Figure 9

Influence of light prevention on the tentacle-thrusting behavior of Oligobrachia mashikoi in the inhabited seabed area. (A) Oligobrachia mashikoi was analyzed at each time point indicated to evaluate whether they thrusted tentacles from their tubes. The Y-axis presents the ratio of the number of times that tentacle-thrusting behavior was observed to the number of analyses (n = 5 to 8). The values are the mean ± S.E.M. of five independent experiments. Experiments were performed on September 24–October 6, 2021. Animals were covered with a case (Fig. S3C) to prevent them from being exposed to light during daytime on October 1–6, 2021 (black circle), while they were not covered on September 24–October 1, 2021 (white circle). The time of sunset and sunrise are indicated by their respective arrows. (B) The average values of the ratios of the number of times that tentacle-thrusting behavior was observed to the number of analyses at each of time point between 6:00 and 17:00 (white bar) or 18:00 to 5:00 (black bar) in (A) are described. The values are the mean ± standard error of the mean (S.E.M.) of five independent experiments. Animals were covered with a case from 1st to 6th October, 2021 (dark conditions), and not covered from 24th September to 1st October, 2021 (natural conditions). A paired t-test was performed to examine the statistical significance of the changes between daytime and nighttime in the same individuals. *p < 0.05.