FOREST, D; LINDSAY, S; University of Maine: Serotonin may influence escape response in a polychaete tube-worm

The neurotransmitter serotonin modulates various behaviors in many animals. During an experiment examining the effects of serotonin on the feeding behavior of a spionid polychaete, Streblospio benedicti, we observed unexpected increases in the number of spontaneous escape responses. Spionids are small, marine worms that inhabit tubes in sediment; a perceived threat by the worm elicits an immediate and complete withdrawal (escape) into its tube. We measured the effect of serotonin on S. benedicti escapes by comparing the number of serotonin-induced tube withdrawals to seawater controls. Significantly more tube withdrawals occurred under the influence of serotonin; the application of a 10 μM solution was enough to elicit the escape response. We used immunohistochemistry and confocal laser scanning microscopy to describe the serotoninergic nervous system in S. benedicti. Serotonin immunoreactivity in the ventral nerve cord of the worm reveals large axons which may mediate the escape response by co-ordinating muscular contractions. Results of this experiment suggest that serotonin influences escape behavior in the spionid polychaete, Streblospio benedicti.