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Honest and dishonest signals of strength in Australian slender crayfish (Cherax dispar): are male's liars and cheaters?
Abstracts / Comparative Biochemistry and Physiology, Part A 146 (2007) S107–S127
A6.39 A method for accurate 3-D reconstruction of skeletal morphology and movement E. Brainerd, S. Gatesy, D. Baier, (Brown University, United States); T. Hedrick, (University of Washington, United States) Accurate 3-D skeletal movement data would be valuable for many areas of biomechanics research. Bone movement sometimes can be inferred from external movement, but loose skin introduces artifacts and many bones are too deep in the body to be tracked externally. We are developing a method “CTX imaging” for visualizing skeletal position during rapid movement. CTX combines bone shape data from CT scans with bone position data from biplanar X-ray video. The result is an accurate movie of 3-D bones moving in 3-D space. Here we describe our work on a marker-based CTX method. Two OEC 9400 C-arm cinefluoroscopes were retrofitted with high-speed video cameras (1000 fps) and arranged such that the intersection of the X-ray beams covers a basketball-sized volume. The steps in marker-based CTX are: 1) at least three radiopaque spheres (1 mm) are surgically implanted into each bone of interest; 2) biplanar X-ray movies of animal movement are collected; 3) distortions introduced by fluoroscope and camera are removed from the movies and XYZ coordinates of the markers are measured; 4) the animal is CT scanned and digital 3-D bone models are made with the markers in still place; 5) the data from marker motion capture (steps 1–3) are used to position and orient the 3-D bone models (from step 4), resulting in an accurate (± 0.1 mm) reconstruction of bone position over time. We are also working on a markerless CTX method that will not require surgical implantation of radiopaque spheres.
S119
A6.41 Honest and dishonest signals of strength in Australian slender crayfish (Cherax dispar): are male's liars and cheaters? R. Wilson, C. Bywater, (University of Queensland, Australia); M. Angilletta, (Indiana State University, United States); R. James, (Coventry University, United Kingdom); C. Navas, (University of Sao Paulo, Brazil); F. Seebacher, (University of Sydney, Australia) Cherax dispar. Crayfish routinely use their enlarged front claws (chelae) for both intimidation and fighting, making them an ideal system to examine the honesty of signals of fighting capacity. We evaluated five competing models relating morphological and physiological traits (body length, body condition, claw size, and claw strength) to dominance during paired competitive bouts. In an honest signaling system, claw size and strength will be good predictors of dominance during competitive interactions. We found females that possessed large chelae were more likely to possess stronger chelae and those individuals with stronger chelae were more likely to win competitive bouts, thus supporting current theory. In contrast, we found chelae strength of individual male C. dispar had no bearing on their dominance ability, indicating that displays of claw size were dishonest signals and the enlarged claws of males function more for intimidation than actual strength. Given the extent of bluffing among male C. dispar, it appears current theory underestimates the potential importance of dishonest signals in intraspecific animal communication. doi:10.1016/j.cbpa.2007.01.215
doi:10.1016/j.cbpa.2007.01.213
A6.40 Swimming performance of a subcarangiform, the blind Mexican cave fish (Astyanax fasciatus)
A6.42 A general model of functional constraints on phenotypic evolution J. Walker, (University of Southern Maine, United States)
R. Holbrook, R. Bomphrey, S. Walker, G. Taylor, A. Thomas, T. Burt de Perera, (University of Oxford, United Kingdom) We aimed to investigate the swimming performance of the blind Mexican cave fish (Astyanax fasciatus), a subcarangiform, in a 3-dimensional environment. Blind Mexican cave fish were recorded swimming freely for one hour in a bare aquarium using two cameras. Automated tracking software was used to generate a track of the fish from each camera view, and a bundle adjustment was performed to generate the 3-dimensional behaviour of the fish. Using this data we were able to benchmark, for the first time, the normal swimming performance of Astyanax fasciatus. doi:10.1016/j.cbpa.2007.01.214
A general model of the functional constraints on the rate and direction of phenotypic evolution is developed using Arnold's decomposition of the multivariate breeder's equation. The important feature of the model is the F matrix of functional performance coefficients reflecting the causal relationship between performance and a suite of morphophysiological (mp) traits. The structure of the F matrix constrains the rate and direction of m-p trait evolution and thus contributes to trait evolvability. The off-diagonal elements of the matrix F^TF summarize net trade-offs and facilitations among performance traits. Simulation data are used to show how the structure of F limits but does not preclude the simultaneous optimization of two performances that trade-off. The off-diagonal elements of the functional integration matrix FF^T reflect the functional correlation between two m-p traits. The model can be used to measure the long-term effects of functional constraints on
A6.39 A method for accurate 3-D reconstruction of skeletal morphology and movement E. Brainerd, S. Gatesy, D. Baier, (Brown University, United States); T. Hedrick, (University of Washington, United States) Accurate 3-D skeletal movement data would be valuable for many areas of biomechanics research. Bone movement sometimes can be inferred from external movement, but loose skin introduces artifacts and many bones are too deep in the body to be tracked externally. We are developing a method “CTX imaging” for visualizing skeletal position during rapid movement. CTX combines bone shape data from CT scans with bone position data from biplanar X-ray video. The result is an accurate movie of 3-D bones moving in 3-D space. Here we describe our work on a marker-based CTX method. Two OEC 9400 C-arm cinefluoroscopes were retrofitted with high-speed video cameras (1000 fps) and arranged such that the intersection of the X-ray beams covers a basketball-sized volume. The steps in marker-based CTX are: 1) at least three radiopaque spheres (1 mm) are surgically implanted into each bone of interest; 2) biplanar X-ray movies of animal movement are collected; 3) distortions introduced by fluoroscope and camera are removed from the movies and XYZ coordinates of the markers are measured; 4) the animal is CT scanned and digital 3-D bone models are made with the markers in still place; 5) the data from marker motion capture (steps 1–3) are used to position and orient the 3-D bone models (from step 4), resulting in an accurate (± 0.1 mm) reconstruction of bone position over time. We are also working on a markerless CTX method that will not require surgical implantation of radiopaque spheres.
S119
A6.41 Honest and dishonest signals of strength in Australian slender crayfish (Cherax dispar): are male's liars and cheaters? R. Wilson, C. Bywater, (University of Queensland, Australia); M. Angilletta, (Indiana State University, United States); R. James, (Coventry University, United Kingdom); C. Navas, (University of Sao Paulo, Brazil); F. Seebacher, (University of Sydney, Australia) Cherax dispar. Crayfish routinely use their enlarged front claws (chelae) for both intimidation and fighting, making them an ideal system to examine the honesty of signals of fighting capacity. We evaluated five competing models relating morphological and physiological traits (body length, body condition, claw size, and claw strength) to dominance during paired competitive bouts. In an honest signaling system, claw size and strength will be good predictors of dominance during competitive interactions. We found females that possessed large chelae were more likely to possess stronger chelae and those individuals with stronger chelae were more likely to win competitive bouts, thus supporting current theory. In contrast, we found chelae strength of individual male C. dispar had no bearing on their dominance ability, indicating that displays of claw size were dishonest signals and the enlarged claws of males function more for intimidation than actual strength. Given the extent of bluffing among male C. dispar, it appears current theory underestimates the potential importance of dishonest signals in intraspecific animal communication. doi:10.1016/j.cbpa.2007.01.215
doi:10.1016/j.cbpa.2007.01.213
A6.40 Swimming performance of a subcarangiform, the blind Mexican cave fish (Astyanax fasciatus)
A6.42 A general model of functional constraints on phenotypic evolution J. Walker, (University of Southern Maine, United States)
R. Holbrook, R. Bomphrey, S. Walker, G. Taylor, A. Thomas, T. Burt de Perera, (University of Oxford, United Kingdom) We aimed to investigate the swimming performance of the blind Mexican cave fish (Astyanax fasciatus), a subcarangiform, in a 3-dimensional environment. Blind Mexican cave fish were recorded swimming freely for one hour in a bare aquarium using two cameras. Automated tracking software was used to generate a track of the fish from each camera view, and a bundle adjustment was performed to generate the 3-dimensional behaviour of the fish. Using this data we were able to benchmark, for the first time, the normal swimming performance of Astyanax fasciatus. doi:10.1016/j.cbpa.2007.01.214
A general model of the functional constraints on the rate and direction of phenotypic evolution is developed using Arnold's decomposition of the multivariate breeder's equation. The important feature of the model is the F matrix of functional performance coefficients reflecting the causal relationship between performance and a suite of morphophysiological (mp) traits. The structure of the F matrix constrains the rate and direction of m-p trait evolution and thus contributes to trait evolvability. The off-diagonal elements of the matrix F^TF summarize net trade-offs and facilitations among performance traits. Simulation data are used to show how the structure of F limits but does not preclude the simultaneous optimization of two performances that trade-off. The off-diagonal elements of the functional integration matrix FF^T reflect the functional correlation between two m-p traits. The model can be used to measure the long-term effects of functional constraints on