MSc Student
Advisor: Georg Brenneis

Unit for Integrative Zoology, Department of Evolutionary Biology
University of Vienna

Abstract

Solifugae (camel spiders) are predominantly nocturnal arachnids, characterized by prominent chelicerae and specialized sensory organs known as malleoli or racquet organs. These fan-shaped structures are densely innervated by presumptive chemoreceptor neurons and oriented ventrally on the fourth pair of walking legs. By probing the substrate with these organs, solifuges detect chemical cues hypothesized to be used for locating prey and mates.

The external morphology of malleoli is well documented, but the internal neuroanatomy, specifically of the malleolar neuropil within the synganglion requires further investigation, to better understand how the signals are integrated and processed. This thesis aims to trace the neuroanatomical pathway of the malleolar system in the camel spider Paragaleodes scalaris (C. L. Koch, 1842). A primary focus is to determine whether the malleolar neuropil exhibits a somatotopic representation of the individual malleoli, a feature recently described in the likewise chemosensory pecten neuropils of scorpions (Drozd et al., 2020). By identifying how afferent projections from individual malleoli are organized within the central nervous system, we can better understand the evolution of specialized chemosensory pathways across Arachnida. This study will utilize neuronal backfill techniques (e.g., lipophilic dyes, neurobiotin) to trace afferent projections from individual malleoli to the synganglion to visualize the malleolar pathway. These techniques are complemented by histological sectioning and 3D reconstruction to provide a high-resolution spatial map of the malleolar neuropil. By tracing the central projection patterns of the malleolar pathway, this research aims to provide a better understanding of the chemosensory processing in Solifugae.