Assessment of negative phototaxis in long-term fasted Glyptocidaris crenularis: a new insight into measuring stress responses of sea urchins in aquaculture

Abstract

A cost-effective method was designed to measure the behavioral response of negativephototaxis to high-intensity illumination in the sea urchin Glyptocidaris crenularis . Ninety sea urchins wererandomly and equally divided into two aquaculture environment groups: a fasted group, which was starvedduring the experiment, and a fed group. After 10 months, the total mortality of each group was recorded.Then, 15 sea urchins were randomly selected from each group and behavioral responses to high-intensityillumination were investigated for each sea urchin. After the behavioral experiment, body measurements ofthe trial sea urchins were taken. The results reveal that food deprivation signifi cantly affected test diameter( P <0.01), body weight ( P <0.01), gonad weight ( P <0.01), and gut weight ( P <0.01). Furthermore, fooddeprivation also affected negative phototaxis behaviors of time to rapid spine movement ( P <0.01), time tothe 1 cm position ( P <0.05), and walking distance in 300 s ( P <0.01), but not time to body reaction ( P >0.05).The mortality rates of fasted and fed urchins were 6.7% and 0%, respectively. The present study providesevidence that food deprivation has a signifi cant effect on phenotypic traits and behavioral responses tohigh-intensity illumination in the sea urchin G . crenularis . With this method, environmental stressors can beeasily detected by measuring proper optional indicators. This study provides a new insight into measuringstress responses of sea urchins in aquaculture. However, further studies should be carried out to understandmore environmental factors and to compare this potential behavioral method with immune, physiological,and epidemiological approaches.