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'''Tunicate'''
== Tunicate ==


The '''Tunicate''' (also known as '''Urochordata''' or '''sea squirts''') is a subphylum of marine invertebrate animals, a part of the Chordata phylum, which also includes the vertebrates (animals with backbones). Tunicates are named for their unique outer covering or "tunic," which is made of a cellulose-like substance.
Tunicates, also known as urochordates, are a group of marine invertebrates that are part of the subphylum [[Tunicata]]. They are notable for their sac-like body structure and are found in oceans worldwide. Tunicates are closely related to vertebrates, sharing a common ancestor, and are considered an important group for understanding the evolution of chordates.


== Anatomy ==
== Description ==


Tunicates are characterized by a tough outer "tunic" made of the polysaccharide tunicin. The body of a tunicate is composed of a trunk and two siphons, through which water enters and exits the body. The interior of a tunicate is composed of a pharynx, which is used for feeding and respiration, and a digestive tract.
Tunicates are characterized by their tough outer "tunic," which is made of a cellulose-like carbohydrate. This tunic provides protection and structural support. The body of a tunicate is divided into two main regions: the thorax and the abdomen. They possess a simple nervous system and a heart that can reverse the direction of blood flow.
 
Tunicates exhibit a wide range of forms and sizes, from solitary individuals to complex colonial structures. They can be sessile, attaching themselves to substrates, or free-floating in the water column.


== Life Cycle ==
== Life Cycle ==


Tunicates have a complex life cycle with a larval stage, which is markedly different from their adult form. The larvae are free-swimming and possess a structure, the notochord, which is characteristic of chordates. The adults are sessile (non-moving) and have lost the notochord.
The life cycle of tunicates includes both sexual and asexual reproduction. Most tunicates are hermaphroditic, possessing both male and female reproductive organs. Fertilization typically occurs in the water column, and the resulting larvae are free-swimming. These larvae resemble tadpoles and possess a notochord, a defining feature of chordates.
 
After a brief planktonic stage, the larvae settle onto a substrate and undergo metamorphosis into the adult form. Some tunicates, such as those in the class Appendicularia, retain their larval characteristics throughout their life.


== Classification ==
== Classification ==


Tunicates are classified into three classes: Ascidiacea (sea squirts), Thaliacea, and Appendicularia (larvaceans). The Ascidiacea are the most diverse and numerous, while the Thaliacea and Appendicularia are less common.
Tunicates are divided into three main classes:
 
* [[Ascidiacea]]: Also known as sea squirts, these are sessile tunicates that attach to surfaces. They can be solitary or colonial.
* [[Thaliacea]]: This class includes free-floating tunicates such as salps and pyrosomes. They are often found in open ocean environments.
* [[Appendicularia]]: Also known as larvaceans, these tunicates retain their larval form throughout their life and are free-swimming.


== Ecology ==
== Ecology ==


Tunicates are found in a wide range of marine environments, from the intertidal zone to the deep sea. They are filter feeders, capturing plankton and other small organisms from the water column.
Tunicates play a significant role in marine ecosystems. They are filter feeders, drawing in water through an incurrent siphon, filtering out plankton and other small particles, and expelling the filtered water through an excurrent siphon. This feeding process helps to clarify the water and recycle nutrients.


== Evolution ==
Some tunicates, particularly colonial species, can form dense mats that cover large areas of the seafloor, providing habitat for other marine organisms. However, certain species can become invasive, outcompeting native species and altering local ecosystems.


Tunicates are of interest in the study of evolution, as they are the closest living relatives of the vertebrates. Despite their simple adult form, their complex life cycle and larval stage provide important clues about the origins of the vertebrates.
== Research and Importance ==


== See Also ==
Tunicates are of interest to scientists due to their evolutionary significance and their potential applications in biotechnology. Their simple body plan and genetic makeup provide insights into the evolution of more complex chordates, including vertebrates.
* [[Chordata]]
 
Additionally, tunicates produce a variety of bioactive compounds that have potential uses in medicine, including anti-cancer and anti-bacterial agents.
 
== Related Pages ==
 
* [[Chordate]]
* [[Invertebrate]]
* [[Invertebrate]]
* [[Marine biology]]
* [[Marine biology]]
* [[Evolutionary biology]]
== References ==
* Barnes, R. D. (1982). Invertebrate Zoology. Holt-Saunders International.
* Ruppert, E. E., Fox, R. S., & Barnes, R. D. (2004). Invertebrate Zoology: A Functional Evolutionary Approach. Brooks/Cole.
* Satoh, N. (2003). The Ascidian Tadpole Larva: Evolutionary Significance of Its Structure and Function. Canadian Journal of Zoology.
== Gallery ==


[[Category:Marine biology]]
<gallery>
[[Category:Invertebrates]]
File:Tunicate_komodo.jpg|Tunicate in Komodo National Park
[[Category:Chordates]]
File:Bluebell_tunicates_Nick_Hobgood.jpg|Bluebell tunicates
File:Botrylloides_violaceus_(cropped).jpg|Botrylloides violaceus
File:Oikopleura_dioica.gif|Oikopleura dioica
File:Appendicularia_(YPM_IZ_096169).jpeg|Appendicularia
File:Pyrosoma_atlanticum.JPG|Pyrosoma atlanticum
File:Salp_colony,_Aorangaia_PA171899.JPG|Salp colony
File:Cyclomyaria.jpg|Cyclomyaria
File:CionaintestinalisR.jpg|Ciona intestinalis
File:Sea_Squirts_Didemnum_molle.jpg|Sea Squirts Didemnum molle
File:Molgula_oculata_001.png|Molgula oculata
File:Tunicate_komodo.jpg|Tunicate in Komodo
File:Microcosmus_sabatieri.jpg|Microcosmus sabatieri
File:Catellocaula.jpg|Catellocaula
File:Tunicate_green.jpg|Green tunicate
File:Uroc005b.png|Urochordate diagram
File:Pyrosoma_001.png|Pyrosoma
File:Oikopleura_(Vexillaria)_cophocerca_001.png|Oikopleura cophocerca
File:Ascidians.jpg|Ascidians
File:Ascidian_(Rhopalaea_Crassa)_(4_cm).png|Rhopalaea Crassa
File:Sea_Squirts_Didemnum_molle.jpg|Sea Squirts Didemnum molle
File:Tunicate_black_orange.jpg|Black and orange tunicate
File:Uroc004b_Jon.png|Urochordate anatomy
File:Ascidia_005.png|Ascidia
File:SeaSquirt.jpg|Sea Squirt
</gallery>


{{stub}}
[[Category:Tunicates]]

Revision as of 01:17, 10 February 2025

Tunicate

Tunicates, also known as urochordates, are a group of marine invertebrates that are part of the subphylum Tunicata. They are notable for their sac-like body structure and are found in oceans worldwide. Tunicates are closely related to vertebrates, sharing a common ancestor, and are considered an important group for understanding the evolution of chordates.

Description

Tunicates are characterized by their tough outer "tunic," which is made of a cellulose-like carbohydrate. This tunic provides protection and structural support. The body of a tunicate is divided into two main regions: the thorax and the abdomen. They possess a simple nervous system and a heart that can reverse the direction of blood flow.

Tunicates exhibit a wide range of forms and sizes, from solitary individuals to complex colonial structures. They can be sessile, attaching themselves to substrates, or free-floating in the water column.

Life Cycle

The life cycle of tunicates includes both sexual and asexual reproduction. Most tunicates are hermaphroditic, possessing both male and female reproductive organs. Fertilization typically occurs in the water column, and the resulting larvae are free-swimming. These larvae resemble tadpoles and possess a notochord, a defining feature of chordates.

After a brief planktonic stage, the larvae settle onto a substrate and undergo metamorphosis into the adult form. Some tunicates, such as those in the class Appendicularia, retain their larval characteristics throughout their life.

Classification

Tunicates are divided into three main classes:

  • Ascidiacea: Also known as sea squirts, these are sessile tunicates that attach to surfaces. They can be solitary or colonial.
  • Thaliacea: This class includes free-floating tunicates such as salps and pyrosomes. They are often found in open ocean environments.
  • Appendicularia: Also known as larvaceans, these tunicates retain their larval form throughout their life and are free-swimming.

Ecology

Tunicates play a significant role in marine ecosystems. They are filter feeders, drawing in water through an incurrent siphon, filtering out plankton and other small particles, and expelling the filtered water through an excurrent siphon. This feeding process helps to clarify the water and recycle nutrients.

Some tunicates, particularly colonial species, can form dense mats that cover large areas of the seafloor, providing habitat for other marine organisms. However, certain species can become invasive, outcompeting native species and altering local ecosystems.

Research and Importance

Tunicates are of interest to scientists due to their evolutionary significance and their potential applications in biotechnology. Their simple body plan and genetic makeup provide insights into the evolution of more complex chordates, including vertebrates.

Additionally, tunicates produce a variety of bioactive compounds that have potential uses in medicine, including anti-cancer and anti-bacterial agents.

Related Pages

References

  • Barnes, R. D. (1982). Invertebrate Zoology. Holt-Saunders International.
  • Ruppert, E. E., Fox, R. S., & Barnes, R. D. (2004). Invertebrate Zoology: A Functional Evolutionary Approach. Brooks/Cole.
  • Satoh, N. (2003). The Ascidian Tadpole Larva: Evolutionary Significance of Its Structure and Function. Canadian Journal of Zoology.

Gallery

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