The brain of a nocturnal migratory insect, the Australian Bogong moth

Abstract

Every year, millions of Australian Bogong moths (Agrotis infusa) complete an astonishing journey: In Spring, they migrate over 1,000 km from their breeding grounds to the alpine regions of the Snowy Mountains, where they endure the hot summer in the cool climate of alpine caves. In autumn, the moths return to their breeding grounds, where they mate, lay eggs and die. These moths can use visual cues in combination with the geomagnetic field to guide their flight, but how these cues are processed and integrated into the brain to drive migratory behavior is unknown. To generate an access point for functional studies, we provide a detailed description of the Bogong moth's brain.Based on immunohistochemical stainings against synapsin and serotonin (5HT), we describe the overall layout as well as the fine structure of all major neuropils, including the regions that have previously been implicated in compass-based navigation. The resulting average brain atlas consists of 3D reconstructions of 25 separate neuropils, comprising the most detailed account of a moth brain to date. Our results show that the Bogong moth brain follows the typical lepidopteran ground pattern, with no major specializations that can be attributed to their spectacular migratory lifestyle. These findings suggest that migratory behavior does not require widespread modifications of brain structure, but might be achievable via small adjustments of neural circuitry in key brain areas. Locating these subtle changes will be a challenging task for the future, for which our study provides an essential anatomical framework. K E Y W O R D S central complex, insect brain, Lepidoptera, mushroom body, noctuid 1 | INTRODUCTION One of the central questions in neuroscience is how animal behaviors result from neural computations. From the sensory input that elicits abehavior to the motor circuits that execute it-the neural processing is complex and, as yet, we only understand small pieces of this multi-level puzzle. To delve deeper into this question, we need an animal model that shows a robust behavior and whose brain is accessible enough to

The brain of Cataglyphis ants: Neuronal organization and visual projections

“…Several neuropils of the central brain are surrounded by glial cells and, thus, exhibit well‐defined boundaries. This applies to the ALs, the neuropils of the CX, the MBs, and the neuropils of the OLs—and is consistent with anatomical studies in other insects (Adden, Wibrand, Pfeiffer, Warrant, & Heinze, 2020; Brandt et al, 2005; Bressan et al, 2015; el Jundi, Huetteroth, Kurylas, & Schachtner, 2009; Groothuis, Pfeiffer, el Jundi, & Smid, 2019; Heinze & Reppert, 2012; Immonen et al, 2017; Ito et al, 2014; von Hadeln et al, 2018). The general shape and structural characteristics of these neuropils in the brain of Cataglyphis nodus are also similar to the findings in the honey bee (Brandt et al, 2005).…”

“…The AOT seems to be a most conserved optic tract in insects. It has been described in diverse insect orders such as Blattodea (Reischig & Stengl, 2002; Rosner et al, 2017), Coleoptera (Immonen et al, 2017), Diptera (Adden et al, 2019; Fischbach & Lyly‐Hünerberg, 1983; Omoto et al, 2017; Power, 1943; Strausfeld, 1976), Lepidoptera (Collett, 1972; Strausfeld & Blest, 1970), Orthoptera (Homberg et al, 2003; Pfeiffer et al, 2005), and Hymenoptera including different Cataglyphis species (Grob et al, 2017; Held et al, 2016; Mota et al, 2011; Pfeiffer & Kinoshita, 2012; Schmitt, Stieb, et al, 2016). The AOT relays optic motion information (Collett, 1972; DeVoe et al, 1982; Paulk et al, 2008) as well as chromatic and polarization cues (Kinoshita et al, 2007; Mota et al, 2011; Pfeiffer et al, 2005) to the AOTU.…”

The head direction circuit of two insect species

“…In this context, it is interesting to note that neither solution to this problem is possible for insects of a different order, the lepidoptera (moths and butterflies). These insects have an almost straight EB, their PB is split along the midline, and right-left connections between the two halves are realised by a neuropil-free fiber bundle (Heinze and Reppert, 2012;Adden et al, 2020). Neither midline crossing E-PG fibers within the PB, nor local connections around the ring of the EB are therefore morphologically possible, suggesting that a functional closure of the heading direction circuit is either not required or achieved via other means in these species.…”

A neural model for insect steering applied to olfaction and path integration

“…CX output neurons project to the LAL. The brain shown is a Bogong moth brain (Agrotis infusa [31] [32]) retrieved from insectbraindb.org, species handle https://hdl.handle.net/20.500.12158/SIN-0000002.1. Photo courtesy of Ajay Narendra.…”