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Metabolic influences of fiber size in aerobic and anaerobic muscles of the blue crab, Callinectes sapidus

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
Lisa K. Johnson (Creator)
Institution
The University of North Carolina Wilmington (UNCW )
Web Site: http://library.uncw.edu/
Advisor
Stephen Kinsey

Abstract: Diameters of some white muscle fibers in the adult blue crab, Callinectes sapidus, exceed 500 µm whereas juvenile white fibers are <100 µm. It is hypothesized that aerobically dependent processes, such as recovery from exercise, will be significantly impeded by size in these large white fibers. In addition, dark aerobic fibers of adults, which do rely on aerobic contraction, grow as large as the white fibers. These large aerobic fibers are subdivided, thus decreasing the effective diameter of the fiber and enabling aerobic contraction. The two goals of this study were: (1) to characterize the development of subdivisions in the dark muscle fibers and (2) to monitor post-contractile metabolism as a function of fiber size. Dark muscle fibers from crabs ranging from <0.1 g to >200 g were examined with transmission electron microscopy to determine the density of mitochondria and subdivision diameters. Mitochondrial fractional areas were consistently 25% of the total subdivision area and subdivision sizes remained constant throughout development, with an average diameter of 36.5 ± 2.7 µm. Citrate synthase (CS) activities in dark muscle were higher and scaled with a steeper negative slope (b=-0.19) than activities in white muscle (b=-0.09). In addition, the time course of [lactate] was monitored during recovery from anaerobic, burst exercise in white and dark muscle and hemolymph. Burst escape responses were elicited in crabs ranging from <1 g to >200 g and [lactate] measured. There were no differences among size classes with respect to lactate accumulation as a result of exercise, however, in white fibers from large crabs, lactate continued to increase after exercise, and lactate removal from tissues required a longer period of time relative to small and medium crabs. Differences in lactate removal among size classes were less pronounced in dark fibers. These data suggest that in addition to normal metabolic scaling, aerobic metabolic processes are limited to SA:V and intracellular diffusion constraints in large white muscle fibers.

Additional Information

Publication
Thesis
A Thesis Submitted to the University of North Carolina at Wilmington in Partial Fulfillment Of the Requirements for the Degree of Master of Science
Language: English
Date: 2009
Keywords
Blue crab--Morphology, Blue crab--Physiology, Callinectes, Crabs--Research, Muscle cells
Subjects
Blue crab -- Morphology
Blue crab -- Physiology
Muscle cells
Crabs -- Research
Callinectes