A crabs' high-order brain center resolved as a mushroom body-like structure

FRANCISCO JAVIER MAZA; JULIETA SZTARKER; MARIA EUGENIA COZZARIN; MARIA GRAZIA LEPORE; ALEJANDRO DELORENZI

JOURNAL OF COMPARATIVE NEUROLOGY

WILEY-LISS, DIV JOHN WILEY & SONS INC

Lugar: New Jersey; Año: 2020 p. 1 - 23

0021-9967

The hypothesis of a common origin for high-order memory centers in bilateral animalspresents the question of how different brain structures, such as the vertebratehippocampus and the arthropod mushroom bodies, are both structurally and functionallycomparable. Obtaining evidence to support the hypothesis that crustaceanspossess structures equivalent to the mushroom bodies that play a role in associativememories has proved challenging. Structural evidence supports that the hemiellipsoidbodies of hermit crabs, crayfish and lobsters, spiny lobsters, and shrimps are homologousto insect mushroom bodies. Although a preliminary description and functionalevidence supporting such homology in true crabs (Brachyura) has recently beenshown, other authors consider the identification of a possible mushroom body homologin Brachyura as problematic. Here we present morphological and immunohistochemicaldata in Neohelice granulata supporting that crabs possess well-developedhemiellipsoid bodies that are resolved as mushroom bodies-like structures. Neoheliceexhibits a peduncle-like tract, from which processes project into proximal and distaldomains with different neuronal specializations. The proximal domains exhibit spinesand en passant-like processes and are proposed here as regions mainly receivinginputs. The distal domains exhibit a ?trauben?-like compartmentalized structure withbulky terminal specializations and are proposed here as output regions. In addition,we found microglomeruli-like complexes, adult neurogenesis, aminergic innervation,and elevated expression of proteins necessary for memory processes. Finally, in vivocalcium imaging suggests that, as in insect mushroom bodies, the output regionsexhibit stimulus-specific activity. Our results support the shared organization ofmemory centers across crustaceans and insects.