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Oikopleura is a genus of Tunicata (sea-squirts) in the class Appendicularia (Larvacea), Order Copelata and Family Oikopleuridae.This tiny pelagic tunicate is abundant in offshore waters of all oceans and seas, having been reported widely in the Caribbean Sea and the western coasts of the Atlantic Ocean.[2][3][4][5][6][7][8][9][10][11][12][13][14]

Oikopleura has a body length of 1 mm. In Monterey Bay and other West Coast locations, it may occur in surface aggregations that form long parallel rows; individuals appear as closely spaced reddish specks. Oikopleura has the typical larvacean tadpole-like appearance with a tail that is 3 to 4 times the body length. When undisturbed, it produces 5 to 10 pea-sized mucous webs (the "house") a day that are used for feeding, protection and buoyancy. It forms a house every four hours at 20 degrees Celsius. The house has a coarse mesh to keep out big particles and a fine mesh that collects small particles, down to the nanoplankton that includes (pelagic) bacteria. The house concentrates tiny food particles, which are transferred to the mouth for ingestion. Discarded or abandoned houses can produce bluish-green bioluminescent flashes and collect organic particles during their descent, contributing to the steady rain of organic material (marine snow) that slowly descends into deeper water. Oikopleura is a very active filterer, using powerful strokes of its tail. The gelatinous body disappears in the preservation process, leaving hardly any trace. Oikopleura has about 15,000 genes.

Oikopleura dioica is an anomaly among chordates. It has retained the fundamental body plan of the chordate, but has lost the mechanism for retinoic acid signaling which operates during chordate development. The loss raises the question of evolutionary constraints that prevented similar changes in the other chordates.[15] O. dioica hox genes are distributed in nine locations around the genome whereas other chordates have a cluster of hox genes.[Nature 2 Sept 2004]. In boreal and Arctic waters, O. dioica is replaced by the more cold tolerant and larger O. vanhoeffeni and O. labradoriensis.


1. World Register of Marine Species: Oikopleura Mertens, 1830 AphiaID: 103367

2. Flores-Coto C. 1965: Notas preliminares sobre la identificación de las apendicularias de las aguas veracruzanas. Anales del Instituto de Biología (México) 35: 293-296.

3. Flores-Coto C.. 1974: Contribución al conocimiento de las apendicularias del arrecife “La Blanquilla” Veracruz, México con descripción de una nueva especie. Anales del Centro de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México 1: 41-60.

4. Flores-Coto, César., Sanvicente-Añorve, Laura. & Sánchez-Ramírez, Marina. 2010: Appendicularian distribution and diversity in the southern Gulf of Mexico. Distribución y diversidad de apendicularias en el sur del golfo de México. Revista Mexicana de Biodiversidad, 81:123- 131. PDF

5. Castellanos, I. A. and E. Suárez-Morales. 2009. Appendicularia (Urochordata) of the Gulf of Mexico, Pp. 1217–1221 in Felder, D.L. and D.K. Camp (eds.), Gulf of Mexico–Origins, Waters, and Biota. Biodiversity. Texas A&M Press, College Station, Texas.

6. Márquez, Brightdoom., Marín, Baumar., Zoppi, Evelyn. & Moreno, Carlos. 2006: Zooplancton del Golfo De Cariaco. Bol. Inst. Oceanogr. Venezuela, Univ. Oriente. 45(1):61-78 PDF

7. Zoopp, Evelyn. 1971: Apendicularias de la Región Oriental de Venezuela. Studies on the Fauna of Curaçao and other caribbean Island, 132:76-109. Lam I – VI.

8. Carvalho, Pedro Freitas de. & Bonecker, Sérgio Luiz Costa. 2010: Seasonal and Spatial Variability of Appendicularian Density and Taxonomic Composition in the Caravelas Estuary (Northeastern Brazil) and Adjacent Coastal Area. Brazilian Archives of Biology and Technology, 53(1):161-169.

9. Esnal G. 1972: Apendicularias de la desembocadura del Río de la Plata. Physis (Argentina) 31: 259-272.

10. Esnal G. 1973: Apendicularias de las costas argentinas. Physis (Argentina) 32: 267-273.

11. Esnal G. 1979: Características generales de la distribución de tunicados pelágicos del Atlántico sudoccidental, con algunas observaciones morfológicas. Physis (Argentina) 38: 91-102.

12. Esnal G. 1981: Apendicularia. In: Boltovskoy (ed) Atlas del zooplancton del Atlántico sudoccidental y métodos de trabajo con el zooplancton marino: 809-820. Publicación Especial, Instituto Nacional de Investigación y Desarrollo Pesquero, Mar del Plata, Argentina. 936 pp.

13. Esnal G. 1999: Appendicularia. In: Boltovskoy D (ed). South Atlantic zooplancton: 1375-1399. Backhuys Publication, Leiden, The Netherlands.

14. Esnal G. & Castro, R. 1977: Distributional and biometrical study of appendicularians from the west south Atlantic. Ocean. Hydrobiologia 56:241.

15. Holland, Linda Z. "Developmental biology: A chordate with a difference." Nature 447.1 (2007): 153-55.


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