Habituatory response decrement in pupae of Tenebrio molitor

Nakamura

Yamawaki

2012

Exarate pupae of the beetle Zophobas atratus Fab. (Coleoptera: Tenebrionidae) have free appendages (antenna, palp, leg, and elytron) that are highly sensitive to mechanical stimulation. A weak tactile stimulus applied to any appendage initiated a rapid rotation of abdominal segments. High-speed photography revealed that one cycle of defensive abdominal rotation was induced in an all-or-none fashion by bending single or multiple mechanosensory hairs on a leg or prodding the cuticular surface of appendages containing campaniform sensilla. The direction of the abdominal rotation completely depended on the side of stimulation; stimulation of a right appendage induced a right-handed rotation about the anterior-posterior axis of the pupal body and vice versa. The trajectories of the abdominal rotations had an ellipsoidal or pear-shaped pattern. Among the trajectory patterns of the rotations induced by stimulating different appendages, there were occasional significant differences in the horizontal (right-left) component of abdominal rotational movements. Simultaneous stimulation of right and left appendages often induced variable and complex patterns of abdominal movements, suggesting an interaction between sensory signals from different sides. When an abdominal rotation was induced in a freely lying pupa, the rotation usually made the pupa move away from or turn its dorsum toward the source of stimulation with the aid of the caudal processes (urogomphi), which served as a fulcrum for transmitting the power of the abdominal rotation to the movement or turning of the whole body. Pattern generation mechanisms for the abdominal rotation were discussed.

Section: Introductionmentioning

confidence: 99%

Defensive Abdominal Rotation Patterns of Tenebrionid Beetle,Zophobas atratus, Pupae

Nakamura

Yamawaki

2012

“…The defensive function of pinching was examined in the pupae of the hawkmoth, Sphinx ligustri (Bate 1973a, b, c), the tenebrionid beetle Tenebrio molitor (Hinton 1946; Wilson 1971), and the ladybird beetle, Cycloneda sanguinea (Eisner and Eisner 1992). The pupae of T. molitor exhibit another type of defensive response: a rapid circular rotation of the abdomen, fringed with many spines, against tactile stimulation of their free appendages (Hollis 1963; Askew and Kurtz 1974). This response may be effective in protecting the pupae from larval cannibalism (Ichikawa and Kurauchi 2009).…”

Section: Introductionmentioning

confidence: 99%

A Third Type of Defensive Behavior in the Tenebrionid BeetleZophobas atratusPupae

Sakamoto

2013

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 pupae of many Coleoptera and some Lepidoptera species are armed with heavily sclerotized projections or jaws near the intersegmental regions of adjacent abdominal segments (Hinton 1946, 1952). The pupae often swing or rotate their abdomen in response to tactile stimulation of their appendages (Hollis 1963; Askew and Kurtz 1974), while they rapidly close the jaws in response to the stimulation of the intersegmental regions of the abdominal segments (Hinton 1946; Wilson 1971; Eisner and Eisner 1992). Hinton (1946) coined the term “gin trap” to describe the pinching device.…”

Section: Introductionmentioning

confidence: 99%

Defensive Gin-Trap Closure Response of Tenebrionid Beetle,Zophobas atratus, Pupae

Kurauchi

Yamawaki

2012

Pupae of the beetle Zophobas atratus Fab. (Coleoptera: Tenebrionidae) have jaws called gin traps on the lateral margin of their jointed abdominal segments. When a weak tactile stimulation was applied to the intersegmental region between the two jaws of a gin trap in a resting pupa, the pupa rapidly closed and reopened single or multiple gin traps adjacent to the stimulated trap for 100200 ms. In response to a strong stimulation, a small or large rotation of the abdominal segments occurred after the rapid closure of the traps. Analyses of trajectory patterns of the last abdominal segment during the rotations revealed that the rotational responses were graded and highly variable with respect to the amplitudes of their horizontal and vertical components. The high variability of these rotational responses is in contrast with the low variability (or constancy) of abdominal rotations induced by the tactile stimulation of cephalic and thoracic appendages. Since the closed state of the gin traps lasts only for a fraction of a second, the response may mainly function to deliver a “painful” stimulus to an attacker rather than to cause serious damage.