Small Food Particles Research Articles

Contactless Printing of Food Micro-Particles Controlled by Ultrasound

Traditional food 3D printing technology, which primarily relies on mechanical control, often faces challenges such as low resolution, stringent material requirements, limited flexibility, and cumbersome equipment. To overcome these limitations, we developed an innovative food 3D printing method utilizing ultrasonic phased arrays and subsequently designed a contactless printing device employing this advanced technology. The device effectively manipulates the phase and amplitude of the ultrasonic phased array to focus the sound field on a specific location. We have successfully demonstrated preliminary control over the suspension of small food particles, including popcorn, chocolate, honey, and marshmallows, using this apparatus. Following this, popcorn particles were selected for detailed practical printing and further analysis.Additionally, we established a software platform, Ultr_printing, based on Ultraino, for intelligent simulation and control of the printing process. Leveraging FPGA and Arduino controllers, this setup facilitates rapid signal transmission from personal computers to sensors, ensuring quick and adaptable movement of suspended particles. Experimental results confirm that the device consistently controls the food particles, irrespective of their motion state. Notably, it achieves a printing precision of 0.16 mm when handling popcorn particles measuring 1.5 mm in diameter. The process, entirely contactless and free from contamination, preserves the original flavor of the food particles. This technology is particularly effective for high-precision printing of micro-scale shapes and offers considerable benefits in assembly and precision manufacturing.

Biomimetic models of fish gill rakers as lateral displacement arrays for particle separation.

Ram suspension-feeding fish, such as herring, use gill rakers to separate small food particles from large water volumes while swimming forward with an open mouth. The fish gill raker function was tested using 3D-printed conical models and computational fluid dynamics simulations over a range of slot aspect ratios. Our hypothesis predicting the exit of particles based on mass flow rates, dividing streamlines (i.e. stagnation streamlines) at the slots between gill rakers, and particle size was supported by the results of experiments with physical models in a recirculating flume. Particle movement in suspension-feeding fish gill raker models was consistent with the physical principles of lateral displacement arrays ('bump arrays') for microfluidic and mesofluidic separation of particles by size. Although the particles were smaller than the slots between the rakers, the particles skipped over the vortical region that was generated downstream from each raker. The particles 'bumped' on anterior raker surfaces during posterior transport. Experiments in a recirculating flume demonstrate that the shortest distance between the dividing streamline and the raker surface preceding the slot predicts the maximum radius of a particle that will exit the model by passing through the slot. This theoretical maximum radius is analogous to the critical separation radius identified with reference to the stagnation streamlines in microfluidic and mesofluidic devices that use deterministic lateral displacement and sieve-based lateral displacement. These conclusions provide new perspectives and metrics for analyzing cross-flow and cross-step filtration in fish with applications to filtration engineering.

Morphology and ultrastructure of the infrabuccal pocket in Strumigenys ants

The morphology of the infrabuccal pocket has been studied with light and electron microscopy (SEM, TEM) in 19 species of Strumigenys ants. The structural organization is similar in workers, queens and males, and supports the involvement of the pocket in the filtration of food particles before they can enter the digestive tract. A carpet of posteriorly oriented bristle hairs on the hypopharynx first guide ingested food into the pocket, where large solid particles are compacted into a pellet that will be regurgitated. The remaining products enter the digestive tract through a filtering wall of parallel hair combs lining the pharynx interior that are directed against the food flow. This mechanical filtering allows only liquids and sufficiently small food particles to enter the digestive system. The wall of the infrabuccal pocket is differentiated into a conspicuous glandular epithelium, of which the ultrastructural characteristics can be understood as an adaptation against the frequent shape changes of the pocket. The gland elaborates a non-proteinaceous secretion, although its functional significance still remains unknown.

Radular force performance of stylommatophoran gastropods (Mollusca) with distinct body masses

The forces exerted by the animal’s food processing structures can be important parameters when studying trophic specializations to specific food spectra. Even though molluscs represent the second largest animal phylum, exhibiting an incredible biodiversity accompanied by the establishment of distinct ecological niches including the foraging on a variety of ingesta types, only few studies focused on the biomechanical performance of their feeding organs. To lay a keystone for future research in this direction, we investigated the in vivo forces exerted by the molluscan food gathering and processing structure, the radula, for five stylommatophoran species (Gastropoda). The chosen species and individuals have a similar radular morphology and motion, but as they represent different body mass classes, we were enabled to relate the forces to body mass. Radular forces were measured along two axes using force transducers which allowed us to correlate forces with the distinct phases of radular motion. A radular force quotient, AFQ = mean Absolute Force/bodymass0.67, of 4.3 could be determined which can be used further for the prediction of forces generated in Gastropoda. Additionally, some specimens were dissected and the radular musculature mass as well as the radular mass and dimensions were documented. Our results depict the positive correlation between body mass, radular musculature mass, and exerted force. Additionally, it was clearly observed that the radular motion phases, exerting the highest forces during feeding, changed with regard to the ingesta size: all smaller gastropods rather approached the food by a horizontal, sawing-like radular motion leading to the consumption of rather small food particles, whereas larger gastropods rather pulled the ingesta in vertical direction by radula and jaw resulting in the tearing of larger pieces.

Analysis of the seasonal impact of three marine bivalves on seston particles in water column

Suspension-feeding bivalves are the keystone species that affect the abundance and composition of phytoplankton communities. This study compares the food selectivity of oysters Crassostrea gigas (Thunberg, 1973), mussels Mytilus galloprovincialis (Lamarck, 1819), and cockles Katelysia rhytiphora (Lamy, 197) on natural particle assemblages in the laboratory using water collected from Coffin Bay, South Australia, in spring, summer, autumn and winter. The phytoplankton community was dominated by Bacillariophyceae (diatoms), Dinophyceae (dinoflagellates), Synechococcus (cyanobacteria), and picophytoplankton (2–5 μm) from September 2016 to August 2017. Diatoms and picoplankton, including cyanobacteria, were dominant in spring and summer, while dinoflagellates were dominant in autumn and winter. Oysters and mussels selectively fed on large food particles (e.g., diatom, dinoflagellate and large picoplankton > 2 μm) regardless of season, but mussels could access a wider size spectrum of food particles compared to oysters. In contrast, cockles selected for both large and small food particles (e.g., Synechococcus and small picoeukaryotes < 2 μm) and fed more efficiently on small particles than both oysters and mussels. Bacteria were more abundant in warmer seasons, but mussels and cockles selectively reduced bacterial abundance. The abundance of virus-like particles was not affected by season nor by filtration of any molluscan species. This study demonstrates that oysters and mussels utilise similar food sources, whereas cockles consume a large range of food particles. Additionally, these three molluscan species do not necessarily compete for food; hence, stocking multiple filter-feeding species in an ecosystem could exploit a wider spectrum of food particle size and increase system productivity.

Benthic responses to an Antarctic regime shift: food particle size and recruitment biology.

Polar ecosystems are bellwether indicators of climate change and offer insights into ecological resilience. In this study, we describe contrasting responses to an apparent regime shift of two very different benthic communities in McMurdo Sound, Antarctica. We compared species‐specific patterns of benthic invertebrate abundance and size between the west (low productivity) and east (higher productivity) sides of McMurdo Sound across multiple decades (1960s–2010) to depths of 60 m. We present possible factors associated with the observed changes. A massive and unprecedented shift in sponge recruitment and growth on artificial substrata observed between the 1980s and 2010 contrasts with lack of dramatic sponge settlement and growth on natural substrata, emphasizing poorly understood sponge recruitment biology. We present observations of changes in populations of sponges, bryozoans, bivalves, and deposit‐feeding invertebrates in the natural communities on both sides of the sound. Scientific data for Antarctic benthic ecosystems are scant, but we gather multiple lines of evidence to examine possible processes in regional‐scale oceanography during the eight years in which the sea ice did not clear out of the southern portion of McMurdo Sound. We suggest that large icebergs blocked currents and advected plankton, allowed thicker multi‐year ice, and reduced light to the benthos. This, in addition to a possible increase in iron released from rapidly melting glaciers, fundamentally shifted the quantity and quality of primary production in McMurdo Sound. A hypothesized shift from large to small food particles is consistent with increased recruitment and growth of sponges on artificial substrata, filter‐feeding polychaetes, and some bryozoans, as well as reduced populations of bivalves and crinoids that favor large particles, and echinoderms Sterechinus neumayeri and Odontaster validus that predominantly feed on benthic diatoms and large phytoplankton mats that drape the seafloor after spring blooms. This response of different guilds of filter feeders to a hypothesized shift from large to small phytoplankton points to the enormous need for and potential value of holistic monitoring programs, particularly in pristine ecosystems, that could yield both fundamental ecological insights and knowledge that can be applied to critical conservation concerns as climate change continues.

Regulatory Immune Mechanisms in Tolerance to Food Allergy.

Oral tolerance can develop after frequent exposure to food allergens. Upon ingestion, food is digested into small protein fragments in the gastrointestinal tract. Small food particles are later absorbed into the human body. Interestingly, some of these ingested food proteins can cause allergic immune responses, which can lead to food allergy. So far it has not been completely elucidated how these proteins become immunogenic and cause food allergies. In contrast, oral tolerance helps to prevent the pathologic reactions against different types of food antigens from animal or plant origin. Tolerance to food is mainly acquired by dendritic cells, epithelial cells in the gut, and the gut microbiome. A subset of CD103+ DCs is capable of inducing T regulatory cells (Treg cells) that express anti-inflammatory cytokines. Anergic T cells also contribute to oral tolerance, by reducing the number of effector cells. Similar to Treg cells, B regulatory cells (Breg cells) suppress effector T cells and contribute to the immune tolerance to food allergens. Furthermore, the human microbiome is an essential mediator in the induction of oral tolerance or food allergy. In this review, we outline the current understanding of regulatory immune mechanisms in oral tolerance. The biological changes reflecting early consequences of immune stimulation with food allergens should provide useful information for the development of novel therapeutic treatments.

Gastric fistula secondary to drainage tube penetration: A report of a rare case.

Cases of gastric fistula secondary to drainage tube penetration have rarely been reported. The current study presents a case of gastric penetration caused by misplacement of a drainage tube after a splenectomy. The patient was admitted to the Department of Hepatobiliary Surgery, (Shaoxing People's Hospital, Shaoxing Hospital of Zhejiang University, Shaoxing, Zhejiang, China) for blunt abdominal trauma due to injuries sustained in an automobile accident. A ruptured spleen was found and successfully removed surgically. On post-operative day 7, the patient complained of slight discomfort and tenderness in the left upper quadrant of the abdomen. In addition, 500 ml of bile-colored fluid with small food particles was noted in the drainage tube. Barium X-ray revealed a gastric fistula in the upper gastrointestinal tract. Gastroscopy indicated infiltration of the drainage tube into the gastric cavity. No significant peritoneal effusion was observed, as revealed by abdominal ultrasound examination. These results confirmed the diagnosis of a gastric fistula secondary to perforation by the drainage tube. Following conservative treatment with antibiotics and total parenteral nutrition, the general condition of the patient improved significantly. The drainage tube was withdrawn progressively, as the amount of fluid being discharged was decreasing. Gastroenterography confirmed perforation closure and the tube was finally removed on post-operative day 44.

Planktonic rotifer feeding in hypertrophic conditions

We studied the role of rotifers as grazers in hypertrophic waters, dominated by poorly edible filamentous and colonial cyanobacteria. Population growth of Anuraeopsis fissa and Brachionus angularis, from hypertrophic lake Albufera in Valencia, was followed for 15 days in three treatments of different food size fractions: (a) 0–15 µm (lake water filtered through 15 µm nytal sieve), (b) 0–3 µm (15 µm lake water filtrate filtered through 3 µm nuclepore filter), and (c) 3–15 µm (re‐suspension, in absolute filtered lake water, of the seston collected on the 3 µm filter, after passing lake water previously filtered through 15 µm). None of the species grew when fed the food size fraction of 3–15 µm that contained a large proportion of filamentous and colonial cyanobacteria. A. fissa showed highest growth parameters when fed the &lt;3 µm food size fraction, which was mainly composed of bacterioplankton, but much reduced growth on the whole &lt;15 µm seston fraction. On the other hand, B. angularis showed highest growth on the whole &lt;15 µm seston fraction and a moderate growth when fed only on the &lt;3 µm seston fraction. Clearance, ingestion, and assimilation rates were measured with 3H‐thymidine plus 3H‐leucine‐labeled lake bacteria community, suspended in the 15 and 3 µm lake water filtrates. B. angularis had higher rates than A. fissa, and both had higher rates when suspended in the &lt;3 µm seston fraction. Our results confirm that bacteria are the dominant food source for both species in this hypertrophic lake, but clear niche differences separate them. A. fissa is more dependent on smaller food particles and is more sensitive to dense blooms of colonial and filamentous cyanobacteria than B. angularis. The distinct feeding abilities of these species shape their differential distributions in space and time.

Particle retention in suspension-feeding fish after removal of filtration structures

The suspension-feeding cichlids Oreochromis aureus (blue tilapia) and Oreochromis esculentus (ngege tilapia) are able to selectively retain small food particles. The gill rakers and microbranchiospines of these species have been assumed to function as filters. However, surgical removal of these oral structures, which also removed associated mucus, did not significantly affect the total number of 11–200μm particles ingested by the fish. This result supports the hypothesis that the branchial arch surfaces themselves play an important role in crossflow filtration. Both species selectively retained microspheres greater than 50μm with gill rakers and microbranchiospines intact as well as removed, demonstrating that neither these structures nor mucus are necessary for size selectivity to occur during biological crossflow filtration. After removal of the gill rakers and microbranchiospines, O. esculentus retained significantly more microspheres 51–70μm in diameter and fewer 91–130μm microspheres compared to retention with intact structures, but the particle size selectivity of O. aureus was not affected significantly. These results support conclusions from previous computational fluid dynamics simulations indicating that particle size can have marked effects on particle trajectory and retention inside the fish oropharyngeal cavity during crossflow filtration. The substantial inter-individual variability in particle retention by suspension-feeding fish is an unexplored area of research with the potential to increase our understanding of the factors influencing particle retention during biological filtration.

Relationship Between Chewing Rate and Masticatory Performance

The influence of mandibular movement timing on food breakdown remains unclear. The authors, therefore, sought to relate chewing rate with masticatory performance. Chewing rate, defined as the number of masticatory cycles habitually achieved per minute, was measured in 55 healthy dentulous subjects (age, 22.2±5.0 years). Subjects were grouped according to obtained values (cycles/minute): slower: <70; middle: 70-90; and faster: >90. Masticatory performance was determined through the sieve method, and the estimated comminuted median particle size (X50). Data was analyzed using the one-way ANOVA and chi-square tests (α=.05). Subjects with slower chewing rates showed higher (p<.05) masticatory performance (X50 = 3.05±0.77 mm). X50 was associated with chewing rate when subjects were categorized as better or poorer performers (chi-square=11.25, p<.005). Thus, chewing rate was related to masticatory performance, with smaller food particles being achieved with a slower chewing rate.

Paleoecology of suspension-feeding echinoderm assemblages from the Upper Ordovician (Katian, Shermanian) Walcott-Rust Quarry of New York

The Walcott-Rust Quarry echinoderm fauna lived at the base of a carbonate ramp in moderately deep water (Benthic Assemblage 5 of Boucot and others) below wave base for all or most storms but within the photic zone. The inhabitants of the soft substrate were buried rapidly by distal carbonate turbidity currents or mudflows. Because of the episodic sedimentation, the organisms were opportunistic. The suspension-feeding echinoderms include nine crinoids, a rhombiferan, and a paracrinoid. They occur with a variety of filter-feeding bryozoan colonies, a few brachiopods, and numerous trilobites. Most suspension-feeding echinoderms were attached by small holdfasts to hard shelly substrates. Some of these substrates lay on the seafloor, whereas others may have been elevated when the larvae settled. Other types of holdfasts are distal stems that are tightly and permanently coiled around crinoid stems, open distal stem coils that lay on the substrate or were wrapped around soft objects, and recumbent stems running along the seafloor. The echinoderms occupied levels from the seafloor to almost a meter above it, whereas the bryozoans and brachiopods ranged from the seabed to a maximum height of about 10 cm. The sizes of the echinoderm food grooves and comparisons with their modern analogues along with filtration theory indicate that they ate food particles that were mostly larger than those taken by bryozoans. In general, the different taxa of suspension-feeding echinoderms living at the same elevation above the seafloor collected food particles of different maximum sizes and different mean sizes; however, they overlapped greatly with respect to smaller food items. The various crinoid species were able to feed at different ranges of ambient current velocities, which also tended to separate them ecologically. Crinoids having narrow food grooves were restricted to feeding on small food particles but they caught food items over a wide range of current velocities; the converse is also true, which suggests an evolutionary or behavioral tradeoff. As in most Ordovician crinoid communities, predation was comparatively low. Regenerated arms in crinoids reflect predation on about 1.8% of the individuals in the fauna and the most likely fossilized culprits are trilobites and straight nautiloids. Competition for space and attachment sites within and between species of the Walcott-Rust Quarry crinoid and rhombiferan assemblages does not seem to have been significant in regulating their ecological structure. Comparison with shallow-water crinoid assemblages of roughly the same age demonstrates that the Walcott-Rust Quarry faunas were less diverse and less complex. This could be caused by one or more of the following conditions that affected the Walcott-Rust fauna: lower average current velocities, the episodic sedimentological disturbances, higher suspended sediment content in the water, and softer substrates.

Effects of leaf litter and its fungal colonization on the diet of Limnomysis benedeni (Crustacea: Mysida)

The strong invasive freshwater mysid Limnomysis benedeni, a detritivorous–herbivorous feeder, has a preference for small food particles, but also feeds on leaf litter. Here, we tested whether leaf litter consumption by L. benedeni depends on the tree species and leaf conditioning (two types of physical and biological leaf conditioning). At the physical leaf conditioning, L. benedeni was fed with shortly leached or extensively leached leaves of five tree species in laboratory food assays. The mysid consumed shortly leached leaves of Copper Beech, Lombardy Poplar, Common Oak, and especially White Willow, and did not feed on shortly leached Black Alder leaves. The consumption of extensively leached leaves by L. benedeni did not depend on the tree species. Overall, 74% of the variation of the leaf consumption by L. benedeni was explained by the significant interaction of the factors carbon content and polyphenol content of the leaves, caused the feeding strategy of L. benedeni. For the biological leaf conditioning, the mysids consumed to a high degree naturally conditioned leaves, followed by leaves colonized by one of three fungi, but oomycete-colonized leaf litter and autoclaved leaves were consumed at similar low levels. Our results indicate that L. benedeni feeds on different types of conditioned leaves to different extents, and therefore may affect leaf litter degradation in many invaded freshwaters.

SURFACTANT DYSFUNCTION IN LUNG CONTUSION WITH AND WITHOUT SUPERIMPOSED GASTRIC ASPIRATION IN A RAT MODEL

This study investigates surfactant dysfunction in rats with lung contusion (LC) induced by blunt chest trauma. Rats at 24 h postcontusion had a decreased percent content of large surfactant aggregates in cell-free bronchoalveolar lavage (BAL) and altered large-aggregate composition with decreased phosphatidylcholine (PC), increased lyso-PC, and increased protein compared with uninjured controls. The surface activity of large aggregates on a pulsating bubble surfactometer was also severely impaired at 24 h postcontusion. Decreases in large surfactant aggregate content and surface activity were improved, but still apparent, at 48 and 72 h postcontusion compared with uninjured control rats and returned to normal by 96 h postcontusion. The functional importance of surfactant abnormalities in LC injury was documented in pilot studies showing that exogenous surfactant replacement at 24 h postcontusion improved inflation/deflation lung volumes. Additional experiments investigated a clinically relevant combination of LC plus gastric aspiration (combined acid and small gastric food particles) and found reductions in large surfactant aggregates in BAL similar to those for LC. However, rats given LC + combined acid and small gastric food particles versus LC had more severe surfactant dysfunction based on decreases in surface activity and alterations in large aggregate composition. Combined data for all animal groups had strong statistical correlations between surfactant dysfunction (increased minimum surface tension, decreased large aggregates in BAL, decreased aggregate PC, and increased aggregate lyso-PC) and the severity of inflammatory lung injury (increased total protein, albumin, protein/phospholipid ratio, neutrophils, and erythrocytes in BAL plus increased whole lung myeloperoxidase activity). These results show that surfactant dysfunction is important in the pathophysiology of LC with or without concurrent gastric aspiration and provides a rationale for surfactant replacement therapy in these prevalent clinical conditions.

Systematics and paleoecology ofHaptocrinus buttsi, a new species of disparid crinoid from the Upper Ordovician Hatter Limestone of central Pennsylvania

Three crinoids are known from the Upper Ordovician Hatter Limestone at Union Furnace in central Pennsylvania, i.e.,Haptocrinus buttsin. sp., an unknown crinoid with a lichenocrinid holdfast, and an indeterminate columnal that probably belongs to a crinoid. Two crowns enableH. buttsin. sp. to be reconstructed. The animal lived about 70 cm above the seafloor and was attached to a strophomenid brachiopod with a lichenocrinid holdfast. Its endotomous arms formed an efficient filtration net that covered much of the water within its planar filtration fan. The application of filtration theory indicates thatH. buttsin. sp. could begin to feed at a comparatively low ambient current velocity and balance its energy budget. Like many other ramulate disparids,H. buttsin. sp. mainly collected moderately small food particles. As a member of the Tornatilicrinidae,H. buttsin. sp. is a relatively primitive disparid. Another crinoid taxon bears a longer and thinner stem and a different type of lichenocrinid holdfast cemented to the same strophomenid shell. A third species, most likely a crinoid, is represented by a single columnal. The fauna lived in a quiet water lagoonal area, which is an unusual habitat for Paleozoic crinoids.

Feeding of tropical cladocerans (Moina micrura, Diaphanosoma excisum) and rotifer (Brachionus calyciflorus) on natural phytoplankton: effect of phytoplankton size-structure

The proliferation of large phytoplankton in tropical shallow freshwater ecosystems may be attributable to inefficient feeding by the dominant zooplankton (small cladocerans and rotifers) on large particles, but more information on the feeding behavior of tropical organisms is required to explore this hypothesis. In this study, food size selectivity and functional feeding responses of three major tropical freshwater zooplankton species (Moina micrura, Diaphanosoma excisum and Brachionus calyciflorus) were studied to test their ability to control phytoplankton. Eleven grazing experiments were performed, using natural phytoplankton assemblages as a food source. Moina micrura fed efficiently on a wide range of sizes of phytoplankton particles, from unicellular picoplankton Chlorella sp. (2–4 μm equivalent spherical diameter, ESD) to large Coelastrum reticulatum coenobia (20–40 μm ESD), but the selectivity depended on the nature and size distribution of the phytoplankton. Diaphanosoma excisum ingested only very small particles (Monoraphidium, Chlorella). Brachionus calyciflorus fed on a wide size range but showed a clear preference for the largest algae (Cyclotella sp, Scenedesmus opoliensis). These three species increased their ingestion rate linearly with the food concentration and the saturation point was reached for M. micrura within the range of experimental conditions. The results suggest a strong food partitioning between these three species and showed that B. calyciflorus and M. micrura were better able to exploit and control algal blooms than D. excisum, which was a more selective feeder controlled by the availability of small food particles.

Leaf Degradation, Macroinvertebrate Shredders &amp; Energy Flow in Streams: A Laboratory-Based Exercise Examining Ecosystem Processes

The degradation of plant material that falls into streams plays a significant role in ecosystem function (Giller & Malmqvist, 1998). For example, Fisher and Likens (1973) estimated that up to 99% of the total energy input in a deciduous woodland stream came from the terrestrial surroundings and that approximately 29% of this input was provided by leaf material alone. Thus, examining factors that influence the degradation of leaf material in streams is critical for understanding ecosystems processes in nature (e.g., Cummins, 1973; Webster & Benfield, 1986; Graca, 1993; Wallace & Webster, 1996). This exercise can be used to provide both high school and college students the opportunity to examine the role that microorganisms and macroinvertebrates play in determining the pattern of leaf degradation in streams. When leaves enter streams, they undergo a predictable sequence of changes that result in degradation. These changes can be categorized into three phases (following Webster & Benfield, 1986): 1. Leaching, in which dissolved organic matter and soluble inorganic constituents leach out from the leaves. 2. Microbial colonization, in which fungi and bacteria colonize the leaves and degrade them by penetrating the surface and digesting cellulose, pectin, chitin, etc. 3. Fragmentation, in which the combined effects of invertebrate shredders (e.g., isopods, amphipods) and mechanical disturbance, caused by the action of the stream, result in the conversion of the large leaf material (coarse particulate organic matter, CPOM) into small particles (fine particulate organic matter, FPOM). Throughout this sequence, energy that was contained in the leaves becomes available to organisms living in the stream. For example, energy is obtained by the microorganisms feeding on the leaves, the shredders feeding on both the leaves and the microorganisms, the filter feeders capturing small food particles that flow downstream, and the predators consuming both the shredders and the collectors. The amount of energy released from leaf material and the retention of that energy in the local area are dependent on the relationship between the microorganisms that colonize the leaves and the macroinvertebrate shredders that feed on the leaves. The microorganisms induce both physical and chemical changes in the leaves that increase their palatability to shredders (Webster & Benfield, 1986; Graca, 1993). As a consequence, shredders exhibit preferences for these conditioned leaves, and individuals that feed on conditioned leaves have higher survivorship, increased fecundity, and faster growth rates than individuals that feed on unconditioned leaves (Graca, 1993). Thus, more of the energy is retained in the local system. In addition, increased feeding activity of shredders will increase the production of FPOM, which provides energy for both the filtering and gathering collectors that live downstream. We present a laboratory-based exercise that demonstrates the relationship between leaf conditioning and the feeding activity of invertebrate shredders. Specifically, students test the hypothesis that leaf conditioning influences the amount of leaf material consumed by invertebrate shredders (stream isopods or amphipods). This exercise provides repeatable results, does not require technical equipment, and can be completed in the laboratory relatively cheaply. In addition, both qualitative and quantitative approaches can be used to describe the data, which allows the exercise to be modified based on the statistical expertise of the students. By the end of the experiment, students will have gained an understanding of the critical role that leaf conditioning plays in determining the pattern of leaf degradation in stream ecosystems. To date, we have used this experiment to demonstrate ecological concepts with a hands-on approach. When the experiment has been completed, we introduce a more inquiry-based approach in which students are given the opportunity to both generate new hypotheses and design experiments to test hypotheses that we provide (see Discussion for specific examples). …

The application of filtration theory to food gathering in Ordovician crinoids

Food gathering of some adult Upper Ordovician crinoids was modeled by means of filtration theory. The arm-branching patterns of the 13 species examined range from nonpinnulate isotomous arms to uniserial and biserial arms with numerous pinnules. Most taxa are roughly equivalent with respect to ambient current velocities and the nutrient contents needed from seawater. Two species with extensively branched arms have markedly higher nutritional requirements at any one ambient current velocity. The results are somewhat correlated with environment in the form of differential current velocities, water flow patterns, and food abundance and composition. The data are generally compatible with filtration theory and the environmental distributions of many Ordovician and other Paleozoic crinoids, and they reveal that Upper Ordovician crinoids had at least partially developed the ecological patterns seen in later Paleozoic crinoids. Various morphological, physiological, and behavioral changes can be employed by crinoids to alter their nutritional balance. The size distributions of food particles that are caught by the crinoids are modeled. These food particle distributions for the Ordovician fossils resemble those of modern crinoids. Relative to the population of food items, the distributions of particles that are trapped are shifted towards larger items because the crinoid filtration nets are more efficient at catching larger particles. Crinoids with relatively open filtration nets and large food-catching tube feet are generalized and feed on a wide range of food particles of a relatively large mean size. The more specialized taxa with extensively branched arms bearing small and closely packed food-catching tube feet are restricted to a more narrow range of smaller food particles.

Feeding Behavior Reveals the Adaptive Nature of Plasticity in Barnacle Feeding Limbs

Barnacle feeding limbs are extremely plastic in response to spatial and temporal differences in wave exposure: individuals have long, thin feeding limbs in habitats with little wave action, and short, thick feeding limbs in wave-exposed habitats. This difference in feeding limb morphology is assumed to be adaptive. Individuals with shorter limbs may have the ability to feed in breaking waves because their limbs are better suited to withstanding drag forces than are those of individuals with longer feeding limbs. I tested this hypothesis by observing the feeding behavior of two populations of Balanus glandula (one from a protected shore and one from a wave-exposed shore) subjected to five different water velocities. Differences between populations in the ability to feed with the cirral net fully extended were highly significant. The wave-exposed population fed with the cirral net fully extended at all velocities tested (up to 49 cm/s), whereas full cirral extension ceased between 7.25 and 21.4 cm/s in all individuals from the protected-shore population. Clearly, barnacles possessing long, thin feeding limbs experience a strong disadvantage when feeding in faster flowing water, confirming earlier hypotheses that differences in feeding limb length between protected and wave-exposed shores are adaptive. Acorn barnacles are suspension feeders that extend three pairs of modified thoracic limbs (cirri) into ambient flow to capture plankton and smaller food particles (1). The feeding apparatus of many barnacle species is remarkably plastic with respect to wave exposure (2‐4). In the northeastern Pacific, the common intertidal barnacle Balanus glandula Darwin, 1854, shows the greatest degree of plasticity in feeding leg form. Individuals from wave-protected shores possess feeding limbs nearly twice as long and 25% thinner at the base than conspecifics living on wave-exposed shores (3), and experiments show that this species can alter the length and width of its feeding limbs to suit local flow conditions in one or two molts (2). Because of the functional importance of barnacle feeding limbs, their phenotypic plasticity is assumed to be adaptive—shorter, stouter legs may allow barnacles to feed in high-velocity flow under breaking waves. However, the consequences of possessing differently shaped feeding limbs have not been investigated, and thus the adaptive nature (5) of differences in feeding limb length remains speculative.

Selective particle feeding by the Chilean oyster, Ostrea chilensis; implications for nursery culture and broodstock conditioning

Hatchery broodstock conditioning and nursery culture of the Chilean flat oyster Ostrea chilensis have been hampered by the poor performance of oysters fed typical microalgal hatchery diets. To determine the feeding capabilities of this species the selective removal and consumption of natural planktonic assemblages and artificial inert particles (polystyrene beads) by juvenile and adult oysters were examined experimentally. The arrangement of the eulaterofrontal cirri of the ctenidia was also examined to infer their potential efficiency of particle selection for feeding. Polystyrene beads of 45 and 15 μm in diameter had high rates of removal from suspensions by both juvenile (45 μm = 70%, 15 μm = 73%) and adult (45 μm = 88%, 15 μm = 87%) oysters. In contrast, beads of 6 μm diameter had lower rates of removal (adults = 68%, juveniles = 53%), while 1 μm beads were not removed at all. Both adult and juvenile oysters feeding upon natural plankton assemblages removed only microphytoplankton (20–75 μm in size) despite the presence of nanophytoplankton (2–20 μm), picophytoplankton (< 2 μm), cyanobacterium Synechoccocus spp. (< 2 μm), and bacterial cells (< 75 μm) in the experimental suspensions. Eulaterofrontal cirri of both juvenile (15.2 μm ± 0.9 SE) and adult oysters (18.9 μm ± 0.3 SE) are the shortest that have been reported for any ostreid species which helps to explain the inability of this species to retain small food particles. The clearance rates for oysters feeding on microphytoplankton only were 1.49 (± 0.05 SE) and 7.1 (± 1.2 SE) l h − 1 g − 1 for juveniles and adults respectively. These values are much higher than previously reported for this species being fed smaller sized cultured microalgae. Our results strongly suggest that the difficulties in the nursery and broodstock hatchery culture of this oyster may be due to inappropriate phytoplankton diets. We recommend the provision of cultured microalgae of 20–75 μm in diameter for improving the performance of hatchery maintained juvenile and adult O. chilensis.