In the first 2 days after metamorphosis, juvenile slugs were observed repeatedly placing their mouths over the lophophores
Each zooid bears a crown of tentacles (lophophores
), which form a tightly packed canopy over the colony (Fig.
These two models complement each other in that one (Grunbaum, 1995) concentrates more on what happens to the flow below the lophophore
canopy, while the other (Eckman and Okamura, 1998) focuses more on the flow above the colony.
The ITO is oriented with its distal pore directed away from the funnel of the lophophore
. Consequently, spermatozeugmata within lophophores
cannot be oriented to enter maternal individuals unless they develop a bend.
Once within the lophophore
region they gain access to maternal zooids through specialized intertentacular organs of the lophophore
, and subsequently effect internal fertilization of eggs within maternal zooids (Temkin, 1994).
Under natural conditions with light from above, the colony is oriented with its frontal surface and lophophore
facing away from the water surface; thus, the colony is shielded from the downward flux of particulate matter.
Alternatively, separating the two shell valves removes the ventral ovaries from the lophophore
and viscera, because these organs invariably remain attached to the dorsal valve.
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).
In the latter case their possible lophophores
must have been rather small.
(1) In contrast to the bivalves, the open constructions of the brachiopods lophophores
prevent from clogging with sediment particles in a high-energy environment.
Newly metamorphosed colonies can be aged, because it takes approximately one day for metamorphosis to proceed from initial settlement of the larvae to development of feeding lophophores
in the twinned initial zooids of the colony.
Since all brachiopods feed with lophophores
, the feeding strategies of different species are similar.