Redirection of ambient light improves predator detection in a diurnal fish

Cases where animals use controlled illumination to improve vision are rare and thus far limited to chemiluminescence, which only functions in darkness. This constraint was recently relaxed by studies on Tripterygion delaisi , a small triplefin that redirects sunlight instead. By reflecting light sideways with its iris, it has been suggested to induce and detect eyeshine in nearby micro-prey. Here, we test whether ‘diurnal active photolocation’ also improves T. delaisi 's ability to detect the cryptobenthic sit-and-wait predator Scorpaena porcus, a scorpionfish with strong daytime retroreflective eyeshine. Three independent experiments revealed that triplefins in which light redirection was artificially suppressed approached scorpionfish significantly closer than two control treatments before moving away to a safer distance. Visual modelling confirmed that ocular light redirection by a triplefin is sufficiently strong to generate a luminance increase in scorpionfish eyeshine that can be perceived by the triplefin over 6–8 cm under average conditions. These distances coincide well with the closest approaches observed. We conclude that light redirection by small, diurnal fish significantly contributes to their ability to visually detect cryptic predators, strongly widening the conditions under which active sensing with light is feasible. We discuss the consequences for fish eye evolution.

Download Full-text

Red fluorescence of the triplefin Tripterygion delaisi is increasingly visible against background light with increasing depth

Royal Society Open Science ◽

10.1098/rsos.161009 ◽

2017 ◽

Vol 4 (3) ◽

pp. 161009 ◽

Cited By ~ 11

Author(s):

Pierre-Paul Bitton ◽

Ulrike K. Harant ◽

Roland Fritsch ◽

Connor M. Champ ◽

Shelby E. Temple ◽

...

Keyword(s):

Colour Vision ◽

Red Light ◽

Field Measurements ◽

Light Environment ◽

Natural Light ◽

Ambient Light ◽

Red Fluorescence ◽

As Species ◽

Tripterygion Delaisi ◽

Red Coloration

The light environment in water bodies changes with depth due to the absorption of short and long wavelengths. Below 10 m depth, red wavelengths are almost completely absent rendering any red-reflecting animal dark and achromatic. However, fluorescence may produce red coloration even when red light is not available for reflection. A large number of marine taxa including over 270 fish species are known to produce red fluorescence, yet it is unclear under which natural light environment fluorescence contributes perceptively to their colours. To address this question we: (i) characterized the visual system of Tripterygion delaisi, which possesses fluorescent irides, (ii) separated the colour of the irides into its reflectance and fluorescence components and (iii) combined these data with field measurements of the ambient light environment to calculate depth-dependent perceptual chromatic and achromatic contrasts using visual modelling. We found that triplefins have cones with at least three different spectral sensitivities, including differences between the two members of the double cones, giving them the potential for trichromatic colour vision. We also show that fluorescence contributes increasingly to the radiance of the irides with increasing depth. Our results support the potential functionality of red fluorescence, including communicative roles such as species and sex identity, and non-communicative roles such as camouflage.

Download Full-text

Ambient light alters temporal-updating behaviour during mate choice in a Neotropical frog

Canadian Journal of Zoology ◽

10.1139/z10-018 ◽

2010 ◽

Vol 88 (5) ◽

pp. 448-453 ◽

Cited By ~ 17

Author(s):

Alexander T. Baugh ◽

Michael J. Ryan

Keyword(s):

Decision Making ◽

Mate Choice ◽

Light Level ◽

Ambient Light ◽

Light Conditions ◽

Predator Detection ◽

Physalaemus Pustulosus ◽

Light Levels ◽

Risk Of Predation ◽

Assessment Time

It is well known that animal decision-making can be influenced by environmental variables, such as the risk of predation. During the breeding season, nocturnal amphibians encounter a range of environmental conditions at breeding aggregations, including variable ambient light conditions. For nocturnal frogs, illumination is expected to minimize conspicuous movement that might increase predator detection. Previous work has shown that female Physalaemus pustulosus (Cope, 1864) (= Engystomops pustulosus (Cope, 1864)) are sensitive to variation in light levels during mate choice. Here we use an acoustic playback design in which stimuli are adjusted for intensity and complexity during female phonotaxis to show that choosiness is influenced by light level. Frogs were more likely to commit to an initial mate choice despite a dynamic reduction in mate attractiveness under dim light conditions compared with darkness. These results suggest that females are trading off the attractiveness of potential mates with the perceived costs of executing mate choice by committing to an initial decision and thereby reducing assessment time and movement. The dynamic playback design used here provides an approach that could be applied in other systems in which context-dependent decision-making is thought to be important.

Download Full-text

Controlled iris radiance in a diurnal fish looking at prey

Royal Society Open Science ◽

10.1098/rsos.170838 ◽

2018 ◽

Vol 5 (2) ◽

pp. 170838 ◽

Cited By ~ 6

Author(s):

Nico K. Michiels ◽

Victoria C. Seeburger ◽

Nadine Kalb ◽

Melissa G. Meadows ◽

Nils Anthes ◽

...

Keyword(s):

Eye Movement ◽

Fish Species ◽

Deep Sea ◽

Side Effect ◽

Active Sensing ◽

Nocturnal Fish ◽

Tripterygion Delaisi

Active sensing using light, or active photolocation, is only known from deep sea and nocturnal fish with chemiluminescent ‘search’ lights. Bright irides in diurnal fish species have recently been proposed as a potential analogue. Here, we contribute to this discussion by testing whether iris radiance is actively modulated. The focus is on behaviourally controlled iris reflections, called ‘ocular sparks’. The triplefin Tripterygion delaisi can alternate between red and blue ocular sparks, allowing us to test the prediction that spark frequency and hue depend on background hue and prey presence. In a first experiment, we found that blue ocular sparks were significantly more often ‘on’ against red backgrounds, and red ocular sparks against blue backgrounds, particularly when copepods were present. A second experiment tested whether hungry fish showed more ocular sparks, which was not the case. However, background hue once more resulted in a significant differential use of ocular sparks. We conclude that iris radiance through ocular sparks in T. delaisi is not a side effect of eye movement, but adaptively modulated in response to the context under which prey are detected. We discuss the possible alternative functions of ocular sparks, including an as yet speculative role in active photolocation.

Download Full-text

Controlled iris radiance in a diurnal fish looking at prey

10.1101/206615 ◽

2017 ◽

Author(s):

Nico K. Michiels ◽

Victoria C. Seeburger ◽

Nadine Kalb ◽

Melissa G. Meadows ◽

Nils Anthes ◽

...

Keyword(s):

Eye Movement ◽

Fish Species ◽

Deep Sea ◽

Side Effect ◽

Active Sensing ◽

Nocturnal Fish ◽

Tripterygion Delaisi

1.SummaryActive sensing using light, or active photolocation, is only known from deep sea and nocturnal fish with chemiluminescent “search” lights. Bright irides in diurnal fish species have recently been proposed as a potential analogue. Here, we contribute to this discussion by testing whether iris radiance is actively modulated. The focus is on behaviourally controlled iris reflections, called “ocular sparks”. The triplefin Tripterygion delaisi can alternate between red and blue ocular sparks, allowing us to test the prediction that spark frequency and hue depend on background hue and prey presence. In a first experiment, we found that blue ocular sparks were significantly more often “on” against red backgrounds, and red ocular sparks against blue backgrounds, particularly when copepods were present. A second experiment tested whether hungry fish showed more ocular sparks, which was not the case. Again, background hue resulted in differential use of ocular spark types. We conclude that iris radiance through ocular sparks in T. delaisi is not a side effect of eye movement, but adaptively modulated in response to the context under which prey are detected. We discuss the possible alternative functions of ocular sparks, including an as yet speculative role in active photolocation.

Download Full-text

Active sensing with light improves predator detection in a diurnal fish

10.1101/324202 ◽

2018 ◽

Cited By ~ 1

Author(s):

Matteo Santon ◽

Pierre-Paul Bitton ◽

Jasha Dehm ◽

Roland Fritsch ◽

Ulrike K. Harant ◽

...

Keyword(s):

Field Experiment ◽

Visual Detection ◽

Average Distance ◽

Detection Threshold ◽

Active Sensing ◽

Predator Detection ◽

Light Organs ◽

Anatomical Arrangement ◽

Favorable Conditions

AbstractActive sensing by means of light is rare. In vertebrates, it is known only from chemiluminescent fish with light organs below their pupils, an anatomical arrangement that is ideal to generate eyeshine in the pupils of nearby organisms. Here, we test whether diurnal fish can achieve the same by redirecting sunlight through reflection instead. We recently showed that small (< 5 cm), benthic, marine triplefin fish actively redirect downwelling light using their iris. We hypothesized that this mechanism allows triplefins to improve detection of a cryptic organism by generating eyeshine in its pupil. Here, we tested this by attaching small dark hats to triplefins to shade their iris from downwelling light. Two controls consisted of triplefins with a clear or no hat. These treatments test the prediction that light redirection increases the visual detection ability of triplefins. To this end, we placed treated fish in a tank with a display compartment containing either a stone as the control stimulus, or a scorpionfish, i.e. a cryptic, motionless triplefin predator with retroreflective eyes. After overnight acclimatization, we determined the average distance triplefins kept from the display compartment over two days. Both in the laboratory (n = 15 replicates per treatment) and in a similar field experiment at 15 m depth (n = 43 replicates per treatment) fish kept longer distances from the scorpionfish than from the stone. This response varied between hat treatments: shaded triplefins stayed significantly closer to the scorpionfish in the laboratory and in one of two orientations tested in the field. A follow-up field experiment at 10 m depth revealed the immediate response of triplefins to a scorpionfish. At first, many individuals (n = 80) moved towards it, with shaded triplefins getting significantly closer. All individuals then gradually moved to a safer distance at the opposite half of the tank. Visual modelling supported the experimental results by showing that triplefins can redirect enough light with their iris to increase a scorpionfish’s pupil brightness above detection threshold at a distance of 7 cm under average field conditions and at more than 12 cm under favorable conditions. We conclude that triplefins are generally good in the visual detection of a cryptic predator, but can significantly improve this ability when able to redirect downwelling light with their iris and induce eyeshine in the predator’s pupil. We discuss the consequences of “diurnal active photolocation” for visual detection and camouflage among fish species.

Download Full-text

Visual modelling supports the potential for prey detection by means of diurnal active photolocation in a small cryptobenthic fish

10.1101/338640 ◽

2018 ◽

Cited By ~ 1

Author(s):

Pierre-Paul Bitton ◽

Sebastian Alejandro Yun Christmann ◽

Matteo Santon ◽

Ulrike Katharina Harant ◽

Nico K. Michiels

Keyword(s):

Visual System ◽

Fish Species ◽

Physical Process ◽

Spectral Properties ◽

Active Sensing ◽

Prey Detection ◽

Potential Prey ◽

Environmental Light ◽

Nocturnal Species ◽

Tripterygion Delaisi

Active sensing has been well documented in animals that use echolocation and electrolocation. Active photolocation, or active sensing using light, has received much less attention, and only in bioluminescent nocturnal species. However, evidence has suggested the diurnal triplefin Tripterygion delaisi uses controlled iris radiance, termed ocular sparks, for prey detection. While this form of diurnal active photolocation was behaviourally described, a study exploring the physical process would provide compelling support for this mechanism. In this paper, we investigate the conditions under which diurnal active photolocation could assist T. delaisi in detecting potential prey. In the field, we sampled gammarids (genus Cheirocratus) and characterized the spectral properties of their eyes, which possess strong directional reflectors. In the laboratory, we quantified ocular sparks size and their angle-dependent radiance. Combined with environmental light measurements and known properties of the visual system of T. delaisi, we modeled diurnal active photolocation under various scenarios. Our results corroborate that diurnal active photolocation should help T. delaisi detect gammarids at distances relevant to foraging, 4.5 cm under favourable conditions and up to 2.5 cm under average conditions. Because ocular sparks are widespread across fish species, diurnal active photolocation for micro-prey may be a common predation strategy.

Download Full-text

Enhanced Contactless Vital Sign Estimation from Real-Time Multimodal 3D Image Data

Journal of Imaging ◽

10.3390/jimaging6110123 ◽

2020 ◽

Vol 6 (11) ◽

pp. 123

Author(s):

Chen Zhang ◽

Ingo Gebhart ◽

Peter Kühmstedt ◽

Maik Rosenberger ◽

Gunther Notni

Keyword(s):

Real Time ◽

3D Imaging ◽

Imaging System ◽

Vital Signs ◽

Image Data ◽

Motion Artifacts ◽

Video Data ◽

Ambient Light ◽

3D Image ◽

Controlled Illumination

The contactless estimation of vital signs using conventional color cameras and ambient light can be affected by motion artifacts and changes in ambient light. On both these problems, a multimodal 3D imaging system with an irritation-free controlled illumination was developed in this work. In this system, real-time 3D imaging was combined with multispectral and thermal imaging. Based on 3D image data, an efficient method was developed for the compensation of head motions, and novel approaches based on the use of 3D regions of interest were proposed for the estimation of various vital signs from multispectral and thermal video data. The developed imaging system and algorithms were demonstrated with test subjects, delivering a proof-of-concept.

Download Full-text

Design, Development and Practical Realization of a VLC Supportive Indoor Lighting System

Light & Engineering ◽

10.33383/2019-048 ◽

2020 ◽

pp. 87-97

Author(s):

Sourish Chatterjee ◽

Biswanath Roy

Keyword(s):

Data Communication ◽

Cost Effective ◽

Ambient Light ◽

Lighting System ◽

Design Development ◽

Led Driver ◽

Communication Performance ◽

Good Communication ◽

Simulink Model ◽

Light Interference

In an office space, an LED-based lighting system allows you to perform the function of a data transmitter. This article discusses the cost-effective design and development of a data-enabled LED driver that can transmit data along with its receiving part. In addition, this paper clearly outlines the application of the proposed VLC system in an office environment where ambient light interference is a severe issue of concern. The result shows satisfactory lighting characteristics in general for this area in terms of average horizontal illuminance and illuminance uniformity. At the same time, to evaluate real-time and static communication performance, Arduino interfaced MATLAB Simulink model is developed, which shows good communication performance in terms of BER (10–7) even in presence of ambient light noise with 6 dB signal to interference plus noise ratio. Our designed system is also flexible to work as a standalone lighting system, whenever data communication is not required.

Download Full-text