Figure 2.

Hydra's body length initially increases and width initially decreases when stimulated at 30°C

(A) Schematic of a representative thermal stimulation protocol. Gray regions (I) indicate non-stimulus periods at Hydra's culture temperature lasting between 30 and 90 s, and blue-colored regions (II) indicate stimulus periods at designated temperatures for 60 s.

(B) Representative frame annotated from DeepLabCut. Top panel describes which body points were annotated, and the bottom panel shows how the length and width of the animals are determined. The hypostome is the end of the body with Hydra's mouth and tentacles (oral end), whereas the basal disc is used to adhere to substrates (aboral end). Scale bar, 500 μm.

(C) Average length and width of Hydra calculated for stimulation periods and time-aligned to stimuli, with 15 s before and after stimulation periods. Curve corresponds to mean, and shaded error bars correspond to standard error of the mean. N = 3 Hydra for No Flow, N = 6 Hydra for 18°C and 30°C.

(D) The change in length (top panel) and width (bottom panel) at 20 s after onset of stimulation (t = 20 s), for each stimulus period. Box-and-whisker plots indicate Q1, median, and Q3; whisker lengths indicate the 2^nd and 98^th percentiles. N = 3 Hydra for No Flow, N = 6 Hydra for 18°C and 30°C. (n.s = not significant, ∗∗p < 0.001, ∗∗∗p < 0.0001, unpaired t test).