Practice question

Sponge choanocytes flagellated collar cells lining radial canals and spongocoel generate water current and filter bacteria, displaying striking morphological homology to free-living choanoflagellates. Each possesses single apical flagellum surrounded by actin-based microvilli collar forming funnel trapping prey against mucoid glycocalyx, basal body with microtubular root, food vacuole formation and similar transcriptional regulators including ETS, Brachyury homologs. Immunocytochemistry reveals hedgehog receptors conserved. This parallel supports hypothesis that metazoan feeding cells evolved by integration of choanoflagellate-like ancestor during early poriferan evolution illustrating direct link between protist and animal bauplan.