Influence of serotonin (5-HT) on locomotor behavior and digestive physiology in the sea cucumber Apostichopus japonicus

Abstract

The sea cucumber Apostichopus japonicus exhibits distinct physiological processes such as aestivation, seasonal reproduction, and regeneration, all of which are significantly regulated by neurohormones. Serotonin (5-hydroxytryptamine, 5-HT) is known to regulate behavior in various species, particularly influencing feeding and locomotion. However, its effects on the behavior of sea cucumbers remain largely unexamined. Gaining insight into the role of 5-HT in sea cucumber behavior is critical for enhancing aquaculture practices and improving their health and productivity. This study investigates the role of 5-HT in modulating the locomotion and feeding behavior of A. japonicus. Administration of exogenous 5-HT notably enhanced the behavior of A. japonicus, with locomotor metrics such as movement distance, speed, and step numbers significantly increasing at higher concentrations of 5-HT. Additionally, the frequency of tentacle feeding rose with elevated 5-HT levels, though there was no significant change in intestinal peristalsis frequency. Complementing these findings, in vitro physiological experiments and biochemical analyses revealed that 5-HT influences digestive physiology, resulting in a marked increase in intestinal digestive enzyme activity, stabilization of glucose levels, and promotion of glycolysis. These results provide crucial evidence of 5-HT's behavioral regulatory functions in A. japonicus, offering a basis for further research into effective aquaculture practices.