Mechanisms and Ecological Implications of Eye Stalk Stability in the Sand Fiddler Crab Uca Pugilator (bosc) PDF Download

Author: John Emerson Layne
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ISBN:
Category : Eye
Languages : en
Pages : 366

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Author: Premraj Rajkumar
Publisher:
ISBN:
Category :
Languages : en
Pages : 120

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Uca pugilator are semi-terrestrial brachyuran fiddler crabs that inhabit inter-tidal sand and mud flats. They are social animals that rely exclusively on visual information during several of their behaviors that include mate choice, predator avoidance, burrow surveillance, courtship and territorial interactions. Through several behavioral and optical experiments, it has been previously shown that they have 360° viewing angle on each eye, high spatial resolution along their eye's midline, improved resolution on the vertical axes and posses excellent optomotor stabilization mechanism. Such understanding of their retinal design has helped us realize that the eyes of fiddler crabs are adapted for specific visual tasks in their geometrically structured habitat. However, the physiological capabilities of this retina are not yet completely understood, especially at the photoreceptor level. The objective of my thesis has been to fill this gap in knowledge, and specifically determine the spatial, temporal and spectral properties of photoreceptor cells through an integrative approach, using several molecular and electrophysiological techniques. Through these experiments, I have shown that the spatial resolution of the eye is best along the eye's midline (~1°), photoreceptor cells are capable of perceiving up to ~45Hz of flickering light stimuli and that they are capable of perceiving color cues including in the ultra-violet.

Author: William F. Herrnkind
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ISBN:
Category : Zoology
Languages : en
Pages : 158

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Category : Dissertation abstracts
Languages : en
Pages : 806

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Author: Gregory Kent Vermeer
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Category :
Languages : en
Pages : 72

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Author: Michelle Anne Duval
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Category : Fiddler crabs
Languages : en
Pages : 310

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Author: Jessica D. Ebie
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ISBN:
Category :
Languages : en
Pages : 63

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Fiddler crabs, like many other organisms, have independently evolved to have compensatory eye movements that help stabilize gaze [1-4]. Humans and non-human taxa have been shown to use these eye movements to help accurately perceive the location of objects in the world around them. This study examines the fiddler crab, Uca pugilator, to investigate whether the role of compensatory eye movements in directional perception has evolved in a similar way as in other taxa. Two experiments were performed with the fiddler crab, Uca pugilator, to study the role of sensory systems in its perception of and interactions with its environment. The first experiment tested the function of the oculomotor reflexes in the maintenance of subjective body axis and awareness of where objects are in space. The second experiment tests the efficiency of magnetic statoliths as replacements for normally non-magnetic statoliths in the statocysts and the role of the statoliths in vertical compensatory eye movements. Oculomotor reflexes (i.e., gaze-stabilizing eye reflexes) were tested to determine whether they contribute to directional perception. Fiddler crabs were exposed to two types of oculomotor stimuli - an optokinetic stimulus alone or optokinetic and vestibulo-ocular reflex stimuli presented simultaneously. Following exposure to the oculomotor stimulus, fiddler crabs were presented with a looming stimulus (i.e., a simulated predator) to invoke an escape response. The direction of escape was recorded and compared to that of looming stimulus treatment crabs that only received the looming stimulus. The escape direction was recorded as an indicator of the role of the oculomotor reflexes in directional perception. There was a significant difference in escape direction between looming stimulus treatment crabs and those receiving only the optokinetic stimulus, which suggests that the optokinetic reflex does not update the mapping of object images on the retina to perceived location of those objects in space. However, there was no significant difference between looming stimulus treatment crabs and those receiving the optokinetic and vestibulo ocular stimuli simultaneously, which is a contradictory result. However, fiddler crabs may be using other information when perceiving direction. During the second experiment, fiddler crabs' normally non-magnetic statoliths were replaced with metal filings and then exposed to an oscillating magnet to simulate movement in the pitch and roll planes. Simulating movement in these planes allows the role of the statolith in vertical compensatory eye movement to be examined in addition to determining the effectiveness of metal filings as a statolith replacement. The eye oscillation lagged behind the magnet oscillation, but the frequencies were consistent. Measured gain (i.e., eye oscillation amplitude divided by magnet oscillation amplitude) was slightly less than what would be expected if the fiddler crab eye perfectly compensated for the simulated body tilt created by the magnetic apparatus. This attenuation may be due to the lagging response of the fiddler crab to the dynamic stimulus. Knowing that metal filings are effective statolith replacements opens up many possibilities for behavioral manipulations to investigate how information provided to the fiddler crab by the statocyst is used in perception.

Author: John Harold Christy
Publisher:
ISBN:
Category : Courtship in animals
Languages : en
Pages : 686

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Author: Teri Butler
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Category : Animal pigments
Languages : en
Pages : 272

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Author: Paul Mazzoni
Publisher:
ISBN:
Category : Ecdysis
Languages : en
Pages : 30

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