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Tuatara: Volume 2, Issue 3, September 1949

New Zealand Littoral Ophiuroids

page 121

New Zealand Littoral Ophiuroids

Approximately 180 species of echinoderms are now known from New Zealand, of which 71 belong to the Class Ophiuroidea, or brittle-stars. These are among the most numerous of all the bottom-dwelling animals of the seas. Most are scavengers, and as such play an important part in the bionomics of the ocean. Near the outlet of the fish-oil factory at Island Bay and where the local fishermen deposit offal, the number of individual ophiuroids must run into many thousands, even within the limits of “Fisherman's Creek” alone. Some 41 species are known to inhabit the littoral zone around New Zealand; the others occurring in deep water are not included in the following key. Colour notes are still required for some species, and in this field local students could do useful work. Some of the colour details given here have not previously been published. The relatively high proportion of species of Amphiuridae is a characteristic of the New Zealand fauna, not paralleled elsewhere.

No glossary is given for the technical terms which have had to be used in the key. The meaning of specialized terms should be sufficiently clear from the diagrams which follow. Before attempting identification, allow specimens to dry out, as this renders the skeletal plates easier to see. When counting oral papillae, include any infradental papillae in the total.

1. Disc and arms covered only by skin, not by calcareous plates. 2
Disc and arms ensheathed by regularly arranged calcareous plates. 11
2. Upper surface of disc prominently ridged by 5 or 10 radially placed bars (the “radial shields”, Figs. 1A, 1B). 5
Upper surface of disc quite smooth. Family OPHIOMYXIDAE 3
Teeth and oral papillae serrated along the free margins (Fig. 2). Genus Ophiomyxa 4
Teeth and oral papillae smooth. Ophioscolex prolifer.
4. Oral papillae set around the margin of the oral plate in each jaw (Fig. 2). Viviparous. Purple-brown with irregular darker blotches on the disc and arms. At low-tide level down to 25 fathoms. Common throughout New Zealand. Ophiomyxa brevirima
Oral papillae overlying and obscuring the oral plates, grey. Down to 22 fathoms. Ophiomyxa duskiensis
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5. Arms ringed at intervals by double rows of small hooklets, Fig. 3B. Family GORGONOCEPHALIDAE 6
Arms not so ringed Family TRICHASTERIDAE 9
Arms branching dichotomously, as many as 11 times, the distal branchlets coiling spirally. Creamy white, the disc pink below owing to the gonads showing through the translucent skin. 25-100 fathoms. Fig. 3. Gorgonocephalus chilensis
Arms unbranched, but usually coiling spirally. 7
7. Colour lemon yellow (fading in dried or preserved examples to uniform cream) Genus Astrotoma 8
Ground colour white, the disc mottled with brown patches, and the arms with a series of transverse brown rings. 70 fathoms. Fig. 4 Astroporpa wilsoni
8. As many as 10 armspines occur on either side of every arm-segment. 25-50 fathoms. Fig. 5. Astrotoma waitei
Not more than 2-3 armspines. Littoral occurrence not certain. Rare Astrotoma benhami
Skin bearing small granules. Genus Astroschema, with two deep-water species, the littoral occurrence of which is uncertain.
Skin smooth. 10
10. Uniformly purple-brown, arms very long, 20 to 25 times the disc-diameter. 4-300 fathoms. Fig. 6. Known from southern fiords. Astrobrachion constrictum
Arms banded with transverse white and red-brown rings, the disc brown with white radial shields. 60-70 fathoms. Astroceras elegans
11. Armspines like small scales, tightly adpressed to the sides of the arms (Fig. 7). 12
Armspines long, not scale-like, projecting from the sides of the arm. 16
12. Disc plates of the upper surface covered over by numerous granules. Family OPHIODERMATIDAE 13
Disc plates exposed. Family OPHIOLEPIDIDAE 15
Armspines 9-10. Animal red-brown. Arms up to 12 inches in length. Oviparous. Low-tide level to 15 fathoms. Fig. 7. Pectinura maculata
Armspines 6-8. Animal grey or black, with white transverse bands on the arms. Viviparous. Arms not more than 1 ½ inches in length. 14
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14. Upper arm plates twice as broad as long. Low-tide level to 65 fathoms, usually under stones or hiding in crevices. Pectinura cylindrica
Upper arm plates as broad as long. Low-tide level to 15 fathoms. Under stones or in crevices. Pectinuara gracilis.
(Note—12 genera are known from New Zealand waters, but only the following three species are likely to be met with in the littoral region; all may be distinguished by their colour patterns, which survive preservation or drying.) Yellowish-white, the radial shields purple-brown and every alternate arm segment purple-brown. North Island, Cook Str., low-water to 65 fathoms, arm up to 1 ½ inches. Ophiozonoida picta
Cream. The upper arm plates in each arm segment subdivided into many smaller platelets. Low-water. Rare. Ophioceres huttoni
White, the radial shields light grey-brown. Known only from Cook Str., 45 fathoms Ophiozonella megaloplax
16. A vertical clump of dental papillae at the tip of each jaw (Fig. 8). 17
No clump of dental papillae. 20
17. A row of close-set oral papillae around the free margin of each jaw (Fig. 8) Family OPHIOCOMIDAE 18
No oral papillae Family OPHIOTRICHIDAE 19
Uppermost armspine of each cluster of armspines bears at its base some supplementary scale-like spines (Fig. 9). Eulittoral, rare. Cook Str. Ophiopteris antipodum
Armspines without supplementary spines, slender, longer than the arm segments. North Island, Cook Str., 5-120 fathoms (Fig. 10.) Ophiocoma bollonsi
Disc bearing spines, the armspines slender, thorny (Fig. 11), much longer than the arm segments. Genus Ophiothrix
Pink, 10 armspines to each cluster. North Island, rare. Fig. 11. Ophiothrix aristulata
Violet, 8 armspines to each cluster. North Island, low-tide to 65 fathoms. Ophiothrix oliveri
20. Arms widest at a point some distance out from the disc, then tapering towards the tip Family OPHIOCHITONIDAE 21
Arms tapering regularly from the disc towards the tip, mainly small species. Family AMPHIURIDAE 23
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Upper arm plates each with a supplementary arm plate on either side (Fig. 12). Genus Ophionereis 22
Upper arm plates without supplementary plates, 3 armspines to each cluster. Genus Ophiochiton, of which one species is known from deep water, but littoral occurrence is uncertain.
22. Upper arm plates twice as broad as long. Grey, mottled with white and black patches. Arms up to 5 inches in length. Common at low-tide level under stones. Fig. 12 Ophionereis fasciata
Upper arm plates as broad as long. White, with brownish bands on the arms. Cook Str., 50 fathoms, rare. Ophionereis novaezelandiae
Paired infradental papillae (Fig. 13) 26
No infradental papillae (Fig. 14). Genus Ophiactis 24
24. Five arms. Olive above, marked with green. Low-tide to 120 fathoms. Arms up to 5 cms. long Ophiactis resiliens
Six or seven arms. 25
25. Spines on the disc. Grey mottled with pale brown. Arms less than 25 mm. long. 50 fathoms plus. Ophiactis hirta
No spines on disc. North Island. 50 fathoms plus. Arms less than 25 mm. long. Ophiactis profundi
26. Oral papillae arranged in a continuous series along each side of the jaw (Fig. 13). 27
Oral papillae separated into distal and proximal groups with a vacant intermediate area on either side of the jaw (Fig. 16). 29
27. Disc almost naked of scales. Rare and incompletely known. Stewart Is., 5-7 fathoms. Ophionephthys stewartensis
Disc bearing scales 28
28. 3 oral papillae on either side of the jaw, the outermost one very broad (Fig. 15). Common in rock pools, in coralline sea-weeds, or in sand. Grey, the arms less than two-thirds of an inch long. Amphipholis squamata
5 oral papillae on either side of jaw, the outermost not broadened. Pale grey, the arms less than half an inch long. Auckland and Campbell Islands, at low-tide level. Amphioplus basilicus
29. Tentacle scales occur at the bases of the tube feet. (Fig. 17). Mostly small forms, abundant in coralline seaweed at low-tide level. Genus Amphiura 30
No tentacle scales. Small spinules on the disc. Pale grey. 35-50 fathoms, rare. Ophiocentrus novae-zealandiae
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30. Genus Amphiura.
(The species of this genus are rather difficult to key out, and in most cases the identification should be regarded as provisional until confirmed against a full description. The following is an attempt to simplify the littoral species. Three further deep-water forms are not included, and another littoral form is awaiting publication, making sixteen species altogether. In all cases where the number of armspines is given, they should be counted on the basal arm-segments—those normally present even in a damaged specimen).
Three armspines on each lateral plate. Oral side of disc without scales. Arms up to 25 mm. length, the disc 6-8 mm. across. Whitish, eulittoral (Fig. 18). A. hinemoae
Four armspines 31
Five armspines 33
Six or seven armspines. 34
31. Oral side of disc lacking scales. Spines as in Fig. 19. Arms exceeding 50 mm. length, disc 10 mm. across. Disc greenish grey, arms white (in alcohol), colour in life unknown. Apparently eulittoral, perhaps rare A. norae
Oral side of disc completely scaled. 32
32. Viviparous, hermaphrodite. White, with a brownish ring around the mouth. Arms 10 mm. length, disc 3 mm. across. At low-tide level. A. annulifera
Oviparous, sexes separate. Auckland-Campbell Islands, low-tide level to 20 fathoms. Arms 20 mm. length, disc 4 mm. across. A. praefecta
33. Radial shields separated by only a single row of scales. Red or purplish, fading to white at the arm-tips. Arms 70 mm. length, disc 2 mm. across. Eulittoral. A. rosea
Radial shields short, divergent, separated by two or three rows of scales. Size and colour not yet reported from New Zealand specimens. A. eugeniae
34. Lowermost spine very long and curved downwards (Fig. 20). 35
Not so. 36
35. Viviparous, hermaphrodite. Arms cream, disc grey above, cream below. Arms 25 mm. length, disc 6 mm. across Low-tide level to 50 fathoms. A. magellanica
Oviparous, sexes separate. Colour very variable—sometimes orange above and cream below, or disc brown with blackish radial shields and the arms fawn with black bands at irregular intervals, or the dsic fawn, spotted with grey
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and grown, the arms fawn banded with grey. 30-65 fathoms. A spinipes
36. Spines flattened (Fig. 21). Greyish, arms 35 mm. length, disc 5 mm. across. Campbell Is., low-tide level. A. amokurae
Not so. 37
37. White. Lowermost spines longest (Fig. 22). Arms 20 mm. length, disc 4 mm. across. Eulittoral. A. alba
Yellowish, speckled with grey or brown. 38
38. Large, arms 140 mm. length, disc. 10 mm. across. Littoral. A. aster
Small, arms 12 mm. length, disc 3 mm. across. Littoral. A. pusilla
Principal references—Trans. Roy. Society N.Z., Discovery Rpts., and Mortensen, Vid. Medd. Dansk naturh. For., 77, p. 91 et seq. (1924).

Explanation of Plates

Plate 1

(The figures are not drawn to scale—where size is of diagnostic significance, the dimensions are given in the key.)

  • Fig. 1. Discs of ophiuroids showing, in 1A (Astrotoma waitei) the ridges produced by the ten underlying radial shields; and in 1B (Astrobrachion constrictum) the radial shields themselves show in the dried specimen.
  • Fig. 2 Ophiomyxa brevirima, jaw.
  • Fig. 3 Gorgonocephalus chilensis, part of disc and part of one arm (A); and portion of arm enlarged to show double rows of hooklets (B).
  • Fig. 4 Astroporpa wilsoni.
  • Fig. 5. Astrotoma waitei.
  • Fig. 6. Astrobrachion constrictum, with arms coiled about an antipatharian coral.
  • Fig. 7. Underside of arm of Pectinura maculata, showing scale-like armspines on lateral plates.

Abbreviations: AD. adoral plate; O.P. oral papilla; OR. oral plate; O.S. oral shield; R.S. radial shield.

page 127

Several images of New Zealand Littoral Ophiuroids.

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Plate 2

  • Fig. 8. Diagram of ophiuroid jaw, seen obliquely from below; lettering explained under heading “Abbreviations” below.
  • Fig. 9. Ophiopteris antipodum, arm-segments seen from above, showing scale-like supplementary armspines.
  • Fig. 10. Ophiocoma bollonsi, arm-segments seen from above.
  • Fig. 11. Ophiothrix aristulata, arm-segments seen from above, showing thorny, slender spines.
  • Fig. 12. Ophioereis fasciata, arm-segments seen from above, showing supplementary plates.
  • Fig. 13. Ophionephthys stewartensis, a jaw.
  • Fig. 14. Ophiactis resiliens, a jaw.
  • Fig. 15. Amphipholis squamata, a jaw, showing enlarged outer oral papilla.
  • Fig. 16. Amphiura spinipes, a jaw.
  • Fig. 17. Amphiura, showing tentacle scales.
  • Fig. 18, 19, 20, 21, 22, transverse sections of one side of an arm-segment, showing lateral plate carrying spines; 18, Amphiura hinemoae; 19. A. norae; 20, A. magellanica; 21, A. amokurae; 22. A. alba.

Abbreviations: A.D., adoral plate; D.P., dental papillae; I.D.P., infradental papillae; LP., lateral armplate; O.P., oral papilla; OR., oral plate; O.S., oral shield; SC.SP., scale-like spines; SP, spine; SP.P., supplementary plate; T., tooth, teeth; T.F., tube-foot; T.S., tentacle-scale; U.P., upper armplate; V.P., lower armplate.

page 129

Several images of New Zealand Littoral Ophiuroids.