Light intensity regulates phototaxis, foraging and righting behaviors of the sea urchin Strongylocentrotus intermedius

Abstract

Small sea urchins Strongylocentrotus intermedius (1–2 cm of test diameter) are exposed to different environments of light intensities after being reseeded to the sea bottom. With little information available about the behavioral responses of S. intermedius to different light intensities in the environment, we carried out an investigation on how S. intermedius is affected by three light intensity environments in terms of phototaxis, foraging and righting behaviors. They were no light (zero lx), low light intensity (24–209 lx) and high light intensity (252–2,280 lx). Light intensity had obvious different effects on phototaxis. In low light intensity, sea urchins moved more and spent significantly more time at the higher intensity (69–209 lx) (P = 0.046). S. intermedius in high light intensity, in contrast, spent significantly more time at lower intensity (252–690 lx) (P = 0.005). Unexpectedly, no significant difference of movement (average velocity and total distance covered) was found among the three light intensities (P > 0.05). Foraging behavior of S. intermedius was significantly different among the light intensities. In the no light environment, only three of ten S. intermedius found food within 7 min. In low light intensity, nine of 10 sea urchins showed successful foraging behavior to the food placed at 209 lx, which was significantly higher than the ratio of the number (two of 10) when food was placed at 24 lx (P = 0.005). In the high light intensity, in contrast, significantly less sea urchins (three of 10) found food placed at the higher light intensity (2,280 lx) compared with the lower light intensity (252 lx) (10/10, P = 0.003). Furthermore, S. intermedius showed significantly longer righting response time in the high light intensity compared with both no light (P = 0.001) and low light intensity (P = 0.031). No significant difference was found in righting behavior between no light and low light intensity (P = 0.892). The present study indicates that light intensity significantly affects phototaxis, foraging and righting behaviors of S. intermedius and that ~200 lx might be the appropriate light intensity for reseeding small S. intermedius.

Fitness benefits and costs of shelters to the sea urchin Glyptocidaris crenularis

“…In the present study, the light intensity was 160.3-296.7 lx in the light areas and 13.6-47.7 lx in the sheltered areas. This result is consistent with a recent finding that the sea urchins S. intermedius exposed to low light intensity (~24 lx) were significantly attracted to high light intensity (~220 lx) (Sun et al, 2019). The current result indicates that long term condition suitable for sheltering behavior enhances the positive phototaxis of sea urchins.…”

Embryo Development and Behavior in Sea Urchin (Tripneustes gratilla) Under Different Light Emitting Diodes Condition

“…Righting behavior is a coordinated and reflexive movement of the neuromuscular system of a sea urchin after a drastic change in the environment (Kleitman, 1941). The behavior has also been used to examine the physiological state of sea urchins exposed to environmental stress, such as chemical pollutants (Böttger et al, 2001), genotoxins (Canty et al, 2009), low salinity (Lawrence, 1975), high partial pressure of carbon dioxide (Challener and McClintock, 2013), high temperature (Brothers and McClintock, 2015), and high light intensity (Sun et al, 2019). According to the literature, when environmental factors cause stress in sea urchins, the urchins become slower in righting, are less likely to right themselves, or even fail to do so, indicating that sea urchins are less able to right themselves in the presence of environmental stress.…”

Decision making and risk in Strongylocentrotus droebachiensis in competitive and non-competitive foraging environments

“…The process of preparing the cages for a trial might be considered a threatening event, even if there was no direct contact as shadows from the experimenters would be detected by the urchins through their light sensitive podia (Yoshida et al 1984;Lesser et al 2011). It is also possible that the covering behavior may have been stimulated solely by the room light (Dumont et al 2007), since long-term white light exposure affects righting and foraging behavior in the congener S. intermedius (Yang et al 2021), a species also sensitive to light intensity (Sun et al 2019), and many urchins are nocturnal.…”