Observations on neurophysiological pattern and behavioural traits as death-feigning mechanism in Eucryptorrhynchus scrobiculatus (Coleoptera: Curculionidae).

Abstract

In adaptation to surrounding environmental stimuli, most insects exhibit defense behaviour (death feigning) to improve survival rates in the wild. However, the underlying mechanism of death feigning remains largely unknown. Here, we tested the neurophysiological pattern and behavioural traits of the death-feigning mechanism in the forestry pest Eucryptorrhynchus scrobiculatus. Using neuroanatomy, LC-MS/MS target metabolomics detection technology and qRT-PCR, we investigated the effects of neurochemicals and metabolic pathways in experimental weevils. Excision and drug tests were conducted to verify the key regulatory body parts involved in regulating the central nervous system in death feigning. Our results reconstructed the death-feigning mechanism of E. scrobiculatus: when the effective stimuli point of arousal weevils received mechanical stimulation, the thoracoabdominal ganglion transmitted signals into the brain through the ventral nerve cord, and then the brain regulated dopamine (DA) and serotonin (5-HT) metabolic pathways, reducing the expression of dopamine (dar2) and octopamine (oar1, oab2) receptor genes, finally inducing death feigning. Our study suggests that the variation of neurotransmitters in the brain is an important indicator of the physiological response of death feigning, and the results provide ecological and theoretical information for future investigations to reveal key behaviour and target genes for pest control.