6 Summary and outlook
6.1 Explored traits
Within the framework of this thesis we identied, quantied and explored physical
and behavioural functional traits of agellates and lter feeders. In the following I
will summarise the essential traits that we worked with, before discussing the related
trade-os in the next section.
For agellates we used an analytical hydrodynamics model to quantify agellar arrangements
and beat patterns through characteristic distributions and movements of
forces (paper I and II). The angular force arrangement is one relevant trait that can
inuence swimming speed, stealth and prey clearance rates in mixotrophic biagellates
(paper II), while for helical swimmers such as Heterosigma akashiwo the force distance
and relative magnitudes of longitudinal and transversal agellum can be of importance
to shape swimming trajectories and ows.
For lter feeders we considered traits describing the morphology, kinematics and
body composition of individual organisms from choanoagellates to centimetre-sized
tunicates (paper III and IV). The feeding ow for choanoagellates in relation to the
design and kinematics of agellum, lter, and lorica was considered in depth in paper
III, where we propose a agellar vane attached to the slender agellum to drive the
feeding ow. The modelled traits include cell size, length, frequency, amplitude, and
wavelength of the agellum, lter spacing and width of the microvilli as well as the
diameter of the lorica chimney related to the width of the vane.
The general lter feeder model in paper IV relates the maximum clearance rate in
lter feeders to a motor force limit and predicts gelatinous life forms to emerge within
large suspension-feeding plankton. The lter area per energy content (relating energy
density and content) as well as the lter speed are considered as the most important
traits in this model.
We further began to explore the sloppiness of direct-interception feeders and the
relation to capture rates and physical prey size selection (paper V). Obvious traits of
such predators are body size, which the prey size range and the characteristic ow
speed depend on, while the foraging rate can be a behavioural trait (foraging eort)
that is also limited by physical constraints such as stickiness or the number and spatial
extent of prey capture sites.