Dolioletta gegenbauri
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| Dolioletta gegenbauri | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Subphylum: | Tunicata |
| Class: | Thaliacea |
| Order: | Doliolida |
| Family: | Doliolidae |
| Genus: | Dolioletta |
| Species: | D. gegenbauri |
| Binomial name | |
| Dolioletta gegenbauri (Uljanin, 1884) [1] | |
| Synonyms[1] | |
| |
Dolioletta gegenbauri is a species of tunicate in the family Doliolidae. It is small, exists in various forms and is sometimes found in great abundance in the Atlantic and Pacific waters where it lives.
Dolioletta gegenbauri is a small, transparent, gelatinous marine invertebrate up to one centimetre long. It has a complex life cycle and exists in several forms of which the gonozooid, or mature zooid with gonads, is the most often seen. It is roughly cylindrical with a siphon at both of the flat ends, and has 8 bands of muscle arranged like hoops round a barrel. The U-shaped gut and other organs can be seen through the test which is pierced by 10 to 40 gill slits. The gonozooid is hermaphrodite and the eggs are fertilised by sperm from another individual. These develop into oozooids which have no reproductive organs. They have 9 bands of muscle and are known as "nurses" as they develop a tail of zooids produced asexually. Some of these are known as gastrozooids, have a nutritional function and are arranged in lateral rows. Others are phorozooids, have a transport function and are arranged in a single central row. Other zooids link to the phorozooids which then detach themselves from the nurse. The zooids develop into gonozooids and when these are mature they separate from the phorozooids to live independently and start the cycle over again. Meanwhile, the phorozooids have served their purpose and die.[2][3]
Under the favourable conditions of a plentiful supply of planktonic food, a single oozooid can produce thousands of gonozooids within a few days.[2] Dense swarms sometimes appear in which there are 500 individuals per cubic metre of water.[2]