Abstract
Suspension feeders (SFs) evolved a high diversity of mechanisms, sometimes with remarkably convergent morphologies, to retain plankton, detritus and man-made particles with particle sizes ranging from less than 1 µm to several centimetres. Based on an extensive literature review, also including the physical and technical principles of solid–liquid separation, we developed a set of 18 ecological and technical parameters to review 35 taxa of suspension-feeding Metazoa covering the diversity of morphological and functional principles. This includes passive SFs, such as gorgonians or crinoids that use the ambient flow to encounter particles, and sponges, bivalves or baleen whales, which actively create a feeding current. Separation media can be flat or funnel-shaped, built externally such as the filter houses in larvaceans, or internally, like the pleated gills in bivalves. Most SFs feed in the intermediate flow region of Reynolds number 1–50 and have cleaning mechanisms that allow for continuous feeding. Comparison of structure–function patterns in SFs to current filtration technologies highlights potential solutions to common technical design challenges, such as mucus nets which increase particle adhesion in ascidians, vanes which reduce pressure losses in whale sharks and changing mesh sizes in the flamingo beak which allow quick adaptation to particle sizes.
Highlights
Suspension feeders (SFs) are a group of organisms with the common ability to separate food particles from suspension for nutrition [1,2], which includes organisms ranging from sponges to birds [3,4]
Most SFs feed in the intermediate flow region of Reynolds number 1–50 and have cleaning mechanisms that allow for continuous feeding
Because suspension-feeding, and especially filter-feeding, is similar to technical definitions of filtration, we propose the description of SFs using 12 technical parameters which are already established in particle separation processes such as particle properties, separation medium, fluid dynamics and cleaning of the separation medium in addition to six ecological parameters from previous biological descriptions
Summary
Suspension feeders (SFs) are a group of organisms with the common ability to separate food particles from suspension for nutrition [1,2], which includes organisms ranging from sponges to birds [3,4]. Suspension-feeding mechanisms (SFMs), which we define as all steps that enable separation of particles from the surrounding water, from the first encounter to the ingestion into the oesophagus, show a high diversity today. This diversity most likely resulted from niche partitioning, i.e. positive selection for the retention of certain particle size ranges from the heterogeneous seston [10,11]. Relevant food sources [17] while bivalves and crustaceans are used as biofilters for water clarification [18,19,20,21] Besides their ecological role, the separation mechanisms by which SFs separate food particles have been of interest for engineers. Based on an extensive literature search, we developed a set of biological and technical parameters to systematically describe and classify SFMs and screened the animal kingdom for different SFMs
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