Three-dimensional odor tracking by Nautilus pompilius

The 'living fossil' Nautilus pompilius is thought to use olfaction as its p rimary sensory system during foraging, yet neither the organs responsible f or olfaction nor the mechanisms or behaviors associated with odor tracking have been subjected to experimentation. Flume testing under dark conditions revealed that Nautilus could consistently detect and follow turbulent odor plumes to the source over distances up to 10 m, exhibiting two types of or ientation behavior while sampling in three dimensions. The paired rhinophor es were necessary for orientation behavior: when they were temporarily bloc ked either uni- or bilaterally, Nautilus detected odor but could not track the plume and locate the source, Animals that were tested post-blockage wer e able to track and locate the source. The role of the 90 thin tentacles re mains enigmatic; they seemed to be able to detect odor, but they were not c apable of guiding orientation behavior towards a distant odor source. Bilat eral chemical sensing by rhinophores in three dimensions may have been the Umwelt of ammonites and belemnites before the evolution of complex eyes and fast locomotion in modern coleoids.