title: Kinetics and rhythm of body contractions in the sponge Tethya wilhelma (Porifera: Demospongiae).
abstract: Sponges of the species Tethya wilhelma display rhythmic body contractions, which were analyzed by digital timelapse imaging and semi-automated image analysis. For the first time, differential, quantitative data on sponge behaviour could be obtained. The sponges are able to reduce their body volume by up to 73.3% during regular contractions. Each contraction cycle follows a characteristic pattern of four phases, permitting analysis of the kinetics of contraction and expansion. Long-term observations (for >7 days) reveal that the sponge contractions display a day-night periodicity in which contraction cycles are significantly longer during the dark hours. The contractions seem to be mediated by the pinacoderm; they are triggered locally and spread over the sponge surface at 12.5 microm s(-1). If two individuals of a clone are fused, the individual contraction rhythm of both sponges persists for several days, until a single new individual sponge is formed with a synchronized rhythm. The reported results and techniques establish T. wilhelma as a model organism for research on the development of aneural signal transduction and integration during early Metazoan evolution.
authors.affiliation: Department of Zoology, Biological Institute, Stuttgart University, D-70550 Stuttgart, Germany. michael.nickel@bio.uni-stuttgart.de
authors.forename: Michael
authors.initials: M
authors.lastname: Nickel
mesh_terms: D000818:Animals; D007091:Image Processing, Computer-Assisted; D007700:Kinetics; D009119:Muscle Contraction / Q000502:physiology*; D009415:Nerve Net / Q000502:physiology; D010507:Periodicity; D011161:Porifera / Q000502:physiology*; D015398:Signal Transduction; D013997:Time Factors; D014741:Video Recording