Catching the particles: role of ciliary bands in filter-feeding marine invertebrates

Claus Nielsen (1938–2024) was an outstanding zoologist and world-wide recognised as an expert of especially ectoprocts (bryozoans) and entoprocts. Here, we describe the ciliary mechanisms of catching particles in these two groups based on our studies made together with Claus Nielsen. Our interdisciplinary collaboration was based on studies of anatomical structures, microscope-video observations and fluid-mechanical calculations. We first give an outline of downstream particle catch-up retention in entoprocts, and next, we describe particle upstream retention in bryozoans (ectoprocts).