Body shape affects the capacity and efficiency of swimming in fishes, and places
constraints on foraging and reproductive performance. Hence, fitness components, such
as aerobic swimming capacity and efficiency, can be determined from analysis of
swimming energetics using active respirometry. In particular, body shape adaptations,
such as streamlining, aim at reducing hydrodynamic drag (resistance), thereby increasing
swimming efficiency in the presence of water flow, which is a principal contributor to
resistance for fish inhabiting rivers. For two populations of bluegill sunfish, one from the
Brazos River and the other from Moelman’s Slough (a Brazos River oxbow lake), the
metabolic transport rate (MTR) was determined to evaluate differences in swimming
efficiency. The standard cost of swimming (SCOS) was also determined to evaluate
differences in swimming capacity, which represents the overall capacity of the skeletal
muscles to generate mechanical power to overcome hydrodynamic resistance. The MTR
and the SCOS describe holistic swimming performance, where the MTR specifies the
hydrodynamic response due to swimming, and the SCOS specifies the physiologic
response due to swimming. The differences in swimming performance are mainly
attributed to factors affecting hydrodynamic resistance and could be predicted by
morphology; because body shape, like water flow, is also a principal contributor to
resistance. Multivariate body shape, from generalized Procrustes analysis, was used to
assess the influence of multiple shape traits on swimming costs. This measure of shape
related to swimming performance using partial least-squares analysis showed the two bluegill populations to be significantly different. The results were as follows: the
shallow-bodied condition in bluegills was highly correlated with efficient swimming and
low swimming capacities; whereas, deep-bodied bluegills were highly correlated with
inefficient swimming and high swimming capacities. This is an empirical case of
divergent natural selection. For convergence, however, the position of the caudal
peduncle is consistent with optimal swimming speed (Um), which depends on standard
metabolic rate (SMR), or metabolic maintenance. Bluegills with erect caudal peduncles
have a high range of swimming speeds without suffering much cost of swimming ability
compared to bluegills with prone caudal peduncles. The adaptive physiological response
to high Um is due to a low SCOS because swimming efficiency is low and metabolic
maintenance is high. In other words, bluegills that are inefficient swimmers and require a
high energy intake cannot survive unless they gain the ability to increase their foraging
capacity by thrust or metabolic power reduction. This is perhaps one of the most
remarkable adaptive physiological responses due to the joint effects of shape and SMR.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-1393 |
| Date | 15 May 2009 |
| Creators | Papadopoulos, Anthony |
| Contributors | DeWitt, Thomas J. |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | electronic, application/pdf, born digital |
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