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Mucous-mesh grazers (pelagic tunicates and thecosome pteropods) are common in oceanic waters and efficiently capture, consume and repackage particles many orders of magnitude smaller than themselves. They feed using an adhesive mucous mesh to capture prey particles from ambient seawater. Historically, their grazing process has been characterized as non-selective, depending only on the size of the prey particle and the pore dimensions of the mesh. The purpose of this review is to reverse this assumption by reviewing recent evidence that shows mucous-mesh feeding can be selective. We focus on large planktonic microphages as a model of selective mucus feeding because of their important roles in the ocean food web: as bacterivores, prey for higher trophic levels, and exporters of carbon via mucous aggregates, faecal pellets and jelly-falls.We identify important functional variations in the filter mechanics and hydrodynamics of different taxa.We review evidence that shows this feeding strategy depends not only on the particle size and dimensions of the mesh pores, but also on particle shape and surface properties, filter mechanics, hydrodynamics and grazer behaviour. As many of these organisms remain critically understudied, we conclude by suggesting priorities for future research. [ABSTRACT FROM AUTHOR]

The article discusses the study of pyrosomes, a type of pelagic tunicate found in the northeast part of the Pacific Ocean. It includes information on the environmental factors that have triggered pyrosomes' growth and the findings of previous studies into the distribution and physiology of pyrosomes. It also mentions the presence of densities of tropical pyrosomes in northeast Pacific region.

Saips are barrel-shaped marine invertebrates that swim by jet propulsion. Morphological variations among species and life-cycle stages are accompanied by differences in swimming mode. The goal of this investigation was to compare propulsive jet wakes and swimming performance variables among morphologically distinct salp species (Pegea con foederata, Weelia (Salpa) cylindrica, Cyclosalpa sp.) and relate swimming patterns to ecological function. Using a combination of in situ dye visualization and particle image velocimetry (PIV) measurements, we describe properties of the jet wake and swimming performance variables including thrust, drag and propulsive efficiency. Locomotion by all species investigated was achieved via vortex ring propulsion. The slow-swimming P. confoederata produced the highest weight-specific thrust (T=53N kg-1) and swam with the highest whole- cycle propulsive efficiency (ηwc=55%). The fast-swimming W. cylindrica had the most streamlined body shape but produced an intermediate weight-specific thrust (T=30 N kg -1) and swam with an intermediate whole-cycle propulsive efficiency (ηwc=52%). Weak swimming performance variables in the slow-swimming C. affinis, including the lowest weight-specific thrust (T=25Nkg1) and lowest whole-cycle propulsive efficiency (i=47%), may be compensated by low energetic requirements. Swimming performance variables are considered in the context of ecological roles and evolutionary relationships. [ABSTRACT FROM AUTHOR]

Salps are common in oceanic waters and have higher per-individual filtration rates than any other zooplankton filter feeder. Although salps are centimeters in length, feeding via particle capture occurs on a fine, mucous mesh (fiber diameter d ∼0.1 μm) at low velocity (U = 1.6 ± 0.6 cm∙s-1, mean ± SD) and is thus a low Reynoldsnumber (Re ∼ 10-3) process. In contrast to the current view that. particle encounter is dictated by simple sieving of particles larger than the mesh spacing, a low-Re mathematical model of encounter rates by the salp feeding apparatus for realistic oceanic particle-size distributions shows that submicron particles, due to their higher abundances, are encountered at higher rates (particles per time) than larger particles. Data from feeding experiments with 0.5-, 1-, and 3-pm diameter polystyrene spheres corroborate these findings. Although particles larger than 1 pm (e.g., flagellates, small diatoms) represent a larger carbon pool, smaller particles in the 0.1to 1-pm range (e.g., bacteria, Prochiorococcus) may be more quickly digestible because they present more surface area, and we find that particles smaller than the mesh size (1.4 pm) can fully satisfy salp energetic needs. Furthermore, by packaging submicrometer particles into rapidly sinking fecal pellets, pelagic tunicates can substantially change particle-size spectra and increase downward fluxes in the ocean. [ABSTRACT FROM AUTHOR]

Salps have higher filtration rates than most other holoplankton, and are capable of packaging and exporting primary production from surface waters. A method of kinematic analysis was employed to accurately measure salp feeding rates. The data were then used to explain how diverse body morphologies and swimming motions among species and lifecycle stages influence salp feeding performance. We selected five species, representing a range of morphologies and swimming styles, and used digitized outlines from video frames to measure body-shape change during a pulse cycle. Time-varying body volume was then calculated from the digitized salp outlines to estimate the amount of fluid passing through the filtering mesh. This non-invasive method produced higher feeding rates than other methods and revealed that body volume, pulse frequency and degree of contraction are important factors for determining volume filtered. Each species possessed a unique combination of these three characteristics that resulted in comparable filtration (range: 0.44–15.33 ml s−1) and normalized filtration rates (range: 0.21–1.27 s−1) across species. The convergence of different species with diverse morphologies on similar normalized filtration suggests a tendency towards a flow optimum. [ABSTRACT FROM AUTHOR]