Flexible Spatial Orientation and Navigational Strategies in Chambered Nautilus

Nautilus is a remnant of an externally shelled cephalopod lineage that flourished between 450 and 60 million years ago. It is a deep-water scavenger that lacks the complex brain and behavioural repertoire of its soft-bodied relatives, the coleoid cephalopods. Nautilus makes repeated, nightly migrations from deep to shallow water along coral reef slopes to forage, thus an ability to navigate to known locations may be selectively advantageous. Alternatively, drifting passively with the current may be sufficient to locate food and mates distributed randomly over a large area. The derived neural structures that support learning and memory in coleoids are absent from the nautilus brain, indicating that substantial differences between learning abilities in nautilus and coleoids are likely. However, our previous work has demonstrated both associative and spatial learning in nautilus. In laboratory experiments, we tested whether Nautilus pompilius could learn to navigate towards a goal location using either visual cues or motor responses. Results indicate that animals relied both on proximate and distant visual cues to orient but did not use egocentric cues, a somewhat surprising finding given that nautilus spends most of its time in near darkness. Animals learned visual information rapidly and in some cases were able to switch to other tactics when salient visual cues were removed or manipulated.