Tiselius, P. Kristineberg Marine Research Station, p.tiselius@kmf.gu.se

 
SELECTIVE PREDATION OF THE COPEPODS ACARTIA BIFILOSA AND TEMORA LONGICORNIS ON THREE OLIGOTRICH CILIATES - ESCAPE RESPONSES ELICITED BY A STRONG FEEDING CURRENT
 
Predation by the copepods Acartia bifilosa and Temora longicornis on ciliates were measured daily for 9 days during an upwelling event at a coastal station in the Baltic. Ciliate abundances increased exponentially over time, while copepod clearance rates were variable but did not increase. A. bifilosa showed similar clearance rates on the three dominant ciliates (26-33 ml female-1 d-1) whereas T. longicornis consistently selected a Strombidium species (51 ml female-1 d-1) over Mesodinium rubrum (31) or Strobilidium spiralis (12 ml female-1 d-1). Selectivity was unrelated to total ciliate abundance. T. longicornis feeds by creating a strong feeding current trapping ciliates whereas Acartia sp. (and presumably A. bifilosa) capture ciliates raptorially while sinking. The different selectivity displayed by the copepods is suggested to depend on ciliate escape capabilities, and specifically on the ciliates ability to detect shear fields and perform strong escape jumps. Strombidium is small and escapes weakly, Mesodinium has very strong escape jumps and the large Strobilidium may swim fast enough to avoid getting trapped in the feeding current of T. longicornis. These shear related escape responses would not affect capture by an ambush predator, hence the invariant predation by Acartia.
 
Day: Wednesday, Feb. 3
Time: 11:15 - 11:30am
Location: Hilton of Santa Fe
 
Code: CS60WE1115H