Effects of handling stresses on fitness related behaviors of small sea cucumbers Apostichopus japonicus: New insights into seed production

Seed production is essential for the profitable and sustainable aquaculture of the sea cucumber Apostichopus japonicus. Stresses are an inevitable consequence of handling in seed production. Here, we investigated the effects of different intensities of handling stresses (air exposure, medicine bath, mechanical perturbation and seawater washing) on the movement, foraging, feeding and defecation behaviors of small A. japonicus. The present study found that small A. japonicus exposed to mechanical perturbation showed significantly longer time to first reaching air-water interface, shorter movement distance and worse foraging ability among the groups. No significant difference of feeding behavior was found between small A. japonicus in exposure to mechanical perturbation and without handling stress. In contrast, small A. japonicus exposed to air, medicine bath and seawater washing showed significantly worse feeding ability compared with those without handling stress. There was no significant difference in foraging behavior of small A. japonicus exposed to air, medicine bath, seawater washing compared with those without handling stress. Further, high-intensity handling stresses significantly inhibited movement, foraging and feeding of small A. japonicus. Feeding behavior of small A. japonicus exposed to high-intensity air exposure had more serious carryover effects than those exposed to low-intensity air exposure. Moreover, air exposure showed serious carryover effects on feeding behavior of small A. japonicus. The present study provides valuable information for seed production of sea cucumbers.