Structure and function of the elastic organ in the tibia of a tenebrionid beetle.

Many insects have a pair of claws on the tip of each foot (tarsus and pretarsus). The movement of the pretarsal claws is mediated by a long apodeme that originates from the claw retractor muscles in the femur. It is generally accepted that the pulling of the apodeme by the muscles flexes the claws to engage with a rough surface of a substrate, and the flexed claws return to their initial position by passive elastic forces within the tarso-pretarsal joint.

A third type of defensive behavior in the tenebrionid beetle Zophobas atratus pupae.

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.

Defensive gin-trap closure response of tenebrionid beetle, Zophobas atratus, pupae.

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.

Defensive abdominal rotation patterns of tenebrionid beetle, Zophobas atratus, pupae.

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.

Partial synchronization dynamics of coupled ultradian oscillators comprising an insect neurosecretory cell system.

An insulin-related peptide, bombyxin, in the silkmoth Bombyx mori is secreted by four pairs of cerebral neurosecretory cells that form a weakly coupled oscillator system to produce a pulsatile pattern of hormone secretion. The activity of individual bombyxin-producing (BP) cells oscillated with different periods (20-70 min). The population of BP cells exhibited complex phase dynamics, including spontaneous synchronization and desynchronization of different combinations of cells.

Larval cannibalism and pupal defense against cannibalism in two species of tenebrionid beetles.

Cannibalism of pupae by larvae has been documented In many species of Insects, but the features of larval cannibalism and pupal defensive mechanisms against larval cannibalism have been largely Ignored. Pupae of tenebrionld beetles rotate their abdominal segments in a circular motion in response to the tactile stimulation of appendages, including legs, antennae, maxillary pulps, and wings. When the pupal abdominal rotation responses of Tenebrio molitor and Zophobas atratus were completely blocked by transecting the ventral nerve cord (VNC) of the pupae, the appendages of the paralytic pupae became initial, major targets for attack by larval cannibals.

Mechanism of hemolymph circulation in the pupal leg of tenebrionid beetle Zophobas atratus.

The long legs of insects require adequate hemolymph flow for maintaining their metabolism and functions. The visualization of hemolymph flow in a pupal leg of the tenebrionid beetle Zophobas atratus revealed that, in addition to a general circuit across all segments (podomeres) of the leg, there were two shortcut channels running within the femur, which is the largest podomere. A unidirectional hemolymph flow was forced by periodic pumping movements of the abdomen and regulated by a valve that exhibited a metamorphic change from a tongue-shaped to a flap-shaped structure.

Periodic abdominal pumping supports leg development during metamorphosis in tenebrionid beetle Zophobas atratus.

Rhythmic abdominal pumping movements in a pupa of giant mealworm beetle Zophobas atratus caused large hemolymph pressure pulses of approximately 20 mmHg. The abdominal pumping movements were completely blocked by transecting the ventral nerve cord (VNC) between the first and second abdominal ganglia. Transection of the VNC until 2 days after pupation caused a developmental defect of adult legs: morphogenesis of the tibial and tarsal segments was severely retarded, and the segments remained covered with a thick pupal cuticle.

Rhythmic firing activity of median neurosecretory cells of the subesophageal ganglion and its coordination with periodically occurring abdominal movements in the tenebrionid [corrected] beetle, Zophobas atratus [corrected].

An immunocytochemical study using an FXPRLamide antiserum revealed three clusters of neurosecretory cells along the midline of the subesophageal ganglion of the tenebrionid [corrected] beetle, Zophobas atratus [corrected] Firing activity of five pairs of neurosecretory cells in the mandibular and maxillary clusters was recorded from an axonal tract of the cells throughout the entire pupal period. The population of neurosecretory cells became active during the middle and late pupal periods, and they usually discharged clusters of action potentials at an interval of 30-90 min. The ultradian activity rhythm of the cells in Z.

Mechanism of neuronal coordination of the rhythmic activities of developing flight muscles and a neurosecretory cell population in the silkmoth, Bombyx mori.

Ultradian rhythmic firing activity (period of 40-90 min) of a population of neurosecretory cells (NSCs) producing FXPRLamide peptides in the subesophageal ganglion (SG) of the silkmoth, Bombyx mori, is closely coordinated with periodically occurring electrical activity of developing flight muscles (FMs) during metamorphosis. To examine neuronal mechanisms and pathways that mediate the coordination of the NSC and flight motor systems, the ventral nerve cord (VNC) or circumesophageal connectives were transected. Transection of the VNC between the SG and thoracic ganglia greatly shortened the period of activity rhythm of the FMs (5-15 min) with no effect on the rhythmicity of NSCs.

Coordination between the electrical activity of developing indirect flight muscles and the firing activity of a population of neurosecretory cells in the silkmoth, Bombyx mori.

The developing indirect flight muscles of pharate moths are characterized by a rhythmic discharge of a long bout of flight-pattern-like muscle potentials in the absence of contractions. The electrical activity of the dorsal longitudinal flight muscles (DLMs) in the silkmoth, Bombyx mori, was discernible as a cluster of many series of muscle potentials that last for several minutes on day 4 of the pupal period. The duration of the active phases and the period of rhythmic activity gradually increased to a peak value on day 7 or 8 and then declined until the end of the pupal period.

Relationship between firing activity of bombyxin-producing neurosecretory cells and hemolymph bombyxin titer in the silkworm Bombyx mori.

Isolated brain-retrocerebral neurohemal complex of the silkworm of Bombyx mori was stimulated electrically and the released bombyxin (an insulin-like neuropeptide) was measured using time-resolved fluoroimmunoassay. The amount of bombyxin release depended on the number of stimulus pulses delivered to the axonal tract of the bombyxin-producing (BP) neurosecretory cells, and 17 fg of bombyxin per pulse was released from a cell. The titer of bombyxin in the hemolymph of bombyxin-II injected pupae decreased exponentially, the half-life being 170 min.

Firing activities of neurosecretory cells producing diapause hormone and its related peptides in the female silkmoth, Bombyx mori. II. mandibular and maxillary cells.

A gene encoding a precursor polyprotein of diapause hormone (DH) and four related peptides is expressed by three groups of neurosecretory cells in the suboesophageal ganglion (SOG) of Bombyx mori. Long-term chronic recordings of firing activities were made from a common axonal tract (the maxillary nerve) of two groups of cells localized in the mandibular and maxillary neuromeres of SOG during pupal-adult development. Mandibular and maxillary cells usually produced a cluster of action potentials at an interval of 30-60 min during pupal-adult development and there was no significant difference in the firing activity profile between diapause-egg and non-diapause-egg producers.

Firing activities of neurosecretory cells producing diapause hormone and its related peptides in the female silkmoth, Bombyx mori. I. labial cells.

There are three known clusters of neurosecretory cells expressing a gene encoding diapause hormone (DH) and four related peptides in the suboesophageal ganglion (SOG) of Bombyx mori. Long-term chronic recordings were made from the axonal tract (NCC-3) of a pair of cells localized in the labial (posterior) neuromere of SOG during pupal-adult development. There was a significant difference in firing activity patterns of the labial neurosecretory cells between diapause-egg and non-diapause-egg producers: labial cells in the former were active throughout pupal-adult development, whereas the same cells in the latter usually maintained an inactive state until the last quarter of pupal-adult development, a time at which a secretion of DH seems to be too late to act on the developing ovary for the induction of diapausing eggs.

Firing activity of "diapause hormone" producing cells in the male silkmoth, Bombyx mori.

Diapause hormone (DH) originally identified to be a factor originating from neurosecretory cells in the suboesophageal ganglion acts on developing ovaries to produce diapause eggs in a female silkmoth, Bombyx mori. A male silkmoth has homologous neurosecretory cells, but little is known of the physiological nature of the cells and actions of their products. We examined the long-term firing activity of putative DH-producing neurosecretory cells and hormonal activity of their products in male pupae that had been experienced different environmental regimens for diapause induction.

Heteronomous rhythmic activity of neurosecretory cells in the silkmoth.

Electrical action potentials of neurosecretory cells producing pheromone biosynthesis-activating neuropeptide (PBAN) and electrocardiograms were recorded from female pupae of Bombyx mori and the correlation between firing activity of the cells and cardiac activity was analyzed. PBAN producing cells localized in the suboesophageal ganglion (SOG) generated clusters of action potentials at an interval of 30-60 min. The firing activity rhythm at a middle pupal period was closely related to heartbeat reversal rhythm: an active phase of the cells was usually apparent during anterograde pulse phases.

Co-ordination of firing activity of neurosecretory cells with cardiac activity in the silkmoth Bombyx mori.

Electrocardiograms and electrical action potentials of cerebral neurosecretory cells producing bombyxin (an insulin-related neuropeptide) were simultaneously recorded from male pupae of the silkmoth Bombyx mori. A pupa showed alternations in the flow of haemolymph due to a rhythmic heartbeat reversal: a train of retrograde heartbeat with a slow pulse rate followed a train of anterograde heartbeat with a higher pulse rate. Intervals of heartbeat reversals changed throughout the pupal period.

Synchronous firing dynamics in a heterogeneous neurosecretory-cell population in an insect.

Five pairs of neurosecretory cells in the subesophageal ganglion of the silkmoth Bombyx mori discharge action potentials in (near) synchrony to release a pheromone biosynthesis-activating neuropeptide (PBAN). Waveforms of compound action potentials recorded extracellularly from axonal tracts were analyzed to determine the firing activity, timing of spikes and the combination of active cells. Analyses revealed a heterogeneous cellular organization of the neurosecretory cell system.