What is "ctenidium"

n. 1 (context zoology English) A respiratory system, in the form of a comb, in some molluscs 2 (context zoology English) A row of spines in some insects

1. n. comb-like respiratory structure serving as the gill of certain mollusks

2. [also: ctenidia (pl)]

Ctenidium may be:

• Ctenidium (mollusc) (plural: ctenidia), a comb-like gill, part of the respiratory system of molluscs
• Ctenidium (plural: ctenidia), a row of peg-like spines in some insects (pronotal ctenidium; genal ctenidium)
• Ctenidium (plant), a genus of mosses in the family Hylocomiaceae

A ctenidium is a respiratory organ or gill which is found in many mollusks. This structure exists in bivalves, cephalopods, and in many aquatic gastropods, i.e. in some freshwater snails and sea snails and also in some sea slugs. Some aquatic gastropods possess one ctenidium, others have a pair of ctenidia (the plural form of the word).

A ctenidium is shaped like a comb or a feather, with a central part from which many filaments or plate-like structures protrude, lined up in a row. It hangs into the mantle cavity and increases the area available for gas exchange. The word is Latinized but is derived from the Greek ktenidion which means "little comb", being a diminutive of the word kteis meaning comb.

inside giant squid mantle cavity.jpg|Pair of large, grey gills visible inside the mantle cavity of a giant squid