Non-visual homing and the current status of navigation in scorpions

Emily Danielle Prévost,Torben Stemme

doi:10.1007/s10071-020-01386-z

Abstract

Within arthropods, the investigation of navigational aspects including homing abilities has mainly focused on insect representatives, while other arthropod taxa have largely been ignored. As such, scorpions are rather underrepresented concerning behavioral studies for reasons such as low participation rates and motivational difficulties. Here, we review the sensory abilities of scorpions related to navigation. Furthermore, we present an improved laboratory setup to shed light on navigational abilities in general and homing behavior in particular. We tracked directed movements towards home shelters of the lesser Asian scorpion Mesobuthus eupeus to give a detailed description of their departure and return movements. To do so, we analyzed the departure and return angles as well as measures of directness like directional deviation, lateral displacement, and straightness indices. We compared these parameters under different light conditions and with blinded scorpions. The motivation of scorpions to leave their shelter depends strongly upon the light condition and the starting time of the experiment; highest participation rates were achieved with infrared conditions or blinded scorpions, and close to dusk. Naïve scorpions are capable of returning to a shelter object in a manner that is directionally consistent with the home vector. The first-occurring homing bouts are characterized by paths consisting of turns about 10 cm to either side of the straightest home path and a distance efficiency of roughly three-quarters of the maximum efficiency. Our results show that neither chemosensation nor vision, but rather path integration based on proprioception, plays a superior role in the homing of scorpions.

Highlights

Introduction and reviewThe Arthropoda, covering such diverse taxa as insects, crustaceans, centipedes, spiders, and their kin, are famous for their exceptional navigational abilities
In the stimulus trials of the light stimulus experiment involving sighted scorpions, 11 individuals out of 54 total trials (20%) returned to their box (Fig. 3), five of which resulted in a legitimate phase 2 homing bout according to the light stimulus experiment trial legitimacy criteria
Our results suggest that path integration based on proprioception plays a crucial role for orientation and navigation

Summary

Introduction

The Arthropoda, covering such diverse taxa as insects, crustaceans, centipedes, spiders, and their kin, are famous for their exceptional navigational abilities. One specific branch of navigation research deals with homing behavior, which is defined as the ability of individuals to return to a fixed location after an excursion therefrom (e.g., Warrant and Dacke 2010). The earliest studies on homing behavior in arthropods were performed approximately 150 years ago by displacing hymenopteran insects (Fabre 1879, 1882). Our knowledge of orientation and homing behavior is based on several model organisms, and conclusions obtained are often extrapolated to the entire taxon to which the model organisms belong, or even to the entire arthropod phylum. In the context of arthropod behavior, a strong bias exists toward insects in general, and hymenopterans in particular. Some excellent work has accumulated in recent years on the navigation and homing of spiders (Dacke et al 1999; Nørgaard et al 2003, 2012), whip spiders (Bingman et al 2017; Wiegmann et al 2019), and harvestmen (Silva et al. Vol.:(0123456789)

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