Factors Controlling the Localizations of Populations of Protodrilus symbioticus Giard

Abstract

Protodrilus symbioticus Giard, an interstitial archiannelid, was found to move towards interstitial water having the highest O tension which in nature, would tend to keep this species at the sand surface. This species tolerated 12 hr. in sea water of salinities of 17-50%, showed no response to salinity gradients and only a slight response to water currents, moving against the flow for short distances in glass tubes. P. symbioticus will tend to be found at the sand surface in response to its preference for high O tensions but will be forced deeper into the sand by high surface temperatures (Gray 1965), by high light intensities (Gray 1966a), and by the presence of dried sand.