A role for nautilus in studies of the evolution of brain and behavior.

Nautilus is an ancient remnant of a largely extinct cephalopod lineage.1 Its status within its clade is the subject of ongoing debate-its morphology, behavior and neuroanatomy may or may not be representative of an ancestral condition, and therefore its value as a model for ancestral cephalopods is uncertain. While the nautilus brain is simpler than that of more derived cephalopods2 (coleoids), it is plausible that this is a secondary simplification related to ecology, and not a precursor to the vertebrate-like CNS of modern cephalopods. However, the absence of the vertical lobe complex, implicated in learning and memory in coleoids, makes studies of cognition in nautilus particularly interesting from a comparative perspective. Our research on the behavior and sensory biology of Nautilus pompilius gives the first indications of learning and memory in this ancient genus,3 and suggests that even with a far simpler brain containing no clearly defined "memory" center, nautilus performs simple cognitive tasks comparably to its more derived relatives.