Migration of the sandworm Nereis virens during winter nights

There have been many previous reports of the sandworm Nereis virens Sars swimming in the water column. This behavior usually has been attributed to reproductive processes. Sandworms were found swimming in surface waters at night on ebb tides during many nights of January, February and March in a Maine (USA) estuary. None of the specimens examined contained gametes or possessed other characteristic spawning or pre-spawning modifications. Several age classes were found, with worms measuring 9 to 38 cm in length, weighing 0.5 to 19.8 g, and having 82 to 187 segments. The greatest numbers of worms were observed during near-average tides on evenings in which low tides occurred a few hours after sunset but prior to moonrise. Up to 83 worms per minute were observed swimming seaward through a 20 m transect, while none were observed swimming landward at any stage of the tide. It is concluded that sandworms swimming during winter nights is unrelated to reproduction and that it is an inherent behavior pattern.Contribution No. 102 of the Ira C. Darling Center, Walpole, Maine 04573, USA.