Fig. 1

Schematic representation of ctenostome bryozoans including main muscle system. a Simple colony morphology as e.g. in Paludicella or Alcyonidium b Zooids with elongated peristomes such as found in the genus Nolella. c stolon-bearing colonies with stolonal kenozooids that interconnect feeding zooids (autozooids) with each other. Abbreviations: a – atrium, am – apertural muscles, dt – digestive tract, l – lophophore, o/a – orifice/aperture of the zooid, pc – pore complex, pm – parietal muscles, rm – retractor muscle, s - stolon, ts – tentacle sheath, v – vestibulum