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

Bitton, Pierre‐Paul; Christmann, Sebastian Alejandro Yun; Santon, Matteo; Harant, Ulrike K.; Michiels, Nico K.

doi:10.1038/s41598-019-44529-0

Cited by 5 publications

(7 citation statements)

References 49 publications

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“…We, therefore, used visual modelling and showed that an ocular spark is strong enough to increase the achromatic contrast in a scorpionfish's pupil above a triplefins's perception threshold over distances that coincide well with the nearest approaches seen in the third field experiment. As has been made clear before [15], this study once more indicates that diurnal active photolocation is not fail-proof, as shown by the predictions from the visual modelling and by the fact that even clear-hatted triplefins approached scorpionfish within ranges that may fall within the striking range of a scorpionfish [41][42][43]. Diurnal active photolocation is also not strictly required for detecting a scorpionfish, as shown by the response of shaded triplefins to scorpionfish relative to stones.…”

Section: Discussionsupporting

confidence: 53%

“…We conclude that diurnal active photolocation is a mechanism that supplements a triplefin's ability to detect scorpionfish. The chromatophore patch on the lower iris of the triplefin T. delaisi on which the ocular spark is focused behaves like a diffuse, Lambertian reflector in the equatorial plane of vision [15]. This produces a light field that covers most of the hemispherical zone over a short distance, as seen by a single eye.…”

Section: Discussionmentioning

confidence: 99%

“…Trade-offs like these may explain variation seen among fish in types of ocular light redirection [13,45]. As for the to-be-detected target, highly reflective structures such as retroreflective eyes in predatory fish [12,18] or reflective eyecups or ommatidia in crustacean prey [13,15] are also common and diverse. Since none of these have been studied in this context, it is too early to speculate which combination of observer/target reflectors and ambient conditions is likely to function.…”

Section: Discussionmentioning

confidence: 99%

“…To validate the results, we computed the contrast change in the pupil of a scorpionfish as perceived by an untreated triplefin when producing an ocular spark. We informed the model using previously published parameters [12,13,15,22,23] supplemented by additional measurements under the conditions of the last field experiment, including the baseline radiance of scorpionfish pupils [12]. We limited ourselves to modelling the effect of blue ocular sparks, which is the stronger of the two types known from T. delaisi [13].…”

Section: (G) Visual Modellingmentioning

confidence: 99%

“…As a result, sunlight is reflected sideways, outside the approximately 97°a ngular range of downwelling light dictated by Snell's window [14]. A recently published model confirmed that ocular sparks allow T. delaisi to induce perceptible eyeshine in micro-prey (gammarid shrimps) under biologically plausible scenarios [15]. We define this as 'diurnal active photolocation', a process by which ocular radiance improves visual detection of nearby cryptic organisms.…”

Section: Introductionmentioning

confidence: 99%

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Redirection of ambient light improves predator detection in a diurnal fish

et al. 2020

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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.

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Section: Discussionsupporting

confidence: 53%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: (G) Visual Modellingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Redirection of ambient light improves predator detection in a diurnal fish

et al. 2020

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Broad spectrum artificial light at night increases the conspicuousness of camouflaged prey

McMahon

Smyth

Davies

2022

Journal of Applied Ecology

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1. The growing global prevalence of energy efficient broad spectrum lighting threatens to disrupt an array of visually guided ecological processes. Broad spectrum lighting likely better enables the discrimination of colour, yet it is potential to increase the conspicuousness of camouflaged prey at night remains little explored.2. Using a well-established visual model, we quantified the impacts of four spectrally distinct narrow and broad spectrum lighting technologies on the conspicuousness of three different polymorphic colour variations of intertidal littorinid snail, as viewed by three model predators.3. Modern broad spectrum lighting technologies increased the conspicuousness of prey compared to 20th-century narrow spectrum lighting. This effect was most prominent in the yellow colour morphs due to greater contrast with their natural fucoid seaweed background.4. Synthesis and applications. Our results provide evidence that the global transition to broad spectrum lighting will decrease the efficacy of camouflage at night in nature, potentially altering selective predation, population dynamics and the genetic structure of polymorphic populations. These findings highlight the need for further consideration in environmental management and planning, to ensure habitats are protected from unnecessary exposure to artificial light.

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Small benthic fish strike at prey over distances that fall within theoretical predictions for active sensing using light

Neiße

Santon

Bitton

et al. 2020

Journal of Fish Biology

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Small, benthic, cryptic fishes represent a species-rich guild on marine substrates. Most of them are micropredators that feed on crustaceans that are often smaller than 1 mm. Typical examples are seahorses and pipefishes (Syngnathidae), most gobies (Gobiidae), dragonets (Callionymidae) and triplefins (Tripterygiidae). Previous work on the yellow black-headed triplefin Tripterygion delaisi demonstrated that it actively redirects downwelling sunlight sideways using its iris and can use this to locally illuminate objects of interest. We call this form of active sensing using light "diurnal active photolocation". Visual modelling predicted that light redirection can be sufficient to induce a perceivable change in luminance in the eyes of one of its prey species, a cryptic gammarid crustacean (Cheirocratus sp.), over distances of 1-2 cm. Empirical validation, however, was not possible because measurements of predation distances have not been quantified for free-ranging, small, benthic fishes before. Here, we present interaction distances measured from videos of T. delaisi approaching and striking at prey in the field. Out of 160 recordings, we were able to quantify 78 prey approaching distances and 100 striking distances. Approaching distances ranged from 2.1 to 4.1 cm (interquartile range, IQR) and involved one to five approaching steps before the actual strike occurred. The distance over which the final strike took place varied from 0.7 to 1.6 cm (IQR). Both approaching and striking distances increased with fish body size. We conclude that most approaching sequences started too far away to be explained by prey detection through light redirection. Striking distances, however, fell well with the distances predicted by the model. We conclude that if diurnal active photolocation plays a role in prey detection, it is during the final decision whether to strike or not.

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

Cited by 5 publications

References 49 publications

Redirection of ambient light improves predator detection in a diurnal fish

Redirection of ambient light improves predator detection in a diurnal fish

Broad spectrum artificial light at night increases the conspicuousness of camouflaged prey

Small benthic fish strike at prey over distances that fall within theoretical predictions for active sensing using light

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