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Tuatara: Volume 15, Issue 2, July 1967

A Guide to the Littoral Balanomorph Barnacles of New Zealand

page 75

A Guide to the Littoral Balanomorph Barnacles of New Zealand


A Key is provided for the identification of the New Zealand intertidal balanomorph barnacles, utilizing the characters of the shell parts. Eleven species are recognized from the New Zealand region which is taken to extend from the North Island to the Campbell Islands. The records of distribution of the species are summarized. Balanus tintinnabulum tintinnabulum and Balanus campbelli are recorded for the first time from the New Zealand mainland.


The suborder Balanomorpha of the subclass Cirripedia includes all those barnacles commonly known as acorn barnacles which are found attached to hard surfaces immersed in the sea, including the bottoms of ships and other man-made installations. Acorn barnacles are particularly successful on the intertidal rocky shores of temperate latitudes where a few species are among the most ecologically important organisms. On New Zealand shores the suborder is represented by eleven species from four genera, although it is possible that this list is still incomplete. Barnacles are usually regarded as difficult to identify, and this is especially so if too much reliance is put on the external appearance of eroded and encrusted adult shells. In the New Zealand species the characters of the hard shell parts are sufficient to provide the basis of a key for the identification of the balanomorph barnacles. References are given to fuller descriptions of shell and body characters as examination of the appendages is often necessary to confirm identification. The four most common species, Elminius modestus, E. plicatus, Chamaesipho columna and C. brunnea, have been described in detail by Moore (1944), but other descriptions are scattered throughout monographs and expedition reports, e.g. Darwin (1854), Filhol (1885) and Broch (1922).

The shell of the adult acorn barnacle consists of a ring of parietal plates the particular arrangement of which is characteristic of the genera (Fig. la). Each parietal plate consists of a central thickly-constructed triangular part, the paries (plural parities) which is winged on either side (Fig. lb). The wings either overlap or are overlapped by those of the adjacent plates and are termed the alae or page 76
Fig. 1: The arrangement and structure of the shell plates of operculate barnacles. la: The arrangement of the parietal plates in different genera — the names of the plates after Darwin, and as follows: c — carina; c.l.—carinal latera; l — latera; r — rostrum; r.l. — rostral latera; s — scutum; t—tergum. 1b: To show the winged structure of a parietal plate. 1c: Internal structure of a scutum. 1d: Internal structure of a tergum.

Fig. 1: The arrangement and structure of the shell plates of operculate barnacles.
la: The arrangement of the parietal plates in different genera — the names of the plates after Darwin, and as follows: c — carina; c.l.—carinal latera; l — latera; r — rostrum; r.l. — rostral latera; s — scutum; t—tergum.
1b: To show the winged structure of a parietal plate.
1c: Internal structure of a scutum.
1d: Internal structure of a tergum.

radii respectively. The plates and the calcareous base can be thought of as constructed on the plan of a double lamina which forms the outer and inner surfaces of the shell. The space between the surfaces may be intersected by numerous septa to give porous plates, or filled entirely with shell to give solid plates. The alae are never porous, but all, any or none of the parieties, radii and base may be permeated by pores which run in the direction of growth. The four opercular plates are arranged on either side of the rostral-carinal axis in the orifice of the shell. The two scuta are placed towards the rostrum and articulate with the terga, which are placed towards the carina. The names of the parts of the opercular plates are shown in Figs. 1c and 1d. When the opercular plates are relaxed the membranes lining the aperture between the plates, through which the cirri are protruded, can be seen. These opercular membranes are often brightly coloured in the living specimen, and the pattern of colouration is constant and species characteristic and therefore provides a useful character for identification, (see Southward and Crisp, 1963).
page 77

Barnacles are one of the main fouling organisms of ships and industrial installations in the sea, and at least three of the intertidal species mentioned in this paper (Balanus amphitrite, Balanus trigonus and Elminius modestus) are frequent fouling species on boats in the north of New Zealand. Much of the study on the biology of barnacles today is directed towards a fuller understanding of the requisites of the various stages of the life-cycle of both fouling and non-fouling species, which will enable more effective research on antifouling methods as well as contributing towards more academic biological knowledge. The identification of what species are present in any area is a necesary first step before further studies of a physiological or an ecological nature are undertaken.


1. Rostrum with radii only; shell composed of 4 or 6 parietal plates in the adult. Family Balanidae — 2
1. Rostrum with alae only; parietal plates fused into a ring in the adult. Family Chthamalidae, Genus Chamaesipho 11
2. Shell with 6 parietal plates. Genus Balanus — 3
2. Shell with 4 parietal plates. — 9
3. Radii of parietal plates permeated by pores. Subgenus Megabalanus — 4
3. Radii of parietal plates not permeated by pores. — 6
4. Parieties and radii dark purple and with strong ribs. The radii have distinct striations parallel to the base of the shell. Scutum with a broad and reflected articular ridge. The base of the tergum forms a straight line on both sides of the spur, which is placed at least its own width from the basi-scutal angle. Opercular membranes deep red with a blue or purple spot on either side. Balanus tintinnabulum (Fig. 2)
4. Parieties and radii white or pink; the parieties may or may not be ribbed. Radii are smooth externally. Scutum with a small articular ridge. The base of the tergum slopes on both sides towards a truncate spur placed half its own width from the basi-scutal angle. Opercular membranes not predominantly red. — 5
5. Parieties and radii white; parieties with prominent radiating ribs. Opercular membrances yellow with a red internal lining, and with blue towards the rostral angle. Balanus campbelli (Fig. 4)
5. Parieties and radii rose pink, and not longitudinally ribbed, Opercular membranes pale pink. Balanus decorus (Fig. 3)
6. Parieties permeated by pores. Subgenus Balanus — 7
page 78

page 79
Figs. 2-13: Diagrams of internal aspects of the opercular plates of 2: Balanus tintinnabulum tintinnabulum 3: Balanus decorus 4: Balanus campbelli 5: Balanus vestitus 6: Balanus trigonus 7: Balanus amphitrite variegatus 8: Balanus amphitrite amphitrite 9: Tetraclita purpurascens 10: Elminius plicatus 11: Elminius modestus 12: Chamaesipho brunnea 13: Chamaesipho columna a — scutum; b — tergum; 6c — external aspects of scutum of Balanus trigonus to show rows of pits.

Figs. 2-13: Diagrams of internal aspects of the opercular plates of
2: Balanus tintinnabulum tintinnabulum
3: Balanus decorus
4: Balanus campbelli
5: Balanus vestitus
6: Balanus trigonus
7: Balanus amphitrite variegatus
8: Balanus amphitrite amphitrite
9: Tetraclita purpurascens
10: Elminius plicatus
11: Elminius modestus
12: Chamaesipho brunnea
13: Chamaesipho columna
a — scutum; b — tergum; 6c — external aspects of scutum of Balanus trigonus to show rows of pits.

page 80
6. Parieties not permeated by pores. Subgenus Austrobalanus Shell pink but covered with a yellow epidermis. Very small orifice, and radii lacking. Parietal plates may be smooth, or slightly or strongly ribbed longitudinally. Scutum with prominent adductor ridge curved towards the rostral angle, and with well developed crests for the lateral depressor muscle. Terga with wide truncated spur placed at the basiscutal angle. Balanus vestitus (Fig. 5)
7. Parieties and radii pink with prominent white external ribs. Orifice generally triangular with the apex towards the carina, and not sharply toothed. Scutum externally with 1 to 5 longitudinal rows of little pits, sometimes none, and internally with a narrow adductor ridge. Terga with a broad truncated spur situated near the basi-scutal angle. Balanus trigonus (Fig. 6)
7. Parieties and radii variable in colour, but smooth externally. Orifice broad and rhomboidal and sharply toothed. Scutum without pits and with a prominent broad adductor ridge. Tergum with a variable shaped spur situated away from the basi-scutal angle. — 8
8. Parieties with narrow, approximate purple stripes, transversely freckled with white. Radii white. Spur of tergum long, narrow and pointed, with the basal margin of the tergum hollowed out on both sides of the spur leaving the crests for the depressor muscles depending below the margin. Shell conical to tubular. Balanus amphitrite variegatus (Fig. 7)
8. Parieties whitish grey with longitudinal purple or violet stripes. Radii white, but flecked with red-brown patches. Spur of tergum comparatively short, broad and truncated; the basal margin of the tergum not hollowed out. Shell a flattened cone. Balanus amphitrite amphitrite (Fig. 8)
9. Parieties permeated by pores. Genus Tetraclita. Shell very depressed; parietal plates permeated by numerous rows of pores. Base membranous. Scutum transversely elongated; tergum with an extremely short and rounded spur. Tetraclita purpurascens (Fig. 9)
9. Parieties not permeated by pores. Genus Elminius — 10
10. Parieties closely plicate internally at base; shell conical to tubular, and often yellow. Tergum with the spur separate from the basi-scutal angle, short and rounded. Basal margin of the tergum not hollowed out. Scutum with adductor ridge and with crests for the rostral depressor muscle. Elminius plicatus (Fig. 10)
10. Parieties smooth internally at base. Shell conical and white. Tergum with spur confluent with the basi-scutal page 81 angle and almost tubular. Basal margin of tergum hollowed out. Scutum without an adductor ridge or crest for the rostral depressor muscle. Elminius modestus (Fig 11)
11. Adult shell conical or depressed and laminate on corrosion. Scutum without an adductor ridge. Body brown. Chamaesipho brunnea (Fig. 12)
11. Adult shell varying from low-conical to columnar, pitted on corrosion. Scutum with an adductor ridge. Body navy-blue Chamaesipho columna (Fig 13)

The ecological and geographical distributions of the species

Balanus tintinnabulum (Linnaeus) Fig. 2

Darwin, 1854. pp. 194-204; pl. 1, figs. a-l; pl. pl. 2, figs, la-lo.

Pilsbry, 1916. pp. 54-72; with figs.

Eighteen subspecies of this variable species are listed by Darwin and Pilsbry. The species is freely carried about on the bottoms of ships, resulting in widespread dispersion and misleading published records of distribution. B. tintinnabulum concinnus was collected from the hull of the ‘Terra Nova’ in the Lyttleton Harbour by Jennings (1917), but this record should not be included in the New Zealand list (Balanus crenatus must be omitted for the same reason). B. tintinnabulum tintinnabulum (communis) is recorded from the Kermadec Islands by Linzey (1942a), and has been found at Goat Island at the entrance to the Hauraki Gulf. Specimens have been collected from Cape Karikari by Dr P. R. Bergquist of the University of Auckland. The species is found in North Auckland in low tidal situations of very exposed points of the coast that would be unlikely to dry out because of the constant surge and wave action. Individuals may attain a basal diameter of 65 mm., and such large specimens are usually heavily encrusted with coralline algae, other barnacles (Elminius plicatus and Tetraclita purpurascens), serpulids and vermetids. The similarity of the habitats of this subspecies on the mainland to those described by Cranwell and Moore (1938) for B. tintinnabulum concinnus on the Poor Knights Islands, suggests that we are dealing with the same subspecies.

Balanus decorus Darwin Fig. 3

Darwin, 1854. pp. 212-213; pl. 2, figs. 6a-6b.

Linzey, 1942b. pp. 1-5.

This is an endemic species to New Zealand where it is widely distributed (Linzey, 1942b), including the Kermadec Islands, the Chatham Islands and Auckland Islands (Jennings, 1917 and Linzey, 1942a). The species has also been collected from the Campbell Islands by P. M. Johns of Canterbury University. Balanus decorus is page 82 characteristically a sublittoral species where it may reach a basal diameter of 40 mm. and a height of 45 mm. B. decorus occurs intertidally, however, at low levels usually in habitats protected from desiccation, e.g. under ledges, in crevices or among mussels. The maximum measured basal diameter of an intertidal specimen was 20 mm, and it is suspected that predation and environment stresses limit the age of B. decorus in the intertidal environment.

Balanus campbelli Filhol Fig. 4

Filhol, 1885. pp. 487-488.

Broch, 1922. pp. 310-314; figs. 54,55.

Linzey, 1942b. pp. 3-5.

This species has been recorded in the literature from intertidal rocks of Campbell Island (Filhol, 1885; Gruvel, 1905; and Broch, 1922). Specimens collected from two feet below low water at Perseverance Harbour, Campbell Island by Mr. P. M. Johns agree with the description given by Filhol, although Filhol's specimens were smaller and were collected from intertidal rocks. Specimens collected from low tidal levels at Little Papanui, Otago Peninsula, have similar opercular and shell plates to the Campbell Island specimens of Johns, and agree with the description of Balanus campbelli given by Filhol. This is the first record of B. campbelli occuring outside Campbell Island. At Little Papanui this species occurs in similar habitats as does Balanus decorus, i.e. under low tidal ledges, amongst Durvillea holdfasts and on mussels — places that are unlikely to experience much desiccation.

The most noticeable feature of this species is the colouration of the opercular membranes as described in the key. It would be of interest to compare the colours of the Little Papanui specimens with those of live specimens from Campbell Island.

Balanus trigonus Darwin Fig. 6

Darwin, 1854. pp. 223-224; pl. 3, figs. 7a-7f.

Pilsbry, 1916. pp. 111; pl. 26, figs. 1-13e.

Balanus trigonus is widely distributed in the Pacific and Atlantic Oceans (Pilsbry, 1916), and has been recorded in New Zealand from Auckland (Jennings, 1917 and Skerman, 1959), Kawau Island (Broch, 1922) and occurs abundantly under low tidal stones at Leigh and Whangarei Heads. It could not be found in any likely habitats on the Otago Peninsula. The Balanus porcatus of Jennings (1917) has been synonymized with B. trigonus by Chilton (1920). It is very likely that the records of Balanus porcatus from Campbell Island (Filhol, 1885) and Stewart Island (Hutton, 1879) are wrong identifications, but whether these can be referred to B. trigonus is uncertain. Consequently there is some doubt as to the geographical range of B. trigonus in New Zealand. At Auckland, it occurs in low tidal habitats that are not subject to too much page 83 desiccation, and is abundant on sublittoral surfaces. It occurs on rock, wood, metal, rubber, mollusc shells and crayfish exoskeletons; and is one of the common forms found on the hulls of boats.

Balanus amphitrite Darwin Figs. 7 and 8

Darwin, 1854. pp. 240-246; pl. 5, figs. 2a-2o.

Pilsbury, 1916. pp. 89-99; figs. 18-24; pl. 19, 20, 24.

Harding, 1962. pp. 273-296; with illustrations.

New Zealand records for this mundane and highly variable species are relatively sparse. The nomenclature of the varieties contained in the Balanus amphitrite complex is still somewhat uncertain. Recent contributions on this matter have been made by Henry (1959) and Harding (1962). Filhol (1885) records the species from Cook Strait and Dunedin, Darwin (1854) gives New Zealand as the locality for the variety variegatus, and Hutton (1879) records this variety from Dunedin. B. amphitrite cirratus (which is hardly distinguishable from variegatus) is recorded as a fouling barnacle on boats at the port of Auckland by Skerman (1959, 1960). B. amphitrite variegatus has been collected off intertidal wooden stacks in the Mahurangi Estuary, where it occurs at low levels and is encaked with layers of mud. The subspecies amphitrite (communis) and variegatus have been collected from the hull of a pleasure boat that had not ventured outside the Hauraki Gulf.

Balanus vestitus Darwin Fig. 5

Darwin, 1854. pp. 286-288; pl. 8, fig. 3.

Gruvel, 1905. pp. 248-249; figs. 277-278.

Broch, 1922. pp. 322-333; fig. 61.

Balanus vestitus has been recorded from the Auckland Islands (Broch, 1922), Stewart Island (Hutton, 1879), Queen Charlotte Sound (Broch, 1922) and the Bay of Islands (Pilsbry, 1916). It has also been collected from Doubtless Bay, Whangarei Heads, Leigh and the Otago Peninsula. Specimens have been collected from the Auckland Islands by Professor G. A. Knox. In the North Auckland Peninsula, B. vestitus occurs intertidally under stones at low tide levels. The Doubtless Bay specimens were comparatively large (maximum basal diameter 14mm. and height 17mm.) and were washed up attached to mollusc shells. On the Otago Peninsula, B. vestitus was found on intertidal mussels (Perna) as well as on low tidal rock surfaces. B. vestitus is possibly a predominantly sublittoral species, and as with B. decorus and B. trigonus extends into the intertidal where environmental stresses are not too severe.

Tetraclita purpurascens (Wood) Fig. 9

Darwin, 1854. pp. 337-339; pl. 11, figs. 1a-1d.

Broch, 1922. pp. 337-339; fig. 71.

T. purpurascens is a widely distributed species in New Zealand, recorded from the Auckland Islands (Broch, 1922) and from the page 84 Kermadec Islands (Linzey, 1942a). The species occurs commonly under rocks and stones and in caves on the lower third of the shore, where it may be attached to the rock surface or to shells of molluscs and other barnacles (e.g. Balanus tintinnabulum and Pollicipes spinosus). It does not appear to occur far below low tide level. The questioned identification of Tetraclita porosa (squamosa) from the encrusting fauna of Balanus tintinnabulum on the Poor Knights Islands by Cranwell and Moore (1938), probably refers to a specimen of T. purpurascens.

Elminius plicatus (Gray) Fig. 10

Darwin, 1854. pp. 351-352; pl. 12, figs. 2a-2f.

Broch, 1922. pp. 341; fig. 74.

Moore, 1944. pp. 326-329; pl. 46, fig. C.

E. plicatus is common throughout the three main islands, and on the Chatham Islands (Moore, 1944). Professor G. A. Knox has collected this species from the Auckland, Snares and Chatham Islands. It appears to be absent from the Campbell Islands (P. M. Johns, pers comm.), and has not been recorded from the Kermadec Islands. E. plicatus is characteristically an intertidal barnacle, found on shores receiving some degree of wave exposure, and occurs from high neap tide to low neap tide levels. It reaches greatest abundance and individual size at about mean sea level in localities that receive some protection from direct wave action but which still offer considerable water turbulence.

Elminius modestus Darwin Fig 11

Darwin, 1854. pp. 350-351; pl. 12, figs, 1a-1e.

Broch, 1922. (As E. sinnuatus) pp. 342-344; fig. 76.

Moore, 1944. pp. 329-333; pl. 46, fig. D.

E. modestus is found throughout the North and South Islands, and also in Stewart and Chatham Islands (Moore, 1944). It has not been recorded or collected from the Kermadec Islands, or from the islands to the south of New Zealand. E. modestus is found abundantly on wave protected shores of harbours and estuaries, but is an infrequent barnacle on wave exposed coasts. It is fairly versatile in relation to tide level and nature of substrate, surviving well on sublittoral surfaces where it may be the main form on the bottom of ships.

Chamaesipho columna (Spengler) Fig. 13

Darwin, 1854. pp. 470-472; pl. 19, figs. 3a-3c.

Broch, 1922. pp. 308-309; fig. 53.

Moore, 1944. pp. 316-320; pl. 46, fig. A.

Pope, 1965. pp. 67-70; pl. 1, fig. 5.

There is some doubt that the C. columna of Australian and New Zealand coasts is the same as that described by Spengler reputedly page 85 from Otaheite (Tahiti). For discussions on this topic see Moore (1944, pp. 316-7) and Pope (1965, pp. 64-7). Chamaesipho columna (sensu Darwin and Moore) is found on the temperate shores of Australia and throughout the three main islands of New Zealand. One specimen has been recorded from the Kermadec Islands (Linzey, 1942a). The species is restricted to the intertidal zones of wave exposed shores, and also penetrates to a limited extent into harbours and estuaries.

Chamaesipho brunnea Moore Fig. 12

Moore, 1944. pp. 320-326; pl. 46, fig. B and pl. 47, fig. 1.

C. brunnea (sensu Moore) is restricted to New Zealand and ranges from throughout the North Island to Banks Peninsula and Cape Foulwind on the east and west of the South Island respectively. The species is restricted to wave exposed shores, where it is always the highest barnacle. It reaches its greatest density and abundance on very exposed shores in the north of the North Island, where the upper limit of the intertidal distribution may be several metres above high tide level.


A travelling grant from the Hutton Memorial Fund of the Royal Society of New Zealand enabled travel to the University of Canterbury, The Canterbury Museum and the Portobello Marine Station. The following people are thanked for help in discussion, reading of manuscripts and for placing collections at my disposal: Dr P. R. Bergquist, Dr E. J. Batham, Prof. G. A. Knox, Mr P. M. Johns and Dr P. A. Luckens.


Broch, H., 1922. Studies on Pacific Cirripedes. Th. Mortensen's Pacific Expedition, 1914-1916. Vidensk Medd. fra Dansk Naturh. Foren., 73; 215-358.

Chilton, C., 1920. Note on two northern cirripedes recorded from New Zealand. N.Z. J. Sci. & Tech., 3; 53.

Cranwell, L. M. and Moore, L. B., 1938. Intertidal communities of the Poor Knights Islands, New Zealand. Trans. Roy. Soc. N.Z., 67; 375-407.

Darwin, C., 1854. A monograph of the sub-class Cirripedia; the Balanidae, Verrucidae, etc. Ray Society, Lond.

Filhol, H., 1885. Mission de I'lle Campbell. Recueil de Memoires, Passage Venus, iii; 349-510.

Gruvel, A., 1905. Monographie des Cirrhipedes. Paris.

Harding, J. P., 1962. Darwin's type specimens of varieties of Balanus amphitrite. Bull. Brit. Mus. (Nat. Hist.), Zool., 9; 273-296.

Henry, D. P., 1959. The distribution of the amphitrite series of Balanus in North American waters. In ‘Marine Boring and Fouling Organisms’. Ed D. L. Ray. Friday Harbour Symposium, Seattle. pp. 212-225.

Hutton, F. W., 1879. List of New Zealand Cirripedia in the Otago Museum, Trans. N.Z. Inst., 11; 328-330.

page 86

Jennings, L. S., 1917. Revision of the Cirripedia of New Zealand. Trans. Roy. Soc. N.Z., 1; 56-63.

Linzey, J. T., 1942a. The balanomorph barnacles of the Kermadec Islands. Trans Roy. Soc. N.Z., 71; 279-281.

Linzey, J. T., 1942b. The body appendages of Balanus decorus. Trans. Roy. Soc. N.Z., 72; 1-5.

Moore, L. B., 1944. Some intertidal sessile barnacles from New Zealand. Trans. Roy. Soc. N.Z., 73; 315-334.

Pilsbry, M. A., 1916. Sessile barnacles (Cirripedia) contained in the collections of the U.S. National Museum, including a monograph of the American species. U.S. Nat. Museum Bull., 93.

Pope, E. C., 1965. A review of Australian and some Indo-Malayan Chthamalidae (Crustacea: Cirripedia). Proc. Linn. Soc. N.S.W., 90; 10-77.

Skerman, T. M., 1959. Marine fouling at the port of Auckland. N.Z. J. Sci., 2; 57.

Skerman, T. M., 1960. Ship fouling in New Zealand waters: a survey of marine fouling organisms from vessels of the coastal and overseas trades. N.Z. J. Sci., 3; 620.

Southward A. J. and Crisp D. J., 1963. Barnacles of European waters. Catalogue of main marine fouling organisms. I Barnacles. 46pp. Organization for economic co-operation and development.