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First published online June 16, 2005
Journal of Experimental Biology 208, 2475-2482 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01655

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Intragel oxygen promotes hypoxia tolerance of scyphomedusae

Erik V. Thuesen^1,*, Ladd D. Rutherford, Jr¹, Patricia L. Brommer¹, Kurt Garrison², Magdalena A. Gutowska³ and Trisha Towanda¹

¹ Laboratory One, The Evergreen State College, Olympia, Washington 98505, USA
² Academia Cotopaxi, Casilla 17-01-199, Quito, Ecuador
³ Alfred Wegener Institute for Polar and Marine Research, Columbusstraße 27568 Bremerhaven, Germany

View larger version (80K): [in a new window]   Fig. 1. Intragel oxygen characteristics of Aurelia labiata. An image of A. labiata showing the location of intragel oxygen measurements. The points labeled t, m and g represent measurements taken in the immediate subsurface of the aboral side mesoglea, the midgel, and the oral subsurface tissue (gonad), respectively.

View larger version (23K): [in a new window]   Fig. 2. Mass-specific oxygen consumption rates in progressive hypoxia for four species of scyphomedusae. Squares, Phacellophora camtschatica (N=7); circles, Aurelia labiata (N=7); triangles, Cyanea capillata (N=1); diamonds, Chrysaora quinquecirrha (N=1). Critical partial pressures of oxygen were determined to be 9.1±1.4, 9.0±1.9, 14.6 and 12.3 hPa for P. camtschatica, A. labiata, C. capillata and C. quinquecirrha, respectively. Values are means ± S.E.M. Temperature and salinity were 10°C and 30 psu for experiments with P. camtschatica, A. labiata, and C. capillata; for C. quinquecirrha, 25°C and 12 psu, respectively.

View larger version (18K): [in a new window]   Fig. 3. Typical intragel oxygen profiles of two harnessed specimens of Aurelia labiata in normoxia. Solid triangles, specimen was harnessed exumbrellar side up. Open triangles, specimen was harnessed with the exumbrellar surface firmly pressed to the bottom of the chamber. Locations of points t and g as in Fig. 1.

View larger version (23K): [in a new window]   Fig. 4. Intragel oxygen measurements of unharnessed specimens of Aurelia labiata under different oxygen conditions. Values are means ± S.E.M. White, black and shaded bars represent measurements made in points t, m and g, respectively (see Fig. 1). Hypoxia=30% air saturation. Anoxia1 and Anoxia2, 1 and 2 h in anoxia, respectively. Recovery, 2 h in anoxia followed by 2.5 h in normoxia. All differences in intragel oxygen partial pressures between treatments are significant, except that and are not significantly different from each other. For N and P values, see text.

View larger version (42K): [in a new window]   Fig. 5. Depth profiles of Aurelia labiata in 80 cm water columns under five oxygen conditions. Each coloured line is the track of an individual specimen over a 1 h period. The five tank conditions were normoxia (100% air saturation oxygen), stratified (with ending oxygen concentrations of 100–130% air saturation oxygen in the surface 20 cm and 0–5% air saturation oxygen in the bottom 40 cm), 30% air saturation oxygen, 18% air saturation oxygen, and anoxia.

View larger version (17K): [in a new window]   Fig. 6. Swimming characteristics of Aurelia labiata in 1 h tank experiments. (A) Vertical distances travelled. (B) Time (min) swimming. (C) Bell pulsation rates. Values are means ± S.E.M. *Significant difference from all other treatments (P<0.01). Tank conditions as in Fig. 5.