Predator-mediated genotypic shifts in a prey population: experimental evidence

We demonstrate the effect of fish predation on genotype frequencies in a laboratory population composed of two Daphnia magna clones, with historically contrasting exposures to fish predation. The two clones differed in their responsiveness to predation via differential avoidance/escape behavior. The clone which coexists with fish in nature is more responsive to the presence of a fish predator, while the clone not exposed to fish predation does not exhibit the defensive reaction. Fish caused a rapid (within 18 h) and significant shift in Daphnia clonal composition, from 1:1 to 8:1, in favor of the responsive clone. Genotype-specific defensive abilities (modus defendi) can contribute greatly to the phenomenon of genotype replacement under selective predation

Differential Levels of Stress Proteins (HSPs) in Male and Female Daphnia magna in Response to Thermal Stress: A Consequence of Sex-Related Behavioral Differences?

In two independent experiments, we compared: (1) water depth selection (and accompanying temperature selection) by male and female Daphnia magna under different kinds of environmental stress, including the presence of filamentous cyanobacteria, the risk of predation from fish, and the presence of toxic compounds; and (2) sex-dependent production of heat shock proteins (HSP60, 70, and 90) in response to a sudden change in temperature. Male D. magna selected deep water strata, which offer a relatively stable environment, and thereby avoided the threat of predation and the presence of toxic compounds in surface waters. Correlated with this behavior, males reduce their molecular defenses against stress, such as the production of heat shock proteins (HSPs), and do not maintain the physiological machinery that triggers an increase in HSP levels in response to stress. In contrast, female D. magna actively select habitats that offer optimal conditions for growth and production of offspring. Consequently, females are exposed to variable environmental conditions that may be associated with increased stress. To permit survival in these different habitats, D. magna females require molecular mechanisms to protect their cells from rapid changes in stress levels. Thus, they maintain high constitutive levels of the heat shock proteins from HSP 60, 70, and 90 families, and they have the potential to further enhance the production of the majority of these proteins under stress conditions. The results of this study indicate that the separate habitats selected by male and female D. magna result in different patterns of HSP production, leading us to hypothesize that that male and female Daphnia magna adopt different strategies to maximize the fitness of the species

Ecological genomics: steps towards unraveling the genetic basis of inducible defenses in Daphnia

Little is known about the genetic mechanisms underlying inducible defenses. Recently, the genome of Daphnia pulex, a model organism for defense studies, has been sequenced. Building on the genome information, recent preliminary studies in BMC Developmental Biology and BMC Molecular Biology have assessed gene response profiles in Daphnia under predation pressure. We review the significance of the findings and highlight future research perspectives

Chaoborus and Gasterosteus Anti-Predator Responses in Daphnia pulex Are Mediated by Independent Cholinergic and Gabaergic Neuronal Signals

Many prey species evolved inducible defense strategies that protect effectively against predation threats. Especially the crustacean Daphnia emerged as a model system for studying the ecology and evolution of inducible defenses. Daphnia pulex e.g. shows different phenotypic adaptations against vertebrate and invertebrate predators. In response to the invertebrate phantom midge larvae Chaoborus (Diptera) D. pulex develops defensive morphological defenses (neckteeth). Cues originating from predatory fish result in life history changes in which resources are allocated from somatic growth to reproduction. While there are hints that responses against Chaoborus cues are transmitted involving cholinergic neuronal pathways, nothing is known about the neurophysiology underlying the transmission of fish related cues. We investigated the neurophysiological basis underlying the activation of inducible defenses in D. pulex using induction assays with the invertebrate predator Chaoborus and the three-spined stickleback Gasterosteus aculeatus. Predator-specific cues were combined with neuro-effective substances that stimulated or inhibited the cholinergic and gabaergic nervous system. We show that cholinergic-dependent pathways are involved in the perception and transmission of Chaoborus cues, while GABA was not involved. Thus, the cholinergic nervous system independently mediates the development of morphological defenses in response to Chaoborus cues. In contrast, only the inhibitory effect of GABA significantly influence fish-induced life history changes, while the application of cholinergic stimulants had no effect in combination with fish related cues. Our results show that cholinergic stimulation mediates signal transmission of Chaoborus cues leading to morphological defenses. Fish cues, which are responsible for predator-specific life history adaptations involve gabaergic control. Our study shows that both pathways are independent and thus potentially allow for adjustment of responses to variable predation regimes

Agricultural holdings as a subjects of bioeconomy – legal aspects

Celem opracowania jest udzielenie odpowiedzi na pytanie, czy na gruncie prawa polskiego uprawnione jest stwierdzenie, że gospodarstwa rolne są podmiotami biogospodarki. W szczególności chodzi o odnalezienie w polskim systemie prawnym norm prawnych regulujących tę kwestię. Rozważania rozpoczęto od poszukiwania definicji legalnej biogospodarki w aktach prawa krajowego i unijnego. Wobec braku definicji legalnej tego pojęcia zaprezentowano definicję pojęcia bazującą na dorobku innych nauk. W celu budowy normy prawnej przyjęto za Komisją Europejską, że rolnictwo jest jednym z sektorów biogospodarki oraz że działalność rolnicza powinna być prowadzona przy uwzględnieniu zasobów naturalnych. W dalszej części opracowania dokonano analizy prawnej tego, czy i na jakich zasadach, a zatem pod warunkiem spełnienia jakich, przewidzianych prawem przesłanek, osoby prowadzące gospodarstwa rolne mogą urzeczywistniać ideę biogospodarki angażując się bezpośrednio w produkcję energii z odnawialnych źródeł.The aim of the study was to answer the question, is it under the Polish law allowed to say, that the agricultural holdings are the subjects of the bio-economy. Considerations began by finding and citing the definition of bioeconomy. As the European Commission stated, the agriculture is one of the sectors of the bio-economy and that agricultural activities should be carried out taking into account the natural resources. In the later part of the study analyzes the author polish law due to the question, if and on what basis, can the farmers realize the idea of bio-economy by engaging directly in the production of energy from renewable energy sources

Diel vertical migration in zooplankton: fixed or inducible behavior?

Inducible migratory behavior can be favored over fixed behavioral patterns under the changing predation regime in a lake when the risk of a contact with a predator is highly unpredictable. Since the strength of behavioral response can be adjusted to predation intensity, and behavioral defensive traits can be reversible along the predator recession, behavioral plasticity is less costly than constant maintenance of fixed defensive traits. An inducible migratory behavior can be favored if the time necessary to complete a phenotypic change is brief enough as related to the time scale of environmental change, fitness costs of producing plastic responses and of displaying such a response do not exceed the gained benefits, and reliable cues which announce the approaching danger are available to individual prey. The sensitivity to different environmental cues depends on lag time between the cue and anticipated danger in relation to the time required to display a defensive response. Whereas complicated and time consuming defenses which require deep morphological and physiological changes should be rather triggered by environmental predictors of predation onsets, unpredictable onset of predation, usually not announced by any of environmental cues, should be recognized directly, via the stimulus coming from a predator itself