endostyle
1. A ciliated groove on the mid-ventral surface of the pharynx of ammocoetes. Food particles are trapped by mucus produced by the pharynx, and then transported toward the oesophagus. The endostyle is also able to take up iodine, a capacity it retains after it is transformed into the thyroid gland of the adult lamprey, when metamorphosis is complete.

2. A mucus-secreting groove in the pharynx of Urochordata and Cephalochordata, and a comparable organ in Hemichordata; it is analogous to the thyroid gland in Chordata.

endostyle A ciliated groove in the wall of the pharynx of lancelets (Cephalochordata), some tunicates, and larval lampreys that contains mucus-secreting glands. Mucus secreted by the endostyle traps food particles in water drawn into the pharynx by the beating action of the cilia.