Walkeria uva

Walkeria uva occurs on either side of the Atlantic Ocean, in the Baltic Sea, the Mediterranean Sea, the Indian Ocean and the South China Sea. It is one of a number of creeping and low-growing bryozoans that are common on hard substrates in the lower tidal and shallow subtidal zones. It often grows on red or brown algae, such as Cystoseira, Corallina officinalis and Halidrys siliquosa or on other bryozoans, and is often associated with Bowerbankia spp.. There are two forms, one is more erect and is found near the tip of algal fronds in habitats where there is little sediment, and the other is more prostrate, and found on various red or brown algae fronds in muddy habitats. It is possible that these two forms are in fact different species.^[2]

Like other bryozoans, Walkeria uva has a crown of eight tentacles called a lophophore which can be extended to catch phytoplankton, bacteria and other minute particles floating past. Cilia on the tentacles actively move the water around to promote feeding. The colony grows by the budding of new zooids at the tips of the stolons. The colony is hermaphrodite; male zooids liberate sperm into the water which the female zooids draw in, retaining their eggs and brooding the embryos. When sufficiently developed the larvae are discharged into the water column, and after a short planktonic phase, settle on a suitable substrate and undergo metamorphosis into primary or ancestral zooids. This bryozoan has an overwintering, spherical form that develops in the autumn, and returns to normal growth when the water warms up in the following spring.^[2]