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MEPS 274:191-198 (2004)
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Abstract
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Assessment of Cryptophyceae ingestion by copepods using alloxanthin pigment: a caution
Elvire Antajan1,3,*, Stéphane Gasparini2
1Laboratorium voor ecologie en systematiek, Vrij Universiteit Brussel, Pleinlaan 2, 1050 Brussel, Belgium
2Laboratoire d'Océanographie de Villefranche, BP 28, 06234 Villefranche-sur-Mer cedex, France
3Present address: Université du Littoral Côte d'Opale, 32 avenue Foch, 62930 Wimereux, France
*Email: antajan@mren2.univ-littoral.fr
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ABSTRACT: The accessory pigment alloxanthin is a well-known taxonomic marker for Cryptophyceae in natural seawater. The use of alloxanthin to estimate in situ zooplankton grazing and selectivity on Cryptophyceae was studied using 2 dominant
copepods of the southern North Sea, Temora longicornis and Centropages hamatus. High-performance liquid chromatography (HPLC) analyses of water samples and of freshly caught copepods, starvation experiments, and feeding experiments
(shipboard bottle-incubations) were carried out. Although alloxanthin was always detected in copepod extracts, (1) no correlation was found with alloxanthin in seawater, and (2) no significant grazing on Cryptophyceae was observed. Results of our
gut-evacuation experiments showed that at least 78% of the initial alloxanthin content of T. longicornis and C. hamatus remained after 90 min, whereas fucoxanthin and chloropigments decreased rapidly with time. Alloxanthin and astaxanthin
esters were the only pigments remaining in the body of T. longicornis after several hours' starvation. It is concluded that most of the detected alloxanthin did not originate from the gut but from the body tissues. Our results suggest that
alloxanthin is not suitable as a biomarker for quantitative or qualitative estimates of copepod grazing on Cryptophyceae.
KEY WORDS: Alloxanthin · Cryptophyceae · Copepod ingestion · HPLC
Full text in pdf format
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Published in MEPS Vol.
274
(2004) on June 24
Print ISSN: 0171-8630; Online ISSN: 1616-1599.
Copyright © Inter-Research, Oldendorf/Luhe, 2004
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