Changes in the anxiety-like and fearful behavior of shrimp following daily threatening experiences.

Abstract

Behavioral variation in animals is often influenced by experience. Previous studies have found that daily threatening experiences can enhance fear- and anxiety-like behaviors in some vertebrates. However, it is unclear whether the change in fear/anxiety behavior occurs in invertebrates. The present study investigated whether fear/anxiety behavior could be affected by a net-chasing treatment in two shrimp species (Neocaridina denticulata ssp. and Palaemon pacificus). The net-chasing treatment was repeated for 8days to simulate daily predator experiences, and behavioral tests (open-field, shelter-seeking, and escape-response tests) were conducted on the day following the last day of treatment. Net-chased N. denticulata ssp. displayed a tendency to remain near a wall compared with the control in the open-field test, whereas net-chased P. pacificus shrimps demonstrated greater escape behavior compared with the control in the escape-response test. These results suggest that fear/anxiety behavior for both shrimp species can be affected by the net-chasing treatment, although the pattern of behavioral change differed between the two species. The findings suggest that daily threatening experiences change the behavior of shrimp and cause them to select a regular avoidance strategy when they encounter risks and unknown situations.