Serotonergic Neurons in the Brain and Gnathal Ganglion of Larval Spodoptera frugiperda

Abstract

The fall armyworm Spodoptera frugiperda (S. frugiperda) (Lepidoptera: Noctuidae) is a worldwide, disruptive, agricultural pest species. The larvae of S. frugiperda feed on seedling, leave, and kernel of crops with chewing mouthparts, resulting in reduced crop yields. Serotonin is an important biogenic amine acting as a neural circuit modulator known to mediate lots of behaviors including feeding in insects. In order to explore the serotonergic neural network in the nervous system of larval S. frugiperda, we performed immunohistochemical experiments to examine the neuropil structure of the brain and the gnathal ganglion with antisynapsin and to examine their serotonergic neurons with antiserotonin serum. Our data show that the brain of larval S. frugiperda contains three neuromeres: the tritocerebrum, the deutocerebrum, and the protocerebrum. The gnathal ganglion also contains three neuromeres: the mandibular neuromere, the maxillary neuromere, and the labial neuromere. There are about 40 serotonergic neurons in the brain and about 24 serotonergic neurons in the gnathal ganglion. Most of these neurons are wide-field neurons giving off processes in several neuropils of the brain and the gnathal ganglion. Serotonergic neuron processes are mainly present in the protocerebrum. A pair of serotonergic neurons associated with the deutocerebrum has arborizations in the contralateral antennal lobe and bilateral superior lateral protocerebra. In the gnathal ganglion, the serotonergic neuron processes are also widespread throughout the neuropil and some process projections extend to the tritocerebrum. These findings on the serotonergic neuron network in larval S. frugiperda allow us to explore the important roles of serotonin in feeding and find a potential approach to modulate the feeding behavior of the gluttonous pest and reduce its damage.

Insane in the brain : How neuroparasites manipulate the insect’s brain function and behaviour

“…The 5HT-IR cells localised in the SOG share a high similarity with the clusters reported for the closely related species M. sexta, H. armigera and S. frugiperda (Griss 1989;Tang et al 2019;Zhang et al 2022). In our findings for S. exigua compared to H. armigera, the AL resembles the GNG-L1, VPL-1 has resemblance in localisation with GNG-L2, our VPL-2 has resemblance with the GNG-L3, DAM resembles the location of GNG-AD and even the less frequently found VC cluster from our study resembles GNG-AV (Tang et al 2019).…”

“…Regarding the projections and commissures, TA-IR and 5HT-IR were the most similar. The locations of the observed cell bodies and projections are similar in location and number to those in CNSs of other insect species, but mostly to the instars of closely related lepidopteran species (Granger et al 1989;Tang et al 2019;Zhang et al 2022). Combining the results of locations of the biogenic amines and their rate limiting enzymes with the location of AcMNPV in the CNS of mid third instar S. exigua larvae, there does not seem to be a one to one overlap between virus and location of the biogenic amine-producing in exactly the same cell bodies (Figure 2).…”

“…bullata (brain: 64, SOG: 22) (both Nässel and Cantera 1985), M. sexta larvae (brain: 36-40, SOG: 20;Granger et al 1989 and Griss 1989, respectively), and lastly the closely related S. frugiperda larvae (brain: around 40, SOG: around 24;Zhang et al 2022).…”

Simulating immunosuppressive mechanism of Microplitis bicoloratus bracovirus coordinately fights Spodoptera frugiperda

“…An interesting research found that starved male cells consume their own proteins ( 33 ). Serotonergic neurons in the brain of larval S. frugiperda are involved in multiple effects in a variety of behaviors, like feeding-related modulation ( 34 ). The stress caused by dsRNA administration may have triggered the nervous system to promote this cannibalism; excluding the cannibalism of 1 st instar, one-time feeding kills individual larva in 1 st and 2 nd instar.…”

Distribution analysis of TRH in Bactrocera dorsalis using a CRISPR/Cas9‐mediated reporter knock‐in strain

“…In accordance with the expression pattern of TRH in D. melanogaster(Neckameyer et al, 2007), BdorTRH was mainly distributed in neural tissues. Although studies on serotonin distribution in the central nervous system of several insect species have been made possible by the availability of specific antibodies against 5-HT(Huser et al, 2012;Tang et al, 2019;Zhang et al, 2022), the expression pattern of neuronal TRH in insects is largely unknown. Our study on the metamorphosis of the TRH-IR system has revealed that, in general, the organisation of neuronal TRH cell clusters persists toF I G U R E 5 Expression pattern of BdorTRH in 15-day-old adult neural tissues based on anti-V5 staining.…”