Ontogenetic change of foraging behaviour during copepodite development of Acartia clausi

Abstract

Swimming behaviour of copepodite stage CI to adults of the planktonic copepod Acartia clausi were observed at different food levels (0, 60, 500 and 2000 cells ml -1 ) of the diatom Thalassiosira weissflogii. Concurrent measures of clearance in bottle incubations were performed for CI and adult females. All indivuduals exhibited typical jump-sink behaviour. At low food concentrations early copepodites filtered 36% of the time, and later stages 18%, yet the increased suspension-feeding effort did not enhance their clearance rate. Older stages and adults did not show feeding-bouts at low food concentrations, which is interpreted as a switch to the ambush-feeding mode, whereby the copepods are assumed to be searching for potentially abundant larger and motile prey, for instance, ciliates. When offered no food, frequent and long jumps were observed in all stages except for CI. Search volumes during ambush feeding were estimated, and the slow sinking of early stages resulted in a small search volume as compared to that in later stages. Early copepodite stages depended to a higher degree on suspension feeding, regardless of food concentration, due to their undeveloped food searching ability. High food availability is therefore crucial for the growth and survival of early copepodite stages of A. clausi. The heavier body of later stages enhanced foraging efficiency both during suspension feeding (by gravity tethering) and in ambush feeding (by faster sinking).KEY WORDS: Swimming behaviour · Suspension feeding · Ambush feeding · Switching behaviour · Lower feeding threshold · Life history · CalanoidResale or republication not permitted without written consent of the publisher

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

“…It is interesting to note the behavioural changes in Oithona davisae nauplii in the presence of the nonmotile prey (longer sinking events, lower transportation velocity and lower jump frequency) agree well with the reported effects of filtered seawater (no food) on Acartia clausi adults (Takahashi & Tiselius 2005). Such behavioural changes could indicate a strategy to save energy in an environment in which they are not able to sustain their normal energy demands through accessible food.…”

Copepod growth and diatoms: insensitivity of Acartia tonsa to the composition of semi-natural plankton mixtures manipulated by silicon:nitrogen ratios in mesocosms

“…tonsa has been reported repeatedly to be able to shift between suspension and ambush feeding and thus between feeding on diatoms and motile protists (Saiz and Kiørboe 1995;Kiørboe et al 1996;Takahashi and Tiselius 2005). The plot in Fig.…”

“…diatoms, and the latter for motile prey, e.g. ciliates and flagellates (Saiz and Kiørboe 1995;Kiørboe et al 1996;Takahashi and Tiselius 2005).…”

High reproduction, but low biomass: mortality estimates of the copepod Acartia tonsa in a hyper-eutrophic estuary

“…Ontogenetic shifts in behaviour of younger stages have been found in the congener Acartia clausi (Takahashi & Tiselius 2005). Stages C1 to C3 engage much more in filter feeding than older stages, and have long jumps directed horizontally instead of vertically as in later developmental stages.…”