Test of the prey-attraction hypothesis for the scorpion fluorescence

Abstract

A striking feature of most scorpion species is fluorescence under ultraviolet light, but few studies have investigated the adaptive benefit of this trait. A hypothesis is that fluorescence may lure prey towards the scorpion improving foraging success. In this study, we investigated whether the fluorescence of the scorpion Centruroides granosus Thorell, 1876 lures the house cricket Acheta domesticus Linnaeus, 1758. We performed two experiments: 1) an arena in which crickets were exposed to both fluorescing and black-painted non-fluorescing scorpions and 2) a tunnel in which crickets could walk out through one of the two exits, each with a scorpion treatment. None of the experiments provided evidence that the scorpion fluorescence is attractive to house crickets since they did not show preference for any of the two scorpion types. Variables such as cricket sex or scorpion sex did not influence their response towards the fluorescence; however, crickets were on average closer to male scorpions in the outdoor arena and closer to female scorpions in the laboratory arenas. Moreover, male crickets were more active than females in the tunnel experiment, in line with the results of the arena experiment showing that male crickets were on average closer to the scorpions in the laboratory. We discuss potential implications and suggest that more experimental work is required to investigate potential adaptive benefits of the scorpion fluorescence under various biotic and abiotic factors.

Photoluminescence in mammal fur: 111 years of research

“…One study found that flying insects avoided photoluminescent scorpions ( Vaejovis spp.) on a full moon ( Kloock 2005 ), whereas another found that house crickets ( Acheta domesticus ) did not react differently to photoluminescent scorpions ( Centruroides granosus ) under a half moon ( Gálvez et al 2020 ). Until field experiments using real fur and natural lighting are conducted, whether a visual function exists or not remains speculative.…”

Luminous Tasmania: seeing the dark in a different light

“…Numerous hypotheses have been proposed as to why they glow, including acting as sunscreen, luring prey, finding mates or protection from parasitic infections (Lourenco & Cloudsley-Thompson 1996, Gálvez et al 2020, Yoshimoto et al 2020. However, the current widely accepted theory, from researchers in California is that fluorescence of the scorpions' own bodies enables them to detect UV light (such as on moon-lit nights), allowing them to make decisions about their activity levels (Kloock et al 2010).…”

Does the photoluminescence of rat fur influence interactions in the field?

“…), with nocturnal flying insects reacting to photoluminescent scorpions on a full moon but not on a new moon (Kloock 2005). However, subsequent experiments on other photoluminescent scorpions (Centruroides granosus) found that their house cricket (Acheta domesticus) prey did not react to photoluminescence or lack thereof in either laboratory trials with moonlight simulation or in natural outdoor lighting under a half moon (Gálvez et al 2020).…”