scholarly journals Mussel memory: bivalves learn to fear parasites

2021 ◽  
Author(s):  
Christian Selbach ◽  
Lo&iumlc Marchant ◽  
Kim N Mouritsen
Keyword(s):  
Avoidance Behaviour ◽  
Feeding Rates ◽  
Dynamic Learning ◽  
Predator Prey ◽  
Defence Behaviour ◽  
Lower Infection ◽  
Underlying Mechanisms ◽  
The Cost ◽  
Fear Effects ◽  
Parasite Avoidance

Fear plays a crucial role in predator-prey interactions and can have cascading impacts on the structure of whole ecosystems. Comparable fear effects have recently been described for hosts and their parasites but our understanding of the underlying mechanisms remains limited by the lack of empirical examples. Here, we experimentally tested if bivalves Mytilus edulis can "learn to fear" the infective transmission stages (cercariae) of the trematode Himasthla elongata and if experienced mussels change their parasite-avoidance behaviour accordingly. Our results show that previous experience with parasites, but not infection per se, lead to a reduced filtration activity in mussels in the presence of cercariae compared to parasite-naive conspecifics. This reduction in filtration activity resulted in lower infection rates in mussels. Since parasite avoidance comes at the cost of lower feeding rates, mussels likely benefit from the ability to adjust their defence behaviour when infection risks are high. Overall, these dynamic learning processes of avoidance behaviour can be expected to play a significant role in regulating the bivalves' ecosystem engineering function in coastal habitats.

scholarly journals Fear of parasitism affects the functional role of ecosystem engineers

2021 ◽  
Author(s):  
Kim N Mouritsen ◽  
Nina P Dalsgaard ◽  
Sarah B Flensburg ◽  
Josefine C Madsen ◽  
Christian Selbach
Keyword(s):  
Predator Prey ◽  
Cascading Effects ◽  
Blue Mussels ◽  
Host Parasite Interactions ◽  
Mere Presence ◽  
Lower Infection ◽  
Underlying Mechanisms ◽  
And Function ◽  
Host Parasite

Fear is an integrated part of predator-prey interactions with cascading effects on the structure and function of ecosystems. Fear of parasitism holds a similar ecological potential but our understanding of the underlying mechanisms in host-parasite interactions is limited by lack of empirical examples. Here, we experimentally test if blue mussels Mytilus edulis respond behaviourally to the mere presence of infective transmission stages of the trematode Himasthla elongata by ceasing filtration activity, thereby avoiding infection. Our results show that blue mussels reduced clearance rates by more than 30% in presences of parasites. The reduced filtration activity resulted in lower infection rates in experimental mussels. The identified parasite-specific avoidance behaviour can be expected to play a significant role in regulating the ecosystem engineering function of blue mussels in coastal habitats.

scholarly journals What drives interaction strengths in complex food webs? A test with feeding rates of a generalist stream predator

2018 ◽  
Author(s):  
Daniel L. Preston ◽  
Jeremy S. Henderson ◽  
Landon P. Falke ◽  
Leah M. Segui ◽  
Tamara J. Layden ◽  
...  
Keyword(s):  
Food Webs ◽  
Body Mass ◽  
Prey Density ◽  
Scaling Laws ◽  
Community Dynamics ◽  
Abiotic Factors ◽  
Interaction Strength ◽  
Feeding Rates ◽  
Predator Prey ◽  
Mass Ratios

AbstractDescribing the mechanisms that drive variation in species interaction strengths is central to understanding, predicting, and managing community dynamics. Multiple factors have been linked to trophic interaction strength variation, including species densities, species traits, and abiotic factors. Yet most empirical tests of the relative roles of multiple mechanisms that drive variation have been limited to simplified experiments that may diverge from the dynamics of natural food webs. Here, we used a field-based observational approach to quantify the roles of prey density, predator density, predator-prey body-mass ratios, prey identity, and abiotic factors in driving variation in feeding rates of reticulate sculpin (Cottus perplexus). We combined data on over 6,000 predator-prey observations with prey identification time functions to estimate 289 prey-specific feeding rates at nine stream sites in Oregon. Feeding rates on 57 prey types showed an approximately log-normal distribution, with few strong and many weak interactions. Model selection indicated that prey density, followed by prey identity, were the two most important predictors of prey-specific sculpin feeding rates. Feeding rates showed a positive, accelerating relationship with prey density that was inconsistent with predator saturation predicted by current functional response models. Feeding rates also exhibited four orders-of-magnitude in variation across prey taxonomic orders, with the lowest feeding rates observed on prey with significant anti-predator defenses. Body-mass ratios were the third most important predictor variable, showing a hump-shaped relationship with the highest feeding rates at intermediate ratios. Sculpin density was negatively correlated with feeding rates, consistent with the presence of intraspecific predator interference. Our results highlight how multiple co-occurring drivers shape trophic interactions in nature and underscore ways in which simplified experiments or reliance on scaling laws alone may lead to biased inferences about the structure and dynamics of species-rich food webs.

scholarly journals Evolution of pathogen and parasite avoidance behaviours

2018 ◽  
Vol 373 (1751) ◽  
pp. 20170256 ◽  
Author(s):  
Cecile Sarabian ◽  
Val Curtis ◽  
Rachel McMullan
Keyword(s):  
Avoidance Behaviour ◽  
Disease Avoidance ◽  
Behavioural Science ◽  
Free Living ◽  
Society Meeting ◽  
Neural Architecture ◽  
Trade Offs ◽  
Wide Range ◽  
Parasite Avoidance ◽  
Behavioural Adaptations

All free-living animals are subject to intense selection pressure from parasites and pathogens resulting in behavioural adaptations that can help potential hosts to avoid falling prey to parasites. This special issue on the evolution of parasite avoidance behaviour was compiled following a Royal Society meeting in 2017. Here we have assembled contributions from a wide range of disciplines including genetics, ecology, parasitology, behavioural science, ecology, psychology and epidemiology on the disease avoidance behaviour of a wide range of species. Taking an interdisciplinary and cross-species perspective allows us to sketch out the strategies, mechanisms and consequences of parasite avoidance and to identify gaps and further questions. Parasite avoidance strategies must include avoiding parasites themselves and cues to their presence in conspecifics, heterospecifics, foods and habitat. Further, parasite avoidance behaviour can be directed at constructing parasite-retardant niches. Mechanisms of parasite avoidance behaviour are generally less well characterized, though nematodes, rodents and human studies are beginning to elucidate the genetic, hormonal and neural architecture that allows animals to recognize and respond to cues of parasite threat. While the consequences of infection are well characterized in humans, we still have much to learn about the epidemiology of parasites of other species, as well as the trade-offs that hosts make in parasite defence versus other beneficial investments like mating and foraging. Finally, in this overview we conclude that it is legitimate to use the word ‘ disgust' to describe parasite avoidance systems, in the same way that ‘fear' is used to describe animal predator avoidance systems. Understanding disgust across species offers an excellent system for investigating the strategies, mechanisms and consequences of behaviour and could be a vital contribution towards the understanding and conservation of our planet's ecosystems. This article is part of the Theo Murphy meeting issue ‘Evolution of pathogen and parasite avoidance behaviours'.

Saponins in management of Hepatic Disorders: a review

2021 ◽  
Vol 11 ◽  
Author(s):  
Jasmine Chaudhary ◽  
Akash Jain ◽  
Randhir Dahiya
Keyword(s):  
Liver Disease ◽  
Side Effects ◽  
Liver Diseases ◽  
Hepatoprotective Activity ◽  
Herbal Drugs ◽  
Cost Of Treatment ◽  
Liver Disorders ◽  
Underlying Mechanisms ◽  
Major Factors ◽  
The Cost

: Liver disease is one of the major factors responsible for increased morbidity and mortality worldwide. Presently, limited therapeutic options are available to treat liver diseases. Moreover, allopathic medications are a double-edged sword due to their unfavorable side effects and exaggerated cost of therapy associated with the treatment. Transplantation of the liver is still in infancy state and is associated with staggering cost as well as non-accessibility of donors. Moreover, the cost of treatment is also a very significant hindrance in the treatment of liver disorders. Therefore, the focus is shifting to evaluate the potential of herbal drugs for the management of liver disorders. Although the course of treatment with the herbals is slow yet, the effects are more promising due to lesser side effects and reduced cost of therapy. Numerous plants have been reported to possess hepatoprotective activity due to the presence of phytochemicals like alkaloids, flavonoids, saponins, etc. Among these phytoconstituents, saponins are considered more promising candidates in the management of hepatic disorders. The present review is focused on the plants containing saponins used in the management of hepatic disorders with their underlying mechanisms.

Qualitative analysis of a diffusive predator–prey model with Allee and fear effects

2021 ◽  
pp. 2150037
Author(s):  
Jia Liu
Keyword(s):  
Allee Effect ◽  
Sufficient Conditions ◽  
Allee Effects ◽  
Predator Prey ◽  
Predator Prey Model ◽  
Fear Effect ◽  
Prey Model ◽  
Strong Allee Effect ◽  
Spatially Homogeneous ◽  
Fear Effects

In this study, we consider a diffusive predator–prey model with multiple Allee effects induced by fear factors. We investigate the existence, boundedness and permanence of the solution of the system. We also discuss the existence and non-existence of non-constant solutions. We derive sufficient conditions for spatially homogeneous (non-homogenous) Hopf bifurcation and steady state bifurcation. Theoretical and numerical simulations show that strong Allee effect and fear effect have great effect on the dynamics of system.

Energetics: the costs of living and reproducing for an individual cephalopod

1996 ◽  
Vol 351 (1343) ◽  
pp. 1083-1104 ◽  
Keyword(s):  
Specific Dynamic Action ◽  
Energy Budgets ◽  
Food Conversion ◽  
Laboratory Studies ◽  
Feeding Rates ◽  
Historical Factors ◽  
In The Wild ◽  
Excretion Rates ◽  
The Cost ◽  
Conversion Efficiencies

Cephalopods, like all other animals, have to decide how to allocate resources; maintenance processes, growth of somatic and reproductive tissues, and locomotor activity all have costs. We should like to be able to identify these costs and discover how efficiently cephalopods make use of the prey that they capture and digest. Cephalopods generally grow fast and mature rapidly; a first task is to determine how accurately laboratory studies reflect growth in the wild, because much of the information we need (such as food conversion efficiencies, excretion rates or the costs of locomotion) can be collected only from animals kept in the laboratory. Comparison of laboratory feeding and growth rates for octopods, sepioids and teuthoids with fisheries data suggests that data collected from cephalopods fed ad libitum in the laboratory may be used validly to construct energy budgets representative of individuals in the wild. The immediate cost of feeding (the specific dynamic action) has been thoroughly documented in Octopus , as has the longer-term elevation or depression of metabolic rate by feeding or starvation; it is assumed that similar costs will be found in squid. The cost of locomotion has been studied in both octopods and squid, but we have only limited data on how much time the animals spend moving, and how rapidly, in the wild. Excretory and faecal losses are assessed from laboratory studies, and maintenance costs estimated from feeding rates that just maintain body mass in the laboratory. Comparison of gross and net food conversion efficiencies suggest that squid convert food into tissues less efficiently than octopods, owing primarily to their greater time spent in locomotion. We present a representative series of energy budgets for octopods (based on Octopus ) and squids (based on Illex and Loligo ), for starving, feeding, migrating and maturing individuals. A major contrast is provided by Nautilus, which lives for ten or twenty years and grows only slowly. Finally we speculate on the possible biochemical and historical factors that may have limited the adaptive radiation of cephalopods, resulting in a group lacking herbivores, detritivores or filter-feeders but extremely successful as carnivores.

scholarly journals Brood parasitism selects for no defence in a cuckoo host

2011 ◽  
Vol 278 (1719) ◽  
pp. 2777-2783 ◽  
Author(s):  
Oliver Krüger
Keyword(s):  
Brood Parasitism ◽  
Adaptive Behaviour ◽  
Arms Races ◽  
Defence Behaviour ◽  
Egg Mimicry ◽  
Evolutionary Lag ◽  
Thick Shells ◽  
Defence Strategies ◽  
Coevolutionary Arms Race ◽  
Parasite Avoidance

In coevolutionary arms races, like between cuckoos and their hosts, it is easy to understand why the host is under selection favouring anti-parasitism behaviour, such as egg rejection, which can lead to parasites evolving remarkable adaptations to ‘trick’ their host, such as mimetic eggs. But what about cases where the cuckoo egg is not mimetic and where the host does not act against it? Classically, such apparently non-adaptive behaviour is put down to evolutionary lag: given enough time, egg mimicry and parasite avoidance strategies will evolve. An alternative is that absence of egg mimicry and of anti-parasite behaviour is stable. Such stability is at first sight highly paradoxical. I show, using both field and experimental data to parametrize a simulation model, that the absence of defence behaviour by Cape bulbuls ( Pycnonotus capensis ) against parasitic eggs of the Jacobin cuckoo ( Clamator jacobinus ) is optimal behaviour. The cuckoo has evolved massive eggs (double the size of bulbul eggs) with thick shells, making it very hard or impossible for the host to eject the cuckoo egg. The host could still avoid brood parasitism by nest desertion. However, higher predation and parasitism risks later in the season makes desertion more costly than accepting the cuckoo egg, a strategy aided by the fact that many cuckoo eggs are incorrectly timed, so do not hatch in time and hence do not reduce host fitness to zero. Selection will therefore prevent the continuation of any coevolutionary arms race. Non-mimetic eggs and absence of defence strategies against cuckoo eggs will be the stable, if at first sight paradoxical, result.

The improbable endotherm: the energetics of the sauropod dinosaur Brachiosaurus

Paleobiology ◽  
1983 ◽  
Vol 9 (2) ◽  
pp. 173-182 ◽  
Author(s):  
Jan C. Weaver
Keyword(s):  
Late Jurassic ◽  
Food Plants ◽  
Testable Hypothesis ◽  
Energetic Cost ◽  
Feeding Rates ◽  
Free Living ◽  
Caloric Density ◽  
The Cost

One testable hypothesis of the theory that dinosaurs were endothermic is the observation that sauropod dinosaurs were too large, their heads were too small, and their food was too indigestible for them to be warm-blooded. Calculations on the daily calorie requirements of the sauropod Brachiosaurus, adjusted for digestibility and the energetic cost of “free-living,” were compared with the caloric density of Late Jurassic food plants and the feeding rates of an elephant and a giraffe. Using Brachiosaurus as a model I concluded that endothermy in large sauropods (greater than 55 metric tons) was impossible. Depending on assumptions about feeding rates and the cost of free-living, endothermy in smaller sauropods ranges from improbable to impossible.

Optimal control of a diffusive eco-epidemiological predator–prey model

2020 ◽  
Vol 13 (07) ◽  
pp. 2050065
Author(s):  
Xuebing Zhang ◽  
Guanglan Wang ◽  
Honglan Zhu
Keyword(s):  
Optimal Control ◽  
Semigroup Theory ◽  
Prey Population ◽  
Optimal Controls ◽  
Controlled System ◽  
Predator Prey ◽  
Predator Prey Model ◽  
Prey Model ◽  
The Cost ◽  
Infected Prey

In this study, we investigate the optimal control problem for a diffusion eco-epidemiological predator–prey model. We applied two controllers to this model. One is the separation control, which separates the uninfected prey from the infected prey population, and the other is used as a treatment control to decrease the mortality caused by the disease. Then, we propose an optimal problem to minimize the infected prey population at the final time and the cost cause by the controls. To do this, by the operator semigroup theory we prove the existence of the solution to the controlled system. Furthermore, we prove the existence of the optimal controls and obtain the first-order necessary optimality condition for the optimal controls. Finally, some numerical simulations are carried out to support the theoretical results.

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