Dataset for "Stereoanatomy analysis of the early cephalized central nervous system in a marine planarian, Stylochoplana pusilla"

Platyhelminthes are a phylum of simple bilaterian invertebrates with prototypic body systems. Compared with non-bilaterians such as cnidarians, the bilaterians are likely to exhibit integrated free-moving behaviors, which require a concentrated nervous system “brain” rather than the distributed nervous system of radiatans. Thus, marine planarians have an early cephalized ‘central’ nervous system compared not only with non-bilaterians but also with those parasitic flatworms or freshwater planarians. Here, we investigated the 3-D structures of the planarian central nervous system by the use of X-ray micro-computed tomography (micro-CT) in a synchrotron radiation facility. We identified, in marine planarians, both an apparent optic chiasm (a well-known feature in vertebrates) and mushroom bodies (prominent in insects). These results suggest that the marine planarian “brain” provides a valuable ‘missing-link brain’ between those of the protostome and deuterostome, especially in the evolutionary aspects of the nervous system.