Story: Marine animals without backbones
Page 4 – Lace corals and lamp shells
The scientific name for lace corals is Bryozoa, from the Latin meaning moss animals – these delicate individuals form colonies in thick, moss-like crusts. New Zealand is a centre for bryozoan diversity. Almost 1,000 species are found in the region’s waters, and about 600 of these occur nowhere else.
They are an ancient group with a well-known fossil record: their calcareous skeletons have been preserved well in compressed marine sediments. Waitomo and Ōamaru limestones are composed mainly of bryozoan remains.
Outwardly, some bryozoans resemble corals or sponges; however, bryozoans are much more complex animals. Their evolutionary relationship is closer to lamp shells (brachiopods), shellfish, and worms. Although tiny (0.5–1 millimetre), individuals form large colonies that spread over stones, shells and the sea floor. A number of species foul the hulls of ships. Others form extensive structures on the sea floor that can be considered the temperate-water equivalents of tropical coral reefs. Bryozoan beds formed by the Tasman Bay ‘coral’ Celleporaria agglutinans around the northern South Island, and Cinctipora elegans in Foveaux Strait, provide important habitats for juvenile fish and shellfish. Some of these beds have been damaged by trawling.
A cure for cancer?
Like sponges, bryozoans contain complex chemicals that may be beneficial to humans. Bryostatin-1 is one anti-cancer drug that has been used in human trials. It was isolated from Bugula neritina, a marine-fouling bryozoan of Mediterranean origin. This animal first turned up in Wellington Harbour in 1949, where it was noticed forming burgundy-coloured growths on wharf pilings and seaweeds.
Lamp shells, or brachiopods, superficially resemble clams or scallops (molluscs), but internally they are quite different. Inside lamp shells are large filamentous structures known as lophophores, which are used for filter-feeding and breathing. New Zealand species range in size from 2 millimetres to 5 centimetres across. Most attach themselves to the sea bed or underwater rock walls with a short stalk, although New Zealand’s largest species, Neothyris lenticularis, is free-living as an adult. Lamp shells once dominated ancient seas, but declined when molluscs gained ascendancy.
New Zealand has 525 fossil species of lamp shell, but only 35 living species. Fiordland is home to one of the richest assemblages of lamp shells in the world. In the dim waters of the fiords, seaweed growth is limited and sedentary animals dominate the steep rock walls. Lamp shells grow at densities of 500 individuals per square metre, alongside bryozoans, soft corals, and sponges.