Biological interactions of the five genera in the dinoflagellate family Kareniaceae with prey and protistan predators

Predatory protists.

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 50:289-299 (2008) - DOI: https://doi.org/10.3354/ame01166 Prey size spectrum and bioenergetics of the mixotrophic dinoflagellate Karlodinium armiger Terje Berge1,2,*, Per Juel Hansen1, Øjvind Moestrup2 1Marine Biological Laboratory, Aquatic Biology Department of Biology, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark 2Phycology Laboratory, Aquatic Biology Department of Biology, University of Copenhagen, Øster Farimagsgade 2D, 1353 Copenhagen K, Denmark *Email: tberge@bi.ku.dk ABSTRACT: We studied the functional and numerical response and prey size spectrum in the tube-feeding dinoflagellate Karlodinium armiger. Growth rates were very low when no food was supplied (0.01 to 0.06 d-1). When K. armiger was fed the dinoflagellate Heterocapsa triquetra and the cryptophyte Rhodomonas salina, maximum growth rates (μ) were 0.48 and 0.55 d-1 and maximum ingestion rates were 215 and 597 pg C cell-1 d-1, respectively. Much lower prey concentrations were required to saturate growth rates compared to the saturation of ingestion rates. The optimal prey size, in terms of ingestion rates, was ~13 µm, which is close to the size of the predator. Smaller prey (<8 µm) were ingested at low rates (20 to 24 pg C cell-1 d-1), but supported fairly high growth rates (0.35 to 0.45 d-1). No upper prey size limit for ingestion was found. Maximum growth rates at food saturation depended more on prey taxa (cryptophytes) than on prey size. K. armiger’s large range of prey types, wide prey size spectrum and nutritional flexibility seem to make it a significant competitor in marine plankton. KEY WORDS: Mixotrophy · Bioenergetics · Prey selection · Peduncle · Karlodinium Full text in pdf format PreviousNextCite this article as: Berge T, Hansen PJ, Moestrup Ø (2008) Prey size spectrum and bioenergetics of the mixotrophic dinoflagellate Karlodinium armiger. Aquat Microb Ecol 50:289-299. https://doi.org/10.3354/ame01166 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 50, No. 3. Online publication date: March 26, 2008 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2008 Inter-Research.

Differential feeding by common heterotrophic protists on 12 different Alexandrium species

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 517:61-74 (2014) - DOI: https://doi.org/10.3354/meps11039 Mechanisms of prey size selection in a suspension-feeding copepod, Temora longicornis Rodrigo J. Gonçalves1,2,3,*, Hans van Someren Gréve1, Damien Couespel1, Thomas Kiørboe1 1Centre for Ocean Life, DTU Aqua, Technical University of Denmark, Kavalergården 6, 2920 Charlottenlund, Denmark 2Estación de Fotobiología Playa Unión, Casilla de Correos N° 15 (9103) Rawson, Chubut, Argentina 3Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. Rivadavia 1917, Caba, Argentina *Corresponding author: rodrigo@efpu.org.ar ABSTRACT: We examined size-dependent prey detection and prey capture in free-swimming Temora longicornis using video observations, particle image velocimetry (PIV), and bottle incubations with phytoplankton prey sizes within the range 6-60 µm equivalent spherical diameter (ESD). T. longicornis generates feeding currents by oscillating its appendages at about 25 Hz. Prey cells >10 µm ESD are perceived and captured individually. A capture response was elicited when prey was touched by (or within a few cell radii from) the setae on the feeding appendages. The extension of the setae defines the prey encounter cross section, which is therefore independent of prey size. The flux of water through the encounter area, estimated from PIV, was ca. 150 ml ind.-1 d-1, which represents the maximum possible clearance rates and was similar to that estimated in incubation experiments. However, while the detection probability was nearly 100% for cells >10-15 µm, it declined rapidly for smaller cells. Conversely, the probability that a cell which elicited a capture response was actually ingested declined with increased cell size, from nearly 100% for small cells, to ~0% for the largest cells examined. The resulting prey size spectrum, predicted as the product of the cell-size-specific encounter rates and capture probabilities, was dome-shaped, with a maximum around 20-30 µm ESD. The prey size spectrum from incubation experiments had a similar shape and an optimum range of 30-50 µm ESD. The mechanistic underpinning of the prey size spectrum suggested here deviates from previous descriptions mainly in the mechanism and range of prey detection. KEY WORDS: Temora longicornis · Calanoid copepods · Prey detection · Feeding currents · Prey capture · Zooplankton · Size spectrum · Prey size Full text in pdf format Supplementary material PreviousNextCite this article as: Gonçalves RJ, van Someren Gréve H, Couespel D, Kiørboe T (2014) Mechanisms of prey size selection in a suspension-feeding copepod, Temora longicornis. Mar Ecol Prog Ser 517:61-74. https://doi.org/10.3354/meps11039 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 517. Online publication date: December 15, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.

The mixotroph Yihiella yeosuensis is a small- and fast-swimming dinoflagellate. To investigate its protistan predators, interactions between Y.yeosuensis and 11 heterotrophic protists were explored. No potential predators were able to feed on actively swimming Y. yeosuensis cells, which escaped via rapid jumps, whereas Aduncodinium glandula, Oxyrrhis marina, and Strombidinopsis sp. (approximately 150μm in cell length) were able to feed on weakly swimming cells that could not jump. Furthermore, Gyrodinium dominans, Luciella masanensis, and Pfiesteria piscicida were able to feed on heat-killed Yihiella cells, whereas Gyrodinium moestrupii, Noctiluca scintillans, Oblea rotunda, Polykrikos kofoidii, and Strombidium sp. (20μm) did not feed on them. Thus, the jumping behavior of Y.yeosuensis might be primarily responsible for the observed lack of predation. With increasing Yihiella concentration, the growth rate of O.marina decreased, whereas that of Strombidinopsis did not change. However, with increasing Yihiella concentration (up to 530ng C/ml), the ingestion rate of Strombidinopsis on Yihiella increased linearly. The highest ingestion rate was 24.1ng C per predator per d. The low daily carbon acquisition from Yihiella relative to the body carbon content of Strombidinopsis might be responsible for its negligible growth. Thus, Y.yeosuensis might have an advantage over its competitors due to its low mortality rate.

Foraging processes in plankton and plank- tivorous fish are constrained by relative prey and predator size and therefore, these are important varia- bles to include in a foraging model. The distribution of prey biomass across different size classes can be char- acterized by a size spectrum slope. We present a for- aging model for anchovy larvae including the most relevant processes such as prey encounter, capture- and pursuit success, all influenced by light, turbulence and prey characteristics. We modelled ingestion rates and specific growth rate by coupling the foraging model with an existing bioenergetic model, and per- formed a sensitivity analysis of prey ingestion in tur- bulent environments assuming either hemispherical or conical perceptive volume. Our results suggest that turbulence has no positive effect because of the low capture ability, small prey size and small visual vol- ume for anchovy larvae. The predicted ingestion is too low to sustain the growth potential of larvae when assuming conical perceptive volume even under prey densities substantially higher than normally found in the field. Ingestion rate is sensitive to the total biomass and the slope of the prey size spectra, specifically because it determines the abundance of prey around the optimal size for the larvae. The model also sug- gests that small larvae benefit from a prey size struc- ture with steep prey size-spectra slope while a large larva benefit from less steep slopes. The model can act as a link between size-spectra measurements from the field and the foraging conditions of larval anchovies.

Size structure of organisms at logarithmic scale (i.e. size spectrum) can often be described by a linear function with a negative slope; however, substantial deviations from linearity have often been found in natural systems. Theoretical studies suggest that greater nonlinearity in community size spectrum is associated with high predator–prey size ratios but low predator–prey abundance ratios; however, empirical evaluation of the effects of predator–prey interactions on nonlinear structures remains scarce. Here, we aim to empirically explore the pattern of the size‐specific residuals (i.e. deviations from the linear regression between the logarithmic fish abundance and the logarithmic mean fish size) by using size spectra of fish communities in 74 German lakes. We found that nonlinearity was strong in lakes with high predator–prey abundance ratios but at low predator–prey size ratios. More specifically, our results suggest that only large predators, even if occurring in low abundances, can control the density of prey fishes in a broad range of size classes in a community and thus promote linearity in the size spectrum. In turn, the lack of large predator fishes may cause high abundances of fish in intermediate size classes, resulting in nonlinear size spectra in these lakes. Moreover, these lakes were characterized by a more intense human use including high fishing pressure and high total phosphorus concentrations, which have negative impacts on the abundance of large, predatory fish. Our findings indicate that nonlinear size spectra may reflect dynamical processes potentially caused by predator–prey interactions. This opens a new perspective in the research on size spectrum, and can be relevant to further quantify the efficiency of energy transfer in aquatic food webs.

Microbial spatial variability: An example from the Celtic Sea

Predator bioenergetics and the prey size spectrum: Do foraging costs determine fish production?

We examined prey preference, growth, and survival of small larval (8-10 mm total length (TL)), large larval (11-17 mm TL), and early juvenile (&gt;18 mm TL) walleye (Stizostedion vitreum) in laboratory aquaria and field mesocosms using multiple prey assemblages that included cladoceran, copepod, and rotifer prey of varied sizes. Both prey taxa and size affected prey preference during the larval period. All sizes of walleye avoided rotifer and nauplii prey. Small and large larvae selected for intermediate-sized (0.4-0.9 mm) cladoceran prey and selected against large prey (&gt;0.9 mm) of both taxa. Although neither capture efficiency nor handling time differed between prey taxa, larvae oriented more frequently towards cladoceran prey suggesting that they were more visible than copepods to these small fish. Larval walleye that were fed exclusively cladoceran prey survived better than fish that were fed other prey. Early juveniles selected primarily on the basis of prey size, choosing large copepods and cladocerans. Prey taxa did not affect early juvenile growth or survival. Prey taxa and prey size interacted with predator size to influence selectivity and its effect on growth and survival. Consequently, these factors must be considered in combination when examining the importance of foraging decisions in young fish.

This study examines the distribution patterns and feeding ecology of chaetognaths in the Catalan Sea in relation to mesoscale features along an inshore–offshore gradient. The study was conducted during two different periods of the year: late spring of 1995 and late summer of 1996. The two periods differed in hydrographic conditions and mesoscale processes, which affected the distribution patterns of the different species of chaetognaths found. The diet of the chaetognaths was mainly composed of copepods and differed between species. Prey size was not always strongly related to chaetognath size and for certain species, there was an overlap in prey size spectrum. Trophic niche breadth (on a ratio scale) appeared to be constant with growth. Ingestion rates and predation pressure by chaetognaths did not follow a clear trend related to the mesoscale features in the area, such as the presence of a density front. The impact of chaetognaths on copepod standing stock appeared to be extremely low (<1%), but it became more relevant when the species and prey size specificity of the chaetognaths was taken into account.

Maximizing the average rate of energy intake (profitability) may not always be the optimal foraging strategy for ectotherms with relatively low energy requirements. To test this hypothesis, we studied the feeding behaviour of captive insectivorous lizards Psammodromus algirus, and we obtained experimental estimates of prey mass, handling time, profitability, and attack distance for several types of prey. Handling time increased linearly with prey mass and differed significantly among prey types when prey size differences were controlled for, and mean profitabilities differed among prey taxa, but profitability was independent of prey size. The attack distance increased with prey length and with the mobility of prey, but it was unrelated to profitability. Thus, lizards did not seem to take account of the rate of energy intake per second as a proximate cue eliciting predatory behavior. This information was combined with pitfall-trap censuses of prey (in late April, mid-June and late July) that allowed us to compare the mass of the prey captured in the environment with that of the arthropods found in the stomachs of sacrificed free-living lizards. In April, when food abundance was low and lizards were reproducing, profitability had a pronounced effect on size selection and lizards selected prey larger than average from all taxa except the least profitable ones. As the active season progressed, and with a higher availability of food, the number of prey per stomach decreased and their mean ize increased. The effect of profitability on size selection decreased (June) and eventually vanished (July-August). This variation is probably related to seasonal changes in the ecology of lizards, e.g. time minimization in the breeding season as a means of saving time for nonforaging activities versus movement minimization by selecting fewer (but larger) prey in the postbreeding season. Thus, the hypothesis that maximizing profitability could be just an optional strategy for a terrestrial ectothermic vertebrate was supported by our data.

Analysis of predator–prey interactions is a core concept of animal ecology, explaining structure and dynamics of animal food webs. Measuring the functional response, i.e. the intake rate of a consumer as a function of prey density, is a powerful method to predict the strength of trophic links and assess motives of prey choice, particularly in arthropod communities. However, due to their reductionist set‐up, functional responses, which are based on laboratory feeding experiments, may not display field conditions, possibly leading to skewed results. Here, we tested the validity of functional responses of centipede predators and their prey by comparing them with empirical gut content data from field‐collected predators. Our predator–prey system included lithobiid and geophilomorph centipedes, abundant and widespread predators of forest soils and their soil‐dwelling prey. First, we calculated the body size‐dependent functional responses of centipedes using a published functional response model in which we included natural prey abundances and animal body masses. This allowed us to calculate relative proportions of specific prey taxa in the centipede diet. In a second step, we screened field‐collected centipedes for DNA of eight abundant soil‐living prey taxa and estimated their body size‐dependent proportion of feeding events. We subsequently compared empirical data for each of the eight prey taxa, on proportional feeding events with functional response‐derived data on prey proportions expected in the gut, showing that both approaches significantly correlate in five out of eight predator–prey links for lithobiid centipedes but only in one case for geophilomorph centipedes. Our findings suggest that purely allometric functional response models, which are based on predator–prey body size ratios are too simple to explain predator–prey interactions in a complex system such as soil. We therefore stress that specific prey traits, such as defence mechanisms, must be considered for accurate predictions.

The present work centers on the predatory performance of Microvelia douglasi adults with reference to diel periodicity. This experiment attempts to determine on whether the foraging efficiency was more at diurnal or nocturnal period, and was there an endogenous rhythm available within them to activate foraging response. The study was conducted in the laboratory for 24 hr with an interval of every three hr. The experiment was divided into Phase I (LD 12:12) and Phase II (DL 12:12). The predatory efficiency of M. douglasi adults was investigated on the first and second instars of Anopheles stephensi at prey densities of 25 and 50, and the experiment was conducted separately for male, female, and for both male and female, in 500 mℓ and 1000 mℓ containers. The bugs showed predatory activity both in diurnal and nocturnal periods. In LD cycle, maximum predatory activity was at 15:00 hr by the female bugs, and a total of 350.0 An. stephensi larvae were predated with 144.6 and 205.4 prey predated at 25 and 50 prey density, respectively. The male bugs predated 110.4 prey, and their response was less than that of females, which showed the highest rate of predation as they predated 129.4 prey. The prey predated when both male and female were put together was 110.2. In DL cycle, maximum predatory activity occurred at 24:00 hr again by the female bugs, and a maximum of 327.8 larval instars were predated with 153.4 and 174.4 prey predated at 25 and 50 prey density, respectively. Female bugs predated (121.2) more prey than male (99.4). However, the prey predated when both male and female were put together was 107.2, which was higher than prey predated by male. In LD cycle, the bugs predated more first instar (186.0) than the second instar (164.0), and in DL cycle, there was not much difference as 163.2 and 164.6 first and second instar, respectively were predated. Overall, the bugs showed more predatory activity during light than in dark, though natural light was changed to dark and dark to light. Predator’s sex, prey size, and different photoperiods testified the predatory performance of M. douglasi, and it was noted that the cumulative interactions of these three parameters were significant. The photoperiods were highly significant. Relatively high statistical significance was also derived in the interaction between the prey size and photoperiod. There was no statistical significance between predator’s sex and prey size and predators’ sex and photoperiod, and when all three parameters interacted, very less significance occurred.

The effect of predators on prey size structure in aquatic communities has been well studied in lentic permanent habits, but less attention has been placed on temporary environments. The biota of seasonal Andean wetlands in Patagonia is basically formed by crustaceans, insects and pond-breeding amphibians. The dominant predators in these wetlands are macroinvertebrates, mostly aquatic insects. The main objectives of this study were to examine the seasonal and interannual variation in the body size of prey and predators in two temporary wetlands located in northwest Patagonia, during two consecutive hydroperiods and to evaluate the effect of different insect predators over different prey sizes and different ontogenetic stages of invertebrate and vertebrate prey. Prey size structure and predator size structure were affected by the wetland type and the sampling months and predator body size was not correlated with prey size structure. The experiments showed that small prey were the most impacted by predaceous insects and all predators showed size-limited predation. Although aquatic insects significantly reduced the number of prey in the predation experiments, they did not significantly affect the body size structure of prey in nature. In this sense, the diversity of aquatic insects with different predatory strategies could maintain the heterogeneity in prey size structure in the wetlands studied.