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Fig. 1 | BMC Biology

Fig. 1

From: Sea urchin larvae utilize light for regulating the pyloric opening

Fig. 1

Photoirradiation opens the pylorus in sea urchin larvae. a Photoirradiation drives the pyloric opening. Images of 5 s and 1 min 30 s after photoirradiation were captured from Supplementary Movie 1. b The set light condition was 10 min of light, overnight in darkness, and photoirradiation by high-intensity light. The graph shows the pyloric opening rates between 0 and 10 min after photoirradiation. The fluorescence images show pyloric closing (left) and opening (right), as visualized by TnI immunohistochemistry. N = 4; n (0 min) = 60, 39, 29, 43; n (1 min) = 45, 21, 30, 32; n (2 min) = 45, 26, 33, 54; n (3 min) = 43, 28, 23, 31; n (4 min) = 38, 28, 37, 24; n (5 min) = 68, 39, 35, 37; n (6 min) = 41, 28, 40, 26; n (7 min) = 72, 27, 23, 39; n (8 min) = 43, 27, 31, 13; n (9 min) = 84, 29, 29, 29; n (10 min) = 76, 38, 24, 21. The increase in the opening rate between 0 and 2 min after photoirradiation was assessed by the Welch two-sample t-test. Error bars show SE. More than 40% of larvae opened their pylorus in response to the photoirradiation (= sum of open rate from 1 to 5 min (8.9% (1 min) + 17.9% (2 min) + 16.1% (3 min) + 10.9% (4 min) + 7.0% (5 min)) was divided by 1.5 min (average open time)). c The region around the anterior neuroectoderm was necessary for pyloric opening induced by photoirradiation. The images in the upper row show the location at which the anterior neuroectoderm and pre-oral arms (− ANE and pre-oral arms) and post-oral arms (− post-oral arms) were removed. The lower images show open and closed pylori 2 min after photoirradiation. The inset of each image shows the bright-field images. The graph shows the opening rate of the pylorus in control larvae, larvae without the AP and pre-oral arms, and larvae without post-oral arms 2 min after photoirradiation. N = 2–4; n (control) = 19, 20, 24, 45; n (ANE and pre-oral arms less) = 13, 15, 17, 17; n (post-oral arms less) = 13, 12. We used one-way ANOVA followed by Tukey’s post hoc test. Error bars show SE. Scale bars in a and b = 20 μm and in c = 50 μm

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