Meeting Abstract
Defecation is a common process of removing undigestible food resources that can be quite copious in suspension feeders. In bryozoans the anus is situated outside of the food processing tentacle crown or lophophore. Bryozoans have a characteristic defensive behaviour that involves the retraction of their soft-body parts (the polypide) into their protective body wall (cystid). As colonial organisms, defecation represents an important task that requires and involves coordination to remove faecal pellets from the colony. This is particularly evident in species with closely spaced zooids. Among cheilostome bryozoans several different defaecation strategies have been recognized, whereas other bryozoans remain little investigated. Especially within ctenostome bryozoans, a small group of non-calcified bryozoans, the position of shows high variability concerning the location on the tentacle sheath. Some species have the anus situated very close to the mouth opening, which implies high interaction with feeding currents, whereas other have the anus located quite distant from the mouth opening. In any case, faecal pellets need to be removed from the colony. In this presentation I analyse the distribution of anal positions among ctenostomes and assess whether this position evolved independently and its consequences for colonial feeding currents.
