Memory-related neural plasticity in the hemiellipsoid bodies, the crab's "mushroom bodies".

LOCATELLI, FERNANDO; DELORENZI, ALEJANDRO; MAZA, FRANCISCO JAVIER; SZTARKER, JULIETA; SHKEDY, AVISHAG

Montevideo

Congreso; XII Congress International Society for Neuroethology; 2016

International Society for Neuroethology

The corpora pedunculata (or mushroom bodies) are complex paired structures in the brain of invertebrate species vastly studied in insects. Since their description in the mid-1850, the corpora pedunculata have been considered to be higher-order brain centers involved in multimodal sensory integration and memory. Although morphologically diverse, a corpora pedunculata common ground plan was described across different invertebrates. Moreover, it has been proposed that the mushroom bodies and the vertebrate pallium evolved from the same structure in a common ancestor circa 600 million years ago. In  crustaceans, neuropils sharing a similar pattern with the corpora  pedunculata are the hemiellipsoid bodies (HBs), which have been  proposed to have an evolutionary common origin. Here, we show in the crab Neohelice granulata morphological and immunohistochemical  studies that parallel the results of well described HBs in other crustaceans. Golgi impregnation shows that, like the MBs in insects, the HB globuli cells project to a tract that is subdivide into lobes and claw cells were present. HBs present CaMKII immunoreaction and neurogenesis. Additionally, we found by in vivo calcium imaging that the intrinsic neurons of the crab´s HBs respond to both mechanical and visual stimulation. Remarkably, specific changes to a visual danger stimulus are induced by a training protocol that generates associative memory. These results provide the first in vivo physiological evidence that supports the idea that the HBs, the crustaceans´ mushroom bodies, are involved in memory processes.