Tuatara: Volume 9, Issue 1, September 1961
Distribution Patterns of New Zealand Echinoderms
Distribution Patterns of New Zealand Echinoderms
Echinoderms appear to be particularly suitable as material for the study of patterns of distribution, owing to their relatively sedentary habits, their aversion to fresh or even brackish water, the brevity or complete absence of a pelagic larval life, and their usually short bathymetric range.
This article deals mainly with patterns of distribution of the shelf fauna, that is, species known to depths of 100 fathoms. The archibenthal and abyssal faunas will also be considered.
Marine Provinces have been defined by Finlay (1925) and Powell (1937) on the basis of Mollusca, and have also been applied to the shelf echinoderms (Fell, 1949, and later references). In this paper an attempt is made to find correlations between the very restricted distribution of some species and physical environmental factors. It would be useful indeed if we could say that some one marine province is bounded to the north by an ocean current and to the south by another current or trench, but with the present state of our knowledge no really definite statements such as this can be made.
The boundaries of the provinces as suggested by the known echinoderms of New Zealand may be at variance with the boundaries indicated by other animal groups, e.g. Mollusca, but this is possibly due to many factors, among them differences in powers of locomotion, mode of reproduction, and others. Probably the most important factor is our lack of a more complete knowledge of the patterns of distribution of the animals concerned.
Of the New Zealand shelf echinoderms, approximately 59% have a scattered distribution pattern, and show no clear provincial pattern. The remaining 41% appear to conform rather well to the provincial system, and may be separated into groups, each group being restricted to a province and typical of that province.
The Kermadec Islands are often excluded from the New Zealand region as they are truly subtropical in position and in the general affinities of their fauna. At first sight the echinoderm fauna of these islands seems to show a generalised Indo-Pacific facies; of the 13 recorded species 6 (46%) are Australian-Indo-Pacific, 5 (39%) are restricted to the Kermadecs, and only 2 (15%) are shared with page 10 the New Zealand mainland. This might seem to exclude the Kermadecs from the New Zealand faunal region.
Closer analysis of the echinoderm fauna, however, leads to a different conclusion. One of the restricted species, Patiriella oliveri, is very closely related to Patiriella regularis of the New Zealand mainland, and the two almost certainly share a common ancestry. Another starfish restricted to the Kermadecs, Astrostole rodolphi, is very closely related to Astrostole scabra of the New Zealand mainland.
Of the two species shared with New Zealand, Ophidiaster kermadecensis ranges the Bay of Plenty and the Kermadecs and is unknown elsewhere in the world. The other is Evechinus chloroticus ranging the entire New Zealand mainland and, apart from the Kermadecs, unknown elsewhere in the world; Evechinus is known fossil in New Zealand, at least from the Pliocene (Nukumaruan). Of the Australian-Indo-Pacific species, Astropecten polyacanthus is also shared with the Aupourian Province of New Zealand.
There is, therefore, good echinoderm evidence for including these islands in the New Zealand region, possibly as a sub-region of the Aupourian Province, but more collecting is obviously required.
The Aupourian Province was established for Mollusca to cover Three Kings Islands and all that part of the North Auckland Peninsula above Ahipara on the west and Whangaroa on the east coast (Powell, 1937). It was known then that the province was distinguished by the presence of a number of subtropical molluscs. Powell (1955) subsequently extended the south-eastern boundary of the province to East Cape, and Fell (1952) had found this to be consistent with the echinoderm evidence. So far as the echinoderms are concerned, the south-western boundary of the Aupourian Province cannot fall north of Cape Egmont (Fig. 1), as otherwise certain species with a distinct Australian-Indo-Pacific facies would present an anomalous distribution.
Some typical Aupourian echinoderms are Asterodiscus truncatus (Powell, 1937); Astropecten polyacanthus (known from as far south as New Plymouth to the west and East Cape to the east); Centro-stephanus rodgersii (from south of Whangaroa); Holopneustes inflatus (from Great Barrier Island); Clypeaster australasiae (off Parengarenga and East Cape) (Fell, 1949b). All of these species are also present in the Australian echinoderm fauna and are typical subtropical forms. Another species, Brissus gigas, from the Bay of Islands (Fell, 1947), is very closely related to a widespread Indo-Pacific species Brissus latecarinatus. At the present time, fifteen species may be named as typical of this province.
If the subtropical forms can only move as far south as Cape Egmont to the west and East Cape to the east, there must be some page 11 barrier preventing their dispersal at least to the more southern regions of the North Island. For shallow water species such as these, factors such as temperature, salinity and water movements should act in some way to produce a barrier.
Deacon (1937) suggested that the northern limit of the subtropical convergence to the west of the North Island lies at about 42° S. and 170° W. and strikes towards the coast in the neighbourhood of Cape Egmont. Garner (1959) noted a pronounced drop in the level of the mean surface temperature between the areas off Capes Egmont and Farewell, and thus tended to agree in part with Deacon's premise. We know that most of the subtropical species tend to be stenothermal, and thus Cape Egmont might form a southern boundary for the Aupourian echinoderms of the west coast. The cooler waters of the Westland Current (Fig. 1) flow past Cape Egmont at varying times throughout the year, but the northern limit of the current is variable (Brodie, 1960). The current, however, may play some part in the regulation of distribution on this coast.
The Canterbury Current, a colder water current, moves northwards near the coast towards East Cape (Fig. 1).
Garner (1959) noted a significant drop in water temperature off East Cape at latitude 37.5° S. (Fig. 1), indicating a localised coastal upwelling of colder water.
Taken together, these physical factors might form an excellent barrier. The shelf echinoderms between East Cape and Hawke Bay are unfortunately not very well known, but those of Hawke Bay have been intensively studied in recent years, and no “strays from the north’ have been encountered as yet among the thousands of specimens taken from that region.
Probably the most important feature of the Cookian Province is the fact that it is an area of mixed waters, the site of the subtropical convergence (Fleming. 1944), and thus it is to be expected that its echinoderm fauna is of mixed composition. This was demonstrated by Fell (1949a). The Cookian Province seems to present a broad section of the New Zealand echinoderm fauna as a whole.
For the echinoderms the northern boundaries of the Cookian Province appear to lie at East Cape and Cape Egmont. The southern page 12 boundaries are rather indefinite (Fig. 1), as the shelf echinoderms of certain important areas of the South Island are not very well known. Garner (1959) recognised an area of mixed waters which extended between Cape Egmont and Fiordland. It is possible that northern Fiordland may form a southern boundary to the west. To the east the boundary appears to fall a little to the north of Dunedin. From this province, 85 shelf echinoderms are known. Of these 16 (19%) are of restricted distribution and 3 (3%) are magellanic. This is the northernmost area in which occur shallow-water New Zealand species which are also found in the Magellanic region. All of the three species concerned are often found in the holdfasts of seaweeds (e.g. Carpophyllum, Macrocystis). The west wind drift (Fig. 1) has a direct effect on the coastal current patterns in this area (Knox. 1960) and the occurrence of Magellanic elements in the Cookian Province is not so very surprising.
The Chatham Islands comprise the Moriorian Province in Finlay's (1925) scheme. These islands lie within the subantarctic mixed water zone and sit astride the subtropical convergence (Knox, 1960). For many other plant and animal groups the distinctiveness of this province lies in the mixed nature of its fauna, which usually contains northern and southern mainland forms, together with elements from the Antipodean Province and a number of forms with restricted distribution patterns.
Figure 1 : New Zealand and outlying islands, showing marine provinces as suggested by the echinoderms. The Aupourian Province includes the northern part the North Island from East Cape and Cape Egmont, and Three Kings Islends. The indefinite southern boundary of the Cookian Province is indicated by a broken line. The Chatham Islands are regarded as members of the Cookian Province. The Antipodean Province includes the Auckland, Campbell, Bounty and Antipoae, Islands, to depths of 100 fathoms. Abbreviations : A, West Auckland Curren; B, East Auckland Current; C, East Cape Current; D, Westland Current; E, Canterbury Current.
The Forsterian Province is subject to the direct influence of the cold subantarctic waters of the west-wind-drift at certain times of the year and at others to the warmer mixed waters of the Southland Current. This province has some subantarctic affinities in its echinoderm fauna, and appears to form a transitional zone between the subantarctic cold temperate and the cold temperate mixed waters.
Echinoderms suggest that the Forsterian Province includes the southern portion of the South Island from Fiordland in the west and Dunedin in the east. Stewart Island and the Snares Islands. Fell (1953) gave reasons for regarding the Snares as part of the Forsterian Province, and Powell (1955, 1961) has confirmed this conclusion on the basis of Molluse. Of the four genera of echinoderms known to have species in the Snares, two are represented on the New Zealand mainland by identical species (Asterodon dilatatus and Stichaster australis) while the other two (Allostichaster insignis and Calvasterias suteri) occur both in the Antipodean Province and on the New Zealand mainland shelf. All Snares echinoderms which are shared with the other outlying islands are also shared with the New Zealand mainland. Thus, for the echinoderms the northern boundary of the Antipodean Province would fall south of the Snares (Fell, 1953). Support for this view is given by Knox (1961, personal communication), who reports Evechinus chloroticus from the Snares. It is interesting to note that the Snares lie on the shallow water plateau which extends southwards beyond Stewart Island. The 100-fathom line (Fig. 1) might suffice as the southern houndary for the Forsterian Province.
In general, the echinoderm fauna of the Forsterian Province resembles the Cookian fauna. Over 60 shelf echinoderms are known from this province. Of these, 6 (10%) are at this time regarded as typical Forsterian species. Subantarctic elements in the province include Trachythyone amokurae and Ocnus brevidentis.
The echinoderms of Fiordland include some forms which have distinct Australian-Indo-Pacific affinities. The presence of these forms in this part of the New Zealand region may be due to the influence of the East Australian Current, but as yet we have insufficient data. There are also northern New Zealand shallow-water species present in Fiordland, separated by a gap of about page 15 700 miles from their other known localities (Fell, 1952). These include Peronella binemoae and Amphiura alba. Another species. Amphiura hinemoae was formerly regarded as having a similar distribution pattern, but it was recently found to be an inhabitant of the abyssal zone, and thus, being a eurythermal species, its pattern of distribution is readily explained. It is possible that Amphiura alba and Peronella hinemoae may also be eurythermal species.
The Antipodean Province (formerly termed Rossian) is taken to comprise the Auckland Islands. Campbell Islands, Bounty Islands and Antipodes Islands. Macquarie Island does not stand on the New Zealand submarine plateau, and its shallow-water echinoderm tauna is strikingly different from that of the Antipodean Province island. The only New Zealand echinoderm in its fauna is Pseudechinus novae-zealandiae, which has a pelagic larva. Its presence in Macquarie Island is thus readily explained. Macquarie Island is therefore to be regarded as a member of the Kerguelenian (i.e. Subantarctic) Province.
The islands Auckland. Campbell, Bounty and Antipodes lie in a direct line with the west-wind-drift (Fig. 1), and it is to be expected that a certain percentage of their echinoderm fauna comprises circum-polar species. However, Mortensen (1925) clearly demonstrated that the bulk of the echinoderm fauna of the Auckland and Campbell Islands is of New Zealand derivation, not subantarctic, and Fell (1953) gave similar data for the Antipodes and Bounty Islands. An analysis of the known echinoderms of the Antipodean Province serves to demonstrate these relationships. Of the 27 known shelf species. 6 (22%) are restricted; 18 (66%) are common to the Antipodean Province and the New Zealand mainland, but are endemic to the New Zealand region as a whole; 2 (possibly 3) are circum-polar (8%), and 1 (4%) is cosmopolitan. There are no Australian-Indo-Pacific elements in the fauna as we know it today.
On the basis of the Asteroidea, Ophiuroidea and Echinoidea, Fell (1953) inferred that the echinoderm fauna of the Antipodean Province islands may have been derived from two sources, namely:
The greater part of the fauna has been derived from an assemblage of species which has been the common heritage of all parts of the New Zealand submarine plateau. This conclusion is based on the number of species which are common to the mainland and the islands of the Antipodean Province.
A small percentage of the fauna has possibly been derived from some originally southern species which have achieved a circumpolar distribution on account of their epiplanktonic habit (on brown seaweed), influenced by the west-wind-drift. In this way they could spread to other southern areas, such as Patagonia, Macquarie Island and Kerguelen Island, and subsequently page 16 speciate there. Examples cited by Fell were Amphiura magellanica, Calvasterias spp. and Pseudechinus spp. Similar conclusions may be drawn from the Holothuroidea (Pawson, 1961). It is interesting to note that the holothurian species Stereoderma leoninoides and Ocnus brevidentis, like the other echinoderms cited above, are known to inhabit the holdfasts of seaweeds in the eulittoral zone. The seaweed would form an excellent raft for dispersal, and the west-wind-drift the dispersal mechanism. Mortensen (1925) recorded two living specimens of Stereoderma leoninoides on a piece of floating Lessonia, one mile to the east of the Auckland Islands. This second source of contributions to the Antipodean Province fauna is of no great significance when the fauna as a whole is considered.
The term ‘Subantarctic Islands’ has been used by New Zealand writers to include the islands of the Antipodean Province, as well as Macquarie Island, Heard, Kerguelen, and many others. But whereas there is obviously a very close echinoderm faunal relationship between New Zealand and the Antipodean Province islands, the echinoderm faunas of the other islands mentioned are of a very different character, comprising mainly circum-polar species, together with some Antarctic genera. The echinoderm fauna of Auckland, Campbell, Antipodes and Bounty Islands is almost entirely New Zealand in character and is extremely dissimilar to that of the other islands under discussion. The two groups of islands are sharply distinguishable, the former belonging to the New Zealand faunal region, the latter belonging to the subantarctic proper. Therefore, so far as the echinoderms are concerned, it is most misleading to use the term ‘Subantarctic Islands of New Zealand’ to cover Auckland, Campbell, Antipodes and Bounty Islands.
Archibenthal and Abyssal Echinoderms
A total of ninety-nine archibenthal and abyssal echinoderm species are known from the New Zealand region. Fell (1958) regards the archibenthal fauna as a mingling of local and cosmopolitan elements, shelf forms occasionally descending the continental slopes either by accident or design (e.g. Astropecten primigenius, Pentagonaster pulchellus, Heterothyone alba, Amphyicyclus thomsoni), and abyssal forms occasionally reaching the shelf. The relatively steep marine profiles facilitate the mingling of deep-water and shallow-water echinoderms, and a number of individual species tend to have a wide bathymetric range. For example, Paracaudina chilensis is common in Cook Strait in depths ranging between forty fathoms and 600 fathoms. This species is probably abyssal, and is also known from off Patagonia, Japan, Australia, California and Florida, probably achieving its distribution by spreading across abyssal bottom water.
The 69 known archibenthal species comprise 45 endemic forms (66%); 16 (22%) Australian-Indo-Pacific forms: 7 (10%) page 17 cosmopolitan species, and 1 (2%) magellanic species. The presence of 22% Australian species points to the Australian region as a source for many of our archibenthal elements. Such species as Araeosoma thetidis, Paramaretia multituberculata, Zoroaster macracantha, Cosmasterias dyscrita and Amphicyclus thomsoni are known from New Zealand and the deeper waters off Australia. More sampling is needed in some critical areas before it can be decided whether the archibenthal echinoderms fit any horizontal distribution pattern. The same is true for the abyssal echinoderms
In conclusion it may be stated that we are continually reminded of our incomplete knowledge of the New Zealand echinoderm fauna. There are many discoveries to be made, and with these discoveries the apparent distribution patterns which have emerged over recent years will no doubt be modified. Nevertheless, it seems unlikely that there will be any drastic change in our present conception of the fauna.
Acknowledgement: I would like to thank Professor Fell of this Department for his instructive criticism throughout the preparation of this paper, and Professor Richardson for his many useful suggestions.
Benham, W. B., 1910. Stellerids and Echinids from the Kermadec Islands. Trans. Roy. Soc. N.Z., 43, pp. 140-63.
Brodie, J. W., 1960. Coastal Surface Currents Around New Zealand. N.Z.J. Geol. Geophys., 3 (2), pp. 235-52.
Deacon, G. E. R., 1937. Hydrology of the Southern Ocean. Disc. Rep. 15, pp. 1-123.
Fell, H. B., 1947. A Giant Heart-Urchin. Rec. Auck. Inst. Mus. 3(3), pp. 145-50.
—— 1949a. The Constitution and Relations of the New Zealand Echinoderm Fauna. Trans. Roy. Soc. N.Z., 77 (5), pp. 208-12.
—— 1949b. The Occurrence of Australian Echinoids in New Zealand Waters. Rec. Auck. Inst. Mus., 3 (6), pp. 343-6.
—— 1952. Echinoderms from Southern New Zealand. Zool. Pubns. Vict. Univ. Coll., 18.
—— 1953. Echinoderms from the Subantarctic Islands of New Zealand: Asteroidea, Ophiuroidea, and Echinoidea. Rec. Dom. Mus. Wellington, 2 (2), pp. 73-111.
—— 1958. Deep-Sea Echinoderms of New Zealand. Zool. Pubns. Vict. Univ. Wellington, 24.
—— 1960. Archibenthal and Littoral Echinoderms of the Chatham Islands. Bull. Dep. Sci. Indus. Res., N.Z., 139 (2), pp. 55-75.
Finlay, H. J., 1925. Some Modern Conceptions Applied to the Study of the Cainozoic Mollusca of New Zealand. Verbeek Mem. Birthday Vol., pp. 161-72.page 18
Fleming. C. A., 1944. Molluscan Evidence of Pliocene Climatic Change in New Zealand. Trans. Roy. Soc. N.Z., 74 (3), pp. 207-20.
Garner, D. M., 1959. The Sub-Tropical Convergence in New Zealand Waters. N.Z. J. Geol. Geophys., 2, pp. 315-37.
Knox, G. A., 1960. Littoral Ecology and Biogeography of the Southern Oceans. Proc. Roy. Soc. (B), 152, pp. 577-624.
Mortensen, Th., 1925. Echinoderms of New Zealand and the Auckland-Campbell Islands. Part IV. Vidensk. Medd. Dansk. Naturh. Foren. Kbh., 79, pp. 322-86.
Pawson, D. L., 1961. Systematic Studies on the Holothuroidea of the New Zealand Region. Unpublished thesis in the library of Victoria University of Wellington.
Powell, A. W. B., 1937. New Species of Marine Mollusca from New Zealand. Disc. Rep. 15, pp. 153-222.
—— 1938. A Starfish of the Genus Asterodiscus New to New Zealand. Trans. Roy. Soc. N.Z., 67. pp. 78-9.
—— 1955. Mollusca of the Southern Islands of New Zealand. Bull. Dep. Sci. Indus. Res., N.Z., Cape Expedition Series, 15, pp. 1-137.
—— 1961. New Zealand Biotic Provinces. Tuatara 9(1) (this issue).