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#choanoflagellates

3 public questions tagged with this topic.

Animal Classification

Choanocytes of sponges are homologous to

Choanocytes are distinctive flagellated collar cells lining internal chambers and spongocoel each bearing single flagellum encircled by actin-rich microvilli forming collar filtering bacteria from water current generated by beating phagocytosing particles. Morphologically virtually identical to free-living unicellular and colonial Choanoflagellata possessing same design. Similarity supports hypothesis Metazoa evolved from choanoflagellate-like ancestor via colonial aggregation sharing adhesion and signaling genes. Such homology considered cornerstone evidence for animal monophyly placing spong

Ref: Campbell Biology, 12th ed., Chapter 32: Choanocytes choanoflagellate homology; NCBI Evolution

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Animal Classification

Choanocytes of sponges resemble

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

Ref: Brusca & Brusca Invertebrates 3rd ed. Porifera Histology; Campbell Biology 12th ed. Chapter 33 Sponge Choanocytes

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Animal Classification

Closest living relatives of animals are

Choanoflagellates unicellular and colonial flagellated protists occupy sister lineage to Metazoa within opisthokont supergroup, diverging most recently compared to green algae belonging to Archaeplastida, amoebae within Amoebozoa or ciliates within SAR. Ultrastructural and genomic evidence includes homologous collar of microvilli surrounding flagellum, receptor tyrosine kinases, cadherin repeats, Myc oncogenes and mitochondrial gene synteny. Genera Monosiga, Salpingoeca and colonial Proterospongia demonstrate rosette formation resembling sponge morula. Therefore phylogeny positions choanoflage

Ref: Campbell Biology 12th ed. Chapter 28 Protists Close to Animals; Nature Scientific Reports Choanoflagellates sister to Metazoa

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