We used laboratory experiments to study the effects of changing food abundance on the
selective feeding of two heterotrophic nanoflagellates on particles of similar size but differing
nutritional quality (latex beads and fluorescently stained bacteria). Both Bodo saltans and
Spumella sp. exhibited similar shifts in selectivity with changes in food concentration.
Flagellates that were cultured under food‐limiting conditions showed a modest but
significant preference for beads when both particles were offered simultaneously. However …

Two heterotrophic nanoflagellates Bodo saltans andSpumella sp. were fed on particles of
similar size but differing nutritional quality (latex beads and fluorescently stained bacteria).
They both exhibited similar shifts in selectivity with changes in food concentration. For
example, as bacterial abundance declined over 24 h, discrimination against the inert beads
gradually relaxed. The observed pattern of concentration-dependent selectivity is in
agreement with the predictions of optimal diet models.