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Related FAQs:  TWA Invertebrates, Fishes of the Tropical West Atlantic, Tropical West Atlantic 2

Related Articles: Algae, Vascular Plants, Introduction to Fishwatcher's Guide Series Pieces/Sections, Lachnolaimus maxiumus/Hogfish, Hogfishes of the Genus Bodianus

Invertebrates, Algae and Vascular Plants of The Tropical West Atlantic: Bahamas to Brazil, Part 13

To: Part 1, Part 2, Part 3, Part 4, Part 5, Part 6, Part 7, Part 8, Part 9, Part 10, Part 11, Part 12, Part 14, Part 15,


Bob Fenner


Tunicates, Sea Squirts: Grouped within the same phylum in zoological classification as the vertebrates are a couple of other subphyla of interest to marine aquarists. The Urochordata don't look much like fishes, birds, mammals, lacking a backbone, but do share four other important characteristics with them. During larval development they possess a tail, a dorsal nerve cord, a dorsal (non-bone) stiffening structure (the notochord), and pharyngeal gill clefts. 

    These "lower" chordates are variously called tunicates (for their cellulose matter that makes up their body covering), Sea Squirts (for their apparent and real capacity to forcibly eject water) and Ascidians (Greek for "little body") for the Class of attached forms. There are pelagic tunicates, grouped in the Class Thalicea, but these are of little interest to aquarists.

A thaliacean "Salp". The (Class) Thaliacea include about seventy barrel-shaped pelagic animals that filter feed (like all urochordates), but from one end opening to the other exiting as they locomote through the water. This Class is further subdivided into three subclasses. The Pyrosomida are colonial and the Salpida and Doliolida are not. 

    The Ascidians on the other hand are a major part of the "cryptic fauna" of  live rock... often making up a sizeable proportion of this material (second only to sponges). Though they may not be easily recognized, tunicates are among the most common marine invertebrates, and an important functional component, for aquarists as well.

Clavelina sp. Bulb Tunicates. Grow in clusters. These ones common in Florida, Bahamas, the Caribbean. Here attached to a clam which is in turn attached to a gorgonian. 

Clavelina picta, the Painted Tunicate. Florida, Bahamas, Caribbean. Frequently found in clusters of hundreds of individuals hanging on to gorgonians, black coral, sponges. Translucent bodies of variable cool colors. Siphon rims reddish to dark purple. A colony in the Bahamas on a Sea Fan, and one off St. Thomas.

Distaplia corolla, Button Tunicate. Small (1/4" or less) oval individuals with one larger outflowing opening. Generally grow in small clusters as these are in Cozumel. Tropical West Atlantic. Found growing on dead coral. Orange or purple in color. 

Trididemum solidum, the Overgrowing Mat Tunicate. 3-12 inches. Tropical West Atlantic. Small individuals embedded into a heavy communal mass. Gray, blue, green or white. Cozumel images by Di. 

To: Part 1, Part 2, Part 3, Part 4, Part 5, Part 6, Part 7, Part 8, Part 9, Part 10, Part 11, Part 12, Part 14, Part 15,

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