The fate of specific motoneurons and sensory neurons of the pregenital abdominal segments inTenebrio molitor (Insecta : Coleoptera) during metamorphosis |
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Authors: | Constantinos Paspalas Christos Consoulas George Theophilidis |
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Institution: | (1) Laboratory of Animal Physiology, Department of Zoology, School of Biology, University of Thessaloniki, GR-54006 Thessaloniki, Macedonia, Greece |
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Abstract: | The anatomy and innervation of the lateral external muscle and sensory cells located in the ventral region of pregenital abdominal
segments were examined at the larval and adult stages ofTenebrio molitor (Coleoptera). All seven muscles located in this region degenerate during the pupal stage, whilst only the lateral external
median (lem) appears in the adult. Backfillings of the motor nerve innervating this muscle reveal that, at both larval and
adult stages, it is innervated by ten neurons. Intracellular records from the muscle fibres show that two neurons are inhibitory,
and at least five are excitatory. There are also two unpaired neurons. A variety of sensory organs are located in the ventral
region of the larvae, whilst only campaniform sensilla are found in the adult. At both stages, the innervation pattern of
the sensory nerve branches is very similar. Also, the central projections of the sensory cells occupy similar neuropilar areas.
Finally, prolonged intracellular records from the lem muscle revealed that, at the larval stage, it participates only in segmental
or intersegmental reflexes, whilst in the adult it has a primary expiratory role in ventilation. The results show that extensive
changes occur in the number of muscles located in the ventral region of the pregenital abdominal segments, as well as in the
arrangement and number of sensory neurons, in the structure of the exoskeleton, and even in the central nervous system. In
contrast, only minor changes are observed in the sensory and motor nerve branches, in the sensory projections, and in the
number and the location of the motoneurons innervating the lateral external median muscle.
Correspondence to: G. Theophilidis |
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Keywords: | Tenebrio molitor Abdominal muscles Motoneurons Sensory neurons Metamorphosis |
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