01156nas a2200145 4500008004100000022001400041245013500055210006900190260001300259300001200272490000700284520064600291100002100937856005200958 1972 eng d a1432-193900aThe responses to current flow of two stream dwelling triclads, Crenobia alpina (Dana) and Polycelis felina (Dalyell)0 aresponses to current flow of two stream dwelling triclads iCreno c1972 Dec a313-3200 v103 a

An apparatus is described which allows triclads to choose between the fast and slow regions of a stirred tank. In the absence of a stone substratum Crenobia alpina preferred or tolerated higher current speeds than Polycelis felina, this effect was enhanced when a stone substratum was added to the apparatus. These results indicate that the absence of Polycelis felina from the steep gradient regions of streams could be accounted for by its preference for slower micro-currents. Conversely the presence of Crenobia alpina in steep gradient regions could be accounted for by its preference for or tolerance to higher micro-currents.

1 aLock, Maurice, A uhttps://continenticola.myspecies.info/node/1714