Hydra response to 1mM linalool (L), 0.04% heptanol (H), 2% urethane (U), and 0.1% chloretone (C).

A. Percent length of anesthetized Hydra polyps compared to their natural state at 10min incubation. n = 10 animals per condition across 2 technical replicates. Anesthetized lengths similar to the average lengths in HM were recorded in linalool at 103% (87, 112; median (25th percentile, 75th percentile)), heptanol at 83% (71, 93) and urethane at 96% (88, 118), while chloretone-treated animals hyperextended at 133% (125, 153). B. Induction times across 2 technical replicates. Linalool n = 13, heptanol n = 14, urethane n = 13, chloretone n = 10. Linalool’s median induction time was 9 min (6, 9) (median (25th percentile, 75th percentile)) and thus significantly longer than that of heptanol at 6 min (4, 9), urethane at 5 min (4, 6) and chloretone at 5 min (3, 7). C. Recovery times across 2 technical replicates. Linalool n = 10, heptanol n = 8, urethane n = 12, chloretone n = 10. Median recovery time was 8 min (7, 17) for linalool, 11 min (7,15) for heptanol, 14 min (12, 26) for urethane and 13 min (7,15) for chloretone. (D-F) Pairwise statistical comparisons of data shown in A-C. Pink, red and dark red indicate a statistically significant difference at p<0.05, p<0.01 and p<0.001 respectively, determined using the Mann-Whitney U test between pairs of anesthetics. D. Comparison between percent length distributions. E. Comparison between induction time distributions. F. Comparison between recovery time distributions. G. Overview of the four anesthetics tested, scored on degree of immobilization, animal health following anesthesia, time to induce anesthesia, time to recover from anesthesia, morphology, and ease of use (see Methods).