The behaviour of Agalma elegans alternates between:
- passive drifting
- active swimming, which maintains the position of the siphonophore in the water and enables it to find food
Once in a suitable location:
- The animal relaxes.
- The stem drifts into arcs above the nectosome (of swimming bells).
- The tentacles extend.
- Side branches of the tentacles also extend and spread out the orange-red tentilla into a feeding net. This feeding net is almost invisible in the water, with only the coloured tentilla visible to potential prey.
How do Agalma species catch prey and feed?
- Species of Agalma may actually jiggle the tentilla up and down slightly to mimic a swimming copepod or other small zooplankton, attracting prey to the tentilla.
- Prey becomes ensnared by the long transparent terminal filaments.
- As the prey struggles to escape, the cnidoband of many nematocysts (17,030 per band in A. elegans) is slapped onto it and toxins are injected, immobilising the prey.
- The tentacles contract, bringing the prey to the mouth.
- The mouth envelops the prey, pours enzymes onto it and digestion begins.