Brachiopods, or Lamp Shells (Phylum Brachiopoda)
Daphne Lee and Franz Smith
Brachiopods, commonly called lamp shells, represent an exclusively marine phylum characterised by small (adult shells are typically 5-50 mm in length), solitary, bilaterally symmetrical, usually biconvex individuals that superficially resemble bivalve molluscs. They can be divided into two major groups, articulated, and inarticulated brachiopods, both of which are well-represented in New Zealand seas. In the generally small (<10 mm diameter) inarticulated forms the shell may be calcareous (Novocrania), or composed of organophosphate (Pelagodiscus), and the valves are held together only by muscles. In the more common articulated brachiopods the calcareous valves open and close by means of teeth and sockets, as well as muscles. In articulated brachiopods the ventral valve is slightly larger than the dorsal valve, and bears a subcircular foramen from which a short muscular stalk, or pedicle, strongly anchors the brachiopod to a hard substrate such as rock or shells. Many New Zealand shallow-water brachiopods are gregarious, and specimens of Calloria, for example, may form "piggy-back" clusters with several generations attached to a single basal individual. Elevation of brachiopods above the substrate by the pedicle may limit non-brachiopod competitors and smothering epibionts, and the rotational ability of the pedicle may also allow optimum orientation to currents as well as limited predator avoidance.
Most brachiopod shells are smooth (eg, Liothyrella and Neothyris), although a few common New Zealand forms are ribbed (eg, Notosaria and Terebratella). Several shallow-water species are brightly coloured: for example, the terebratulides Terebratella sanguinea and Calloria inconspicua are bright red, Neothyris species are light pink, while the rhynchonellide Notosaria nigricans is black. Internally, the body cavity is mostly occupied by a filamentous feeding structure called a lophophore that is generally supported by short calcareous crura or a delicate calcareous loop.
Brachiopods are suspension feeders which orient with their shells slightly open to allow the passage of water, and use their lophophore to produce feeding currents and trap microplankton and organic particles, which are then transported to the mouth. There are relatively few studies internationally of aspects of the biology and ecology of living brachiopods, but many of these have been carried out on brachiopods from New Zealand because of their relative abundance in accessible shallow-water sites, including the fiords. Many species appear to brood their larvae in their shell cavities, and are regarded as having very short dispersal capabilities. Life spans are poorly known, but may vary between three years for small species, and up to thirty years for large, slow-growing species. Growth and recruitment of brachiopods within the New Zealand region are poorly known.
Brachiopods have an exceptionally good fossil record, and are among the oldest groups of hard-shelled organisms, dating back more than 500 million years to the Early Cambrian. Over 95% of the 4500 brachiopod genera and 30,000 species are extinct, with only 350 or so species in some 100 genera still living in modern seas. Because of the vast numbers of extinct forms, and the relatively few living species, paleontologists and biologists internationally are extremely interested in studying living brachiopods including the thirty-two or so species from New Zealand seas which include representatives of all five extant brachiopod orders.
Around New Zealand brachiopods are widely distributed from the Kermadec and the Chatham Islands to the subantarctic islands, and live animals have been recorded from more than 1000 sites, although their distribution appears to be patchy. In part this may be due to the fact that they are typically attached to rock substrates which are notoriously difficult to sample, unless in shallow water at diveable depths. Most of the endemic genera and species occur at depths of less than 200 m, whereas the majority of species with broader geographic distributions are found in deeper water, down to ~2000 m.
Brachiopods may occur intertidally and in shallow subtidal areas on the protected undersides of boulders or rocky reefs, while some species can be found among kelp holdfasts. They are often cryptic, and/or well-camouflaged by encrusting epibionts including bryozoans, sponges, barnacles, and red algae. The smaller species, particularly the cemented craniids (Novocrania, Valdiviathyris), and the subtropical Thecidellina are unlikely to be noticed or recognised as brachiopods except by a specialist. One area of particular interest for the occurrence of brachiopods is the Fiordland region of the southern South Island, where dense aggregations of Liothyrella neozelanica, Notosaria nigricans, Calloria inconspicua and Terebratella sanguinea can be found at depths of 10-20 m. Other areas of the Marlborough Sounds and Paterson Inlet, Stewart Island are also significant for the occurrence of the genus Neothyris, a group of brachiopods that may become free-lying as adults, with five recognised species, all of which are endemic to New Zealand.
The New Zealand brachiopod fauna consists of 32 species in 22 genera, representing 15 families in 5 orders. There are 5 endemic genera-the rhynchonellide Notosaria, the tiny kraussinoid Pumilus, the widespread terebratelloids Calloria and Neothyris, and the small, recently described thecideoid Kakanuiella. Overall, 50% of the species are endemic. The family with the highest proportion of endemics is the Terebratellidae, with 9 of 12 species being restricted to the New Zealand region.
No living brachiopod species appears threatened by extinction in New Zealand. One population in Lyttelton Harbour, one of the few intertidal localities in the world where three unrelated brachiopod species occur together, appears to have been destroyed by human interference (boulders occupied by brachiopods lifted out of the water, and/or removed from the pool, possibly by scientists/students studying the brachiopods). Other populations of small brachiopods in Otago Harbour appear to be declining, though lack of information makes this difficult to quantify.
Brachiopods are found throughout New Zealand. Key areas for taxonomically diverse and/or numerically abundant brachiopod assemblages include deep-water sites off the Three Kings Islands; shallow subtidal localities around the Kermadec Islands, the Hauraki Gulf and northern offshore islands; off Ranfurly Bank; areas of Cook Strait and the Marlborough Sounds; Lyttelton Harbour; subtidal localities along the Otago coast from Oamaru to Waikawa; Otago Harbour and Otago Shelf; parts of Foveaux Strait; parts of the Chatham Rise where rare species are associated with coral thickets; and areas of the Campbell Plateau where large quantities of live and dead shells of Neothyris, Gyrothyris, and associated species have been dredged. The Cook Strait region has a diverse brachiopod fauna that represents the northern limit of several key species (eg, Notosaria nigricans). In the Stewart Island region, the brachiopods of Paterson Inlet represent a major component of the benthic biomass. Fiordland is regarded as a globally significant area for brachiopods, with a diverse and abundant brachiopod fauna found in shallow water. The Chatham Rise represents a biogeographic limit for many of the southern and subantarctic species.
Summary of Threats
Aquaculture development in key areas for the large free-living brachiopods, Neothyris sp. and associated species, such as in the Marlborough Sounds and Paterson Inlet, Stewart Island, represent a major threat to these associations. The increase in sedimentation and changes in water quality associated with mussel and salmon farms can potentially alter environmental conditions and affect the survivorship and reproduction of these species. Bottom trawling of the seabed could destroy brachiopod communities. Some brachiopod communities in intertidal and subtidal localities may be at risk from collectors, and public attention should not be drawn to such sites.
Brachiopods are typically attached to hard substrates in low-sediment areas. They may live on the undersides of boulders, in rock crevices, or on rock walls as in the fiords, and are also relatively common on areas of the shelf dominated by coarse biogenic sediment. Overall their distribution is somewhat patchy, but some species (eg, Calloria inconspicua) may occur at very high densities of more than 1000 per square metre. Brachiopod diversity and richness are greatest between subtidal depths and about 200 m. Small, cemented, cryptic brachiopods such as Novocrania, Valdiviathyris, and Thecidellina may be much more common than is currently realised.
State of Information
The taxonomy of living brachiopods is comparatively well known and there is a reasonable amount of information available on their shallow-water distributions, though less for those from deeper-water habitats. Because brachiopods are fairly easily obtained from shallow-water habitats, New Zealand has become an international centre for brachiopod research, and local species have figured prominently in recent international scientific literature on brachiopod anatomy, biomineralisation, ecology, and molecular phylogeny. In spite of this international interest, many aspects of the general ecology of brachiopods in terms of their life history, feeding, reproduction, and recruitment are poorly known. As yet, no comprehensive account of the living brachiopod fauna of New Zealand has been produced.
Significance for Maori
No specific use or significance of brachiopods to Maori is known.
Dawson, E W. 1990. The systematics and biogeography of the living Brachiopoda of New Zealand. 431-437pp in Mackinnon, D I, Lee, D E and J D Campbell (eds) Brachiopods Through Time. Proceedings of the 2nd International Brachiopod Congress, University of Otago, Dunedin, New Zealand, 5-9 February 1990. A.A. Balkema, Rotterdam, Brookfield.
Lee, D E. 1978. Aspects of the ecology and paleoecology of the brachiopod Notosaria nigricans (Sowerby). Journal of the Royal Society of New Zealand 8:395-417.
Lee, D E. 1987. Cenozoic and Recent inarticulate brachiopods from New Zealand: Discinisca, Pelagodiscus and Neocrania. Journal of the Royal Society of New Zealand 17:49-72.
Lee, D E. 1990. Aspects of the ecology and distribution of the living Brachiopoda of New Zealand. 273-279pp in Mackinnon, D I, Lee, D E and J D Campbell (eds). Brachiopods Through Time. Proceedings of the 2nd International Brachiopod Congress, University of Otago, Dunedin, New Zealand, 5-9 February 1990. Balkema, A A, Rotterdam, Brookfield.
MacFarlan, D A B, Bradshaw, M A, Campbell, H J, Cooper, R A, Lee, D E, MacKinnon, D I, Waterhouse, J B and A J Wright. In press: Phylum Brachiopoda-lamp shells. In: Gordon, D P (ed). The New Zealand inventory of biodiversity. Volume 1. Kingdom Animalia. Radiata, Lophotrochozoa, and Deuterostomia. Canterbury University Press, Christchurch.
Richardson, J R. 1981 (compiler). Recent brachiopods from New Zealand.
Collected offprints of a suite of eleven papers on brachiopods from Stewart Island and Fiordland published in New Zealand Journal of Zoology 8 (2): 133-248.
Table 22: Brachiopods (Phylum Brachiopoda) in New Zealand
|Class||Order||Family||Endemic Species||Other Species||Total Species|
Figure 59: Dwarf white lamp shell Pumulis antiquates annual distribution.