A note on the asymmetry of male fiddler-crabs (UCA pugilator)

1933 ◽  
Vol 129 (2) ◽  
pp. 379-392 ◽  
Author(s):  
J. S. Huxley ◽  
F. S. Callow
Keyword(s):  
Fiddler Crabs ◽  
Uca Pugilator ◽  
The Asymmetry

How dear is my enemy: Intruder-resident and resident-resident encounters in male sand fiddler crabs (Uca pugilator)

Behaviour ◽  
2006 ◽  
Vol 143 (5) ◽  
pp. 597-617 ◽  
Author(s):  
Ann E. Pratt ◽  
Denson Kelly McLain
Keyword(s):  
Energy Expenditure ◽  
Fiddler Crabs ◽  
Uca Pugilator ◽  
Dear Enemy ◽  
Surface Activities ◽  
Display Area ◽  
Mating Opportunities

AbstractMale sand fiddler crabs (Uca pugilator) defend territories that consist of a breeding burrow and a display area where they wave their claw to attract females. Burrow-holding males engage in agonistic contests with both intruding males that attempt burrow take-overs and with other territory-holding neighbors that apparently attempt to limit waving or other surface activities of rivals. Contests employ one or more behavioral elements that range from no claw contact to use of the claw to push, grip, or flip an opponent. We placed each observed element into one of six groups ranked by intensity, which was based on the degree of claw contact and apparent energy expenditure. In the field, contests with intruders began at higher intensity and escalated more rapidly than did those with neighbors. Thus, U. pugilator males exhibit a dear enemy response toward neighbors. However, resident-resident contests increased in intensity when burrows were close, neighbors faced each other when exiting burrows, and neighbors were of similar size. Proximity and orientation determine the ease with which a neighbor may be engaged. Also, neighbors that are close and of similar size pose a greater threat to mating opportunities, favoring heightened intensity of contests.

Fiddler Crabs Use the Visual Horizon to Distinguish Predators from Conspecifics: A Review of the Evidence

1997 ◽  
Vol 77 (1) ◽  
pp. 43-54 ◽  
Author(s):  
John Layne ◽  
Michael Land ◽  
Jochen Zeil
Keyword(s):  
Field Experiments ◽  
Angular Size ◽  
White Background ◽  
Fiddler Crabs ◽  
Absolute Size ◽  
Uca Pugilator ◽  
Glass Dish ◽  
Escape Responses ◽  
The Absolute

Male fiddler crabs, Uca pugilator (Crustacea: Decapoda), respond to conspecifics by claw waving, and to predators by freezing or escape. In field experiments it was found that this distinction was not made on the basis of angular size and speed, nor was shape important. The remaining possibilities were either the absolute size of the stimulus, determined from angular size and distance, or the position of the stimulus relative to the horizon. To distinguish between these, a crab was placed in a glass dish, and moved black stimuli on a white background, at a distance of 22 cm. Stimuli below the crab's horizon hardly ever evoked escape. However, identical stimuli partially or wholly above the crab's horizon produced escape responses whose frequency varied with the angular size of the stimulus. Halving the distance of the stimulus showed that it was angular and not absolute size that determines escape frequency; and experiments with a tilted horizon showed that it is the position of the stimulus relative to the eye equator that is important, rather than the geographical horizon itself. It has been concluded that crabs categorize stimuli as dangerous or otherwise by their position relative to the crabs’ visual horizon.

Recruitment to adult habitats following marine planktonic development in the fiddler crabs, Uca pugilator, U. pugnax, and U. minax

2005 ◽  
Vol 147 (1) ◽  
pp. 105-111 ◽  
Author(s):  
R. J. Brodie ◽  
M. E. Behum ◽  
E. Monroe ◽  
N. Glenn ◽  
J. L. Staton
Keyword(s):  
Fiddler Crabs ◽  
Uca Pugilator

Retinal location is the key to identifying predators in fiddler crabs (Uca pugilator).

1998 ◽  
Vol 201 (15) ◽  
pp. 2253-2261 ◽  
Author(s):  
J E Layne
Keyword(s):  
Angular Size ◽  
Vertical Axis ◽  
Fiddler Crabs ◽  
Absolute Size ◽  
Uca Pugilator ◽  
Natural Behavior ◽  
Light Gradient ◽  
External Cues ◽  
Moving Stimulus ◽  
Escape Responses

Fiddler crabs (Uca pugilator Bosc; Crustacea, Decapoda) feed and court in open, flat spaces. Their visual system has several putative adaptations to their flat habitat, including the tendency to keep the vertical axis of their eyes perpendicular to the plane of the substratum. It is hypothesized that one of the functions of this behavior is to distinguish accurately predators from conspecifics by aligning the region of the eye sensitive to predators with the region in space in which predators occur. To test this hypothesis, a crab was placed in a glass dish, and a moving stimulus was presented between 20 degrees above and below eye level (horizontal). Stimuli below the crab's horizon hardly ever evoked escape responses, while identical stimuli above the horizon produced escape responses whose frequency varied with the angular size, not the absolute size, of the stimulus. Experiments with artificial horizons showed that it is the position of the stimulus relative to the eye that is important, rather than its position relative to external cues such as the visible horizon, the vertical light gradient or the gravitational horizon. It is concluded that a crab responds to stimuli according to their position relative to its retinal equator. This conclusion is discussed in light of the crabs' natural behavior with respect to supra-horizontal stimuli.

Variation in the Boldness of Courting Sand Fiddler Crabs (Uca pugilator)

Ethology ◽  
2005 ◽  
Vol 111 (1) ◽  
pp. 63-76 ◽  
Author(s):  
Ann E. Pratt ◽  
Denson K. McLain ◽  
Allison S. Berry
Keyword(s):  
Fiddler Crabs ◽  
Uca Pugilator

Microcalorimetric monitoring during adaptation to hypo- and hyperosmotic media of fiddler crabs uca pugilator

1985 ◽  
Vol 94 (1) ◽  
pp. 151-160 ◽  
Author(s):  
Gunnar B. Joachimsohn ◽  
Ingolf Lamprecht ◽  
Kai Graszynski
Keyword(s):  
Fiddler Crabs ◽  
Uca Pugilator
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