Prey Particles Research Articles

Nutrient limitation determines biological interactions between a mixotrophic Chrysophyte and toxin-producing Microcystis

Abstract Blooms of toxigenic cyanobacteria pose a mounting risk to aquatic ecosystems. Relative to abiotic drivers of cyanobacteria success, biotic processes have received less attention. Mixotrophic nanoflagellates that combine heterotrophic ingestion of particulate prey with photoautotrophy are among the eukaryotes that can resist cyanotoxins. We used laboratory experiments in culture to integrate top-down (herbivory) and bottom-up (nitrogen and phosphorus limitation) controls on the growth and production of microcystin-LR, including biodegradation products, of Microcystis by Ochromonas (mixotroph) and Spumella (heterotroph). A notable reduction in the growth rate of toxic Microcystis was evident in co-culture with either Ochromonas or Spumella under P-limitation. Under P-limitation, the co-culture of toxic Microcystis with Ochromonas also led to a reduction in concentration of microcystin-LR (MC-LR and an increase in biodegradation products. Grazing rates up to 31 and 50 cell−1 day−1 on toxic Microcystis were recorded for Ochromonas and Spumella, respectively. The highest grazing rates by Ochromonas were observed on toxic Microcystis under N-limitation. Hence, it is likely that Ochromonas is an herbivore of toxic Microcystis under N-limitation and a competitor for nutrients under P-limitation. Collectively, these results suggest a role of eukaryotic nanoflagellates in decreasing the biomass and toxicity associated with cyanobacteria blooms that vary with nutrient availability.

Relating ciliary propulsion morphology and flow to particle acquisition in marine planktonic ciliates II: the oligotrich ciliate Strombidium capitatum

Abstract The marine oligotrich ciliate Strombidium capitatum is a cruise-feeder, relying on ciliary motion and propulsion flow to individually detect and capture particles. High-speed, high-magnification digital imaging revealed that the cell swims forward by sweeping its anterior adoral membranelles (AAMs) backward, achieving a mean path-averaged speed of U = 1.7 mm s−1 (31 cell-lengths per second). Particle detection occurs through either hydrodynamic signal perception or ciliary contact perception, with a mean reaction distance of R = 20.4 μm. While executing a ciliary reversal of AAMs to handle and capture a perceived particle, the cell coordinates the ciliary motion of ventral adoral membranelles (VAMs, the “lapel”) with the ciliary reversal of AAMs (the “collar”), causing a sudden halt of cell motion, thereby functioning as a motion “brake” that is crucial for effective particle capture. The encounter rate with small prey particles is calculated using πR2U (~8.0 μL h−1, equivalent to ~ 3.5 × 106 cell volumes per day). Based on hydrodynamic modeling results, it is hypothesized that spatial structures of the flow velocity vector and acceleration fields in front of the swimming cell are essential for pushing an embedded particle forward, creating a strong enough slip velocity and hydrodynamic signal for prey perception, even for a neutrally buoyant small particle.

Occurrence of microplastics in gastrointestinal tracts of planktivorous fish from the Thoothukudi region.

Planktivorous fish are easily susceptible to passive microplastic ingestion during their feeding behaviour and may be transferred along with the marine food web. Hence, the present study was conducted to assess the microplastics prevalence in the planktivorous fish (677 individuals) collected from 2 landing centres in the Thoothukudi, Gulf of Mannar region, South Tamil Nadu, India. The prevalence of microplastics was detected in 118 out of 677 individuals, with a mean abundance and percent occurrence of 1.22 ± 0.47 items/individual and 17%, respectively. The ingestion of microplastics in planktivorous fish was primarily due to their feeding habitat, in which they were prone to the accidental or passive intake of microplastics regardless of the fish's length and body weight. The microplastics abundance was significantly higher in Sardinella gibbosa (1.34 ± 0.56 items/individual), which might be due to their pelagic and planktivorous feeding habitat, highest filtration capacity, presence of closed gill rakers, and also due to the passive ingestion of microplastics as food items. Fibres, blue, and 1 to 2mmsized microplastics were predominant in the guts of Sardinella gibbosa, accounting for 95.74, 47.87, and 46.80%, respectively, whereas in Leiognathus lineolatus, fragments, black, and 1 to 2mmsized microplastics were highly prevalent with 62.96, 72.22, and 79.62%, respectively. The predominance of various shapes (fragments, fibres), sizes (1-2mm), and colours (blue and black) of microplastics in the guts of fish was influenced by their passive ingestion, ingestion of contaminated planktonic prey, lack of selectivity of prey particles and their resemblance to plankton species. Polypropylene polymers predominated (96.77% and 95.23%) in both fish, followed by polystyrene (3.22% and 4.76%). Furthermore, this study provides baseline data and insists that there is a need for continuous monitoring of the distribution of microplastics.

Hunting active Brownian particles: Learning optimal behavior.

We numerically study active Brownian particles that can respond to environmental cues through a small set of actions (switching their motility and turning left or right with respect to some direction) which are motivated by recent experiments with colloidal self-propelled Janus particles. We employ reinforcement learning to find optimal mappings between the state of particles and these actions. Specifically, we first consider a predator-prey situation in which prey particles try to avoid a predator. Using as reward the squared distance from the predator, we discuss the merits of three state-action sets and show that turning away from the predator is the most successful strategy. We then remove the predator and employ as collective reward the local concentration of signaling molecules exuded by all particles and show that aligning with the concentration gradient leads to chemotactic collapse into a single cluster. Our results illustrate a promising route to obtain local interaction rules and design collective states in active matter.

Chase-Escape percolation on the 2D square lattice

Chase-escape percolation is a variation of the standard epidemic spread models. In this model, each site can be in one of three states: unoccupied, occupied by a single prey, or occupied by a single predator. Prey particles spread to neighboring empty sites at rate p, and predator particles spread only to neighboring sites occupied by prey particles at rate 1, killing the prey particle that existed at that site. It was found that the prey can survive forever with non-zero probability, if p>pc with pc<1. Earlier simulations showed that pc is very close to 1∕2. Using Monte Carlo simulations in D=2, we estimate the value of pc to be 0.49451±0.00001 and the critical exponents are consistent with the undirected percolation universality class. We check that at pc, the correlation functions at large length scales are rotationally invariant. We define a discrete-time parallel-update version of the model, which brings out the relation between chase-escape and undirected bond percolation. We further show that for all p<pc, in D dimensions, the probability that the number of predators in the absorbing configuration is greater than s is bounded from below by exp(−Kp−1s1∕D), where K is some p-independent constant. This is in contrast to the exponentially decaying cluster size distribution in the standard percolation theory. Even so, the scaling function for the cluster size distribution for p near pc decays exponentially: the stretched exponential behavior dominates for s≫s∗, but s∗ diverges near pc. We also study the problem starting from an initial condition with predator particles on all lattice points of the line y=0 and prey particles on the line y=1. In this case, for pc<p<1, the center of mass of the fluctuating prey and predator fronts travel at the same speed. This speed is strictly smaller than the speed of an Eden front with the same value of p, but with no predators. This is caused by the prey sites at the leading edge being eaten up by predators. The fluctuations of the front follow KPZ scaling both above and below the depinning transition at p=1.

Effects of surface proximity and force orientation on the feeding flows of microorganisms on solid surfaces

Many aquatic microorganisms attach to solid surfaces while creating feeding flows that bring prey particles to them. A theoretical exploration quantifies the flow structures, clearance rates, and recirculation times in such flows using a simple low-Reynolds-number flow model.

Paddling motion of a free-swimming jellyfish and Lagrangian coherent structure analysis

Swimming and prey capture by prolate and oblate jellyfishes are numerically examined in two-dimensions using multi-relaxation-time lattice Boltzmann (MRT-LB) and immersed boundary (IB) methods. The near-field fluid structure interaction (FSI) and predator-prey interaction mechanisms are revealed via the simulated Eulerian flow characteristics, finite-time Lyapunov exponent (FTLE) field, and Lagrangian coherent structures (LCS). We implement appropriate periodic body force (Fb) distribution at nodal points of the elastic bell in radial direction to model the paddled swimming as well as complex feeding behavior. For a paddling jellyfish the evolved starting and stopping vortices, as move close to each other in near-wake, create the necessary vortex induced thrust that facilitate the forward body motion. The forced bell contraction in power stroke assists quicker propulsive swimming, whereas passive bell expansion in resting phase facilitates the continued vortex induced forward movement for larger duration, via the refilled fluid momentum. For feeding the detailed prey interception and precise capture areas for various jellyfish models are identified hereby via the computed prey tracks, forward and backward time FTLE fields, and LCS. Swimming performances are analyzed based on interactive thrust and drag forces, input power (energy rate required for bell contraction), output power (thrust multiplied by centroid velocity), and cost of transport (COT). At low Reynolds number (Re) the COT becomes higher for an oblate jellyfish than that of a prolate one; while with increased Re the oblate species appears more economical. However, for enhanced paddling force (Fb) or reduced flapping frequency of bell, the COT for an oblate jellyfish steadily decreases. Hereby impacts of the varied force duration, flapping amplitude, flapping frequency, and bell-elasticity on the swimming are analyzed in greater detail. Notably, the propulsion efficiency increased for higher flapping frequency. The present numerical model efficiently unfolds prey capture mechanisms that are adopted by prolate and oblate medusae and quantifies their success rate (clearance rate, CR) in prey capture. Unlike in past studies, the FTLE fields and LCS that are computed here by tracking the transient motion of a large number of suspended Lagrangian prey particles exhibit the realistic predator-prey interaction and precise prey capture surface, which are difficult to measure or analyze empirically.

Active Micromotor Systems Built from Passive Particles with Biomimetic Predator-Prey Interactions.

Inspired by chasing-escaping behaviors of predator and swarming prey in nature, here we demonstrate a concept to create active micromotor systems from two species of passive microparticles with biomimetic predator-prey interactions. In this concept, the biomimetic predator-prey interactions are established in a binary particle system comprising the diffusiophoretic attractive microparticles (prey particles) and the diffusiophoretic repulsive ones (predator particles). In the absence of additional chemical fuels and external fields, the predator particles are attracted by and constantly chase the swarming prey particles, which, in response, escape from the former and show dynamic group reconfigurations because of the local repulsion. Based on this concept, various synthetic active micromotor systems have been demonstrated, including active ZnO-TiO2, Ag3PO4-TiO2, and ZnO-AgBr micromotor systems. As the predator and prey particles are powered by each other through the biomimetic predator-prey interactions, the concept proposed here provides an advanced method to develop not only a class of single micromotors powered by passive particles or "solid fuels" but also micromotor swarms capable of manipulating "moving cargo". In addition, it also illustrates a proof-of-concept implementation of intelligent micro/nanomotor systems composed of heterogeneous individuals with complementary or cooperative functions.

Mammoth grazers on the ocean's minuteness: a review of selective feeding using mucous meshes.

Mucous-mesh grazers (pelagic tunicates and thecosome pteropods) are common in oceanic waters and efficiently capture, consume and repackage particles many orders of magnitude smaller than themselves. They feed using an adhesive mucous mesh to capture prey particles from ambient seawater. Historically, their grazing process has been characterized as non-selective, depending only on the size of the prey particle and the pore dimensions of the mesh. The purpose of this review is to reverse this assumption by reviewing recent evidence that shows mucous-mesh feeding can be selective. We focus on large planktonic microphages as a model of selective mucus feeding because of their important roles in the ocean food web: as bacterivores, prey for higher trophic levels, and exporters of carbon via mucous aggregates, faecal pellets and jelly-falls. We identify important functional variations in the filter mechanics and hydrodynamics of different taxa. We review evidence that shows this feeding strategy depends not only on the particle size and dimensions of the mesh pores, but also on particle shape and surface properties, filter mechanics, hydrodynamics and grazer behaviour. As many of these organisms remain critically understudied, we conclude by suggesting priorities for future research.

Time series models of decadal trends in the harmful algal species Karlodinium veneficum in Chesapeake Bay

The harmful dinoflagellate, Karlodnium veneficum, has been implicated in fish-kill and other toxic, harmful algal bloom (HAB) events in waters worldwide. Blooms of K. veneficum are known to be related to coastal nutrient enrichment but the relationship is complex because this HAB taxon relies not only on dissolved nutrients but also particulate prey, both of which have also changed over time. Here, applying cross-correlations of climate-related physical factors, nutrients and prey, with abundance of K. veneficum over a 10-year (2002–2011) period, a synthesis of the interactive effects of multiple factors on this species was developed for Chesapeake Bay, where blooms of the HAB have been increasing. Significant upward trends in the time series of K. veneficum were observed in the mesohaline stations of the Bay, but not in oligohaline tributary stations. For the mesohaline regions, riverine sources of nutrients with seasonal lags, together with particulate prey with zero lag, explained 15%–46% of the variation in the K. veneficum time series. For the oligohaline regions, nutrients and particulate prey generally showed significant decreasing trends with time, likely a reflection of nutrient reduction efforts. A conceptual model of mid-Bay blooms is presented, in which K. veneficum, derived from the oceanic end member of the Bay, may experience enhanced growth if it encounters prey originating from the tributaries with different patterns of nutrient loading and which are enriched in nitrogen. For all correlation models developed herein, prey abundance was a primary factor in predicting K. veneficum abundance.

Short-term hydrothermal generation scheduling using improved predator influenced civilized swarm optimization technique

An improved predator influenced civilized swarm optimization (IPCSO) technique is proposed to solve short-term conventional hydro-thermal generation scheduling (HTGS) and profit-based HTGS (PB-HTGS) problems. In the proposed IPCSO technique, prey swarm is divided into the number of societies and each society is influenced by its own predator’s effect. In every society, prey particles interact with each other and the best performing prey particle acts as a society leader. The predator particle chases the society leader and society leader tries to escape from it. In this process, predator effect improves the exploitation capability of the algorithm by searching around the respective society leader. Further, society leader of each society interacts with each other and helps to improve the performance of society leaders. The best performing society leader becomes the leader of civilization. For HTGS problem, a multi-chain cascaded hydro model is undertaken along with consideration of water transport delay between reservoirs. The problem is formulated with due consideration of thermal unit valve point effect, prohibited operating zones on reservoir discharge rate and ramp rate limits on thermal unit power generation. The technique is tested on three HTGS systems and one PB-HTGS system. The obtained results have been compared with the results reported in the literature and found satisfactory. The statistical analysis of the results is carried out to verify the robustness of the proposed technique. Further, a nonparametric test is also applied to compare the performance of the proposed technique.

Hydro-thermal generation scheduling using integrated gravitational search algorithm and predator–prey optimization technique

In this research work, an integrated optimization technique has been proposed by coordinating gravitational search algorithm (GSA) and predator–prey optimization (PPO) in a suitable manner to improve the search capability of algorithm. The integrated technique is applied to obtain the optimum generation schedule of hydro-thermal generation system considering some of the practical constraints and transmission losses. For the hydro-thermal systems, the multi-chain hydro model has been undertaken with due consideration of water transport delay between reservoirs. In PPO algorithm, the search is performed by considering the experience of other prey particles along with the effect of predator particle. The predator effect helps to avoid any possible stagnation of global best prey on local optima due to the fear created by predator particle. In PPO algorithm, the quality of the solutions has not been considered while updating the position of prey or predator, whereas in GSA, the agent direction is computed based on the overall force, and it is proportional to the quality of the solutions. Further, GSA is memory less and agent direction is not influenced by best positions. In the proposed integrated technique, the position of agent/prey is directed by overall force around themselves, global best prey position and predator effect. The proposed integrated technique is tested on three hydro-thermal systems. A penalty-free constraint handling approach is employed to satisfy all equality and inequality constraints. The results obtained from proposed technique have been compared with the results reported with the existing technique, and it is experienced that proposed technique is able to provide a better solution with improved convergence characteristics. The statistical analysis of results is also done to measure the sensitivity and robustness of the proposed technique.

Metabarcoding and metabolome analyses of copepod grazing reveal feeding preference and linkage to metabolite classes in dynamic microbial plankton communities.

In order to characterize copepod feeding in relation to microbial plankton community dynamics, we combined metabarcoding and metabolome analyses during a 22-day seawater mesocosm experiment. Nutrient amendment of mesocosms promoted the development of haptophyte (Phaeocystis pouchetii)- and diatom (Skeletonema marinoi)-dominated plankton communities in mesocosms, in which Calanus sp. copepods were incubated for 24h in flow-through chambers to allow access to prey particles (<500μm). Copepods and mesocosm water sampled six times spanning the experiment were analysed using metabarcoding, while intracellular metabolite profiles of mesocosm plankton communities were generated for all experimental days. Taxon-specific metabarcoding ratios (ratio of consumed prey to available prey in the surrounding seawater) revealed diverse and dynamic copepod feeding selection, with positive selection on large diatoms, heterotrophic nanoflagellates and fungi, while smaller phytoplankton, including P.pouchetii, were passively consumed or even negatively selected according to our indicator. Our analysis of the relationship between Calanus grazing ratios and intracellular metabolite profiles indicates the importance of carbohydrates and lipids in plankton succession and copepod-prey interactions. This molecular characterization of Calanus sp. grazing therefore provides new evidence for selective feeding in mixed plankton assemblages and corroborates previous findings that copepod grazing may be coupled to the developmental and metabolic stage of the entire prey community rather than to individual prey abundances.

Fluid dynamic constraints on resource acquisition in small pelagic organisms

Physicists have long examined the fluid dynamics of swimming at low Reynolds number, but the main scope has rarely been to understand the behavior and ecology of microorganisms. However, many ecological questions about the functioning of small aquatic organisms can only be addressed by the application of formal fluid physics. Here, I examine resource acquisition mechanisms in small aquatic organisms, ranging from uptake of dissolved molecules to feeding on suspended particulate prey, and examine how organism behaviors and morphologies may be shaped by the often non-intuitive small-scale fluid physics.

Integrated search technique for parameter determination of SVM for speech recognition

Support vector machine (SVM) has a good application prospect for speech recognition problems; still optimum parameter selection is a vital issue for it. To improve the learning ability of SVM, a method for searching the optimal parameters based on integration of predator prey optimization (PPO) and Hooke-Jeeves method has been proposed. In PPO technique, population consists of prey and predator particles. The prey particles search the optimum solution and predator always attacks the global best prey particle. The solution obtained by PPO is further improved by applying Hooke-Jeeves method. Proposed method is applied to recognize isolated words in a Hindi speech database and also to recognize words in a benchmark database TI-20 in clean and noisy environment. A recognition rate of 81.5% for Hindi database and 92.2% for TI-20 database has been achieved using proposed technique.

Quantitative Proteome Analysis of Temporally Resolved Phagosomes Following Uptake Via Key Phagocytic Receptors

Macrophages operate at the forefront of innate immunity and their discrimination of foreign versus “self” particles is critical for a number of responses including efficient pathogen killing, antigen presentation, and cytokine induction. In order to efficiently destroy the particles and detect potential threats, macrophages express an array of receptors to sense and phagocytose prey particles. In this study, we accurately quantified a proteomic time-course of isolated phagosomes from murine bone marrow-derived macrophages induced by particles conjugated to seven different ligands representing pathogen-associated molecular patterns, immune opsonins or apoptotic cell markers. We identified a clear functional differentiation over the three timepoints and detected subtle differences between certain ligand-phagosomes, indicating that triggering of receptors through a single ligand type has mild, but distinct, effects on phagosome proteome and function. Moreover, our data shows that uptake of phosphatidylserine-coated beads induces an active repression of NF-κB immune responses upon Toll-like receptor (TLR)-activation by recruitment of anti-inflammatory regulators to the phagosome. This data shows for the first time a systematic time-course analysis of bone marrow-derived macrophages phagosomes and how phagosome fate is regulated by the receptors triggered for phagocytosis.

Feast or flee: bioelectrical regulation of feeding and predator evasion behaviors in the planktonic alveolate Favella sp. (Spirotrichia).

Alveolate (ciliates and dinoflagellates) grazers are integral components of the marine food web and must therefore be able to sense a range of mechanical and chemical signals produced by prey and predators, integrating them via signal transduction mechanisms to respond with effective prey capture and predator evasion behaviors. However, the sensory biology of alveolate grazers is poorly understood. Using novel techniques that combine electrophysiological measurements and high-speed videomicroscopy, we investigated the sensory biology of Favella sp., a model alveolate grazer, in the context of its trophic ecology. Favella sp. produced frequent rhythmic depolarizations (∼500 ms long) that caused backward swimming and are responsible for endogenous swimming patterns relevant to foraging. Contact of both prey cells and non-prey polystyrene microspheres at the cilia produced immediate mechanostimulated depolarizations (∼500 ms long) that caused backward swimming, and likely underlie aggregative swimming patterns of Favella sp. in response to patches of prey. Contact of particles at the peristomal cavity that were not suitable for ingestion resulted in depolarizations after a lag of ∼600 ms, allowing time for particles to be processed before rejection. Ingestion of preferred prey particles was accompanied by transient hyperpolarizations (∼1 s) that likely regulate this step of the feeding process. Predation attempts by the copepod Acartia tonsa elicited fast (∼20 ms) animal-like action potentials accompanied by rapid contraction of the cell to avoid predation. We have shown that the sensory mechanisms of Favella sp. are finely tuned to the type, location, and intensity of stimuli from prey and predators.

Capture of algae promotes growth and propagation in aquatic Utricularia.

Some carnivorous plants trap not only small animals but also algae and pollen grains. However, it remains unclear if these trapped particles are useless bycatch or whether they provide nutrients for the plant. The present study examines this question in Utricularia, which forms the largest and most widely spread genus of carnivorous plants, and which captures prey by means of sophisticated suction traps. Utricularia plants of three different species (U. australis, U. vulgaris and U. minor) were collected in eight different water bodies including peat bogs, lakes and artificial ponds in three regions of Austria. The prey spectrum of each population was analysed qualitatively and quantitatively, and correlated with data on growth and propagation, C/N ratio and δ(15)N. More than 50 % of the prey of the Utricularia populations investigated consisted of algae and pollen, and U. vulgaris in particular was found to capture large amounts of gymnosperm pollen. The capture of algae and pollen grains was strongly correlated with most growth parameters, including weight, length, budding and elongation of internodes. The C/N ratio, however, was less well correlated. Other prey, such as moss leaflets, fungal hyphae and mineral particles, were negatively correlated with most growth parameters. δ(15)N was positively correlated with prey capture, but in situations where algae were the main prey objects it was found that the standard formula for calculation of prey-derived N was no longer applicable. The mass capture of immotile particles confirms the ecological importance of autonomous firing of the traps. Although the C/N ratio was little influenced by algae, they clearly provide other nutrients, possibly including phosphorus and trace elements. By contrast, mosses, fungi and mineral particles appear to be useless bycatch. Correlations with chemical parameters indicate that Utricularia benefits from nutrient-rich waters by uptake of inorganic nutrients from the water, by the production of more traps per unit of shoot length, and by the capture of more prey particles per trap, as nutrient-rich waters harbour more prey organisms.

Multiobjective fixed head hydrothermal scheduling using integrated predator-prey optimization and Powell search method

An integrated methodology that embeds global and local search technique is explored for solving multiobjective hydrothermal scheduling. Predator-prey optimization (PPO) is used as a base level search in the global search space and Powell's method as a local search technique. Predator-prey model is based on particle swarm optimization (PSO). In spite of several advantages of PSO as compared to other evolutionary methods, it has some major drawbacks such as local optimal trapping and lack of efficient capability to treat the constraints. PPO model includes predator and prey particles in population. The prey objective is to escape from the predators reaching to its lair, while predator's goal is to capture the prey that increase exploration and exploitation capability of PSO. Powell's method aims to fine tune the solution obtained from PPO and to enhance the search capability of proposed method. In addition, a penalty less constraint handling method is employed for considering equality and inequality constraints. Fuzzy methodology has also been exploited to find the best compromised solution. The proposed integrated technique is applied to three hydrothermal scheduling problems with valve-point effect of thermal generators and transmission losses. The proposed method yields high quality solution while satisfying all constraints.

How zooplankton feed: mechanisms, traits and trade-offs

Zooplankton is a morphologically and taxonomically diverse group and includes organisms that vary in size by many orders of magnitude, but they are all faced with the common problem of collecting food from a very dilute suspension. In order to maintain a viable population in the face of mortality, zooplankton in the ocean have to clear daily a volume of ambient water for prey particles that is equivalent to about 10(6) times their own body volume. While most size-specific vital rates and mortality rates decline with size, the clearance requirement is largely size-independent because food availability also declines with size. There is a limited number of solutions to the problem of concentrating dilute prey from a sticky medium: passive and active ambush feeding; feeding-current feeding, where the prey is either intercepted directly, retained on a filter, or individually perceived and extracted from the feeding current; cruise feeding; and colonization of large particles and marine snow aggregates. The basic mechanics of these food-collection mechanisms are described, and it is shown that their efficiencies are inherently different and that each of these mechanisms becomes less efficient with increasing size. Mechanisms that compensate for this decline in efficiency are described, including inflation of feeding structures and development of vision. Each feeding mode has implications beyond feeding in terms of risk of encountering predators and chance of meeting mates, and they partly target different types of prey. The main dichotomy is between (inefficient) ambush feeding on motile prey and the more efficient active feeding modes; a secondary dichotomy is between (efficient) hovering and (less efficient) cruising feeding modes. The efficiencies of the various feeding modes are traded off against feeding-mode-dependent metabolic expenses, predation risks, and mating chances. The optimality of feeding strategies, evaluated as the ratio of gain over risk, varies with the environment, and may explain both size-dependent and spatio-temporal differences in distributions of various feeding types as well as other aspects of the biology of zooplankton (mating behaviour, predator defence strategies).