Lace Corals (Phylum Bryozoa)
Fingers of red Steginoporella neozelanica and delicate branching white Cellaria tenuirostris, Poor Knights Islands. Photographer Franz Smith
Dennis Gordon and Franz Smith
General Description
Bryozoans, more commonly known as "lace corals", form colonies made up of box-like or tubular modules called zooids. These can take on various forms but the fundamental unit, a feeding zooid, comprises a body wall enclosing a polypide (the feeding apparatus and digestive tract). Bryozoan colonies are mostly encrusting, on rocks, shells, and seaweeds, but they can also be bushy, resembling hydroids or turfing algae, or large and foliaceous like some corals. Some species are free-living, forming small discus-like colonies on offshore sand. The largest New Zealand species may achieve colony sizes half a metre across and more than 30 centimetres high while the smallest are tiny runner-like colonies with microscopic zooids, either on rock and shell or boring into shells.
Three orders of bryozoans are represented in modern seas - the Cyclostomata, Ctenostomata, and Cheilostomata, distinguished by the structure of individual zooids. Cheilostomes, which didn't originate until the latest Jurassic, have box-like zooids and today comprise the majority of species, outnumbering the cyclostomes (with calcified tubular zooids) and the ctenostomes (which are uncalcified). Cheilostomes have a special lid (operculum) at one end that opens to allow the feeding tentacles to emerge. The muscle that pulls the tentacles back if the zooid is disturbed is the fastest contracting in the animal kingdom.
The most useful feature for distinguishing cheilostomes and classifying them is the design of the front wall of the box (zooid). This can either be a delicate uncalcified membrane or it can be partly calcified, or there is some kind of skeletal shelf above or below the membrane, or even protective spines that overarch it. In cyclostomes and ctenostomes, the arrangement of the zooids in the colony is more important in classification. A microscope is usually necessary to identify bryozoans but many can be recognised by their colonies, especially if they have distinctive colours and shapes.
Bryozoans are suspension-feeders, capturing food particles from the water using a ciliated tentacle cluster called a lophophore. In most bryozoans, some zooids have been modified to perform a role other than feeding, like reproduction, defence, or nutrient storage. In some, called avicularia, the operculum has been modified to form either a jaw-like mandible that snaps shut upon disturbance or a bristle-like seta that lashes the zooid surface and keeps it clean. In free-living discoidal colonies, a whole series of bristle-like setae around the colony perimeter can lift the colony above the sand and propel it forward.
Most bryozoans have short-lived, non-feeding larvae that settle after an hour or so and metamorphose into the founding individual of a new colony. Budding of new zooids from this and later zooids increases the size of the colony. A small percentage of species (mostly cheilostomes) have planktonic larvae that can feed. These may survive for a few weeks before settling. Studies of growth rates of bryozoans in the Hauraki Gulf and Fiordland show considerable variation. In general, encrusting colonies can form circular patches 2-5 centimetres across in a year, but encrusters of Ecklonia radiata, especially lightly calcified Membranipora membranacea, can grow 10 or more centimetres in length and contain tens of thousands of feeding individuals. In Doubtful Sound, an undescribed species of Adeonellopsis that forms football-sized colonies of flattened stagshorn-like branches has been measured as growing around 1 cm per year, so a 20-cm-high colony should be around twenty years old.
Bryozoans abound in New Zealand waters (and in the fossil record). Worldwide, there are about 6000 living species and 15,000 fossil species. New Zealand has one of the richest bryofaunas in the world, with some 948 species in the exclusive economic zone, representing 339 genera in 118 families. Approximately 325 of these species have yet to be described. Overall, 62% of the species are endemic to the New Zealand region.
In New Zealand, common examples of the Cheilostomata include the alien species of ports and harbours, like Bugula neritina with bushy burgundy colonies and Watersipora subtorquata with crustose to foliaceous colonies, grey-black with orange edges. Membranipora membranacea is a common sheet-encruster of kelp fronds, while on subtidal rock walls the brown rods of Steginoporella neozelanica stick out into the water. Here, the large bushy colonies of catenicellids are often found, with their zooids separated by joints like beads on a string. An important habitat-former is Celleporaria agglutinans ("Tasman Bay coral"), whose large coralline colonies are used to create a nursery habitat for juveniles of commercial fish off Abel Tasman National Park. Ctenostomes tend to be more cryptic, being small and transparent. An exception is the alien Zoobotryon verticillatum in the warm summer waters of Auckland and Northland ports and harbours where it forms large branching colonies whose stems resemble thin egg noodles. The colonies of Amathia species can also be conspicuous in northern parts of the country. Cyclostomes tend to be found in deeper water or offshore, particularly on coarse shell bottoms. Best known is the endemic family Cinctiporidae, with giant zooids. There are two living species - Cinctipora elegans and Attinopora zealandica. The former forms an important habitat of thicket-like colonies on Otago Shelf and in Foveaux Strait. Several species of cyclostomes encrust Sargassum sinclairii in Auckland Harbour.
Status
No bryozoan species appears threatened by extinction in New Zealand but some species have very limited distributions or form important bryozoan habitat in certain locations and these are vulnerable to benthic disturbance. The habitat of "Tasman Bay coral" off Separation Point, Abel Tasman National Park, has been closed to bottom trawling since 1980 but regeneration is slow and there has not yet been reversion to pre-trawled habitat. An area off Spirits Bay has been closed to scallop dredging but the endemic monotypic cyclostome genus Spiritopora, which forms bryoliths, is excluded from the protected area.
Key Locations
Key areas for taxonomically diverse and numerically abundant bryozoan assemblages in New Zealand include Raoul Island, the Three Kings Shelf (Three Kings Islands, Pandora Bank, Spirits Bay, Cape Maria van Diemen), Cavalli seamounts, rock walls of the Poor Knights (and other northern offshore islands), Stephens Hole (Cook Strait), headlands and certain current-swept areas off Abel Tasman National Park and Marlborough Sounds, Mernoo Bank (Chatham Rise), Otago Shelf, Puysegur Bank, and parts of Foveaux Strait and Stewart Island.
Summary of Threats
Bottom trawling of the seabed can damage bryozoan thickets. Sedimentation from terrestrial runoff can also smother colonies and reduce epifaunal diversity and density. Alien species are likely to reduce native bryozoan diversity in parts of ports and harbours.
Typical Habitats
The richest habitats (numerically and taxonomically) are rock walls and other hard substrata in relatively low-sediment, current-swept areas. A plot of diversity with depth shows that numbers of species increase from intertidal to shelf depths, declining evenly to the deep sea, with a slight peak between 900 and 1100 m. Hence, across all of New Zealand there are 267 species from 0-25 m, 461 from 26-100 m, 395 from 101-200 m, 94 from 801-900 m, and 127 from 901-1000 m.
State of Information
Three monographs describe bryozoans from the Kermadec Ridge and western South Island, referencing all previous literature, and an illustrated chapter is in press in a volume on New Zealand coastal invertebrates. A review of knowledge of New Zealand Bryozoa, with a checklist of all known species is also in press. The NIWA-based "New Zealand Bryozoan Biodiversity Database" [www.nzbbd.niwa.co.nz] is available online, giving map-based distributional data. Of the approximately 325 species of bryozoan yet to be described, most are from seamounts and the deep sea.
Significance for Maori
No specific use or significance of bryozoans to Maori is known. The fourth edition of Powell's Native Animals of New Zealand (David Bateman, 1998) gives the Maori name "takapau moana" for bryozoans.
Key References
Batson, P B and Probert, P K. 2000. Bryozoan thickets off Otago Peninsula. New Zealand Fisheries Assessment Report 2000/46: 1-31.
Boardman, R S, McKinney, F K and P D Taylor. 1992. Morphology, anatomy and systematics of the Cinctiporidae, new family (Bryozoa: Stenolaemata). Smithsonian Contributions to Paleobiology No. 70: 1-81.
Gordon, D P. 1984. The marine fauna of New Zealand: Bryozoa: Gymnolaemata from the Kermadec Ridge. New Zealand Oceanographic Institute Memoir 91: 1-198.
Gordon, D P. 1986. The marine fauna of New Zealand: Bryozoa: Gymnolaemata (Ctenostomata and Cheilostomata Anasca) from the western South Island continental shelf and slope. New Zealand Oceanographic Institute Memoir 95: 1-121.
Gordon, D P. 1989. The marine fauna of New Zealand: Bryozoa: Gymnolaemata (Cheilostomida Ascophorina) from the western South Island continental shelf and slope. New Zealand Oceanographic Institute Memoir 97: 1-158.
Gordon, D P. 1999. Bryozoan diversity in New Zealand and Australia. 32-37pp. In Ponder, W, Lunney, D. (eds), The other 99%. The conservation and biodiversity of invertebrates. Royal Zoological Society of New South Wales, Mosman.
Gordon, D P. 2003. Living lace. New Zealand Geographic 61: 78-93.
Gordon, D P. In press: Phylum Bryozoa. In Cook, S. de C. (ed) New Zealand coastal invertebrates. Canterbury University Press, Christchurch.
Gordon, D P, Taylor P D and F P Bigey. In press: Phylum Bryozoa-moss animals, sea mats, lace corals. In: Gordon, D P (ed), The New Zealand inventory of biodiversity. Volume 1. Kingdom Animalia. Radiata, Lophotrochozoa, and Deuterostomia. Canterbury University Press, Christchurch.
Grange, K R, Tovey, A and A F Hill. 2003. The spatial extent and nature of the bryozoan communities at Separation Point, Tasman Bay. Marine Biodiversity Biosecurity Report No. 4: 1-22.
Rowden, A A, Warwick, R M and D P Gordon. 2004. Bryozoan biodiversity in the New Zealand region and implications for marine conservation. Biodiversity and Conservation 13: 2695-2721.
Smith, F and Gordon, D P. 2003. Sessile invertebrates. Pp. 80-91 in: Andrew, N, Francis, M (eds), The Living Reef: The ecology of New Zealand's rocky reefs. Craig Potton Publishing, Nelson. 283pp.
Taylor, P D, and Gordon, D P. 2003. Endemic new cyclostome bryozoans from Spirits Bay, a New Zealand marine-biodiversity "hotspot". New Zealand Journal of Marine and Freshwater Research 37: 653-669.
Table 21: Bryozoans (Phylum Bryozoa) in New Zealand
| Class | Order | Family | Endemic Species | Total Species |
|---|---|---|---|---|
| GYMNOLAEMATA | CHEILOSTOMATA | Adeonidae | 2 | 3 |
| Aeteidae | 0 | 3 | ||
| Arachnopusiidae | 4 | 6 | ||
| Aspidostomatidae | 1 | 3 | ||
| Batoporidae | 0 | 1 | ||
| Beaniidae | 12 | 20 | ||
| Bifaxariidae | 6 | 7 | ||
| Bitectiporidae | 33 | 39 | ||
| Bryopastoridae | 2 | 5 | ||
| Buffonellodidae | 10 | 14 | ||
| Bugulidae | 22 | 48 | ||
| Calescharidae | 1 | 3 | ||
| Calloporidae | 48 | 67 | ||
| Calwelliidae | 1 | 6 | ||
| Candidae | 25 | 52 | ||
| Catenicellidae | 7 | 30 | ||
| Cellariidae | 10 | 21 | ||
| Celleporidae | 41 | 51 | ||
| Chaperiidae | 27 | 32 | ||
| Chorizoporidae | 7 | 8 | ||
| Cleidochasmatidae | 5 | 6 | ||
| Conescharellinidae | 7 | 11 | ||
| Crepidacanthidae | 0 | 4 | ||
| Cribrilinidae | 19 | 21 | ||
| Cryptosulidae | 0 | 1 | ||
| Cyclicoporidae | 0 | 1 | ||
| Dhondtiscidae (End.) | 2 | 2 | ||
| Didymosellidae | 1 | 1 | ||
| Electridae | 2 | 7 | ||
| Epistomiidae | 0 | 1 | ||
| Escharinidae | 11 | 13 | ||
| Euoplozoidae | 0 | 1 | ||
| Eurystomellidae | 6 | 6 | ||
| Euthyroididae | 2 | 3 | ||
| Exechonellidae | 0 | 1 | ||
| Farciminariidae | 2 | 6 | ||
| Flustridae | 3 | 7 | ||
| Gigantoporidae | 1 | 3 | ||
| Hiantoporidae | 1 | 1 | ||
| Hippopodinidae | 7 | 7 | ||
| Hippoporidridae | 1 | 1 | ||
| Hippothoidae | 9 | 14 | ||
| Inversiulidae | 1 | 1 | ||
| Lacernidae | 19 | 25 | ||
| Lanceoporidae | 2 | 3 | ||
| Leiosalpingidae | 0 | 1 | ||
| Lekythoporidae | 4 | 5 | ||
| Lepraliellidae | 7 | 14 | ||
| Lunulariidae | 0 | 1 | ||
| Macroporidae | 6 | 7 | ||
| Margarettidae | 0 | 1 | ||
| Mawatariidae | 2 | 2 | ||
| Membraniporidae | 0 | 4 | ||
| Microporellidae | 22 | 28 | ||
| Microporidae | 12 | 17 | ||
| Monoporellidae | 0 | 1 | ||
| Onychocellidae | 1 | 1 | ||
| Otionellidae | 6 | 6 | ||
| Pasytheidae | 0 | 1 | ||
| Petalostegidae | 3 | 4 | ||
| Petraliellidae | 5 | 7 | ||
| Phidoloporidae | 22 | 33 | ||
| Phorioppniidae | 2 | 4 | ||
| Poricellariidae | 0 | 1 | ||
| Porinidae | 2 | 4 | ||
| Quadricellariidae | 0 | 2 | ||
| Rhabdozoidae | 0 | 1 | ||
| Romancheinidae | 10 | 14 | ||
| Schizoporellidae | 1 | 2 | ||
| Sclerodomidae | 1 | 1 | ||
| Scrupariidae | 0 | 2 | ||
| Selenariidae | 0 | 2 | ||
| Smittinidae | 23 | 37 | ||
| Steginoporellidae | 4 | 5 | ||
| Teuchoporidae | 1 | 2 | ||
| Thalamoporellidae | 1 | 1 | ||
| Trypostegidae | 0 | 1 | ||
| Urceoliporidae | 1 | 1 | ||
| Vinculariidae | 1 | 1 | ||
| Watersiporidae | 0 | 3 | ||
| Cheilostomata Total | 497 | 783 | ||
| CTENOSTOMATA | Aeverrilliidae | 0 | 1 | |
| Alcyonidiidae | 5 | 7 | ||
| Arachnidiidae | 2 | 3 | ||
| Buskiidae | 0 | 3 | ||
| Clavoporidae | 2 | 2 | ||
| Flustrellidridae | 1 | 2 | ||
| Haywardozoidae | 0 | 1 | ||
| Immergentiidae | 1 | 2 | ||
| Mimosellidae | 0 | 1 | ||
| Nolellidae | 0 | 6 | ||
| Pachyzoidae | 3 | 3 | ||
| Penetrantiidae | 1 | 2 | ||
| Sundanellidae | 0 | 1 | ||
| Terebriporidae | 1 | 1 | ||
| Triticellidae | 3 | 3 | ||
| Vesiculariidae | 0 | 8 | ||
| Walkeriidae | 0 | 1 | ||
| Ctenostomata Total | 19 | 47 | ||
| GYMNOLAEMATA Total | 522 | 826 | ||
| STENOLAEMATA | CYCLOSTOMATA | Annectocymidae | 4 | 5 |
| Canuellidae | 2 | 2 | ||
| Cerioporidae | 3 | 3 | ||
| Cinctiporidae (End.) | 2 | 2 | ||
| Crisiidae | 1 | 7 | ||
| Crisinidae | 1 | 1 | ||
| Densiporidae | 6 | 6 | ||
| Diaperoeciidae | 7 | 8 | ||
| Diastoporidae | 11 | 15 | ||
| Fascigeridae | 0 | 3 | ||
| Hastingsiidae | 3 | 3 | ||
| Horneridae | 5 | 6 | ||
| Lichenoporidae | 10 | 14 | ||
| Oncousoeciidae | 0 | 2 | ||
| Stomatoporidae | 0 | 1 | ||
| Terviidae | 2 | 2 | ||
| Theonoidae | 5 | 6 | ||
| Tubuliporidae | 7 | 31 | ||
| STENOLAEMATA Total | 69 | 117 | ||
| Grand Total | 585 | 943 |
End. = endemic family
Figure 56: Spirits Bay invertebrate complex annual distribution.
Figure 57: Bryozoan complex bryozoa annual distribution.
Figure 58: O'Shea's tree bryozoan Calvetia osheai annual distribution.