Topographic Organization of the Pectine Neuropils in Scorpions An Analysis of Chemosensory Afferents and the Projection Pattern in the Central Nervous System 1st by Denise Drozd 3658251549 9783658251543

ISBN 10: 3658251549

ISBN 13: 9783658251543

Author: Denise Drozd

Chelicerates do not possess dedicated antennae like the Mandibulata but have evolved their second sets of appendages into the eponymous chelicerae. In scorpions, pectines are specialized comb-like structures, located on the ninth body segment, used for examining the substrate for chemo- and mechanosensory signals. The comb teeth, or pegs, are truncated beveled structures facing the substrate for probing, and are studded with numerous sensory receptors. Afferents from the pectines project into a distinct neuropil of the central nervous system, located behind the fourth walking leg neuropils. Denise Drozd analyzes afferents of single pegs in Mesobuthus eupeus by backfilling, combined with immunohistological labeling of neuropil regions. Her results suggest a topographic representation of the chemosensory fibers within the pectine neuropil instead of the typical chemotopic representation.

1 Introduction

1.1 Chemo- and mechanoreception in arthropods

1.1.1 Chemosensitive structures in arthropods

1.1.2 Mechanosensitive structures in arthropods

1.2 Processing of sensory information in the arthropod nervous system

1.3 Sensory structures in arachnids

1.4 Mechano- and chemoreceptors in arachnids

1.4.1 Sensory appendages in scorpions – the pectines

1.4.2 The nervous system of scorpions and the pectine neuropil

1.5 Goal of this thesis

2 Material and methods

2.1 Animals – Mesobuthus eupeus

2.2 Backfill of afferents fibers

2.3 Dissection, embedding and sectioning

2.4 Immunohistochemistry and mounting

2.5 Microscopy and image analysis

3 Results

3.1 Establishment of methods

3.2 Structural analysis of the posterior pectine neuropil and associated tracts

3.3 Projection areas of sensory afferents

4 Discussion

4.1 Discussion of methods

4.2 Analysis of the architecture of the posterior pectine neuropil

4.2.1 The structure of the disc-like area

4.2.2 The structure of the cap-like area and the large lobulus area

4.2.3 Somatotopic innervation of the pectine neuropil

5 Conclusion

5.1 Outlook