Crustaceans (subphylum Crustacea)
A large male red rock lobster, Jasus edwardsii, at 20 m depth on the edge of Tabletop Reef, Cape Rodney, Okakari Point Marine Reserve, 1985. Photographer, Alison MacDiarmid.
Neil Bruce and Taoho Patuawa
General description
Crustaceans show the greatest diversity of any animal group on the planet, and include among their numbers the many well-known commercially exploited groups such as the prawns, crabs, and lobsters. The crustacean body has a number of defining characters that include, the arthropod exoskeleton, a five-segmented head and an elongate body that is usually divided into two more-or-less distinct sections, each of these sections bearing multi-segmented appendages. Brusca and Brusca (2002) give a brief summary of crustacean characteristics. The Crustacea show an enormous diversity of form, and a great range of size from microscopic species measuring as little as a tenth of a millimetre to giant crabs, lobsters, and isopods with a body size of up to half a metre in length or breadth, and weighing up to 20 kilograms. By virtue of their highly prized edibility the crustaceans are arguably the most popular invertebrates.
The number of named species of Crustacea worldwide is estimated at approximately 50,000 to 67,000. The potential number of species ranges from as many as ten times to one hundred times that number. The "small" species may eventually be found in numbers comparable those of the insects on land. For example, the isopods (pill bugs, sea slaters) currently number approximately 5800 marine species, but recent estimates suggest that as many as 50,000 species of isopods could exist on coral reef habitats alone (Kensley 1988), a figure close the current total for all Crustacea, while Wilson (2003) estimated a total of 400,000 deep-sea species. Crustacean diversity is huge.
Six classes of Crustacea are recognised (Martin & Davis 2001) and representatives of all classes except one minor group-the Remipedia-are found in New Zealand. As one moves down the classification from class to species the level of endemism increases. Most major orders of Crustacea are to be found in New Zealand waters, though many families and genera are rare or absent, particularly among those groups with strong warm-water representation, such as the commercially and gastronomically desirable prawns and crabs.
Crustaceans are widely distributed throughout the New Zealand region occurring from the Kermadec Islands to the subantarctic islands. They are found on land, in coastal streams, in groundwaters, and from the intertidal to a depth of about 7 km in the Kermadec Trench. Crustaceans reach their greatest diversity in the sea and are a quintessential component of the marine fauna. Apart from the large lobsters, crabs and such, distributional limits are poorly known within the New Zealand region. Decapods (shrimps and crabs) are intolerant of cold conditions, and there is a known decrease in diversity as latitude increases, with southern parts of New Zealand, including the subantarctic islands, being depauperate in comparison to the subtropical northern North Island. In contrast, the southern hemisphere marine region loosely termed the southwestern Pacific is of extreme high diversity in many groups. Though not well-documented, it is apparent that the small-sized crustaceans such as the "sea slaters" (isopods), "sea fleas" (amphipods), and related groups, will prove to have both high diversity and endemism, with many indigenous species and genera, forming a characteristic New Zealand faunal component.
Status
Conservation status of most species is poorly known. Commercially and recreationally exploited species may be locally reduced in numbers or even threatened. Species from restricted habitats such as maritime springs, streams or beach drainages should be considered vulnerable. Endemism is high, particularly in benthic and epibenthic forms, ranging from 96% (Isopoda-sea slaters) to 67% (Decapoda-shrimps and crabs etc); pelagic taxa, such as the copepods, typically have low endemicity (11%).
Key Locations
Key locations cannot be specifically identified, though mixed-habitat shallow reefs, seamounts, and calcareous sediments are all known to be of high diversity. The southwestern Pacific region is known to have great invertebrate diversity, only a small proportion of which has been documented in New Zealand.
Summary of Threats
Crustacean diversity is vulnerable to anthropogenic habitat loss in all habitats. Some species, restricted to maritime streams or inshore habitats (eg, harbours), may be acutely vulnerable. The crustacean fauna from intertidal rocky shores to approximately 50 metres will be very diverse, but is very poorly known. This habitat is susceptible to threats from pollution, and urban and agricultural development. Seamounts, and the ocean floor in general, are threatened by fishing activities, which modify the habitat at even the lowest levels of disturbance.
Typical Habitats
Crustaceans are known from all habitats, terrestrial and aquatic, though the weakest representation is in estuaries and lagoons. Diversity is high in marine habitats, lower in estuaries and high-silt habitats. As in most parts of the world, structural complexity increases crustacean diversity, so mixed rocky bottom and macro-algal reefs and any "coral" reef, deep or shallow, will have high diversity.
State of Information
Recent publications giving excellent coverage of crustacean diversity worldwide include a photographic guide by Debelius (1999) and a guide to decapods by Poore (2004); there are no comprehensive guides to crustaceans of New Zealand.
For those groups other than the decapods (shrimps and crabs, etc) and copepods (NIWA monographs published (Bradford-Grieve 1999 and earlier)), the level of information and documentation of New Zealand groups and species ranges from minimal to poor. There are no comprehensive and up-to-date guides to even relatively well-known groups such as the Decapoda, though there are some recent guides delimited by taxon (eg, McLay 1998) or habitat (eg, Webber et al. 1990) and some monographs (eg, Forest et al. 2000). For the highly diverse but small (<10 mm) crustaceans such as isopods and amphipods the percentage known may be as little as 10%-20% of the potential fauna. A complete listing of all known New Zealand crustaceans, including fossils, is to be found in The New Zealand Inventory of Biodiversity (Gordon in press).
Significance for Maori
Of the marine crustaceans found in New Zealand, three species were of particular significance for Maori, these being the red rock lobster (koura, matapara, or matapuku), packhorse lobster (koura, papatia, or pawharu), and paddle crabs (papaka). Papatia were restricted to the waters of the northern North Island, while matapara and papaka have a wide distribution around New Zealand. These crustaceans were an important food source for early Maori, and two techniques were employed to catch them. Both species of lobster were primarily caught using a lobster pot (which were referred to as taruke koura, tukutuku, humete or punga), and also by hand. Taruke koura were constructed out of thin manuka rods and assembled in much the same way as modern pots.
Key References
Bradford-Grieve, J M. 1999. The Marine Fauna of New Zealand: Pelagic Calanoid Copepoda: Arietellidae, Augaptilidae, Heterorhabdidae, Lucicutiidae, Metridinidae, Phyllopodidae, Centropagidae, Pseudodiaptomidae, Temoridae, Candaciidae, Pontellidae, Sulcanidae, Acartiidae, Tortanidae. NIWA Biodiversity Memoir 111: 1-268.
Brusca, R C and Brusca, G J. (2002). Invertebrates. Second edition. Sinauer Associates, Sunderland, Maryland. i-xx, 1-936pp.
Debelius, H. 1999. Crustacea. Guide of the World. IKAN, Frankfurt. 321pp.
Forest, J, de Saint Laurent, M, McLaughlin, P A, and R Lemaitre. (2000). The Marine Fauna of New Zealand: Paguridea (Decapoda: Anomura) exclusive of the Lithodidae. NIWA Biodiversity Memoir 114: 1-250.
Gordon, D P (ed). (in press). The New Zealand Inventory of Biodiversity. Volume 2: Kingdom Animalia - Radiata, Lophotrochozoa, and Deuterostomia. Christchurch, Canterbury University Press.
Kensley, B. 1988. Preliminary observation on the isopod crustacean fauna of Aldabra Atoll. Bulletin of the Biological Society of Washington 8: 40-44.
Martin, J W and Davis, G E. 2001. An updated classification of the recent Crustacea. Natural History Museum of Los Angeles County, Science Series 39: i-vi, 1-124.
McLay, C L. 1998. Crabs of New Zealand. Leigh Laboratory Bulletin 22: 1-463.
Poore, G C B. 2004. Marine Decapod Crustacea of Southern Australia. A guide to identification. CSIRO Publishing, Melbourne. i-ix, 1-574pp.
Webber, W R, Fenaughty, C M and R M Clark. 1990. A guide to some common offshore shrimp and prawn species of New Zealand. New Zealand Fisheries Occasional Publication 6: 1-42.
Wilson, G D F. 2003 Deep-sea biodiversity. Australian Museum. Available at http://www-personal.usyd.edu.au/~buz/deepsea.html (accessed 2005).
Table 23: Crustaceans (sub-phylum Crustacea) in New Zealand
| Class Order | Described species | Known undescribed species | Adventive species | Endemic species | Total species |
|---|---|---|---|---|---|
| Branchiopoda | 45 | 3 | 2? | 4 | 48 |
| Cephalocarida | 1 | 0 | - | 1 | 1 |
| Maxillopoda | |||||
| Thecostraca | 74 | 5 | 3 | 28 | 79 |
| Tantulocarida | 3 | ? | 0 | 3 | 3 |
| Branchiura | 1 | ? | 1? | 0 | 1 |
| Pentastomida | 1? | ? | ? | ? | 1 |
| Copepoda | 568 | 129 | 2 | 103 | 697 |
| 646 | 134 | 5 | 134 | 781 | |
| Ostracoda | |||||
| Palaeocopida | 3 | 3 | 3 | ||
| Podocopida | 269 | 74 | 3 | 42 | 343 |
| Myodocopida | 78 | 4 | 24 | 82 | |
| 350 | 78 | 3 | 69 | 428 | |
| Malacostraca | |||||
| Phyllocarida | 3 | 2 | 0 | 1 | 5 |
| Hoplocarida | 7 | ? | 0 | ? | 7 |
| Bathynellacea | 2 | 4 | 0 | 6 | |
| Syncarida | 5 | 3 | 0 | 0 | 8 |
| Lophogastrida | 4 | 1 | 0 | 0 | 5 |
| Mysida | 16 | 2 | 0 | 11 | 18 |
| Amphipoda | 389 | 25 | 8 | 249 | 414 |
| Isopoda | 315 | 60 | 6 | 245 | 375 |
| Tanaidacea | 40 | 41 | 0 | 6 | 81 |
| Cumacea | 47 | 27 | 0 | 65 | 74 |
| Euphausiacaea | 20 | - | 0 | 0 | 20 |
| Amphionidacea | 0 | 0 | 0 | 0 | - |
| Decapoda | 341 | 119 | 10 | 131 | 460 |
| 1189 | 284 | 24 | 708 | 1473 | |
| Remipedia | - | - | - | ||
| Total | 2232 | 499 | 34? | 915 | 2731 |
Figure 60: Red rock lobster Jasus edwardsii annual distribution.
Figure 61: Scampi Metanephrops challengeri annual distribution.
Figure 62: Paddle crab Ovalipes catharus annual distribution.
Figure 63: Primitive acorn barnacle Chionelasmus crosnieri annual distribution.
Figure 64: O'Shea's vent barnacle Vulcanolepas osheai annual distribution.