A Third Type of Defensive Behavior in the Tenebrionid BeetleZophobas atratusPupae

Abstract

Pupae of the tenebrionid beetle Zophobas atratus Fabricius (Coleoptera: Tenebrionidae) exhibit two types of reflex abdominal motions in response to tactile stimulation: circular rotation and lateral bending to close pinching devices (gin-traps). In the present study, the pupa exhibited novel, sequential abdominal movements at 0.3–2.2 sec after the onset of mechanical stimulation. The most effective stimulation was gentle, double brushing on the ventral surface of an abdominal segment (sternite). The sequential abdominal movements consisted of the following three types of discrete elementary motions (100–350 ms in duration): rapid vibration of 30–40 Hz, circular rotation (or swing), and small wiggling movements. A sequence of abdominal movements generally started with a few bouts of vibration, but the number and order of subsequent motions varied considerably among different sessions and conditions. A restrained pupa often showed a prolonged sequence of many motions, including several rotations, whereas an unrestrained pupa often shortened the sequence by skipping a few rotations after the displacement of its whole body induced by the first abdominal rotation. Stimulation of two types of mechanosensitive sensilla, the hair sensilla (touch sensors) and campaniform sensilla (strain sensors), seemed to be necessary to initiate the defensive response. In natural environments, crawling of a small predator (or parasitoid) on the surface of the abdomen or repeated attacks of a large predator may induce this defensive response in the pupae.

The Superworm, Zophobas morio (Coleoptera:Tenebrionidae): A ‘Sleeping Giant’ in Nutrient Sources

“…The pupae ( Fig. 2C ) are mostly quiescent, however, when tactile stimulated, they have the ability to rotate their abdominal segments in a circular motion ( Ichikawa and Kurauchi 2009 , Ichikawa et al 2012b ) or exhibit other physical responses ( Ichikawa et al 2012a , Ichikawa and Sakamoto 2013 ). All these reactions are considered to be an effective pupal defense mechanism against predator attacks and larval cannibalistic behaviors and are triggered by the stimulation of different types of mechanoreceptive sensilla on the pupal body surface ( Kurauchi et al 2011 ).…”

Sex and stress modulate pupal defense response in tobacco hornworm

“…Previous studies have been documented in the pupae of other species which undergo similar wriggling motion against predators such as Kiwi, Weka, and Rock wren. For instance, Atijebde et al (2020) observed vibrational stimuli-activated defenses in Wiseana viette (Lepidoptera: Hepialidae) pupae; similar behavior was also observed in Zophobas atratus (Coleoptera: Tenebrionidae) beetle pupae ( Grosman et al 2008 ; Ichikawa et al 2012 ; Ichikawa and Sakamoto 2013 ).…”

“…This external stimulus can originate from physical presence as well as vibrational signals emitted by enemies which induce antipredatory behavior ( Chandrasegaran et al 2020 ), leading to abdominal movements commonly known as sinusoidal wriggling and lateral bending/up–down forth motion (pulsating events). These responses are a direct result of neuronal activation that culminates in the movement of abdominal segments, turning their dorsum away from the enemy ( Ichikawa and Sakamoto 2013 ). In our study, the observed wriggling and pulsating movement in M. sexta pupae upon the introduction of vibrational signals to the pupal abdomen for 3 s were also an attempt of pupae to turn themselves (by turning their dorsum) away in the wake of an enemy or any warning signals.…”