
increased greatly when food density was changed from a high food level to a low level. This food condition, of low availability,
might be the condition to which the Daphnia populations were exposed at their density peak. The synergism of the negative impacts of anthropogenic and natural stresses
such as insecticides and food shortage may control aquatic populations. 相似文献
13.
Michail I. Gladyshev Nadezhda N. Sushchik Olga P. Dubovskaya Olesia N. Makhutova Galina S. Kalachova 《Aquatic Ecology》2008,42(4):617-627
Specific growth rates (based on biomass increment in unit time) of Daphnia fed natural reservoir seston from a eutrophic Siberian reservoir were studied during four vegetation seasons in a laboratory
flow-through system. Concentrations of particulate C, N, and P in reservoir seston <115 μm were comparatively high, 1.9, 0.2,
and 0.05 mg l−1, respectively; maximum C:P ratio was 259 mol:mol. According to conventional thresholds, concentrations of elements and their
stoichiometry did not limit the growth rate of Daphnia. Eicosapentaenoic acid (EPA) in seston significantly effected the growth rates at concentrations up to ∼13 μg l−1 (regression ANOVAR F-test value was 7.91), but not above this concentration. Thus, we consider this concentration of EPA in seston <115 μm to
be the limiting concentration of EPA for the growth of Daphnia (longispina group), i.e., below this concentration EPA was the best single predictor of the growth of Daphnia. 相似文献
14.
Studies on spatial avoidance behaviour of predators by prey often ignored the fact that prey typically face multiple predators which themselves interact and show a spatial pattern in abundance and predation rates (PRs). In a series of laboratory experiments, we investigated predation risk (PRI) and horizontal migration of the cladoceran Daphnia magna between open water and vegetation in response to two important invertebrate predators with a contrasting spatial distribution: pelagic Choaborus and vegetation-associated Ischnura. As expected, PRI by Chaoborus was higher in open water due to higher numbers and higher PRs of Chaoborus, while for Ischnura, PRI was highest in the vegetation due to higher densities, despite lower PRs of Ischnura. In accordance with this, Daphnia moved into the vegetation in the presence of the pelagic Chaoborus alone. In the presence of Ischnura alone, however, Daphnia showed no response. We hypothesize this may be the result of a constitutive behaviour of Daphnia to avoid pelagic fish, which impedes a response to the open water. In the combined predator treatment, Daphnia migrated to the open water zone. The increased risk of predation in the vegetation, due to a facilitating effect of Chaoborus on Ischnura PRs is believed to have caused this migration of the Daphnia. This response of Daphnia declined through time and Daphnia moved toward the vegetation. A decline in the activity of the Ischnura larvae through time may have switched the risk balance in favour of the vegetation environment. 相似文献
15.
1. The combined effect of the insecticide carbaryl and the predator (Leptodora kindtii) kairomone was assessed on the development of protuberant morphology in the small cladoceran Bosmina fatalis, a feature which evolved originally as a response to the kairomone. The experiment showed that Bosmina changed its morphology in response to the kairomone, but development was inhibited by carbaryl at a sub‐lethal concentration even in the presence of the kairomone. At the same time, reduction of fecundity was observed in animals exposed to carbaryl. 2. A short‐term feeding experiment (B. fatalis versus Leptodora) indicated that such low concentrations of the insecticide had no impact on predation by Leptodora. Thus, it is suggested that the inhibition of development of anti‐predatory defences in Bosmina can increase its vulnerability to predation. 3. Such disturbance of chemical communication by the insecticide reduces the individual survival rate of prey Bosmina in the environment with high predator density. On the other hand, reduction of fecundity may result in decreased population growth rate of animals. 4. The impact of the insecticide on the anti‐predator morphology in Bosmina (inhibition) was opposite to that in Daphnia (enhancement). This suggests that biochemical induction processes in the development of anti‐predatory morphology are evolutionally different between Daphnia and Bosmina. 相似文献
16.
The prevalence of diapause response to the simulated threat of fish predation was compared in three species of planktonic
crustaceans of the genus Daphnia (D. magna, D. pulicaria and D. longispina), which due to their different body size vary in vulnerability to fish predation pressure in natural conditions. Higher incidence
of diapause response was presumed in the larger-bodied species, which due to their higher conspicuousness and higher energetic
content experience the greatest size-selective pressure from visually foraging fish. Small-bodied species were expected to
utilize less costly yet less effective active defences, e.g. lower conspicuousness achieved due to slower body growth when
facing risk of size-selective predation. Proportions of females forming diapausing structures as well as females body size
at the maturation period were compared in experimental beakers containing or not containing fish kairomones (chemical cues
of fish predation) in a few clonal lineages of 3 species of Daphnia derived from a single lake inhabited by fish. The highest incidence of diapause response to fish kairomones was observed
in D. magna (when measured both as proportion of sensitive individuals and as proportion of inductive clones), the largest of the tested
Daphnia species. The lowest proportion of individuals and clones that employed diapause was reported in the smallest tested species,
D. longispina. In addition, the large-bodied Daphnia (D. magna) showed a greater reduction in body size in response to fish kairomones than the small-bodied species (D. longispina). The results of the present study support the assumption of higher prevalence of diapause response to the threat of selective
predation in larger and more vulnerable prey species. 相似文献
17.
Accounting for morphological plasticity in phytoplankton populations is relevant for taxonomy, systematic/evolutionary, and
ecological studies. In this work, the green alga Pediastrum tetras (Ehrenberg) Ralfs was used to describe the variation in population size structure over its growth cycle and to analyze responses
to changes in biotic and abiotic factors. Pediastrum cultures reached a final stable concentration in approximately 10 days. This density (8 × 105 cells ml−1) remained stable for at least another 13 days and the intrinsic growth rate was 0.24 ± 0.01 day−1. In the exponential phase, the relative number of single cells and the proportion of large cells (with vesicles inside) within
colonies increased. When density peaked, a relative increase of single cells as well as small cells in new colonies took place.
Finally, during the stationary phase, the trend reversed: fewer single cells and a larger cell size (without vesicles) were
observed. Results indicated that nutrient supply could affect population structure, diminishing the proportion of eight-cell
colonies. Daphnia
magna Straus significantly reduced the Pediastrum population density due to predation, and this led to a significant decrease in the density of the largest colonies. In addition,
info-chemicals induced a slight increase in the density of the largest colonies compared to the control treatment. Our study
suggests a possible trade-off in P. tetras colonial size in natural environments: during the stationary growth period in a lake, Pediastrum populations tend to increase in size for efficient use of nutrients, while they decrease in size in the presence of herbivores.
Handling editor: J. Padisak 相似文献
18.
Adrianna Wojtal Piotr Frankiewicz Magorzata Andziak Maciej Zalewski 《International Review of Hydrobiology》2007,92(1):23-32
The behavioural response of Daphnia cucullata to the presence of the pelagic invertebrate predator Leptodora kindtii, and the predation rate of littoral dragonfly nymphs on this species were investigated under laboratory conditions. Results of this study revealed a strong hiding response of Daphnia cucullata in the presence of the predatory cladoceran, L. kindtii, which was similar to the response of Daphnia in the presence of juvenile perch. This suggests that pelagic invertebrate predators may cause Daphnia to hide in the littoral zone which could result in increased exposure to predation by littoral invertebrates. A strong influence of dragonfly nymphs on D. cucullata, both in the presence and absence of macrophytes, was found. The average predation rate of Odonata larvae was about 5 prey ind–1 h–1 and did not differ significantly between treatments. Quantification of dragonfly pressure on Daphnia populations will require cross‐verification with field experiments since in the natural conditions Daphnia seeks a shelter in the vegetation stands against predation by Leptodora, despite the occurrence of odonates. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
19.
Diurnal vertical migration (DVM) of Daphnia hyalina in Lake Bled was most intense during summer stratification. The extent of DVM varied with the size of the animal and its reproductive state. Migration distances were shortest in immature specimens and longest in ovigerous females. During daytime, ovigerous females stayed deeper in the water column than females without ova or immatures. The daytime temperature of water at the median depth of the ovigerous females did not exceed 10 °C, even in the warmest season. At night they migrated upward to an environment which was warmer by as much as 9 °C.Laboratory observations indicate that specimen's size and water temperature determine the velocity of passive sinking, such that morning descent of the different groups of Daphnia can be explained by passive sinking alone.Our hypothesis is that the distribution of different groups of D. hyalina in Lake Bled is influenced by two types of predators: fish (Perca fluviatilis L. and Rutilus rutilus (L.)) and larvae of Chaoborus flavicans (Meig.), the latter appearing in the epilimnion during the night. Fish predation has a key-role at the beginning of thermal stratification. Supposing that in spring the gene pool of Daphnia consists of a mix of different genotypes, distributed at different depths during the day, fish predation combined with a presence of fish chemicals favored genotypes with a lower day-depth during the spring/summer period. 相似文献
20.
Luc De Meester 《Evolution; international journal of organic evolution》1996,50(3):1293-1298
The frequent use of neutral markers to quantify genetic variation in natural populations emphasizes the role of stochastic events in explaining genetic differentiation between populations. Complementary studies on ecologically relevant traits are needed to assess the role of natural selection acting on adaptive variation in the development of local genetic differentiation. To test the hypothesis of local adaptation in the cyclical parthenogenetic species Daphnia magna, the phototactic behavior in the absence and presence of fish kairomone was assayed for 30 clones derived from resting eggs isolated from three habitats characterized by a different predation pressure by fish. Clones derived from populations in which fish are present were, on average, more negatively phototactic in and more responsive to the presence of fish kairomone than clones derived from a fishless habitat. In addition, the results show a high genetic diversity for the traits studied in all three gene pools investigated, indicating a high potential for microevolutionary changes in behavior of these Daphnia populations in the face of changes in predation pressure. The results of the present study indicate that working with large samples at the expense of having less precise estimates of genotypic values for specific genotypes may result in a loss of information with regard to the evolutionary potential of local populations. 相似文献