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Grazing by Pyrosoma atlanticum (Tunicata, Thaliacea) in the south Indian Ocean

2007; Inter-Research; Volume: 330; Linguagem: Inglês

10.3354/meps330001

1616-1599

Renzo Perissinotto, Patrick Mayzaud, PD Nichols, JP Labat,

Marine and fisheries research

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 330:1-11 (2007) - doi:10.3354/meps330001 Grazing by Pyrosoma atlanticum (Tunicata, Thaliacea) in the south Indian Ocean R. Perissinotto1,*, P. Mayzaud2, P. D. Nichols3, J. P. Labat2 1School of Biological & Conservation Sciences, G. Campbell Building, University of KwaZulu-Natal, Howard College Campus, Durban 4041, South Africa 2Océanographie Biochimique, Observatoire Océanologique, LOV-UMR CNRS 7093, BP 28, 06230 Villefranche-sur-Mer, France 3Commonwealth Scientific and Industrial Research Organisation (CSIRO), Marine and Atmospheric Research, Castray Esplanade, Hobart, Tasmania 7001, Australia *Email: perissinottor@ukzn.ac.za ABSTRACT: Pyrosomas are colonial tunicates capable of forming dense aggregations. Their trophic function in the ocean, as well as their ecology and physiology in general, are extremely poorly known. During the ANTARES-4 survey (January and February 1999) their feeding dynamics were investigated in the south Indian Ocean. Results show that their in situ clearance rates may be among the highest recorded in any pelagic grazer, with up to 35 l h–1 per colony (length: 17.9 ± 4.3 [SD] cm). Gut pigment destruction rates, estimated for the first time in this tunicate group, are higher than those previously measured in salps and appendicularians, ranging from 54 to virtually 100% (mean: 79.7 ± 19.8%) of total pigment ingested. Although individual colony ingestion rates were high (39.6 ± 17.3 [SD] µg pigment d–1), the total impact on the phytoplankton biomass and production in the Agulhas Front was relatively low, 0.01 to 4.91% and 0.02 to 5.74% respectively, as a result of the low abundance of colonies. Colonies showed higher retention efficiency for particles larger than 10 µm. Low levels of lipids and percentages of triacylglycerols and free fatty acids were found in zooids. Markers for diatoms (C16 PUFA), dinoflagellates (22:6n-3, 18:5n-3) and prymnesiophytes (18:1n-9, 18:4n-3) were observed. Stepwise discriminant analysis of published data on phytoplankton fatty acid showed a strong similarity between the composition of the 2 neutral lipid classes found in P. atlanticum and that of both dinoflagellates and prymnesiophytes. The sterol composition confirmed this result with the contribution of 24-methylcholest-5,22-dien-3β-ol, cholesterol, 24-methylenecholesterol and 24-ethylcholesterol. Colonies exhibited large numbers of ciliate protozoans (possibly Strombidium sp.). It is not clear whether this constituted a mere opportunistic intrusion, or rather a more stable association between the 2 organisms. KEY WORDS: Pyrosoma · Pelagic tunicates · Gut pigment content · Gut turnover time · Ingestion rates · Clearance rates · Lipid content · Agulhas Front Full text in pdf format NextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 330. Online publication date: January 25, 2007 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2007 Inter-Research.