Ceriodaphnia Reticulata Research Articles

Nanosilica size-dependent toxicity in Ceriodaphnia reticulata (Cladocera)

Silica nanoparticles (SiNP) are the most produced nanomaterials due to their variety of applications. When released to environments, surface water bodies are their main final sink. SiNP toxicity is still inconclusive and may vary according to particle properties such as their size. We analyzed the size-related effects of SiNP (22 and 244 nm) on mortality, life history traits, and oxidative stress in the cladoceran Ceriodaphnia reticulata. The smaller SiNP (LC5072 h: 105.5 µg/ml) were more lethal than the larger ones (LC5072 h >500 µg/ml). The 22 nm-sized SiNP decreased the number of molts and neonates, increased superoxide dismutase and inhibited glutathione S-transferase activities, while larger SiNP did not exert substantial effects on the organisms at the tested concentrations. In conclusion, SiNP toxicity depended on their size, and this information should be considered for regulatory purposes and to the development of safe-by-design nanoproducts to ultimately guarantee the environment protection.

Ecotoxicity of nanosilver on cladocerans and the role of algae provision.

Silver nanoparticles (AgNPs) are applied in diverse industries due to their biocide and physicochemical properties; therefore, they can be released into aquatic systems, interact with environmental factors, and ultimately exert adverse effects on the biota. We analyzed AgNPs effects on Ceriodaphnia reticulata (Cladocera) through mortality and life-history traits, considering the influence of food (Tetradesmus obliquus, Chlorophyceae) presence and concentration. C. reticulata was exposed to AgNPs in acute (absence and two algae concentrations plus five AgNPs treatments) and chronic assays (two algae concentrations plus three AgNPs treatments). AgNPs did not affect algae flocculation but increased Ag+ release, being these ions less toxic than AgNPs (as proved by the exposure to AgNO3). A reduction in AgNPs acute toxicity was observed when algae concentration increased. Acute AgNP exposure decreased C. reticulata body size and heart rate. The chronic AgNP exposure reduced C. reticulata molt number, growth, heart rate, and neonate size:number ratio, being these effects mitigated at the highest algae concentration. Increases in relative size and number of neonates were observed in AgNP treatments suggesting energy trade off. The increased Ag+ release with food presence suggests that the AgNP-algae interaction might be responsible of the decreased toxicity. Although algae reduced AgNP toxicity, they still exerted adverse effects on C. reticulata below predicted environmental concentrations. Since algae presence reduces AgNP effects but increases Ag+ release, studies should be continued to provide evidence on their toxicity to other organisms.

Zooplankton of the Brackish Lakes in Turan-Uyuk Basin (Republic of Tyva)

The study addresses the species composition of zooplankton in five mineralized water bodies located in the Turan-Uyuk basin (Tyva). Lake Beloye is a regional natural landmark. In total, 36 species of 22 genera, 9 families, 4 orders were identified. Cladocera constitute 67 % of the species. The major species are Daphnia magna, Brachionus plicatilis, Daphnia pulex, Daphnia longispina, Megacyclops viridis, Ceriodaphnia reticulata, Chydorus cf. sphaericus, Simocephalus expinosus, Acanthodiaptomus denticornis, Arctodiaptomus baсillifer, Moina macrocopa, Keratella quadrata, Brachionus quadridentatus brevispinus, and Daphnia hyalina. The main abundant species in two lakes, Beloye and Arzhaan, is D. magna, which has been the dominant species in Lake Beloye for decades. The zooplankton of Lakes Beloye and Arzhaan include Macrotrix tabrizensis, a rare species, which is known to occur only in one Russian region – Tyva. Tretocephala ambigua lives in Lake Beloye. In the study period, we observed an increase in the abundance of zooplankton: by a factor of 6 in Lake Beloye and by a factor of 2 in Lakes Kisloe and Arzhaan. We believe that this is a consequence of an increase in organic load on water bodies, resulting from shallowing of the lakes and human impact. The occurrence of the species such as Moina macrocopa and Brachionus quadridentatus brevispinus, which inhabit water bodies rich in organic matter and have not been previously detected in the study lakes, confirms this assumption. Cladocerans, which have a high filtration capacity, remain dominant in Lakes Beloye and Arzhaan, and this is beneficial for the lakes. The increasing abundance of Brachionus plicatilis in Lake Kisloye performs a compensatory function in the processes of natural self-purification. At the same time, the fact that species rare for the fauna of Russia have been constantly found in the study lakes indicates the presence of favorable conditions for their development and life, which further increases the value of these unique natural environments

Phylogenetic analysis of eight species of Anomopoda based on transcriptomic and mitochondrial DNA sequences.

Anomopoda is the widespread planktonic microcrustacean, which plays a crucial role in aquatic ecosystem. There are few studies about the evolutionary relationships among various Anomopoda basing on molecular data. In the present study, phylogenetic analysis of eight Anomopoda was carried out. Firstly, the culture system was developed to breed cladocerans. By using this system, eight species (Daphnia magna, D. pulex, D. sinensis, Ceriodaphnia reticulata, Moina micrura, Scapholeberis kingi, Simocephalus vetulus and Eurycercus lamellatus) were purified and cultured stably in the laboratory. Then, transcriptomic sequences and partial mitochondrial DNA sequences were both used to reconstruct the phylogenetic tree among 8 species. Transcriptomic sequences were sequenced on Illumina Hiseq 2500 platform. After assembly and annotation, transcriptomic sequences were spliced together and aligned for phylogenetic analysis. Basing on the orthologous genes derived from transcriptomic sequences, the phylogenetic analysis showed that 4 genera of Daphniidae were clustered into one group, and among the 4 genera, Ceriodaphnia was closer to Daphnia than Simocephalus, while Scapholeberis was farthest from other species. In addition, Eurycercidae was closer to Daphniidae than Moinidae. The phylogenetic trees based on both 12S rRNA and 16S rRNA sequences were similar with that based on transcriptomic sequences. Meanwhile, the phylogenetic tree based on 16S rRNA sequences was more suitable than that based on 12S rRNA sequences. These results suggested that the phylogenetic analysis basing on the transcriptomic sequences was available in cladocerans, which will help us to effectively understand the phylogenetic relationships among various cladocerans.

Comparative Study of Present and Past Cladoceran Diversity in Manasbal Lake of Kashmir (India)

Present research was carried out to study the diversity of Cladocera in Manasbal Lake and compare it with previous studies. In present study, 21 species of cladocerans were recorded belonging to 5 families: Chydoridae, Daphnidae, Bosminidae, Macrothricidae and Sididae. Chydorids were responsible for major cladoceran diversity followed by daphnids. The frequently species found were Chydorus sphaericus, Graptoleberis testudinaria, Daphnia pulex, Ceriodaphnia reticulata and Bosmina longirostris. While comparing the cladoceran diversity of present study with earlier studies, many species present earlier were not found in present study due to increasing pollution of the lake. However, five species (Chydorus sphaericus, Graptoleberis testudinaria, Bosmina longirostris, Sida crystallina and Diaphanosoma brachyurum) recorded earlier were still present and were reported by all authors. This depicted that these species can tolerate wide range of fluctuations in environmental changes. Further, Daphnia pulex was not recorded in earlier studies but was recorded latter which also showed increased pollution in the lake as this species prefers polluted water. Environmental changes have great influence on distribution of cladocerans and therefore, they act as excellent indicators of pollution.

Modifying the functional diversity in the zooplankton assemblage of an oligotrophic lake differentially affects pelagic community structure and biomass

Experimental ecology represents a fundamental tool to predict how a system reacts to the loss of functional groups in response to contingent disturbance.Zooplankton, the heart of pelagic food webs, is characterized by short life cycles; therefore it can serve as a model system to test ecological theories.In this study we performed a removal experiment to test the hypothesis that the absence of calanoid or cyclopoid copepods could have a different effect on plankton dynamics due to their distinct functional roles in freshwater ecosystems.We selectively removed either Calanoida or Cyclopoida from the original zooplankton assemblage of the oligotrophic lake Brunnsee (Bavaria, Germany), then inspecting temporal changes in plankton community structure and biomass. Experimental communities were incubated in plastic enclosures, fed with cultured phytoplankton and analysed at four time steps over four weeks.Our manipulations led to significant variations in environmental parameters (i.e. chlorophyll-a and microalgae concentration), in zooplankton community composition (dominance, diversity and equitability) and in normalized biomass spectra of zooplankton. The main driver of such changes was the small cladoceran Ceriodaphnia reticulata, the most abundant species at the final sampling in all the treatments. Calanoida facilitated the development of C. reticulata; Cyclopoida played a keystone role, indirectly regulating the abundance of this cladoceran through predation on Calanoida.Our results offer a wider picture of the pelagic food web in oligotrophic freshwater environments and strongly support the view that ecological studies should rely on the measurement of both specific and functional diversity.

Cyclomorphosis in Daphnia magna and Ceriodaphnia reticulata (Cladocera) from northern Tunisian groundwater: influence of temperature and invertebrates?

In the present study, we investigated cyclomorphosis in two cladocerans,DaphniamagnaandCeriodaphnia reticulata, sampled from northern Tunisian groundwater (wells) during two seasons (spring and summer). Seasonal distribution of the two species was apparent, with dominance ofD. magnaonly in spring andC. reticulataduring the whole study period. Our results showed correlations between caudal spine length ofD. magnaand water temperature (, ), and between caudal spine length and the density of coleopteran larvae (Stictonectes escheri,Graptodytessp.,Gyrinus urinator, andHaliplus lineaticollis) (, ). InC. reticulata, we registered a correlation (, ) only between its size and the density of larvae of Ephemeroptera (Cloeon cognatum) but no correlation with water temperature was found.

CRUSTACEA OF THE POND OF TOMASHEV KOLOK IN THE SAMARA CITY

The species composition and seasonal dynamics of quantity of Crustacean populations in small urban pond is studied. The list of 15 Crustacean species is presented. Daphnia longispina, Ceriodaphnia reticulata and Cyclops copepodits dominate in the first half of summer to July, Chydorus sphaericus dominate in August and September.

Unravelling stability‐complexity relationships

image [ The consumer Ceriodaphnia reticulata. This experiment used a very similar species to the one shown here, namely Ceriodaphnia reticulata. This freshwater cladoceran grazer can consume phytoplankton species that have a maximal axial dimension of upto ∼35 μm. As a result, Pediastrum simplex (CPCC 431), Fragilaria crotonensis (CPCC 269), Asterionella formosa (CPCC 605), and Staurastrum pingue (UTEX1606) would have inedible for Ceriodaphnia dubia. Ankistrodesmus falcatus (UTEX 101) may also have been selected against in some instances due to its large size. Neither C. dubia density nor stability were affected by resource species diversity, although resource community composition did matter. ]Narwani, A. & Mazumder, A. (2012) Bottom‐up effects of species diversity on the functioning and stability of food webs. Journal of Animal Ecology, 81, 702–714.Defining the characteristics of persistent species assemblages is a major focus in ecology. A key set of questions is: how to scale up from interactions between two species to multiple species, what is the role of species characteristics in coexistence and what are the ecosystem level consequences of the characteristics of coexistence. Narwani & Mazumder use meticulous experimental work to look at these three questions simultaneously using carefully controlled microcosms. A key finding is that the relationships between stability and diversity as measured by effects on different trophic levels and different aspects of ecosystem function depend critically on the community composition. The particular species involved are more important than the overall diversity.

Temperature effects of interspecies competition between cladoceran species in experimental conditions

In experiments with mono- and polycultures the hypothesis that small-size cladoceran species (Diaphanosoma brachyurum Lievin and Ceriodaphnia reticulata Jurine) are more successful at higher temperatures whereas large-size species (Daphnia magna Straus and Simocephalus vetulus O.F. Muller) under low temperatures was tested. The biomass of Simocephalus vetulus exceeded the biomass of the other species both in mono- and polycultures. An increase of temperature from 18 up to 25°C led to reduction of the biomass of all species. The largest species, D. magna, responded to higher temperature by increased mortality. We assume that the reduction of the biomass of the large species allowed the small C. reticulata to develop successfully in mixed cultures at higher temperature; however it was completely eliminated at lower temperature. Apparently, the survival strategy of large cladocerans involves delayed juvenile development at lower temperatures. However, at higher temperatures, juvenile development of large species accelerates, and their mortality increases. Individual strategies of the studied species to survive at different temperatures are analyzed. On the whole the increase of temperature can result in decrease of the biomass of cladocerans and prevailence of small-size species over large-size ones.

Influence of trophic conditions on biotic interactions under introduction of new species into communities of cladocera

We studied the influence of food concentration on success of introduction of alien species into zooplankton communities. Abundance dynamics of the studied species were simulated under different levels of food supply corresponding to oligo- and eutrophic conditions. Computer-simulated experiments indicated that success of the species introduction was affected by equilibrium food concentration. Species with less equilibrium food concentration were more successful. Among the studied species, more competitive ones were Simocephalus vetulus (large-bodied species) and Ceriodaphnia reticulata (small-bodied species). Indeed, Ceriodaphnia reticulata was the most successful under oligotrophic conditions, and Simocephalus vetulus was so under eutrophic conditions. We suggested that large-bodied species could not compete with the small ones under oligotrophic conditions owing to longer life cycle duration and higher energy requirements at the juvenile stage, especially under food insufficiency. The results of experimental and field studies were analyzed to confirm the success of Ceriodaphnia in competition with larger cladocerans under oligotrophic conditions.

Biological diversity of copepods and cladocerans in Mediterranean temporary ponds under periods of contrasting rainfall

The zooplankton communities of 5 temporary ponds in the Northern part of the Natural Park of the Southwest and Vicentina Coast (PNCSV), Southwestern Portugal, were studied during two consecutive years of contrasting rainfall. A total of ten cladoceran species and eleven copepod species (3 diaptomids, 5 cyclopoids and 3 harpacticoids) were recorded. The community structure varied along the hydrological period of the ponds. Some species were restricted to the early period of the pond (Diaptomus kenitraensis, Hemidiaptomus roubaui, Daphnia hispanica) while others started to build large populations in the middle of the hydroperiod and dominated the communities at the later stages of the hydroperiod: Dussartius baeticus and Ceriodaphnia reticulata dominated the larger ponds, while C. reticulata and Simocephalus exspinosus dominated the smaller ponds. Alpha and beta diversity of cladoceran and copepod species were calculated for the ponds of different hydroperiod length (i.e., water residence time) and area. Alpha diversity was defined as the total diversity of species associated with each pond throughout the annual hydrological period. Copepod and cladoceran communities associated with larger ponds were more diverse than the communities of smaller ponds. As several pond species occur in succession during the length of hydrological period, a longer hydroperiod (2006/2007) allowed for the establishment of a larger number of species than a shorter hydroperiod (2007/2008). Beta diversity was considered as the turnover of species in the gradient of pond area and was higher in the longer hydrological period than in the shorter hydrological period. The degree of diversity change between pairs of ponds was larger between any of the two smaller ponds and any of the larger ponds. This is the first study on the richness of planktonic micro-crustaceans in Portuguese temporary ponds. It is our purpose to increase the knowledge on these taxa to highlight the importance of including this little known, albeit unique, biological diversity when evaluating Mediterranean temporary ponds to conservation purposes.

Effect of benomile fungicide in the demographic parameters of Ceriodaphnia reticulata Jurine, 1820 (Crustacea: Cladocera)

Benomile is one of the most used fungicides in the growing fields. In the rainy season brings benomilo with the planktonic communities. The effect of nominal concentrations of benomile under acute and chronic exposure was tested in the cladoceran Ceriodaphnia reticulata that were used. The value of LC50 was calculated as 2.0 mg L− 1± 0.15 mg L− 1 of benomile. In all concentrations, the demographic variables showed inhibition of reproduction. The unique behaviour of Ceriodaphnia reticulata with this particular toxicant is the diminution in the reproduction without affecting the survivorship.

Cladoceran Periodicity Patterns in Relation to Selected Environmental Factors in Two Cascading Warm-Water Reservoirs Over a Decade

Temporal changes in occurrence, population density and reproductive intensity (% of breeding individuals, clutch size) of species of the planktonic cladoceran assemblage in two adjacent, cascading, warm, monomictic reservoirs were studied over roughly 10 years. Findings are explored in relation to seasonal changes and inter-annual variability in water temperature (and stratification intensity), water transparency, water level, chlorophyll content and presence and abundance of other species in the assemblage as determinants or modifiers of species periodicity. Most of the numerically significant taxa present (4 in upstream Midmar, 7 in downstream Albert Falls) showed repeated patterns of periodicity. Large daphniids (Daphnia pulex and longispina) were virtually perennial occupants, except during conditions of elevated suspended sediment associated with fresh river inflows during floods, or sediment re-suspension at annual turnover and/or low water levels during drought phases of the hydrological cycle. Most other taxa (D. laevis, Diaphanosoma excisum, Ceriodaphnia reticulata, and Moina micrura) were essentially summer species, although some temporal separation was reflected in intra-seasonal, and between-lake differences in their occurrence. D. laevis occurred during early and/or late summer. C. reticulata was confined to late summer; significant densities arose in Midmar only in the final years of study, when it effectively replaced D. laevis. Diaphanosoma was a protracted summer occupant, with a more extended (and bimodal) presence in the warmer waters of Albert Falls. Moina and Bosmina were restricted to Albert Falls, and contrasted in seasonal occurrence. Moina was restricted to the mid-summer period, while Bosmina showed the greatest temporal variation of all taxa, generally appearing during periods of physical disturbance. Mean instantaneous birth rates for the entire study period contrasted widely among taxa (0.09–0.35 day−1), but ranked concordantly with the seasonal categorisations given above – with highest and lowest rates among seasonally restricted and perennial taxa, respectively. Correlation analysis revealed overall that the abundance of most individual species related to water transparency (≅ suspended sediment), chlorophyll content and temperature (in rank order), although correlations were generally stronger with temperature than with chlorophyll. Several correlates were directionally inconsistent (+ vs −) for given species between lakes. However, these correlates of species densities undoubtedly translate into influences on species composition, and hence 'patterns' of periodicity. Positive pair-wise associations (Jaccard Index) existed for many species, reflecting temporal congruencies related to their periodicity. Collectively, however, the species in each reservoir were negatively associated, indicating separation on some undetermined basis (competition?).

Vulnerability of cladoceran species to predation by the copepod Mesocyclops leuckarti: laboratory observations on the behavioural interactions between predator and prey

SUMMARY 1. We analysed the vulnerability of a number of cladoceran species (Bosmina longirostris, B. fatalis, Diaphanosoma brachyurum, Ceriodaphnia reticulata, Daphnia ambigua and D. pulex) to predation by Mesocyclops leuckarti in the laboratory.2. The prey species represented a wide range of body size, morphology, and swimming behaviour. To compare vulnerability, we measured the efficiency of capture and ingestion of each prey species by Mesocyclops. We also measured the rate at which prey were damaged in attacks by Mesocyclops.3. Mesocyclops preyed effectively on Diaphanosoma and small juvenile Ceriodaphnia but not on Bosmina or Daphnia. Observations suggested that various defence mechanisms, including protruding structures and swimming behaviour and speed, are important in determining prey vulnerability.4. The body size of Daphnia and Ceriodaphnia seems to be important, because larger animals were better able to escape Mesocyclops attacks. Attacks by Mesocyclops often caused fatal damage, however, even to large Daphnia.

The role of habitat connectivity and landscape geometry in experimental zooplankton metacommunities

Theory predicts that inter‐patch dispersal rates and patterns of patch heterogeneity both have the potential to alter patterns of local and regional species diversity. To test this, we manipulated both rates of habitat connectivity and the geometric arrangement of habitat heterogeneity within regions of experimental zooplankton communities. We found no effects of habitat geometry on any metric of species diversity or composition. Additionally, we found no effect of habitat connectivity rate on local species diversity. We did, however, find that increasing connectivity led to a decrease in regional diversity, as well as an increase in the percent similarity of local communities within regions. Of all of the species in these communities, the relatively large cladoceran Ceriodaphnia reticulata significantly responded to the treatments, and had a higher probability of achieving high densities when connectance was high. As such, we suggest that this species played a large role in driving the increased local community similarity and decreased regional species richness as connectivity increased. These findings are in opposition to previous experimental studies of metacommunities, but support the notion that increased connectance among local patches may decrease regional diversity when patches are heterogeneous.

Cladoceran assemblages in a mineralization gradient

Cladoceran assemblages were studied in littoral samples from 44 water bodies in Central Spain, showing great differences in salinity and permanence of water. Principal component analyses (PCA) were performed with data on cladoceran relative abundances to identify the main groups of species. Five main groups of species were found, defining the following types of environments: (I) Small but deep hard water lakes (II) permanent but shallow hard water lakes fed by surface springs, rich in macrophytes (III) ephemeral and shallow soft waters lakes (IV) subsaline and hyposaline lakes in their lower range, specially the permanent ones and (V) saline lakes (salinities>6 mg l−1) subject to short or long periods of dryness. The main species constituting these groups were: Group (I): Acroperus neglectus, Alona guttata, Pleuroxus truncatus, Daphnia longispina; group II: Phrixura leei, Latonura rectirostris, Eurycercus lamellatus; Alonella excisa, Daphnia pulicaria; group III: Ephemeroporus phintonicus, Macrothrix rosea, Moina micrura; group IV: Alona rectangula, Ceriodaphnia reticulata, Tetrocephala ambigua, Diaphanosoma mongolianum; group V: Alona salina, Pleuroxus letourneuxi, Dunhevedia crassa, Moina brachiata, Daphnia magna and Daphnia mediterranea. Sample scores from PCA extracted from the correlation matrix of cladoceran proportions were correlated with limnological measurements. Significant correlations with salinity, alkalinity anions and cations indicate that salinity is an important factor in the distribution of the species. However, species assemblages also reflect other factors, such as temporality and littoral development.

Food of introduced pumpkinseed sunfish: ontogenetic diet shift and seasonal variation

The pumpkinseed sunfish Lepomis gibbosus introduced into Lake Banyoles (Spain) were predominantly littoral but there was a tendency of large fish to use deeper zones. Their diet was dominated by littoral macrobenthos, particularly amphipods (Echinogammarus sp.). There was ontogenetic variation in the diet, with small young‐of‐the‐year (LF<4 cm) feeding on several littoral microcrustaceans, especially the cladoceran Ceriodaphnia reticulata, whereas larger fish shifted to a freshwater shrimp (Atyaephyra desmaresti), snails and damselfly larvae. Seasonal variation in diet was linked to resource availability, with consumption of fish eggs and plant debris in spring and summer. In autumn, pumpkinseeds were partially zooplanktivores, preying on the cladoceran Daphnia longispina. The diet of pumpkinseeds in Lake Banyoles and other Iberian populations shows less molluscivory than North American populations. The potential ecological impact of this successful exotic species involves mainly predation on fish eggs and molluscs.

Food of introduced mosquitofish: ontogenetic diet shift and prey selection

The mosquitofish Gambusia holbrooki of Lake Banyoles, Catalonia, Spain, were strictly littoral. Their population was dominated by females throughout the year, except in spring when males were more common. Their diet was based on littoral cladocerans, particularly Chydorus sphaericus, Scapholeberis ramneri, Ceriodaphnia reticulata, and Pleuroxus laevis, and nematoceran (basically chironomid) adults. There was a large variety of prey of terrestrial (collembolans, ants) or aquatic neustonic origin (S. ramneri, emerging nematoceran adults), showing the microhabitat of mosquitofish closely linked to the water surface. In contrast to other studies, terrestrial insects were not especially important in summer. In addition to seasonal and between‐site variation, there was an ontogenetic diet shift from microcrustaceans, particularly cladocerans (smallest fish also using diatoms and copepod nauplii) to larger prey, namely nematoceran adults. However, there was an unusual, inverse relationship between fish length and the size of two prey (S. ramneri and the collembolan Sminthurides sp.), paralleling the overall increase in mean prey size.

Odour‐induced antipredator behaviour of the water flea, Ceriodaphnia reticulata, in varying predator and prey densities

1. A new marking technique was developed and used to track individual water flea behaviour. A single clone of Ceriodaphnia reticulata exhibited no significant differences in mean depth, mean activity (antennae beats used in swimming), and mean travel (total vertical displacement) for fast‐green dyed and control animals (n = 30, each treatment).2. Individual and group antipredator responses were recorded in three vertebrate predator densities (three odour concentrations of green sunfish Lepomis cyanellus; 0.00, 0.03 and 0.10 fish L–1) and four water flea group sizes (1, 5, 15 and 25), with n = 18 for each of the twelve treatment combinations. Water flea groups were probably mixtures of clones. Differences in behaviour after addition of predator odour showed that increasing predator density increased mean depth of marked individuals and mean proportion of water fleas descending. Additionally, increasing prey density decreased both mean depth of marked individuals and mean proportion of water fleas descending.3. Predator density and prey density had opposing affects on activity and travel for marked individuals. Higher predator density decreased mean activity (antennae beats), yet increased mean travel. Higher prey density increased mean activity, but decreased mean travel. Descending animals altered their swimming pattern by using fewer swimming beats to travel greater vertical distances in the presence of predator odour.