''Walkeria uva'' is a species of

colonial Colonial or The Colonial may refer to: * Colonial, of, relating to, or characteristic of a colony or colony (biology) Architecture * American colonial architecture * French Colonial * Spanish Colonial architecture Automobiles * Colonial (1920 a ...

bryozoan in the

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

Ctenostomatida. It occurs on either side of the Atlantic Ocean, in the Baltic Sea, in the Mediterranean Sea and in the Indo-Pacific region.

Description

''Walkeria uva'' is a colonial bryozoan that has thread-like

stolon In biology, stolons (from Latin '' stolō'', genitive ''stolōnis'' – "branch"), also known as runners, are horizontal connections between organisms. They may be part of the organism, or of its skeleton; typically, animal stolons are external s ...

s that creep across the

substrate Substrate may refer to: Physical layers *Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached ** Substrate (locomotion), the surface over which an organism lo ...

from which small clusters of zooids grow. The zooids have no stalks and are ovoid or tubular, growing direct from the stolon which seldom branches. There are up to ten zooids in each group, and the zooids are tipped by a bulge from which a pair of short lateral branches grow at right-angles. The whole colony is only about across. The colour is light beige or pale grey. The colonies are so small and inconspicuous that they may only be discovered by chance when the seaweed on which they are growing is examined in the laboratory.

Distribution and habitat

''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 ''Corallina officinalis'' is a calcareous red seaweed which grows in the lower and mid-littoral zones on rocky shores. It is primarily found growing around the rims of tide pools, but can be found in shallow crevices anywhere on the rocky shor ...

'' and ''

Halidrys siliquosa ''Halidrys siliquosa'' is a large marine brown algae. Description ''Halidrys siliquosa'' is a large brown alga growing to a length of . The fronds are somewhat flattened, tough and leathery. They and less than 1 cm broad. The branches occu ...

'' 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.

Ecology

Like other bryozoans, ''Walkeria uva'' has a crown of eight tentacles called a lophophore which can be extended to catch

phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems. The name comes from the Greek words (), meaning 'plant', and (), meaning 'wanderer' or 'drifter'. Ph ...

, 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 In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many Taxonomy (biology), taxonomic groups of animals (mostly invertebrate ...

; 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 Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...

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.

References

{{Taxonbar, from=Q4192347 Ctenostomatida Fauna of the Atlantic Ocean Fauna of the Indian Ocean Fauna of the Pacific Ocean Fauna of the Baltic Sea Fauna of the Mediterranean Sea Animals described in 1758 Taxa named by Carl Linnaeus