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Trididemnum sp.

Georgina Walker (2013)

 

 

Fact Sheet

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Summary


Physical Description


Ecology


Life History & Behaviour


Anatomy & Physiology


Evolution & Systematics


Biogeographic Distribution


Conservation & Threats


References & Links

Anatomy & Physiology 

As the species of Trididemnum was not identified, only common internal anatomy and external morphology of ascidians will be described in this section

Internal Anatomy:

Pharynx

The pharynx of an ascidian creates the water current that draws food particles into the body (Peterson 2007)(Pennachetti, 1984)(Arkett et al, 1989). Water travels from the buccal siphon, through the pharynx (branchial basket) and leaves through the atrial siphon. The mucous net that lines the pharynx and is used to trap food is secreted by the endostyle.

Digestive

Once the mucous net is full it is rolled into a thread and moved downwards into the oesophagus.  The oesophagus is the descending portion of an ascidian’s U-shaped gut. The base of the U is the location of the stomach and site of extracellular digestion. The ascending arm is the intestine which ends in the anus. The anus discharges into the atrium and out the atrial siphon. 

Circulatory 

Ascidians possess a hemal system with well-developed blood pathways (Mukai et al, 1978)(Ruppert et al, 2004). Ascidian blood does not contain respiratory pigments. Their hearts are usually located at the base of the gut loop, however location can be significantly different between species.

Reproductive

Being (mostly) hermaphroditic, ascidians possess both a testis and ovary which are usually located in the gut loop. Some species have numerous gonads which are located in the body wall. Sperm and eggs are released into the atrium via separate oviduct and sperm ducts before being discharged through the atrial siphon. Species with sexual seasonality, such as the three photosymbiotic Trididemnum species, T. miniatum, T. clinides and T. nubilum, lack gonads and/or embryos during winter (Hirose et al, 2007). 

Didemnum ascidians reproduce asexually via pyloric budding. This involves a single zooid producing two buds from the base of the endostyle or oesophagus. One bud differentiates into a new branchial sac and fuses to the old abdomen while the other differentiates to a new abdomen and fuses to the old branchial sac (Brown & Swalla, 2012).

Nervous

The nervous system of adult ascidians comprises of a hollow cerebral ganglion. Nerves which arise from the anterior end supply the buccal siphon and musculature while nerves from the posterior end supply the rest of the body. Although adults lack sense organs, sense cells are abundant in the siphons and atrium. 

External Morphology:

Tunic & Siphons

Ascidians possess a protective exoskeleton, called a tunic, that surrounds its body. The tunic can vary between species from soft and delicate to thick and tough and is the point of attachment to the substratum. The tunic is composed of different carbohydrates and proteins. The presence of tunicin fibers which provide strength and toughness to the tunic is unique to ascidians. The presence of blood cells indicates that the tunic is a living tissue similar to connective tissue. Ascidians are the only animal with an exoskeleton, not to moult as they grow.

The tunic of Trididemnum sp. is clear around the extended edge but the presence of the Prochloron bacterium in the main body of the colony gives it a green colouration. 

Ascidians have two siphons; the buccal and atrial siphons. The buccal siphon is the inhalant siphon and the atrial siphon is used for expulsion of water, eggs and sperm and waste. In the Trididemnum sp. the individual zooids are arranged in a pattern of circular systems with inhalant siphons situated around a shared exhalant siphon (Figures one & two).

Figure one: (a) The circular arrangement of Trididemnum sp. zooids with buccal siphons surrounding a common exhalant siphon. (b) Common system and integration of zooids in a colonial ascidian, redrawn and modified from Rupert. EE, Fox. RS & Barnes. RD 2004, Invertebrate Zoology, Seventh Edition Thomson brooks/cole.
Figure two: Vertical section of two zooids from a single system sharing a common atrial siphon. Redrawn and modified from Rupert. EE, Fox. RS & Barnes. RD 2004, Invertebrate Zoology, Seventh Edition Thomson brooks/cole.

Classification

Minimize
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum

Synonyms

Didemnum areolatum (Herdman, 1906)
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum

Synonyms

Trididemnum africanum (Michaelsen, 1915)
Trididemnum luderitzi (Michaelsen, 1919)
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum

Synonyms

Didemnum cereum (Giard, 1872)
Didemnum niveum (Giard, 1872)
Didemnum sargassicola (Giard, 1872)
Trididemnum fallax ((Lahille, 1890))
Trididemnum graphicum (Lahille, 1890)
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum

Synonyms

Trididemnum symbioticum (Peres, 1962)
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum

Synonyms

Didemnopsis jolense (Van Name, 1918)
Leptoclinum discrepans (Sluiter, 1909)
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum

Synonyms

Didemnum dispersum (Sluiter, 1909)
Trididemnum tegulum (Kott, 1984)
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum

Synonyms

Didemnum farrago (Kott, 2004)
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum

Synonyms

Didemnoides inarmata ((Drasche, 1883))
Didemnopsis inarmata ((Drasche, 1883))
Didemnum inarmatum (Drasche, 1883)
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum

Synonyms

Leptoclinum marmoratum (Sluiter, 1909)
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum

Synonyms

Didemnopsis microzoa (Redikorzev, 1913)
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum

Synonyms

Trididemnum nube (Monniot F., 1991)
Kingdom
Animalia
Phylum
Chordata
Class
Ascidiacea
Order
Aplousobranchia
Family
Didemnidae
Genus
Trididemnum

Synonyms

Didemnum opacum (Ritter, 1907)
Trididemnum dellavallei (Ritter & Forsyth, 1917)
Trididemnum dellavalley (Ritter & Forsyth, 1917)

Images

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(2 objects, created 5/6/2011)

Album: This is a private album that is not visible to anonymous users Great Barrier Reef Invertebrates

Summary:

Date:

Album: 2012

Album: 2011