MEPS 331:119-129 (2007)  -  doi:10.3354/meps331119

Feeding activity and swimming patterns of Acartia grani and Oithona davisae nauplii in the presence of motile and non-motile prey

Casper Ingerslev Henriksen1,2, Enric Saiz2,*, Albert Calbet2, Benni Winding Hansen1

1Roskilde University, Department of Life Sciences and Chemistry, 4000 Roskilde, Denmark
2Institut de Ciències del Mar, CSIC, P. Marítim de la Barceloneta 37–49, 08003 Barcelona, Catalunya, Spain
*Corresponding author. Email:

ABSTRACT: The feeding behaviour of the nauplii of the copepods Acartia grani (calanoid) and Oithona davisae (cyclopoid) was investigated in relation to the different motility capabilities of their prey. The prey were the motile dinoflagellate Heterocapsa sp. (equivalent spherical diameter, ESD = 12.8 µm) and the non-motile diatom Thalassiosira weissflogii (ESD = 14.4 µm). Functional response feeding experiments showed that A. grani nauplii exhibited higher ingestion rates on the motile than on the non-motile prey, with maximum daily rations of, respectively, 299 and 185% body C d–1. O. davisae nauplii showed lower ingestion rates (121% body C d–1) and were unable to feed on the non-motile prey. Video observations showed that A. grani nauplii moved with a continuous hopping behaviour, either in a straight or helical pattern; feeding events were observed mainly while swimming in helicoids. O. davisae nauplii exhibited a jump and sink behaviour, typical of ambush feeding. Both species showed changes in their behaviour when presented with the motile prey Heterocapsa sp. This indicates that the nauplii are capable of adjusting their feeding behaviour to the different prey characteristics, thereby optimising ingestion rates.

KEY WORDS: Oithona davisae · Acartia grani · Nauplii · Feeding rates · Prey motility · Swimming patterns

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