Abstract
A population of descending neurons connect the brain and thoracic motor center, playing a critical role in controlling behavior. We examined the anatomical organization of descending neurons (DNs) in the brain of the silkmoth Bombyx mori. Moth pheromone orientation is a good model to investigate neuronal mechanisms of behavior. Based on mass staining and single-cell staining, we evaluated the anatomical organization of neurite distribution by DNs in the brain. Dense innervation was observed in the posterior–ventral part of the brain called the posterior slope (PS). We analyzed the morphology of DNs innervating the lateral accessory lobe (LAL), which is considered important for moth olfactory behavior. We observed that all LAL DNs also innervate the PS, suggesting the integration of signals from the LAL and PS. We also identified a set of DNs innervating the PS but not the LAL. These DNs were sensitive to the sex pheromone, suggesting a role of the PS in motor control for pheromone processing. Here we discuss the organization of descending pathways for pheromone orientation.
Highlights
Male moths orient toward conspecific females based on their sex pheromones
There are interneurons whose dendrites are confined within the lateral accessory lobe (LAL) and ventral protocerebrum (VPC), but no interneurons whose dendrites are confined within the VPC have been reported[16]
We examined the morphology of descending neurons (DNs) innervating the LAL in B
Summary
Male moths orient toward conspecific females based on their sex pheromones. Sex pheromones have been demonstrated to reliably elicit stereotyped behavior in moths, and are a good model for investigating the general mechanisms underlying olfactory navigation[1]. A specific group of descending neurons (DNs), which connect the brain and ventral nervous system, have been identified as an important element for pheromone orientation in the silkmoth Bombyx mori[2]. These DNs have neurites innervating a specific brain region called the lateral accessory lobe (LAL), which is a key area in insect brains connecting the central complex with other parts of the protocerebrum[3,4]. A fraction of DNs innervate the LAL and the individual morphology is largely unknown for DNs innervating other brain regions in the moth. The organization of the descending pathway for pheromone orientation is discussed based on the neuroanatomy
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