Costs of transport for the scyphomedusa Stomolophus meleagris L. Agassiz

Abstract

The rhizostome scyphomedusa Stomolophus meleagris swims continuously at speeds up to 15 cm∙s−1. Mean velocities increased as a power function of wet weight up to 70 g but were mostly constant thereafter. Bell pulsations ranged from 1.7 to 3.6 Hz. Reynolds numbers equalled 900 – 13 000. During activity, medusae consumed 0.05 mL O2∙h−1∙g WW−1 (1.2 mL O2∙h−1∙g DW−1), at 30 °C. Rates for inactive medusae were 50% less. The estimated cost of transport ranged from 2 J∙kg−1∙m−1 at 5 g to 1 J∙kg−1∙m−1 at 1 kg. These rates are comparable to those of fishes and about 1/50th that of planktonic crustaceans. These results were unexpected in light of the typical inefficiency (power output/power input) of jet swimming. However, S. meleagris has a very low respiration rate relative to crustaceans and fish, which probably compensated for low swimming efficiency.

Ontogenetic propulsive transitions by medusaeSarsia tubulosa

“…9B). Although these values were higher than those reported for S. meleagris (Larson, 1987), the results here represent size ranges smaller than those reported for S. meleagris. For organisms with a body mass of 0.01 g, the values of HCOT for S. tubulosa were consistent with COT values for S. atra and G. vertens (Daniel, 1985).…”

“…The maximum swimming speed over ontogeny for S. tubulosa was also non-linear; after a linear increase for the smallest bell exit diameters, the maximum swimming speed reached a constant (approximately 4 cm s −1 ) for bell exit diameters larger than 5 mm. Non-linearity of COT (on log-log plots) and maximum swimming speed has been reported for S. meleagris, and was attributed to insufficiently powerful muscle mass in larger organisms (Larson, 1987).…”

“…Although the HCOT provides only a minimum estimate of metabolic economy, we expect that the behavior of HCOT across ontogeny will reflect the COT. Metabolic rates for other medusae utilizing rowing propulsion have been collected for Aurelia aurita, Stomolophus meleagris and Stomotoca atra (Uye and Shimauchi, 2005;Larson, 1987;Daniel, 1985). Although respiration rates have been quantified for similarly sized Gonionemus vertens (Daniel, 1985), metabolic rates across ontogeny for jet-propelled medusae have yet to be measured.…”

Passive energy recapture in jellyfish contributes to propulsive advantage over other metazoans

“…By this measure, the moon jellyfish, Aurelia aurita, expends significantly less energy per unit of wet mass per unit distance traveled than other animals. The ability to exhibit a low COT has also been reported in another jellyfish species (Stomolophus meleagris) (12).…”

“…Jellyfish have low body carbon relative to other swimmers (13), which results in ≤1% of the body mass represented by muscle (12,14). Fish, in comparison, have a body mass that is ≥50% muscle (15).…”