Organization and neural connections of the lateral complex in the brain of the desert locust

Abstract

The lateral complexes (LXs) are bilaterally paired neuropils in the insect brain that mediate communication between the central complex (CX), a brain center controlling spatial orientation, various sensory processing areas, and thoracic motor centers that execute locomotion. The LX of the desert locust consists of the lateral accessory lobe (LAL), and the medial and lateral bulb. We have analyzed the anatomical organization and the neuronal connections of the LX in the locust, to provide a basis for future functional studies. Reanalyzing the morphology of neurons connecting the CX and the LX revealed likely feedback loops in the sky compass network of the CX via connections in the gall of the LAL and a newly identified neuropil termed ovoid body. In addition, we characterized 16 different types of neuron that connect the LAL with other areas in the brain. Eight types of neuron provide information flow between both LALs, five types are LAL input neurons, and three types are LAL output neurons. Among these are neurons providing input from sensory brain areas such as the lobula and antennal neuropils. Brain regions most often targeted by LAL neurons are the posterior slope, the wedge, and the crepine. Two descending neurons with dendrites in the LAL were identified. Our data support and complement existing knowledge about how the LAL is embedded in the neuronal network involved in processing of sensory information and generation of appropriate behavioral output for goal‐directed locomotion.

3D‐atlas of the brain of the cockroach Rhyparobia maderae

“…The GA has been identified as a distinct target area of columnar CL1 neurons connecting slices of the CBL and PB in the fruit fly (Wolff et al, 2015), dung beetles (Immonen et al, 2017), the honeybee (Hensgen et al, 2021a), and the monarch butterfly (Heinze & Reppert, 2012). In the cockroach it is, unlike in the locust (Hensgen et al, 2021b), visible as a distinct area in synapsin staining and was confirmed to be the GA by tracer injection into a single CL1 neuron (Figure 7b). An additional subunit of the LLAL, the PRO, is described here for the first time in an insect.…”

“…Heinze & Homberg, 2008; Hensgen et al., 2021a), but their axonal terminals are usually more diffusely distributed throughout the LAL. As targets of various CX outputs, the LALs, as shown in flies, locusts, and silk moths provide input to descending pathways and play an important role in navigational motor control (Hensgen et al., 2021b; Namiki et al., 2018; Rayshubskiy et al., 2020).…”

Myoinhibitory peptides in the central complex of the locust Schistocerca gregaria and colocalization with locustatachykinin‐related peptides

“…Cell bodies were marked using the Landmark module and neuropils were reconstructed as described by Hensgen et al. (2021). Briefly, several layers of each neuropil were manually marked in the x‐, y‐, and z‐plane in the segmentation editor.…”

“…The antibody has been used to label synaptic neuropils in different insect species. In S. gregaria, neuropil labeling has been demonstrated by Kurylas et al (2008), el Jundi et al (2010), von Hadeln et al (2018, and Hensgen et al (2021).…”

“…Primary processing of image stacks from the confocal laser scanning microscope was done in Amira 5.6 (ThermoFisher Scientific, Waltham, MA; RRID: SCR_007353). Cell bodies were marked using the Landmark module and neuropils were reconstructed as described by Hensgen et al (2021). Briefly, several layers of each neuropil were manually marked in the x-, y-, and z-plane in the segmentation editor.…”