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Urochordata (sometimes known as tunicata and commonly called urochordates, tunicates, sea squirts or cunji) is the subphylum of saclike filter feeders with incurrent and excurrent siphons. There are also a few exceptions to this plan, like the predatory Megalodicopia hians, looking something like a cross between a jellyfish and a Venus Flytrap. They are members of the phylum Chordata, which also includes lancelets, hagfish and all vertebrates including man. As with other chordates, tunicates possess a notochord during their early stages of development. They lack segmentation, even in the tail. Metanephridia are absent. The original coelom is degenerated to a pericardial cavity and gonads. Except for the pharynx, heart and gonads, the organs are enclosed in a membrane called an epicardium, which is surrounded by a jelly like matrix known as mesenchyme. The motile larval stages may have the appearance of a tadpole, whereas the adult stage has a barrel-like, sedentary form. They feed by filtering sea water through a gill basket.
Most tunicates are hermaphroditic. The eggs are kept inside their body, while sperm is released into the water where it fertilises other individuals when brought in with incoming water. The eggs stay inside the body until they hatch.
Tunicates have two openings in their body cavity: an incurrent and an excurrent siphon. The incurrent siphon is used to intake food and water and the excurrent siphon expels waste and water. The tunicate's primary food source is plankton. Plankton gets entangled in the mucus secreted from the endostyle. The tunicate's pharynx is covered by miniature hairs called ciliated cells which allow the consumed plankton to pass down through to the esophagus.Tunicates are also the only animals able to create cellulose.
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UROCHORDATA RAH RAH RAH!!! RT @NMNH: Tunicates come in an astonishing variety of colors and patterns. http://ow.ly/L79u
oystersgarter (Miriam Goldstein) Sat, 12 Dec 2009 01:55:39 -0000
UROCHORDATA RAH RAH RAH!!! RT @NMNH: Tunicates come in an astonishing variety of colors and patterns. http://ow.ly/L79u
Archives of Tunicata E-mail List - Subscription information and archives.
Ascidian Home Page for the United States - Home page for Ascidian News, a twice yearly newsletter published by Charles and Gretchen Lambert, with recent worldwide publication citations, meetings abstracts and work in progress. The Ascidiaceae are a family in the Phylum Urochordata and are commonly known as tunicates or sea squirts.
Meta Description: [ Home page for Ascidian News , a twice yearly newsletter published by Charles and Gretchen Lambert, with recent worldwide publication citations, meetings abstracts and work in progress. ]
Just Blue - South African organization conducting research on the ascidians or tunicates, commonly known as sea squirts, mostly for the Coral Reef Research Foundation. Website contains many photographs of tunicates.
Meta Description: [ Just Blue researches the taxonomy of ascidians (tunicates), commonly known as sea squirts. We also do ascidian identification and sample collection. ]
Urochordata - Introduction to the Urochordata, with photos.
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