The lophophore of a Cristatella zooid is clearly horseshoe shaped with two rows of tentacles. Upper right in the inner curve of the horseshoe is the mouth with above the esophagus. The semicircular structure that can be seen through the tentacles and above the mouth (it hides the mouth in this photo) is used to trap food particles in order to enhance the chance of capturing and eating them.

The lophophores are packed densely together

At the base of the polyps the dense packing can be clearly seen. Each round opening is a different zooid. The important parts of the zooid, like the stomach and gut, are coupled to the lophophore and move outward or inward as the lophophore is retracted or extended. The muscles that retract the lophophore can be seen as thin lines angling upwards from the round oping to the zooid. The round opening is apparently enforced with a ring shaped tissue structure.
The zooids live in a communal body cavity that extends upwards from the colony sack through the round opening and around the zooid.

A zooid can be extended significantly beyond the round opening.
This photo shows a second set of muscles attached to the bottom of the zooid that also aid in retracting the zooid into the body cavity. This is not only muscle tissue. Lower on this tissue cord the male sexual organs - producing sperm for sexual reproduction - can be found. Also the statoblasts are produced from this tissue.

The zooid base is round to oval. This seems to be changing over time per zooid.
Click on a photo for an enlargement.

The zooid's anus (Ectoprocts => anus outside the polyp) ends below the polyp. On this photo a faeces pellet in developing state can be seen. The lower-righthand side of the faeces pellet is the anus opening. The polyp is on the far righthand side. Above the faeces pellet are the esophagus (right) and the stomach (left)
Besides these large structures small muscles can be seen running to the polyp basis (the lophophore). Presumably these are used for moving the polyp.

he last photo shows how densly the polyps are packed together.
It shall be clear that working together in this way it is far easier to prevent silt covering a colony then it is for other species where each zooid has to fend for itself.

Video through a microscope

The videos below are in WMV format and require a compatible player, such as windows media player, to view.
Each video is 30 to 60 seconds and about 1.5 MB in size. Playing across a slow internet link may take a lot of time.

(click on the photo to start the video)

	This video shows a Cristatella mucedo polyp during normal activities. I found it facinating to see how the water flows, how tentacles and even the whole polyp moves and how the polyp reacts on an external disruption (small animal swimming into it) and rapidly recovers. Apologies for a not completely stable image. The table that holds the microscope could and should have been more sturdy.
	This video is of the same Cristatella mucedo colony. In this video i moved the focus across the polyp to show how the water current flows through the polyp. The first 30 seconds of the video show in flowing water. In the later part the out flowing water can be seen. It is my intention to show how exactly the water current runs and how hard the polyp works to create it. Early in the video the polyps are slightly retracted and they further expand (relax) as time progresses. About 45 seconds before the start of the video i moved the container holding the colony for my microscopy activities, causing the colony to retract.
	This video is of a later data and shows a zooid eating. The sucking action can be seen a few times. The lophophore moves around. This video is about 4.2 MB in size.
	This video is of a later date and shows the basis of a zooid as the zooid swallows some food particle. I was amazed at how forceful the swallowing action must be to have such an impact at the zooid basis.
	This video is also of a later date and shows the activities as seen below the lophophores between the zooids. This video is about 3 MB in size.