Tunicates, pelagic

Fig.1 Generalized pelagic food web [ 13]. The old view of a simple food chain vertical line in this figure) with phytoplankton (mainly diatoms) at the base, herbivorous mesozoo-plankton (mainly copepods) at the second trophic level, and planktivorous fish has been extended to a pelagic food web including nanoplankton (<20 pm), picoplankton (<2 pm), and their protozoan feeders lower left). Herbivorous tunicates and jellyfish as primary carnivores also play a role, as do mixotrophic flagellates. The main pathway of energy flow depends on the nutrient scenarios [13]. DOC=dissolved organic carbon, HNF=heterotrophic nanoflageUates. From [13] with permission of Kluwer Academic Press...

Symbiosis with algae and bacteria (including Cyanobacteria) is widespread in ascidians and is responsible for coloration as well as defensive metabolites, which may themselves be colorful. Symbiotic bacteria are also responsible for the (probably defensive) bioluminescence of their pelagic relatives, the Thaliacea.96 Brooding of the young tadpole larva may facilitate the transfer of symbionts from one generation to the next. Many of the metabolites in ascidians are quite similar to those known to be produced by bacteria, and the taxonomic distribution of the metabolites in the animals tends to confirm this.97 Others, however, are evidently produced by the tunicates themselves. 

Andersen, V., Salp and pyrosomid blooms and their importance in biogeochemical cycles, in The Biology of Pelagic Tunicates, Bone, Q., Ed., Oxford University Press, New York, 1998, 340. 

Alldredge, A.L. and Madin, L.P., Pelagic tunicates unique herbivores in the marine plankton, Bio-Science, 32, 655, 1982. 

Heron, A.C., A specialized predator-prey relationship between the copepod Sapphirina augusta and the pelagic tunicate Thalia democratia, J. Mar. Biol. Assoc. UK, 53, 429, 1973. 

Deibel, D., and Lee, S. H. (1992). Retention efficiency of sub-micrometer particles by the pharyngeal filter of the pelagic tunicate Oikopleura vanhoejfeni. Mar. Ecol. Prog. Ser. 81, 25—30. 

The structural features of cellulose microfibrils in these pelagic tunicates are quite similar to that of ascidians. This evidence indicates that the cellulose-synthesizing ability is an inherited character common to ascidians and thaliaceans. It is also reported that the basic structures of the tunic and the epidermis of ascidians and thaliaceans are almost the same (Hirose et al. 1999). The timic cellulose in the thaliaceans may be synthesized by TCs on the plasma membrane of epidermal cells similar to the ascidians. 

Flood RR. and Deibel D. 1998. The appendicularian house. In Bone Q. (ed.), The Biology of Pelagic Tunicates. Oxford University Press, Oxford, pp 105-124. 

Christen, R. (1998) Molecular phylogeny of tunicates. A preliminary study using 28S ribosomal RNA partial sequences Implications in terms of evolution and ecology , in Bone, Q. (ed.) The biology of pelagic tunicates, Oxford Oxford University Press, pp. 265-71. 

Deibel, D. G.-A. Paffenhofer. 1988. Cinematographic analysis of the feeding mechanism of the pelagic tunicate Doliolum nationalis. Bull. Mar. Sci. 43 404-412. 

Deibel, D Cavaletto, J.F., Riehl, M., and Gardner, WS. (1992) Lipid and lipid class content of the pelagic tunicate Oolcopleura vanhoefieni. Mar. Ecol. Prog. Ser, 88, 297-302. 

Mayzaud, P., Boutoute, M., Perissinotto, R., and Nichols, P. (2007) Polar and neutral lipid composition in the pelagic tunicate Pyrosoma atlanticum. Lipids, 42, 647-657. 

Pond, D.W. and Sargent, J.R. (1998) lipid composition of the pelagic tunicate Diolioletta gegenbauri (Turricata, Thaliacea). J. Plankton Res., 20,169-174. 

---