To test the hypothesis that high excurrent flow speed induces chimney formation, I injected seawater under the canopy of lophophores through a small tube to locally increase the excurrent flow speed out the canopy edge (Fig.
The sites were equidistant from one another, and three to four lophophores away from the canopy edge.
Injuries to the colony would be expected to reduce flow to neighboring chimneys since injuries reduce the number of lophophores pumping fluid under the canopy to the chimneys.
Chimneys were selected in which the lophophores were clearly visible but which were separated by no fewer than four lophophores from the canopy edge.
Incurrent velocity scaled significantly differently with distance from the lophophores among treatments (Fig.
At least in small colonies, what happens above the colony (refiltration and the incurrent velocity far from the lophophores) may thus be more important than what happens below the lophophore canopy within the colony.
The movements of spermatozeugmata within paternal coeloms, in seawater after spawning, and within the tentacle crown of maternal lophophores were videorecorded.
Spawned spermatozeugmata were commonly swept into the lophophores of conspecifics by feeding currents.
This indicates that in all situations, boundary layer thicknesses were much greater than the heights of lophophores
; colonies were thus hidden from mainstream flows in both studies.
Metamorphosis is the time from eversion of the larval metasomal sac to eversion of the lophophore
of the ancestrular polypide.
The similarity between the feeding apparatus of pterobranchs and the lophophore
of bryozoans, brachiopods, and phoronids has long been known; the earliest reports on the pterobranchs considered them either related to, or included in, the Bryozoa (13-15).
Once drawn into lophophores
, strong undulating movements of midpieces begin after spermatozeugmata contact the tentacles.