Bryozoans and Hydroids
Bryozoans and hydroids are members of different Phyla (different types of animal), but they can look similar in their growth forms and often occupy similar habitats.
Most shipwrecks in Welsh waters are likely to have very high abundance and species diversity of bryozoa and hydroids, but due to the often small size and difficulty of identification it is less easy to record and appreciate this from videos and photos. Most of the hydroids and bryozoans, along with sponges, on wrecks will form a turf on hard surfaces, but some species are large in form and can be readily seen by divers and from dive footage. They are filter feeders, and so can take advantage of the solid structure and exposure to faster currents that wrecks provide.
Branched antenna hydroid Nemertesia ramosa
This is a large hydroid species formed of yellowish to orange stiff branched stems, with the branching distinguishing it from the antenna hydroid. Branched stems can reach up to 40 cm in length, which together form a shrub-like formation growing upwards from the attachment surface. The stems have small branches coming off them with the feeding polyps along them. The Doto spp. sea slugs can be seen feeding on the branched antenna hydroid and will often lay its eggs on the stems, as seen on the wreck of the SS Derbent off Anglesey.
Antenna hydroid Nemertesia antennina
This is a large hydroid species formed of yellowish to orange stiff individual stems of up to 30 cm in length, which together form a tuft like formation, growing upwards from the attachment surface. The stems have small branches coming off them with polyps along them. The Doto spp. sea slugs can be seen feeding on the antenna hydroid and will often lay its eggs on the stems (seen in the image as pink coils), as seen on the wreck of the SS Derbent off Anglesey.
(Branched) Oaten Pipes hydroid Tubularia
The branched oaten pipes hydroid and oaten pipes hydroid are often seen on shipwrecks as they favour sheltered high current areas. Both species have pink polyps with fine tentacles atop a yellowish to orange rigid stem. As the name suggests the branched oaten pipes hydroid have stems that branch at the base, while the oaten pipes hydroid stems are simply fused or independent.