Selective Feeding Behaviour Research Articles

The Dynamics of Trophic Cascades on Phytoplankton Induced by Mesozooplankton in Coastal Water, Daya Bay, Northern South China Sea

Daya Bay, a semi-enclosed bay in the northern South China Sea and to the east of the Pearl River Estuary, is rich in biological resources and diverse habitats. Current research on mesozooplankton in Daya Bay has mainly focused on aspects such as species composition, biomass, and biodiversity in the zooplankton community. However, there is limited research on the top-down effects of mesozooplankton on prey communities. This study conducted seasonal in-situ cultivation experiments from 2015 to 2017. By combining mesozooplankton grazing experiments and microzooplankton dilution experiments, the mesozooplankton clearance rate and trophic cascading effect on low trophic levels were calculated. Results showed evident mesozooplankton selective feeding behavior and corresponding trophic cascades with seasonal variations, these being significantly higher in the spring and summer and lower in the autumn and winter. Different sizes of phytoplankton showed significant differences; large-sized phytoplankton received high feeding rates but low trophic cascades by mesozooplankton, while the opposite was true for small-sized phytoplankton. Trophic cascades contribute in three ways: offsetting direct grazing mortality, changing prey community structure via its effects on different phytoplankton sizes, and reducing ciliate grazing impacts at an average of 14.4 ± 7.8%, maintaining around 70% ciliate grazing impacts in nature. The composition of mesozooplankton was the primary reason for explaining feeding preferences, including size selectivity and omnivory. For instance, high cladoceran abundance caused high feeding rates while, on the other hand, high omnivorous copepods abundance caused high trophic cascades on small-sized phytoplankton. General additive model (GAM) analysis revealed that the changes in trophic cascades were highly dependent on temperature, ciliate abundance, mesozooplankton feeding rates on ciliates, and ciliate feeding rates on phytoplankton. The significance of this study lies in its contribution to providing valuable insights into the role of mesozooplankton in the marine food web and their impact on lower trophic levels. In addition, the findings can help inform the management and conservation of marine ecosystems, as well as guide future research in this field.

Dietary flexibility of insectivorous bats, Eptesicus fuscus and Myotis lucifugus, during Magicicada spp. Brood X emergence

Emergence of periodical cicadas, Magicicada spp. Davis, 1925, presents an ideal opportunity to study dietary flexibility and selective feeding behavior of bats. It is known that a wide array of taxa prey upon Magicicada spp., but few bat species have been documented to consume them. When larger than typical prey items, such as periodical cicadas, become abundant for a short time frame, insectivorous bats may exhibit alteration in dietary selection that provides insight into capacity and conditions for feeding. Evidence of Magicicada spp. consumption was detected in guano via polymerase chain reaction (PCR) and physical detection in both Eptesicus fuscus (Palisot de Beauvois, 1796) and Myotis lucifugus (Le Conte, 1831), two bat species of different sizes and with different dietary profiles. The consumption of these larger prey items, when they are locally abundant, supports a display of opportunistic behavior and diet flexibility in these two bat species.

Predator-prey trait associations and feeding preferences of demersal fishes in the southern North Sea

In marine ecosystems under ongoing long-term changes, reducing complex food webs to their functionally important properties enables systematic analysis of bottom-up/top-down regulations and species turnover. The assessment of feeding interactions in the form of predator and prey trait associations provides a better understanding of predators’ criteria for prey selection and thus is a promising approach to reduce complexity. Here, we tested RLQ ordination and fourth-corner analysis, complementary multivariate approaches, as tools to identify ecologically relevant associations between the traits of 8 demersal fish species in the southern North Sea and their fish or benthic prey. To scrutinize the trait-based results in their appropriateness to reflect selective feeding behaviour of the predator species, we compared them with a taxon-based electivity index, Chesson’s α. Among 7 predator traits investigated, body tissue composition represented by omega-3 polyunsaturated fatty acid content was significantly associated with prey traits, being positively correlated with energy density of the prey and negatively with prey of low mobility. Comparisons with the electivity indices showed that the prey preferred by predators corresponded relatively well with the identified prey trait preferences. The results of the tested analysis approach support its use when assessing the mutual dependences of predator and prey populations on a functional level. Provided the data availability and quality of feeding-related traits is sufficiently high, trait-based predator-prey analysis with RLQ and fourth-corner analyses offers new possibilities for understanding food web dynamics in the context of climate-change-induced species distribution shifts.

Exploring the co-exposure effects of environmentally relevant microplastics and an estrogenic mixture on the metabolome of the Sydney rock oyster

In aquatic environments the concurrent exposure of molluscs to microplastics (MPs) and estrogens is common, as these pollutants are frequently released by wastewater treatment plants into estuaries. Therefore, this study aimed to evaluate the independent and co-exposure impacts of polyethylene microplastics (PE-MPs) and estrogenic endocrine-disrupting chemicals (EEDCs) at environmentally relevant concentrations on polar metabolites and morphological parameters of the Sydney rock oyster. A seven-day acute exposure revealed no discernible differences in morphology; however, significant variations in polar metabolites were observed across oyster tissues. The altered metabolites were mostly amino acids, carbohydrates and intermediates of the Kreb's cycle. The perturbation of metabolites were tissue and sex-specific. All treatments generally showed an increase of metabolites relative to controls – a possible stimulatory and/or a potential hormetic response. The presence of MPs impeded the exposure of adsorbed and free EEDCs potentially due to the selective feeding behaviour of oysters to microplastics, favouring algae over similar-sized PE-MPs, and the formation of an eco/bio-corona involving faeces, pseudo-faeces, natural organic matter, and algae.

Fate and effects of microplastic particles in a periphyton-grazer system

In the aquatic environment, microplastic particles (MP) can accumulate in microbial communities that cover submerged substrata, i.e. in periphyton. Despite periphyton being the essential food source for grazers in the benthic zones, MP transfer from periphyton to benthic biota and its ecotoxicological consequences are unknown. Therefore, in this study, we investigated the effects of 1) MP on embryonal development of freshwater gastropod Physa acuta embryos, 2) MP on adult Physa acuta individuals through dietary exposure and 3) on the MP surface properties. Embryonal development tests were carried out with spherical polyethylene MP in the size of 1–4 μm (MP). Over a period of 28 days, embryonal development and hatching rate were calculated. In the feeding experiments, periphyton was grown in the presence and absence of MP and was then offered to the adult Physa acuta for 42–152 h. The snails readily ingested and subsequently egested MP, together with the periphyton as shown by MP quantification in periphyton, snail soft body tissue and feces. No selective feeding behavior upon MP exposure was detected. The ingestion of MP had no effect on mortality, feeding and defecation rate. Yet, the reproductive output of snails, measured as the number of egg clutches and numbers of eggs per clutch, decreased after the ingestion of MPs, while the hatching success of snail embryos those parents were exposed remained unaffected. In contrast, hatching rate of snail embryos was significantly reduced upon direct MP exposure. MP optical properties were changed upon the incorporation into the periphyton and the passage through the digestive tract. Our results indicate that MP incorporated in periphyton are bioavailable to aquatic grazers, facilitating the introduction of MP into the food chain and having direct adverse effects on the grazers’ reproductive fitness.

ROLE OF SPACE IN AN ECO-EPIDEMIC PREDATOR-PREY SYSTEM WITH THE EFFECT OF FEAR AND SELECTIVE PREDATION

In ecological systems, the fear of predation risk asserts a privilege to the prey species by restricting their exposure to the potential predators. It also imposes costs by constraining the exploration of optimal resources. Additional foods for predators play a pivotal role in the biological conservation programs. The predators have ability to distinguish between the susceptible and infected prey items, and they avoid the latter ones to reduce their fitness cost. A predator-prey model with disease in prey is investigated in this study with an aim to explore the effects of fear factor, additional foods and selective predation on the ecological systems. We also investigate the spatio-temporal model to incorporate the facts that the prey and predator populations perform active movements in the spatial directions for their biological relevance. Both the temporal and spatio-temporal models are analyzed through noteworthy mathematical as well as numerical techniques. Our simulation results show that the level of fear responsible for the reduction in the birth rate of susceptible prey, rate of disease transmission and the selective feeding behavior of predators have potentials to create instability in the ecosystem. In contrast, the level of fear responsible for reduction in the disease prevalence can restore stability in the ecosystem by killing the persistent oscillations. Our eco-epidemic system exhibits chaotic nature if the growth of predators due to additional food sources is very low. We find that the spatio-temporal model demonstrates different spatial patterns of the prey and predator populations in the ecosystem.

A Review on the Role of Earthworms in Plastics Degradation: Issues and Challenges.

Recently, the contribution of earthworms to plastic degradation and their capability to swallow smaller plastic fragments, known as microplastics, has been emphasized. The worm physically changes the size of microplastics and enhances microbial activities to increase the possibility of degradation. However, no research has shown that earthworms can chemically degrade microplastics to an element form, CO2 or H2O. In this review, previous research has been thoroughly explored to analyse the role that earthworms could play in plastic degradation in the soil. Earthworms can significantly affect the physical characteristics of plastics. However, earthworms' abilities to chemically degrade or change the chemical structure of plastics and microplastics have not been observed. Additionally, earthworms exhibit selective feeding behaviour, avoiding areas containing a high plastics concentration and rejecting plastics. Consequently, earthworms' abilities to adapt to the microplastics in soil in the environment can cause a problem. Based on this review, the challenges faced in earthworm application for plastic degradation are mostly expected to be associated with the toxicity and complexity of the plastic material and environmental factors, such as the moisture content of the soil and its temperature, microbial population, and feeding method.

Photoautotrophs and macroinvertebrate trophic relations in calcareous semiarid streams: The role of Cyanobacteria

Photoautotrophs and macroinvertebrate trophic relations in Mediterranean streams, especially from semiarid areas, are still poorly known, as is the role of Cyanobacteria, which is the most frequently dominant photoautotroph. To investigate the role of Cyanobacteria as a food resource in these systems, the fatty acid composition of primary and secondary producers was investigated in two streams on a semiarid climatic gradient between 200 and 500 mm of rainfall in SE Spain. Fatty acid composition of photoautotrophs and macroinvertebrates differed among streams in summer and among seasons in each stream. Fatty acid fingerprints show that macroinvertebrates usually fed on the dominant photoautotroph assemblage and that Cyanobacteria represent the main food for all the feeding groups in the Alhárabe stream in winter although filamentous green algae were preferred in summer. Only scrapers consuming Chlorophyta displayed a selective feeding behaviour. The results show the importance of cyanobacteria as food for all collected macroinvertebrates in winter in some semiarid streams and confirm that fatty acids can be used as temporal and spatial markers in fluvial systems.

Selective Feeding of a Mixotrophic Dinoflagellate (Lepidodinium sp.) in Response to Experimental Warming and Inorganic Nutrient Imbalance.

Mixotrophic protists are widely observed in the aquatic ecosystems, while how they respond to inorganic nutrient imbalance and ocean warming remains understudied. We conducted a series of experiments on a mixotrophic dinoflagellate Lepidodinium sp. isolated from subtropical coastal waters to investigate the combined effect of temperature and medium nitrate to phosphate ratio (N:P ratio) on the ingestion activities of mixotrophic protists. We found Lepidodinium sp. displayed selective feeding behaviour with a higher ingestion rate on high-N prey (N-rich Rhodomonas salina) when the ambient inorganic N:P ratio was equal to or below the Redfield ratio. The Chesson selectivity index α increased with increasing temperature, suggesting that warming exacerbated the selective feeding of Lepidodinium sp. Under inorganic nitrogen sufficient conditions (N:P ratio = 64), no selective feeding was observed at 25 and 28°C, while it occurs at 31°C, which also indicates that warming alters the feeding behaviour of Lepidodinium sp. In addition, our results revealed that the total ingestion rate of Lepidodinium sp. under the condition with normal inorganic nutrients (Redfield ratio) was significantly lower than that under nutrient-imbalanced conditions, which indicates that Lepidodinium sp. developed compensatory feeding to balance their cellular stoichiometry and satisfy their growth. Our study is the first attempt on revealing the selective feeding behaviours of mixotrophic protists on prey under different inorganic nutrient environments and rising temperatures, which will contribute to our understanding of the response of marine plankton food web to projected climate changes.

Particle Size Distribution of Organic Complete Diets for Laying Hens during Feed Offering

Complete diets for laying hens are usually offered in meal form. This form initially promotes the laying hens’ natural feed intake behavior and allows them to satisfy their pecking behavior. At the same time, it can also cause difficulties, because it consists of different particles and is not a homogeneous unit. A homogeneous mixture is essential to ensure that each laying hen in the flock can meet its nutritional needs. If feed exhibits a wide particle size distribution, this can promote feed segregation during transport and selective feed intake behavior of laying hens. These two processes sometimes lead to significant differences between the composition of the feed produced and the composition of the feed that is finally ingested by the laying hens. Multi-stage sampling can be used to investigate progressing differences in feed composition. In this study, samples of different complete diets for laying hens (n = 76) were collected from ten organic farms in Germany to examine their particle size distributions (dry sieve analysis). Samples were taken at four different locations (V1 = loading, V2 = silo, V3 = at the beginning of the feed chain, V4 = at the end of the feed chain) in each farm. There was a tendency for V1 and V2 to be characterized by high proportions of particles between 1400 and 3150 µm (V1 = 61.2%, V2 = 43.5%). V3 and V4 consisted mainly of particles of size 500–800 µm and 200–400 µm, respectively. The lowest proportions across all variants were in the range above 3150 µm (V1 = 2.20%, V2 = 1.30%, V3 = 1.00%, V4 = 0.400%) and between 400 and 500 µm (V1 = 2.50%, V2 = 4.50%, V3 = 5.70%, V4 = 6.60%). The mean value comparison of the proportions of sieve mesh sizes from 200 to 1000 µm resulted in: V1 < V2 < V3 < V4; and of sieve mesh sizes between 1400 and 2000 µm in: V1 > V2 > V3 > V4. This observation can be explained by segregation of the feed during transport and a selective feeding behavior of the laying hens. However, trends were discontinuous and varied between the farms. Deviations from the guideline values were found in particular for particle sizes in the range of 1000 to 1400 µm.

Influence of the addition of water to total mixed rations on the feeding behaviour, feed intake and milk performance of high-yielding dairy cows

The goal of this study was to investigate the influence of the addition of water to total mixed rations (TMR) with a dry matter (DM) content of 42 - 47% and high proportions of ensiled forage on feeding behaviour, DM intake (DMI) and milk performance, as well as changes in TMR temperature. The underlying hypothesis was a reduction in the selective feeding behaviour and a resulting increase in DMI of the cows, which were provided with a moist TMR. During two feeding trials, 48 German Holstein cows per trial were split into 2 groups (Trial I, winter: 85 ± 28 d in milk (DIM); Trial II, summer: 67 ± 34 DIM). Both trials were set up as a crossover design with period lengths of 45 (Trial I) and 35 (Trial II) d. The rations in each trial were made of the same components, had the same energy and nutrient concentrations and had slightly different DM contents. In Trial I, a TMR with 46.4% DM (dry TMR) was mixed with 12.5 kg water per cow per day, to reduce the DM content of the TMR to 37.3% DM (wet TMR). In Trial II, the DM content of 41.8% (dry TMR) was reduced to 33.9% (Wet TMR) after 14 kg of water per cow per day were added. The DMI of the individual animals and their milk yield were measured daily, and the milk composition was determined weekly. To judge the feeding behaviour, samples were taken from each feeding group at five points throughout the day during Trial I, and three during Trial II. The samples were tested for particle size distribution using a Penn State Particle Separator (PSPS). In both trials, the selective feeding behaviour was reduced as a consequence of the addition of water to TMR. In the case of the dry TMR, a change in particle size distribution in the troughs was already discernible 10 h after the feed was provided. In both trials, the addition of water had a positive influence on the DMI. In Trial I, the cows consumed 1.3 kg DM/d more as a consequence of the addition of water (p < 0.001), and in Trial II the difference equated to 0.6 kg DM/d after the addition of water (p < 0.001). The increased energy and nutrient intake of the cows that had been fed with the moistened TMR led to higher daily milk yield (Trial I: +0.6 kg/d; Trial II: +0.5 kg/d) and drinking water intake (p < 0.001). During the first 24 h after mixing the rations in Trial II (summer), no temperature differences were observed between the dry and moistened TMR. During the time period of 24–48 h after feeding, the dry TMR had an average temperature of 36.8 °C and the wet TMR had a temperature of 40.1 °C, which was a significant difference (p < 0.001). Furthermore, in Trial II, the increased energy and nutrient intake was reflected in a higher fat and protein yield and in an increased energy-corrected milk yield by 0.8 kg/d (p = 0.015). These results confirm that by adding water to TMR, selective feeding behaviour can be reduced and DMI increased, both during summer and winter trials. The importance of a uniform, non-selective feed intake in high-performing dairy cows is also evident from the results.

Effects of replacing steam-flaked corn with shredded sugar beet pulp on feed sorting, behavior, blood metabolites, and growth performance of dairy calves.

This experiment was conducted to investigate the effects of partial replacement of steam-flaked corn (SFC) with shredded sugar beet pulp (SBP) in the starter diet on selective intake (sorting), feeding and chewing behavior, blood biochemical parameters, and growth in newborn female Holstein dairy calves. A total of 48 calves (3 d old; 40.1 ± 0.84 kg body weight; mean ± SE) were randomly assigned to 1 of 2 feeding treatments containing 0 or 25% SBP (percentage of dry matter [DM]) in the starter diet. Calves were weaned on d 61 and remained in the study until d 81. Intake of starter feed and total intake of DM (milk DM + starter feed DM), crude protein, and neutral detergent fiber were increased (P < 0.05) by feeding SBP; however, intake of starch (P < 0.01) and total intake of ether extract (P = 0.03) were decreased with no apparent effect on total intake of ME. Average daily gain, feed efficiency, final weight, and skeletal growth also showed no significant changes. Circulating concentrations of glucose, total protein, and albumin were not affected by partial replacement of SBP with SFC; however, higher concentrations of blood urea-N (P = 0.01) and a lower albumin-to-globulin ratio (P = 0.03) were observed in SBP- vs. SFC-fed calves. Calves fed SBP sorted more for particles retained on the 4.75-mm sieve (P = 0.02) and against particles retained on the 0.6-mm sieve and bottom pan (P < 0.01). Intake of neutral detergent fibers and starch from particles retained on all sieve fractions was increased and decreased (P < 0.01), respectively, by replacing SFC with SBP. Replacement of SBP with SFC was associated with increased meal length and meal size and increased rumination frequency and length, but decreased intervals between rumination (P ≤ 0.01). Calves fed SBP spent more time eating, rumination, and standing and less time lying and non-nutritive oral behaviors (P < 0.01). In general, 25% replacement of SFC with SBP did not affect calf performance but increased time spent rumination and eating and decreased non-nutritive oral behaviors.

Influence of the Calcium Carbonate Shell of Coccolithophores on Ingestion and Growth of a Dinoflagellate Predator

Coccolithophores are an important group of ∼200 marine phytoplankton species which cover themselves with a calcium carbonate shell called “coccosphere.” Coccolithophores are ecologically and biogeochemically important but the reason why they calcify remains elusive. One key function may be that the coccosphere offers protection against microzooplankton predation, which is one of the main causes of phytoplankton death in the ocean. Here, we investigated the effect of the coccosphere on ingestion and growth of the heterotrophic dinoflagellate Oxyrrhis marina. Calcified and decalcified cells of the coccolithophore species Emiliania huxleyi, Pleurochrysis carterae, and Gephyrocapsa oceanica were offered separately to the predator as well as in an initial ∼1:1 mixture. The decrease of the prey concentrations and predator abundances were monitored over a period of 48–72 h. We found that O. marina did not actively select against calcified cells, but rather showed a size selective feeding behavior. Thus, the coccosphere does not provide a direct protection against grazing by O. marina. However, O. marina showed slower growth when calcified coccolithophores were fed. This could be due to reduced digestion rates of calcified cells and/or increased swimming efforts when ballasted with heavy calcium carbonate. Furthermore, we show that the coccosphere reduces the ingestion capacity simply by occupying much of the intracellular space of the predator. We speculate that the slower growth of the grazer when feeding on calcified cells is of limited benefit to the coccolithophore population because other co-occurring phytoplankton species within the community that do not invest energy in the formation of a calcite shell could also benefit from the reduced growth of the predators. Altogether, these new insights constitute a step forward in our understanding of the ecological relevance of calcification in coccolithophores.

Effect of High Concentrate Corn Stalk Particle Size on Physical State and Production Performance of Lactating Dairy Cows

In order to realize the application of corn stalk in cow feed, we designed experiments to explore the effect of a certain proportion of corn stalk on the performance of lactating dairy cows. 9 multiparous mid-lactating cows were allocated at random to three groups, each containing 3 intact cows. The trial consisted of three periods and three dietary treatments with a 3 × 3 Latin square design. The diets were normal concentrats plus dried corn stalk chopped to 5 - 8 cm long (N), high concentrates plus dried corn stalks chopped to a length of approximately 5 - 8 cm by a mower (H) while the milled corn stalks were passed through a pulviser with a 2 cm pore size (MH). Each cow was measured for dry matter intake (DMI), ruminal pH, rumen fermentation, selective feeding behavior and production performance. The results showed that MH led to a significantly higher intake of DM, neutral detergent fiber (NDF), forage NDF (FNDF), acid detergent fiber (ADF), crude protein (CP) and organic matter (OM) than N and H (P ity for the dietary component. MH resulted in a significantly higher milk production (P P = 0.055). There were no significant differences in the milk components (P = 0.424) and lactose (P = 0.113) between cows fed N and MH. The high-concentrates plus milled corn stalk diet can increase the milk yield under the premise of normal rumen pH in dairy cows, thereby generating higher economic benefits. And milled corn stalk can effectively inhibit the cow’s selective eating of low-quality roughage.

Effects of changing phytoplankton species composition on carbon and nitrogen uptake in benthic invertebrates

AbstractPelagic primary production is the main input of organic energy for benthic production below the photic zone. In the Baltic Sea, spring phytoplankton blooms are dominated by diatoms that sink out rapidly and export nutritionally favorable matter to benthic secondary production, while the summer blooms have more variable sedimentation rates and nutritional profile. Changes in phytoplankton species composition and bloom dynamics, as a consequence of climate change and eutrophication are reducing high quality diatoms reaching the benthic fauna, while promoting cyanobacteria. Here, we test uptake and assimilation of changing phytoplankton composition for three common benthic invertebrates, a clam, an amphipod and a polychaete under varying degrees of spring‐bloom associated diatoms (Skeletonema costatum) and summer‐bloom associated cyanobacteria (Nodularia spumigena). The phytoplankton were labeled with stable isotopes (15N and 13C, respectively) in order to trace assimilation in consumers' tissues. We found that all three macrofauna species fed on both diatoms and cyanobacteria. A linear pattern was found for all three species in assimilation of carbon and nitrogen from diatoms, with increasing assimilation associated with higher proportion of diatoms. There was no clear pattern found between proportion of cyanobacteria and assimilation of carbon and nitrogen for any of the species. This study shows that the investigated macrofaunal species display a selective feeding behavior with preference for spring‐bloom associated diatoms. Thus, changes in phytoplankton bloom composition are likely affecting benthic species composition and production.

Oxidative damage and decreased aerobic energy production due to ingestion of polyethylene microplastics by Chironomus riparius (Diptera) larvae

Riverine sediments are major sinks of microplastics from inland anthropogenic activities, imposing a threat to freshwater benthic invertebrates. This study investigated the ingestion of three size-classes (SC) of irregularly shaped polyethylene microplastics (PE-MPs; SC I: 32−63 μm; II: 63−250 μm; III: 125−500 μm) after 48 h by dipteran larvae (detritivore/collector) Chironomus riparius, and the consequent effects on neurotransmission, energy allocation and oxidative stress. The tested PE-MPs concentrations (1.25; 5; 20 g kg−1) were within the range of concentrations reported in riverbanks from highly urbanised areas (1 - 9 g kg−1), except for 20 g kg−1 representing the worst-case scenario. After exposure to SC I, larvae presented high amounts (up to ∼2400 particles/organism) of PE-MPs in their guts, with an average size-range of 30−60 μm. In the SC II and III, larvae presented PE-MPs of higher diameter (up to 125 μm) and a visible gut obstruction. The high number of particles in the larval gut (SC I) and/or difficulties for their egestion (SC I, II and III) induced oxidative damage and reduced aerobic energy production. In addition, larvae exposed to SC II and III revealed depletion in their total lipid reserves as a consequence of lacking nutrients, and the ones exposed to SC III presented a decrease in their detoxification capacity.These results highlight that freshwater detritivores with low selective feeding behaviour (e.g., chironomids) are more prone to ingest microplastics, with potentially adverse effects on cellular metabolism, redox status and antioxidant-detoxification defences. These harmful effects at lower levels of the biological organisation may ultimately affect organisms’ physiology and fitness.

Multifaceted linkages among eco-physiological factors, seasonal plankton dynamics and selective feeding behavior of the green mussel (Perna viridis) in the south-east coast of the Bay of Bengal

Feeding behavior of marine bivalves is largely regulated by the interactive effects of various intrinsic biological factors and extrinsic ecological factors. Therefore, an integrated multivariate approach was applied to explore a deeper knowledge about the feeding biology of the green mussel (Perna viridis), collected from the south-east coastal regions of the Bay of Bengal in Bangladesh, by interlinking among ecological factors, seasonal plankton dynamics, reproductive traits and plankton ingestion data. The correlation test, multivariate approaches and cluster analysis displayed that both the water parameters and ingested gut plankton abundance and their compositions were predominantly influenced by the seasonality and ecological factors of the environment. The selectivity indices analysis confirmed that green mussels preferentially ingested on the selective taxa of plankton. The multivariate analyses revealed that plankton ingestion by green mussels was not discriminated by their sexual dimorphism, however, it displayed an enhancement during their gonad development and maturation stages confirming that P. viridis espouses opportunistic patterns to build up their gonads by utilizing energy from the ingested planktons available in the water column. The correlation outcomes consistently demonstrated that the quantitative ingestion of plankton was positively correlated with the gonadosomatic index value of the green mussels. Although, green mussels predominantly ingested the Coscinodiscophyceae (20–60% of total ingestion), they also selectively ingested an increased amount of Bacillariophyceae, Fragillariophyceae, Dinophyceae and zooplankton during their gonad development and maturation stages to meet the special and unique metabolic requirements of crucial gametogenesis stages. Taken together all datasets, principal component analysis (PCA) was applied: the first two principal components showed that seasonality and reproductive cycle explained >47% of the variability. In both cases, PCA analysis revealed that the multiplex scenario of selective ingestion of P. viridis on different plankton taxa were predominantly interlinked with the seasonality, ecological drivers, and plankton biomass and their community structure in the water column depending on the metabolic energy requirement during their crucial gametogenesis stages. Finally, the outcomes from these broad datasets provide a better understanding about the selective feeding behavior of P. viridis, which is essential to maintain the sustainability of the ecosystems as well as to improve the growth and productivity of the existing production systems of this important species.

Summer diet selection of a rock specialist: the Wolffsohn´s viscacha (Lagidium wolffsohni) in protected natural area of Pinturas River, Cueva de las Manos, Patagonia, Argentina

ABSTRACT Rock specialists are mainly herbivores with similar morphological and behavioral characteristics such as spatial activity and feeding near rocky outcrops. In mountain areas, they are vulnerable due to restrictions in food searching and many are also sensitive to warm temperatures. The Wolffsohn’s viscacha (Lagidium wolffsohni) is a high-altitude rock specialist whose conservation status IUCN is Data Deficient. This study investigates its feeding behavior in relation to food availability and evaluates the degree of trophic specialization in summer. Percent vegetation cover was estimated on three rocky outcrops inhabited by the Wolffsohn’s viscacha, and diet was estimated conducting a microhistological analysis of fecal pellets from 83 fresh fecal pellet groups. Wolffsohn’s viscacha was a selective consumer of grasses and its trophic niche was narrow (Bst = 0.31 ± 0.04). Its diet consisted of 17 food items. The grasses Festuca pallescens, Pappostipa spp., Poa spp., and shrub Berberis heterophyla composed 81% of the diet. The selective feeding behavior by grasses was similar to the southern vizcacha. Both herbivores selected a high-quality shrub and grasses in summer. This feeding behavior suggests a selection based on the availability of quality food near rocky outcrops representing a low cost of searching time and high contribution of nutrients.

Predator-prey interactions associated with larval Gilchristella aestuaria (family clupeidae) in mangrove and non-mangrove estuaries

The predator-prey interactions between the larvae of a common mid-trophic species, Gilchristella aestuaria, and dominant zooplankton were compared between similar warm temperate estuaries with and without mangroves. It is hypothesized that higher abundances of G. aestuaria larvae and their prey species will be found in estuaries with mangroves as these systems would provide an enhanced feeding environment for all species, compared to estuaries devoid of mangroves. Generalized Additive Models found that an interaction of mangrove presence, turbidity, copepod prey density and competition pressures by predatory mysids were the most significant at explaining postflexion G. aestuaria densities. Postflexion G. aestuaria negatively selected Paracartia longipatella in the four sampled estuaries, despite co-occurring at high densities. Postflexion larvae consumed more of the larger copepod species, Pseudodiaptomus hessei, within the two mangrove estuaries than the two non-mangrove estuaries, despite other prey species occurring at similar densities. This selective feeding behaviour may be as a consequence of the relatively low prey densities found in all the sampled estuaries as well as the lower turbidity seen in the mangrove estuaries. This study is the first of its kind investigating the relationship between mangroves and fodder fish populations. It highlights the importance of predator-prey interactions when assessing the nursery value of mangrove habitats to fishes.

Amplicon-Based Illumina Sequencing and Quantitative PCR Reveals Nanoplankton Diversity and Biomass in Surface Water of Qinhuangdao Coastal Area, China

Aureococcus anophagefferens caused brown tides for three consecutive years from2009 to2011 in the coastal waters of Qinhuangdao, China, with numerous, widespread ecological and economic impact on ecosystems. To understand the population dynamics of nanoplankton during the brown tides, sequences of the V9 region of the 18S rDNA gene, used as a marker, were analyzed by Illumina sequencing to assess nanoplankton biomass, and real-time fluorescence quantitative PCR was performed to analyze spatial variation in the 18S rDNA copy concentrations of nanoplankton off the Qinhuangdao coast in July,2011. The results showed that A. anophagefferens and Minutocellus polymorphus were the dominant species in the local phytoplankton community during the brown tide in July2011. The highest 18S rDNA copy concentrations of A. anophagefferens and M. polymorphus were detected at stations SHG and FN, respectively. The central area most strongly affected by the brown tide migrated southward from2011 to2013. Redundancy analysis (RDA) showed that the decreasing NOx concentration might provide suitable nutrient conditions for the A. anophagefferens outbreak. During the brown tide caused by A. anophagefferens, other phytoplankton, such as diatoms, cryptophytes, chlorophytes, dinoflagellates and other flagellates, could co-occur with it. For zooplankton, due to less selective feeding behavior, Amoebozoa was the most abundant zooplankton at station SHG, while Ciliophora was the most abundant zooplankton at other stations for its more selective feeding.