Social signaling via bioluminescent blinks determines nearest neighbor distance in schools of flashlight fish Anomalops katoptron

Peter Jägers,Gino V Limmon,Robin Schütz,Maximilian Mucke,Budiono Senen,Louisa Wagner,Jens Hellinger,Stefan Herlitze

doi:10.1038/s41598-021-85770-w

Peter Jägers, Gino V Limmon + Show 6 more

Open Access

https://doi.org/10.1038/s41598-021-85770-w

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Journal: Scientific Reports	Publication Date: Mar 19, 2021
Citations: 3	License type: open-access

Affiliation: Ruhr University Bochum, University of Pattimura

Abstract

The schooling flashlight fish Anomalops katoptron can be found at dark nights at the water surface in the Indo-Pacific. Schools are characterized by bioluminescent blink patterns of sub-ocular light organs densely-packed with bioluminescent, symbiotic bacteria. Here we analyzed how blink patterns of A. katoptron are used in social interactions. We demonstrate that isolated specimen of A. katoptron showed a high motivation to align with fixed or moving artificial light organs in an experimental tank. This intraspecific recognition of A. katoptron is mediated by blinking light and not the body shape. In addition, A. katoptron adjusts its blinking frequencies according to the light intensities. LED pulse frequencies determine the swimming speed and the blink frequency response of A. katoptron, which is modified by light organ occlusion and not exposure. In the natural environment A. katoptron is changing its blink frequencies and nearest neighbor distance in a context specific manner. Blink frequencies are also modified by changes in the occlusion time and are increased from day to night and during avoidance behavior, while group cohesion is higher with increasing blink frequencies. Our results suggest that specific blink patterns in schooling flashlight fish A. katoptron define nearest neighbor distance and determine intraspecific communication.

Highlights

Bioluminescence is a widespread phenomenon in ocean-dwelling organisms including a broad phylogenetic distribution in marine fish[1]
To investigate how bioluminescent signaling emitted by the light organs of the splitfin flashlight fish Anomalops katoptron is used for intraspecific communication, we investigated the behavioral responses of isolated flashlight fish to artificial light pulses in the laboratory
In this study we found that variation in blink frequencies of the bioluminescent splitfin flashlight fish Anomalops katoptron is used for intraspecific communication important for schooling behavior

Summary

Introduction

Bioluminescence is a widespread phenomenon in ocean-dwelling organisms including a broad phylogenetic distribution in marine fish[1]. Light is emitted via own photophores, bioluminescent bacteria hosted within specialized light organs or kleptoproteins acquired from p rey[2]. Photoblepharon reside solitary- or pairwise in territories (e.g. reef caves) while Anomalops katoptron (Anomalopidae) occur in large, moving schools during moonless n ights[8,13]. Symbiotic bacteria are densely packed in numerous tubules that are aligned at right angles to the light-emitting surface of light organs[8,16,17]. At the anterior edge light organs are attached to suborbital cavities via the rod like “Ligament of Diogenes” which allows a downward rotation. This exposes the dark pigmented back of light organs and disrupts light output. Group size and cohesion play an important role in schooling and can reduce the risks of being preyed through attack abatement[28] or confusion of predators[29]

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