Practice question

Corona crowns rotifer head and derives from modified ciliary wreath consisting of trochus anterior ring and cingulum posterior band surrounding mouth field. Metachronal beating creates water currents drawing nanoplankton bacteria algae toward mouth and provides swimming locomotion rotating animal through water column with spiral motion. Retractable corona allows protection upon disturbance withdrawing into lorica. Ciliation ultrastructure and pattern provide taxonomic characters among loricate and illoricate forms. Respiration occurs across body surface, excretion via paired protonephridia with flame cells, thus corona functions exclusively in trophic and locomotor roles, representing key gnathiferan adaptation enabling filter feeding efficiency in freshwater planktonic habitats worldwide.