Proceedings of The Physiological Society

Future Physiology (Leeds, UK) (2017) Proc Physiol Soc 39, C10

Oral Communications

Oxygen consumption in planarians as a function of temperature, specific dynamic action, taxon, and reproductive mode

M. Lewallen1, W. W. Burggren1

1. Biology, University of North Texas, Denton, Texas, United States.

Measuring metabolic rate quantifies energetic investment and impact of environment, reproduction, genetics, and diet, providing a greater understanding of whole organismal physiology. Planarians are studied for ability to regenerate completely when cut into fragments due to abundant pluripotent stem cells, longevity due to cellular renewal, and ability to remodel tissues with food availability. They may reproduce asexually, sexually, or both, allowing metabolic study of reproductive modes. Information in modern literature on planarian metabolic rates is lacking, with a need to establish consistent measurement techniques using current methodologies in commonly studied species. We determined metabolic rates in planaria as a function of temperature, feeding, taxon, and reproductive mode via oxygen consumption (VO2), using high throughput closed respirometry in asexual and sexual S. mediterranea, and G. dorotocephala over a range of 13° to 28° C, and before, during, and after feeding at 18° C. Data are presented as means ± SE, as analyzed by two-way ANOVAs and Tukey's post-hoc tests (n values: 13-49 for temperature data and 7-8 for specific dynamic action (SDA) data). VO2 over 13° to 28° C ranged from 7.6±1.5 to 19.1±1.7 µL O2/g/h and was significantly higher at 28° C (p<0.001) in asexual S. mediterranea, from 13.8±2.2 to 28.8±3.3 µL O2/g/h and was significantly higher at 18° and 28° C over 13° C (p=0.019) in sexual S. mediterranea, and from 7.6±0.7 to 25.9±1.7 µL O2/g/h and was significantly higher at 18° and 28° C over 13° and 23° C, respectively (p<0.001) in G. dorotocephala. Between species, VO2 was significantly higher than all others in sexual S. mediterranea at temperatures between 13° to 23° C (p<0.001), and at 28° C, compared to asexual S. mediterranea (p=0.02). VO2 showed a strong SDA effect. At 24 h prior and 2 h, 1, 2, 3, 5, and 7 d post feeding, VO2 was 15.2±2.1, 12.0±1.8, 34.3±3.6, 30.0±4.2, 18.8±7.9, 18.4±1.6, and 12.6±2.7 µL O2/g/h for asexual S. mediterranea, 23.2±4.2, 18.9±1.6, 55.0±7.4, 34.8±6.7, 32.4±4.5, 27.5±3.6, and 21.5±5.8 µL O2/g/h for sexual S. mediterranea, and 13.6±3.3, 21.5±4.7, 35.7± 8.9, 30.2±8.9, 24.7±5.1,17.7±3.8, and 16.4±4.5 µL O2/g/h for G. dorotocephala, respectively. Between species, VO2 was significantly higher in sexual S. mediterranea at 24 h prior, 1 d, and 3 d post feeding. A significant SDA effect was seen in all species with rates 1.5 to 2.2 times greater than fasting levels 24 h after feeding at 18°C, and a return to fasting levels by day 7. In summary, these data suggest that VO2 in planarians varies by species in a temperature-dependent fashion. Additionally, VO2 is higher in sexually reproducing strains of S. mediterranea than in asexually reproducing strains, revealing the cost of sexual reproduction. Finally, there is a strong SDA effect not previously shown for planarians.

Where applicable, experiments conform with Society ethical requirements