One of the mysteries of the English language finally explained.
(in a rotifer) a ring of cilia that is used in feeding and (in most kinds) swimming.
- ‘The corona is retractile, with two trochal discs which are highly reduced, in Philodinavus to a small, bilobated, ciliated area; in Abrotrocha to a pair of lobes on either side of the prominent rostrum.’
- ‘There are many variations to the corona pattern and in bdelloids it is composed of two ciliary rings: the anterior named trochus (divided into right and left each known as trochal disks) and the posterior called cingulum.’
- ‘In living animals, such as in Macrotrachela quadricornifera, the trochal discs with their beating cilia resemble rotating wheels, which is why these animals are called ‘rotifers’ or ‘wheel animalcules’.’
Mid 19th century: trochal from Greek trokhos ‘wheel’ + -al.
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