Light receptors identify the habits of flashlight fish

Biologists at the Ruhr-Universität Bochum characterized new, unknown photoreceptors from the bioluminescent flashlight fish Anomalops katoptron. The photoreceptors known as opsins enable the fish to detect light with a specific wavelength.

As released on the 11th July 2018 in PLOS ONE the scientists found brand-new opsin variants, which are specialized to detect low intensity blue light in the wavelength series of bioluminescent light discharged by the fish. Heaven light can be used to affect the fish practices.

The authors conclude that this specific blue light receptors and light handling is an transformative adaptation to the environmental environment of the fish. The research study is an interdisciplinary organic approach combining the experience of geneticist Dr Minou Nowrousian as well as Prof Dr Ulrich Kück, molecular biologist Dr Melanie Mark, zoologists Dr Jens Hellinger and also Dr Marcel Donner in addition to physiologist and also optogeneticist Prof Dr Stefan Herlitze.

Two opsin variants to discover blue light

Besides the fact that bioluminescence is a widespread phenomenon in marine settings it is presently not understood, how bioluminescence is refined as well as which physical and behavioural repercussions bioluminescence is evoking in most varieties. The flashlight fish Anomalops katoptron can be seen in shallow waters of reefs reeves at moonless nights and also is discovered during the day in caverns approximately 400 metres deep. Light organs are positioned under the eye, which produce blue light with a wavelength of 490 nanometres, which is made use of to identify as well as quest victim.

The research study group evaluated the photoreceptor structure of the retina and also located two aesthetic pigments, which look like the aesthetic pigments shared in the animal retina. Both of these photoreceptors are turned on by low intensity blue light in the range of 490 nanometres, which match the wavelength variety of its own bioluminescent light.

Fish are conditioned during feeding

Next off, the research team evaluated if Anomalops katoptron uses blue light for behavioral responses. They executed a Pavlovian conditioning job with 8 fish, where the fish needed to associate feeding with a particular light pulse. « The fish were fed in darkness, however we utilized a solid red flashlight to brighten the feeding location. We believed originally that the fish can not see the traffic signal,» states Jens Hellinger, « but located that they can connect the red light with food. Thus, once we turned on the red light at the edge of the fish tank, the fish swam right into the beam.»

» The researchers used this phenomenon to execute a behavioral test, to show that flashlight fish would react just to specific wavelength of light. They utilized a much reduced light strength in contrast to the red flashlight and also located that the fish now just reacted to reduced intensity blue however not traffic signal.

Adjustment to star light and bioluminescence

« The aesthetic system of flashlight fish seems to be adapted to identify low strength light, such as star light or bioluminescent light to adjust their own behaviour,» ended Stefan Herlitze. The reduced light discovery exposes a new behavioural feature of bioluminescence in fish.


Bioluminescence involves a chemical process where totally free power is exchanged light. The phenomenon is discovered in various different varieties from fungis, bacteria and bugs to vertebrates. Bioluminescent light is usually created in specialized cell organelles or light organs. Light organs loaded with symbiotic bacteria are for example usually found in deep-sea fish to create behaviour-relevant light signals.

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