Feeding of Boeckella gracilipes (Copepoda, Calanoida) on ciliates and phytoflagellates in an ultraoligotrophic Andean lake: the accessibility to Ophrydium naumanni (Ciliophora, Peritricha)

BALSEIRO, EG; MODENUTTI, BE; QUEIMALIÑOS, CP

JOURNAL OF PLANKTON RESEARCH

Oxford University Press

Lugar: Oxford; Año: 2001 vol. 23 p. 849 - 857

0142-7873

The calanoid copepod, Boeckella gracilipes, is the dominant crustacean zooplankton in south Andean ultraoligotrophic deep lakes. Combining field and experimental data we explored the feeding of the copepod and its access to the mixotrophic ciliate Ophrydium naumanni, in Lake Moreno Oeste (Patagonia, Argentina). Phytoplankton was dominated by nanoflaglellates throughout the water column. Ophrydium naumanni, which accumulates much of the chlorophyll a, as do copepodites and adults of B. gracilipes, has a deep distribution during the day, with maximal abundances around 30 m depth. Mouth-part morphology analysis of B. gracilipes indicated that the copepod has an omnivorous diet. Laboratory experiments showed that B. gracilipes could access only when it is offered as a single food item. However, when natural phytoplankton and ciliate assemblages (including O. naumanni) are offered, B. gracilipes did not feed Ophrydium and preyed on the oligotrich, Strombidium viride, and phytoflagellates like Chrysochromulina parva. The range of ingested sizes was broad (3.9-33 µm of equivalent spherical diameter) but all selected particles were motile ones with distinctive movements, which would enhance the copepod particle detection.