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Synaptic connections of first‐stage visual neurons in the locust Schistocerca gregaria extend evolution of tetrad synapses back 200 million years
Author(s) -
Wernitznig Stefan,
Rind Frances Claire,
Pölt Peter,
Zankel Armin,
Pritz Elisabeth,
Kolb Dagmar,
Bock Elisabeth,
Leitinger Gerd
Publication year - 2014
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.23682
Subject(s) - locust , schistocerca , biology , tetrad , arthropod , neuroscience , postsynaptic potential , synapse , insect , anatomy , botany , ecology , receptor , biochemistry
The small size of some insects, and the crystalline regularity of their eyes, have made them ideal for large‐scale reconstructions of visual circuits. In phylogenetically recent muscomorph flies, like Drosophila , precisely coordinated output to different motion‐processing pathways is delivered by photoreceptors (R cells), targeting four different postsynaptic cells at each synapse (tetrad). Tetrads were linked to the evolution of aerial agility. To reconstruct circuits for vision in the larger brain of a locust, a phylogenetically old, flying insect, we adapted serial block‐face scanning electron microscopy (SBEM). Locust lamina monopolar cells, L1 and L2, were the main targets of the R cell pathway, L1 and L2 each fed a different circuit, only L1 providing feedback onto R cells. Unexpectedly, 40% of all locust R cell synapses onto both L1 and L2 were tetrads, revealing the emergence of tetrads in an arthropod group present 200 million years before muscomorph flies appeared, coinciding with the early evolution of flight. J. Comp. Neurol. 523:298–312, 2015. © 2014 Wiley Periodicals, Inc.