Figure 4

Morphology of the brain in Mictocaris halope . Acetylated α-tubulin immunoreactivity and nuclear counterstaining. A-I: Dorsal view on confocal laser-scans of horizontal vibratome sections (50 μm) labeled for acetylated α-tubulin immunoreactivity (green) and nuclear marker (blue). A: Overview of distal protocerebral neuropil (Ia) and lateral protocerebrum (Ib). B: The neuropilar subunits of the protocerebral bridge (PB) are visible as a negative imprint at the anterior part of the median protocerebrum (Ic). C, D: The central body (CB) is subdivided into several elongated or spheroidal compartments (asterisks), which are connected posteriorly via numerous fine neurites (arrowheads in C) to the 3^rd transverse tract (TT3, red arrows). The 2^nd transverse tract (TT2, yellow arrows) passes the CB anteriorly, sending fine processes into the neuropil (arrowheads in D). The 1^st transverse tract (TT1) lies dorsal to the CB. E, F: The paired branches of the OGT form a characteristic chiasm (X in E) in the center of the median protocerebrum (Ic) and connect the olfactory neuropil (ON) to the lateral protocerebrum (Ib). Before reaching the target structure in the medial part of the lateral protocerebrum, the OGT splits into two neurite bundles (arrows in F). G: Overview of the deutocerebrum (II). H: Higher magnification of the medial part of the deutocerebrum (II). The 4^th transverse tract (TT4) seems to originate in the nerves of the antenna 1 (A1Nv), forming a deutocerebral commissure (arrows). I: The antenna 1 nerves (A1Nv) enter the deutocerebrum from the anterior direction, each splitting into a thick medial and a slender lateral branch. Several neurite bundles from the medial branch project into the lateral deutocerebral neuropil (arrowheads), while others constitute to the 4^th transverse tract (TT4) (arrows in H). The lateral branch innervates the olfactory neuropil (arrows). Scale bars: 50 μm.