The endostyle is an organ which assists lower-chordates (urochordates and cephalochordates, as well as the larvae of lampreys) in filter-feeding. This pharyngeal organ coats itself with mucus using cilia. The mucus produced by the endostyle adheres to food particles that are in the water and this mixture is then passed through the pharynx of the organism and into the esophagus through the sweeping movement of the cilia. The endostyle in larval lampreys (ammocoetes) metamorphoses into the thyroid gland in adults, and is regarded as being homologous to the thyroid gland in vertebrates due to its iodine-concentrating activity. Since the endostyle is found in the three branches of chordates, it is presumed to have arisen in the common ancestor of these taxa, along with a shift to internal feeding for extracting suspended food from the water.
- L., Jordan, E. (1967). Chordate Zoology. Delhi: S. Chanda & Co. ISBN 8121916399. OCLC 712010960.
- Ogasawara, Michio; Di Lauro, Roberto; Satoh, Nori (1 June 1999). "Ascidian Homologs of Mammalian Thyroid Transcription Factor-1 Gene Are Expressed in the Endostyle". Zoological Science. 16 (3): 559–565. doi:10.2108/zsj.16.559. ISSN 0289-0003.
- Dumont, Jacques; Opitz, R.; Christophe, D.; Vassart, Gilbert; Roger, P.P.; Maenhaut, C. (30 November 2011). "Ontogeny, Anatomy, Metabolism and Physiology of the Thyroid". Thyroid Disease Manager. PMID 25905409. Retrieved 2013-09-21. Cite journal requires
- Marine, David. 1913. The Metamorphosis of the Endostyle (Thyroid Gland) of Ammocoetes branchialis (Larval Land-Locked Petromyzon marinus (Jordan) or Petromyzon dorsatus (Wilder), The Journal of Experimental Medicine, 17:379-395.
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