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First published online November 10, 2003

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Influences of thermal acclimation and acute temperature change on the motility of epithelial wound-healing cells (keratocytes) of tropical, temperate and Antarctic fish

Rachael A. Ream¹, Julie A. Theriot¹ and George N. Somero^2,*

¹ Biochemistry Department, Beckman Center, Room 473A, Stanford University School of Medicine, Stanford, CA 94305-5307, USA
² Hopkins Marine Station, Pacific Grove, CA 93950, USA

View larger version (46K): [in a new window]   Fig. 1. Phase-contrast images of keratocytes from G. mirabilis display the range of variation observed in keratocyte morphology. Morphological features include: (A) stereotypical `canoe shape', (B) small ruffling at the leading edge, (C) ruffling at the edges of the cell and (D) large, phase-dense ruffles in the forward third of the lamellipodium. Scale bar, 10 µm.

View larger version (16K): [in a new window]   Fig. 2. Time-lapse picture of crawling keratocyte cultured from G. mirabilis at 2(40x). Scale bar, 15 µm. Images were taken 30 s apart.

View larger version (34K): [in a new window]   Fig. 3. The velocity of each cell was analyzed in regard to speed and trajectory. Examples show four types of analysis for four cells cultured from G. mirabilis, two moving in straight lines and two moving in circles: (A) a trajectory plot of (x,y) coordinates of the positions of four cells over 20 min, beginning at the origin and rotated such that the first step is along the y-axis (x=0); (B) speed histograms of the frequency of instantaneous cell speeds; (C) autocorrelation analysis of cell speed shows memory (correlation) and oscillation; and (D) cosine analysis shows the magnitude of turning angles () made by the cell over time.

View larger version (24K): [in a new window]   Fig. 4. The mean cell speed ± S.D. for 20 cells at each experimental temperature. Cells cultured from a thermal acclimation group denoted by an asterisk move at a mean speed significantly different from the cells of other thermal acclimations at that experimental temperature. (A) Keratocytes from G. mirabilis acclimated to 10°C (blue), 16°C (black) and 25°C (red); (B) keratocytes from C. salinus acclimated to 26°C (blue) and 35°C (red); (C) keratocytes from A. percula acclimated to 26°C (black); and (D) keratocytes from T. bernacchii acclimated to -1.86°C (blue; inset) and 5°C (red; main figure) move at speeds 10-100x slower than other cells. (E-H) Arrhenius plots of 1000/T vs. ln(speed) for cells cultured from G. mirabilis (E), C. salinus (F), A. percula (G) and T. bernacchii (H). Acclimation groups are delineated by the corresponding color codes in panels A-D.

View larger version (18K): [in a new window]   Fig. 5. Mean keratocyte speed as a function of experimental temperature. Speed is conserved at physiological temperatures for the three non-Antarctic species, as indicated by the zone bounded by the two horizontal lines.

View larger version (35K): [in a new window]   Fig. 6. Cell centroid positions were tracked over a total time of 15 min at 15 s intervals for 20-21 cells at each experimental condition. For population comparisons, each cell's path was plotted as a separate colored line beginning at the origin and reoriented so that the first segment of any trajectory is along the y-axis (x=0). Trajectories of each cell measured are shown at 10°C and 20°C for all acclimation groups of all species. Systematic variations in both speed and turning behavior are apparent.

View larger version (25K): [in a new window]   Fig. 7. Cos () versus path length is plotted at 10°C and 20°C for cells from each species at each thermal acclimation. As turning magnitude increases, cosine values begin to approach zero. (A) Keratocytes from G. mirabilis acclimated to 10°C (blue), 16°C (black) and 25°C (red); (B) keratocytes from C. salinus acclimated to 26°C (blue) and 35°C (red); (C) keratocytes from A. percula acclimated to 26°C (black); and (D) keratocytes from T. bernacchii acclimated to -1.86°C (black) and 4°C (red).