Filter-feeding demosponges are modular organisms that consist of modules each with one water-exit osculum. Once a mature module has been formed, the weight-specific filtration and respiration rates ...do not change. Sponge modules only grow to a certain size and for a sponge to increase in size, new modules must be formed. However, the growth characteristics of a small single-osculum module sponge are fundamentally different from those of multi-modular sponges, and a theoretically derived volume-specific filtration rate scales as F/V=V-1/3, indicating a decrease with increasing total module volume (V, cm3). Here, we studied filtration rate (F, l h-1), respiration rate (R, ml O2 h-1), volume-specific (F/V) and weight-specific (F/W) filtration rates, and the ratios F/R and F/W along with growth rates of small single-osculum demosponge Halichondria panicea explants of various sizes exposed to various concentrations of algal cells. The following relationships were found: F/V=7.08V-0.24, F=a1W1.05, and R=a2W0.68 where W is the dry weight (mg). The F/R and F/W ratios were constant and essentially independent of W, and other data indicate exponential growth. It is concluded that the experimental data support the theoretical F/V∝V-1/3.
Measured Air Flow Leakage in Facemask Usage Larsen, Poul S; Heebøll, John; Meyer, Knud Erik
International journal of environmental research and public health,
01/2023, Volume:
20, Issue:
3
Journal Article
Peer reviewed
Open access
The importance of wearing a facemask during a pandemic has been widely discussed, and a number of studies have been undertaken to provide evidence of a reduced infectious virus dose because of ...wearing facemasks. Here, one aspect that has received little attention is the fraction of breathing flow that is not filtered because it passes as leak flow between the mask and face. Its reduction would be beneficial in reducing the dose response. The results of the present study include the filter material pressure loss parameters, pressure distributions under masks, and the fraction of breathing flow leaked versus steady breathing flow in the range of 5 to 30 L min
, for two commonly used facemasks mounted on mannequins, in the usual 'casual' way and in a 'tight' way by means of three different fitters placed over the mask to improve the seals. For the 'casual' mount, leaks were high: 83% to 99% for both masks at both exhalation and inhalation flows. For the 'tight' mount with different fitters, the masks showed different lower levels in the range of 18 to 66% of leakage, which, for exhalation, were nearly independent of flow rate, while for inhalation, were decreasing with increasing rates of respiration flows, probably because suction improved the sealing. In practice, masks are worn in a 'casual' mount, which would imply that nearly all contagious viruses found in aerosols small enough to follow air streams would be exhaled to and inhaled from the ambient air.
A large number of suspension-feeding aquatic animals (e.g. bivalves, polychaetes, ascidians, bryozoans, crustaceans, sponges, echinoderms, cnidarians) have specialized in grazing on not only the 2 to ...200 μm phytoplankton but frequently also the 0.5 to 2 μm free-living bacteria, or they have specialized in capturing larger prey, e.g. zooplankton organisms. We review the different particle capture mechanisms in order to illustrate the many solutions to the common problem of obtaining nourishment from a dilute suspension of microscopic food particles. Despite the many differences in morphology and living conditions, particle capture mechanisms may be divided into 2 main types. (1) Filtering or sieving (e.g. through mucus nets, stiff cilia, filter setae), which is found in passive suspension feeders that rely on external currents to bring suspended particles to the filter, and in active suspension feeders that themselves produce a feeding flow by a variety of pump systems. Here the inventiveness of nature does not lie in the capture mechanism but in the type of pump system and filter pore-size. (2) A paddle-like flow manipulating system (e.g. cilia, cirri, tentacles, hair-bearing appendages) that acts to redirect an approaching suspended particle, often along with a surrounding ‘fluid parcel’, to a strategic location for arrest or further transport. Examples include (1) sieving (e.g. by microvilli in sponge choanocytes, mucus nets in polychaetes, acidians, and salps among others), filter setae in crustaceans, ‘ciliary sieving’ by stiff laterofrontal cilia in bryozoans and phoronids; and (2) ‘cirri trapping’ in mussels and other bivalves with eu-laterofrontal cirri, ciliary ‘catch-up’ in bivalve and gastropod veliger larvae, some polychaetes, entroprocts, and cycliophores. These capture mechanisms may involve contact with a particle, and possibly mechanoreception or chemoreception, or may include redirection of particles by the interaction of multiple currents (e.g. in scallops and other bivalves without eu-laterofrontal cirri). Based on the review, we discuss the current physical and biological understanding of the capture process and suggest a number of specific problems related to particle capture, which may be solved in the future using advanced theoretical, computational and experimental techniques.
Copepods can respond to predators by powerful escape jumps that in some surface-dwelling forms may propel the copepod out of the water. We studied the kinematics and energetics of submerged and ...out-of-water jumps of two neustonic pontellid copepods,
and
, and one pelagic calanoid copepod,
(
). We show that jumping out of the water does not happen just by inertia gained during the copepod's acceleration underwater, but also requires the force generated by the thoracic limbs when breaking through the water's surface to overcome surface tension, drag and gravity. The timing of this appears to be necessary for success. At the moment of breaking the water interface, the instantaneous velocity of the two pontellids reached 125 cm s
, while their maximum underwater speed (115 cm s
) was close to that of similarly sized
(106 cm s
). The average specific power produced by the two pontellids during out-of-water jumps (1700-3300 W kg
muscle mass) was close to that during submerged jumps (900-1600 W kg
muscle mass) and, in turn, similar to that produced during submerged jumps of
(1300 W kg
muscle mass). The pontellids may shake off water adhering to their body by repeated strokes of the limbs during flight, which leads to a slight acceleration in the air. Our observations suggest that out-of-water jumps of pontellids are not dependent on any exceptional ability to perform this behavior but have the same energetic cost and are based on the same kinematic patterns and contractive capabilities of muscles as those of copepods swimming submerged.
Calanoid copepods have two swimming gaits, namely cruise swimming that is propelled by the beating of the cephalic feeding appendages and short-lasting jumps that are propelled by the power strokes ...of the four or five pairs of thoracal swimming legs. The latter may be 100 times faster than the former, and the required forces and power production are consequently much larger. Here, we estimated the magnitude and size scaling of swimming speed, leg beat frequency, forces, power requirements, and energetics of these two propulsion modes. We used data from the literature together with new data to estimate forces by two different approaches in 37 species of calanoid copepods: the direct measurement of forces produced by copepods attached to a tensiometer and the indirect estimation of forces from swimming speed or acceleration in combination with experimentally estimated drag coefficients. Depending on the approach, we found that the propulsive forces, both for cruise swimming and escape jumps, scaled with prosome length (L) to a power between 2 and 3. We further found that power requirements scales for both type of swimming as L3. Finally, we found that the cost of transportation (i.e., calories per unit body mass and distance transported) was higher for swimming-by-jumping than for cruise swimming by a factor of 7 for large copepods but only a factor of 3 for small ones. This may explain why only small cyclopoid copepods can afford this hydrodynamically stealthy transportation mode as their routine, while large copepods are cruise swimmers.
Demosponges are modular filter-feeding organisms that are made up of aquiferous units or modules with one osculum per module. Such modules may grow to reach a maximal size. Various demosponge species ...show a high degree of morphological complexity, which makes it difficult to classify and scale them regarding filtration rate versus sponge size. In this regard, we distinguish between: (i) small single-osculum sponges consisting of one aquiferous module, which includes very small explants and larger explants; (ii) multi-oscula sponges consisting of many modules, each with a separate osculum leading to the ambient; and (iii) large single-osculum sponges composed of many aquiferous modules, each with an exhalant opening (true osculum) leading into a common large spongocoel (atrium), which opens to the ambient via a static pseudo-osculum. We found the theoretical scaling relation between the filtration rate (F) versus volume (V) for (i) a single-osculum demosponge to be F = a3V2/3, and hence the volume-specific filtration rate to scale as F/V ≈ V−1/3. This relation is partly supported by experimental data for explants of Halichondria panicea, showing F/V = 2.66V−0.41. However, for multi-oscula sponges, many of their modules may have reached their maximal size and hence their maximal filtration rate, which would imply the scaling F/V ≈ constant. A similar scaling would be expected for large pseudo-osculum sponges, provided their volume was taken to be the structural tissue volume that holds the pumping units, and not the total volume that includes the large atrium volume of water. This may explain the hitherto confusing picture that has emerged from the power-law correlation (F/V = aVb) of many various types of demosponges that show a range of negative b-exponents. The observed sharp decline in the volume-specific filtration rate of demosponges from their very small to larger sizes is discussed.
Sponges are one of the earliest-evolved and simplest groups of animals, but they share basic characteristics with more advanced and later-evolved filter-feeding invertebrates, such as mussels. ...Sponges are abundant in many coastal regions where they filter large amounts of water for food particles and thus play an important ecological role. Therefore, a better understanding of the bioenergetics and growth of sponges compared to other filter-feeders is important. While the filtration (pumping) rates of many sponge species have been measured as a function of their size, little is known about their rate of growth. Here, we use a bioenergetic growth model for demosponges, based on the energy budget and observations of filtration (F) and respiration rates (R). Because F versus dry weight (W) can be expressed as F = a1Wb1 and the maintenance respiratory rate can be expressed as Rm = a2Wb2, we show that if b1~ b2 the growth rate can be expressed as: G = aWb1, and, consequently, the weight-specific growth rate is µ = G/W = aWb1−1 = aWb where the constant a depends on ambient sponge-available food particles (free-living bacteria and phytoplankton with diameter < ostia diameter). Because the exponent b1 is close to 1, then b ~ 0, which implies µ = a and thus exponential growth as confirmed in field growth studies. Exponential growth in sponges and in at least some bryozoans is probably unique among filter-feeding invertebrates. Finally, we show that the F/R-ratio and the derived oxygen extraction efficiency in these sponges are similar to other filter-feeding invertebrates, thus reflecting a comparable adaptation to feeding on a thin suspension of bacteria and phytoplankton.
Hydrodynamics of the leucon sponge pump Asadzadeh, Seyed Saeed; Larsen, Poul S; Riisgård, Hans Ulrik ...
Journal of the Royal Society interface,
01/2019, Volume:
16, Issue:
150
Journal Article
Peer reviewed
Open access
Leuconoid sponges are filter-feeders with a complex system of branching inhalant and exhalant canals leading to and from the close-packed choanocyte chambers. Each of these choanocyte chambers holds ...many choanocytes that act as pumping units delivering the relatively high pressure rise needed to overcome the system pressure losses in canals and constrictions. Here, we test the hypothesis that, in order to deliver the high pressures observed, each choanocyte operates as a leaky, positive displacement-type pump owing to the interaction between its beating flagellar vane and the collar, open at the base for inflow but sealed above. The leaking backflow is caused by small gaps between the vaned flagellum and the collar. The choanocyte pumps act in parallel, each delivering the same high pressure, because low-pressure and high-pressure zones in the choanocyte chamber are separated by a seal (secondary reticulum). A simple analytical model is derived for the pump characteristic, and by imposing an estimated system characteristic we obtain the back-pressure characteristic that shows good agreement with available experimental data. Computational fluid dynamics is used to verify a simple model for the dependence of leak flow through gaps in a conceptual collar-vane-flagellum system and then applied to models of a choanocyte tailored to the parameters of the freshwater demosponge Spongilla lacustris to study its flows in detail. It is found that both the impermeable glycocalyx mesh covering the upper part of the collar and the secondary reticulum are indispensable features for the choanocyte pump to deliver the observed high pressures. Finally, the mechanical pump power expended by the beating flagellum is compared with the useful (reversible) pumping power received by the water flow to arrive at a typical mechanical pump efficiency of about 70%.
Filter-feeding invertebrates are found in almost all of the animal classes that are represented in the sea, where they are the necessary links between suspended food particles (phytoplankton and ...free-living bacteria) and the higher trophic levels in the food chains. Their common challenge is to grow on the dilute concentrations of food particles. In this review, we consider examples of sponges, jellyfish, bryozoans, polychaetes, copepods, bivalves, and ascideans. We examine their growth with the aid of a simple bioenergetic growth model for size-specific growth, i.e., in terms of dry weight (W), µ = (1/W) dW/dt = aWb, which is based on the power functions for rates of filtration (F ≈ Wb1) and respiration (R ≈ Wb2). Our theory is that the exponents have (during the evolution) become near equal (b1 ≈ b2), depending on the species, the stage of ontogeny, and their adaptation to the living site. Much of the compiled data support this theory and show that the size-specific rate of growth (excluding spawning and the terminal phase) may be constant (b = 0) or decreasing with size (b < 0). This corresponds to the growth rate that is exponential or a power function of time; however, with no general trend to follow a suggested 3/4 law of growth. Many features are common to filter-feeding invertebrates, but modularity applies only to bryozoans and sponges, implying exponential growth, which is probably a rather unique feature among the herein examined filter feeders, although the growth may be near exponential in the early ontogenetic stages of mussels, for example.
The authors present simulations showing flow lines and vortices crossing the sponge skeleton from the upstream to the downstream side of the tube in crossflow and conclude that the skeletal motifs ...give rise to internal recirculation patterns favouring the sponge's feeding and sexual reproduction. Unlike other studies that focus on the mechanical properties of the skeleton6, Falcucci et al.1 aimed to study the "fluid dynamic performance of the deep-sea glass sponge E. aspergillum in its actual living conditions, reproduced via in silico experiments." The flow pattern in tube-like sponges is driven by the choanocyte pumps and is unidirectional, so that water is drawn from around the tube, through tiny canals in the body wall, and out through the upper common opening, the osculum (Fig. 2, Supplementary Video 1). Because of the low permeability of the tissue structure, it is highly unlikely that an imposed crossflow will change this pattern to that suggested by the simulations of Falcucci et al.1, with water flowing across the entire tube rather than exiting through the osculum. ...any future modelling of the interaction of sponges with flow must consider the whole animal and not only its bare skeleton.
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