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

2018 ◽  
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.

scholarly journals Controlled iris radiance in a diurnal fish looking at prey

2018 ◽  
Vol 5 (2) ◽  
pp. 170838 ◽  
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.

scholarly journals Controlled iris radiance in a diurnal fish looking at prey

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.

Predator and prey detection in two species of water bear (Tardigrada)

2019 ◽  
Vol 188 (3) ◽  
pp. 860-864 ◽  
Author(s):  
Harry A Meyer ◽  
Hannah E Larsen ◽  
Nézira O Akobi ◽  
Garret Broussard
Keyword(s):  
Environmental Conditions ◽  
The Other ◽  
Physical Contact ◽  
Nutrient Agar ◽  
Control Treatment ◽  
Prey Detection ◽  
Potential Prey ◽  
Predator Prey ◽  
Petri Dishes

Abstract Tardigrade behavioural studies have focused on responses to abiotic environmental conditions. Predator–prey interactions have received some attention, but not how predators and prey might detect one another. Here, we investigate whether a predatory tardigrade species is attracted to, and a potential prey tardigrade avoids, areas previously occupied by the other. In our experiments, Milnesium lagniappe was the predator and Macrobiotus acadianus the prey. Petri dishes with non-nutrient agar were used as experimental arenas. In one treatment, we allowed Macrobiotus to roam over half of the agar for 20 h, while leaving the other half free of Macrobiotus. We then removed the prey and introduced the predator. In the control treatment, no prey were added. Results indicated that Milnesium individuals were significantly concentrated in the area previously occupied by Macrobiotus, whereas no such concentration was evident when Macrobiotus had not been present. A similar protocol was used to test whether Macrobiotus avoided areas previously occupied by the predator. As expected, Macrobiotus were significantly concentrated in the area never occupied by Milnesium, unlike the control treatment. These results suggest that both species can detect the other without physical contact and react accordingly. Given that the experiments were conducted in darkness, detection is probably olfactory.

scholarly journals Predator-specific camouflage in chameleons

2008 ◽  
Vol 4 (4) ◽  
pp. 326-329 ◽  
Author(s):  
Devi Stuart-Fox ◽  
Adnan Moussalli ◽  
Martin J Whiting
Keyword(s):  
Visual System ◽  
Colour Change ◽  
Prey Detection ◽  
Colour Discrimination ◽  
Colour Perception ◽  
Crucial Problem ◽  
Potential Strategy

A crucial problem for most animals is how to deal with multiple types of predator, which differ in their sensory capabilities and methods of prey detection. For animals capable of rapid colour change, one potential strategy is to change their appearance in relation to the threat posed by different predators. Here, we show that the dwarf chameleon, Bradypodion taeniabronchum , exhibits different colour responses to two predators that differ in their visual capabilities. Using a model of animal colour perception to gain a ‘predator's eye view’, we show that chameleons showed better background colour matching in response to birds than snakes, yet they appear significantly more camouflaged to the snake visual system because snakes have poorer colour discrimination.

Implications of chemosensory feeding in catfishes: an analysis of the diets of Ictalurus nebulosus and I. natalis

1985 ◽  
Vol 63 (3) ◽  
pp. 590-602 ◽  
Author(s):  
Allen Keast
Keyword(s):  
Young Adults ◽  
Food Availability ◽  
Fish Species ◽  
Metabolic Efficiency ◽  
Potential Prey ◽  
Brown Bullhead ◽  
Chironomid Larvae ◽  
Age Class ◽  
Ictalurus Nebulosus ◽  
Lower Standard

The implications of chemosensory feeding and associated ictalurid morphology were investigated through a seasonal study of the diets of the brown bullhead (Ictalurus nebulosus) and yellow bullhead (I. natalis) relative to food availability. Based on the attributes of chemosensory feeding (little discrimination between prey types) and bullhead morphology (poor sight, broad mouth), it was predicted that bullheads would be food generalists and opportunists, and that age-class diets would overlap. These predictions were generally supported for the brown bullhead. Some food types (amphipods) were harvested when most abundant; however, others (chironomid larvae) were consistently taken, and a few potential prey types were underutilized. The yellow bullhead, by contrast, was a food generalist only when young. Adults were specialized piscivores and crayfish feeders. The brown bullhead showed greater weight and length increases than co-occurring visually feeding centrarchids with diets of similar calorific values. Because of the similarity in calorific intake among species, a greater metabolic efficiency in brown bullheads was indicated. Other workers have shown that brown bullheads have lower standard and active metabolisms than some fish species.

Functional morphology of the piper Hyporhamphus ihi with reference to the role of the lateral line in feeding

1985 ◽  
Vol 224 (1235) ◽  
pp. 197-208 ◽  
Keyword(s):  
Visual System ◽  
Functional Morphology ◽  
Lateral Line ◽  
Mandibular Canal ◽  
Lateral Line System ◽  
Prey Detection ◽  
Line System ◽  
Body Form ◽  
Lower Jaw

As a basis for understanding the function of the halfbeak of the piper Hyporhamphus ihi (Phillips), details of the structure and dimensions of the anterior lateral line on the head and lower jaw of the piper are described. The anterior lateral line is composed of a series of cranial canals; the supraorbital–postorbital canal; the suborbital canal; and the preopercular—mandibular canal which extends along the lower jaw. Each canal opens to the surface by a series of pores, and individual neuromasts exist in specialized regions of the canals between each of the pores. Piper are nocturnal plankivores and they possess the feeding structures and digestive tract suited to this diet. The hypothesis is proposed that they use the anterior lateral line system in prey detection, and this paper shows that the piper’s elongate body form, swimming behaviour, and lack of a specialized visual system are all consistent with this hypothesis.

scholarly journals Prey detection in a cruising copepod

2011 ◽  
Vol 8 (3) ◽  
pp. 438-441 ◽  
Author(s):  
Sanne Kjellerup ◽  
Thomas Kiørboe
Keyword(s):  
Boundary Layer ◽  
Chemical Cues ◽  
Prey Capture ◽  
Reynolds Numbers ◽  
Prey Detection ◽  
Potential Prey ◽  
Viscous Boundary Layer ◽  
Low Reynolds Numbers ◽  
Low Reynolds ◽  
Viscous Boundary

Small cruising zooplankton depend on remote prey detection and active prey capture for efficient feeding. Direct, passive interception of prey is inherently very inefficient at low Reynolds numbers because the viscous boundary layer surrounding the approaching predator will push away potential prey. Yet, direct interception has been proposed to explain how rapidly cruising, blind copepods feed on non-motile phytoplankton prey. Here, we demonstrate a novel mechanism for prey detection in a cruising copepod, and describe how motile and non-motile prey are discovered by hydromechanical and tactile or, likely, chemical cues, respectively.

scholarly journals Redirection of ambient light improves predator detection in a diurnal fish

2020 ◽  
Vol 287 (1919) ◽  
pp. 20192292 ◽  
Author(s):  
Matteo Santon ◽  
Pierre-Paul Bitton ◽  
Jasha Dehm ◽  
Roland Fritsch ◽  
Ulrike K. Harant ◽  
...  
Keyword(s):  
Active Sensing ◽  
Ambient Light ◽  
Predator Detection ◽  
Eye Evolution ◽  
Controlled Illumination ◽  
Fish Eye ◽  
Tripterygion Delaisi ◽  
Scorpaena Porcus

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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