Extended movements of particles in stolons of colonial hydroids of the family Campanulariidae

The range of movement of food particles along the distribution system in colonies with a length of 8 stolon modules was studied in colonies of four species of hydroids from the Campanulariidae family (Gonothyraea loveni, Laomedea flexuosa, Obelia longissima, O. geniculata). Visual scanning, i.e. tracking under a microscope the movement of individual particles or their clusters along the gastrovascular cavity of the stolon was carried out continuously for 90 minutes for each of six to seven recording sessions. For the first time, the range and duration of movement of individual particles in the stolon cavity of the studied species in a state of trophic pause, which lasted a day, were established. The distribution system functions quite efficiently even during fasting. This is expressed in transcolonial continuous transfers of particles from one end of the colony to the opposite. The most extended movements of particles along the stolon of the colony occur relatively rarely: in G. loveni, L. flexuosa and O. geniculata from one to three times in 90 minutes, and in O. longissima 12 times in the same period. Against the backdrop of an abundance of short trajectories (more than 200 in 90 minutes), transcolonial movements of particles may be missed if registrations are not long enough, which was the basis for erroneous claims about the chaotic functioning of the distribution system.