Diel patterns of covering behavior by male and female Strongylocentrotus intermedius

Abstract

Covering behavior refers to echinoids using their tube feet and spines to move objects, such as shells, stones, and algae fragments, onto their dorsal surface. Little information is available on the diel pattern of covering behavior in sea urchins. Here, we studied diel rhythms of covering behavior in male and female Strongylocentrotus intermedius in the laboratory. Both sexes of S. intermedius showed significant patterns in their diel covering behavior. Both the number of sea urchins covered (p = 0.012) and the number of shells used for covering (p = 0.006) show a significant rhythm. Sex, as a factor, did not show significant difference of covering behavior (p > 0.05). However, one-way repeated measured ANOVA showed that the interaction between diel cycle and sex had significant differences in both the number of sea urchins covered (p = 0.043) and the number of shells used for covering (p = 0.026). This indicates that the diel pattern of covering behavior was significantly different between males and females. Pearson correction analysis revealed that intensity of light was significantly correlated with both the number of sea urchins covered (R2 = 0.669, p < 0.001) and the number of shells used for covering (R2 = 0.672, p < 0.001) in males but not in females.