Tunicate.They are marine animals that have a notochord in their tail (hence their name). They are also called tunicates because the adults have a brightly colored and often phosphorescent tunic or sac . They comprise almost 2,800 marine species, and with different types of mobility: benthic , planktonic , solitary or colonial. Among them are sea squirts, salps and appendicularias. Sea squirts have a gill basket that is used to breathe and trap food by filtering.
They are hermaphrodites (they have both sexes). The larvae are tadpole-shaped. Urochordates can feed by filtering large amounts of water. They are hermaphrodites . fertilization _It is usually external. The gametes are expelled through the exhalant siphon. Upon completion of fertilization, a zygote is formed that develops into a tadpole -like larva in morphology.
Summary
[ hide ]
- 1 Features
- 2Clases
- 3 Fountains
- 4 See also
Features
- Group etymology: Urochordate(having notochord in the caudal region) and Tunicata : (having a tunic).
- They comprise 3,620 species.
- Adults retain only one or two of the features unique to chordates, gill or pharyngeal slits and/or notocardium.
- Not segmented.
- Sin celoma.
- With unistratified epithelium that secretes an acellular matrix called the tunic.
- No skeleton.
- It is characterized by persistent notochord in the adult of the larvaceaclass and dorsal nerve cord, mainly in the embryonic and/or larval stage of the Ascideans .
- With two siphons, one inhalant and one exhalant.
- Respiration through a branchial pharynx and with an endostyle.
- Excretion by simple diffusion.
- Circulatory system without true vessels (they lack endothelium), with a unicameral tubular heart .
- Sexes united (monoecious).
- Fertilization: external.
- indirect development.
- Exclusively marine habitat.
- Solitary or Colonial.
- Free-living (pelagic) or fixed to the bottom of the sea, from the coast to 5 thousand m depth.
Lessons
- Ascidiaceousclass : they are common and well known “sea squirts”. Generally sessile. They are barrel-shaped, the most primitive or colonial are solitary or the most evolved are compound. They expel a stream of water through the inhalant siphon. Metamorphosis.
- Class larvaceous appendiculariaceous): Adults have a motor tail. They are pelagic (they live in areas far from the coast), without metamorphosis. Solitary or Colonial.
- Taliaceousclass : they are pelagic, solitary or colonial, they swim by contractions of the transverse bands. They are barrel-shaped, have a transparent body with transverse (annular) musculature.
