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Deep-Sea Echinoderms of New Zealand

Ophiacantha Mueller & Troschel, 1842

Ophiacantha Mueller & Troschel, 1842

This deep water genus, formerly represented by only one species in the recorded New Zealand fauna, figures prominently in the deepest Cook Strait hauls made by the Victoria University deep sea expeditions at the head of the great depression that leads north-east from Cook Strait towards the Kermadec Trench. Seven species now can be assigned to the fauna, and consequently a key will be useful.

1. 6 to 8 arm-spines 2
11 arm-spines. Disc covered with short spinules. Tentacle scale large, thick, pointed. 4 or 5 oral papillae, outer ones leaf-like, inner ones more spiniform rosea
2. 5 to 9 irregular oral papillae; tentacle scale minute, apparently lacking beyond fourth joint yaldwyni
3 to 4 oral papillae, tentacle scale on all joints 3
3. Outer oral papilla(e) broader than inner ones 4
Oral papillae not obviously differentiated 5
4. Lower arm-plates distinctly broader than long abyssicola
Lower arm-plates about as broad as long levispina
5. Disc covered above by granules, with some erect smooth spines in a cluster near centre vepratica
Disc more or less uniformly covered with small thorny stumps or spinules 6
6. Tentacle-scale large. Not viviparous vilis
Tentacle-scale minute. Viviparous imago
Ophiacantha levispina Lyman
  • Lyman, T., 1882. Challenger Ophiuroidea, p. 196–7, Pl. 25 (1–3).

Material Examined: Three specimens, all from abyssal stations. 1,300 fathoms, Cook Strait, VUZ Station 58, 1 specimen (3 oral papillae, the outer one broad); 1,200–1,300 fathoms, Cook Strait, VUZ Station 56, 2 specimens (one with 4 oral papillae, the other with 3, in both cases the outer papilla is broadened).

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The species was taken by the Challenger at Station 214, off the Philippine Islands, in 500 fathoms.

Mr. J. C. Yaldwyn recorded that the arms were pink in the two specimens obtained from Station 56.

Ophiacantha imago Lyman
  • Lyman, T., 1882. Challenger Ophiuroidea, p. 186, Pl. 25 (4–6).

Material Examined: Three specimens, all from a deep-water haul, 550 fathoms, Cook Strait, VUZ Station 83.

The species is viviparous. The arms of young individuals can be seen protruding from the genital clefts. In alcohol the specimens are pure white, but colour notes from life made by Mr. J. C. Yaldwyn state that the specimens were all pink when brought to the surface.

Ophiacantha yaldwyni sp. nov. Plate 4, Figs. F, H, I, holotype.

Diagnosis: Similar to Ophiacantha truncata Koehler, but having rhomboidal mouth-shields, shorter arm-spines and shorter oral papillae.

Description: Disc carrying thorny granules, about 12 to the square millimeter, not densely packed but permitting the outlines of the disc scales to be seen between them, usually one granule to each disc scale. Disc, arm and mouth-plates all invested in skin, making the borders between the plates somewhat indistinct when dried. Oral papillae 5 to 9, very irregularly arranged, with spiniform and leaf-shaped papillae indiscriminately mingled and crowded, some spines encroaching upon the adoral plates. Oral shields small, transversely rhombic, an angle within and without. Adoral plates rectangular, meeting broadly within, and resting upon the first lateral arm-plate without. Ventral arm-plates pentagonal, an obtuse angle within, the distal borders more or less rounded. Tentacle-scale single, prominent on the first arm-joint, smaller on the second, very minute or lacking on the third and fourth joints, and lacking from the rest of the joints. Lateral arm-plates not meeting above on the basal joints, but meeting very narrowly below, somewhat prominent, carrying 6 thorny spines, the upper ones longer than an arm-joint, the lower ones shorter. Further out on the arm all the spines become relatively shorter, forming a close, robust comb shorter than the arm-joint at that level. Dorsal arm-plates of the so-called "cup-shaped" form at the base of the arm, broadly in contact, with a narrow proximal border, long concave lateral borders, and a broad convex distal border; they are a little longer than broad at the base of the arm, as also further out. The basal one or two dorsal plates carry two or three granules in a transverse row along the distal margin, these two plates having a somewhat different shape from the rest of the basal dorsal armplates. Genital cleft longer than three arm-joints.

Holotype: In the Department of Zoology, Victoria University of Wellington; R approximately 25 mm, r 5 mm.

Material Examined: The holotype from 550 fathoms, Cook Strait, VUZ Station 75. Mr. J. C. Yaldwyn recorded that the colour in life is pink. The specimen, with other ophiuroids, was taken from crevices in a rock fragment from the sea-floor.

Ophiacantha rosea Lyman. Plate 4, Figs. J, K.
  • Lyman, T. 1882. Challenger Ophiuroidea, p. 184, Pl. 25.

Material Examined: 275 fathoms, Canyon A ENE of Otago Heads, Alert Station 54.13, E. Batham, 2/3/54. The specimen is in the collection of the Portobello Marine Station, Otago.

The specimen, recorded by Dr. Batham as pink when taken, is a large one, R ca 70 mm, r 9 mm. It differs from Lyman's Pl. 25 in having fewer and blunter and broader outer oral papillae (Fig. J). The length of the 11 arm-spines differs a little from Lyman's account, being, in terms of the length of a segment, ·5, 3·5, 3·5, 3·5, 3, 2·8, 2·5, 2·2, 2, 1·5, 1·5 respectively as taken from upper to lower. The dorsal spines of the disc also appear to be longer than in Lyman's (somewhat obscure) illustration. The differences may be regarded as relatively trivial.

This large, deep-water species was originally taken by the Challenger in 310 fathoms off the Crozets (S. Indian Ocean), in 420–775 fathoms off Japan, and in 175 fathoms off southern Chile. Its occurrence in New Zealand waters is therefore not surprising, and indeed it may prove to be cosmopolitan. It has not yet been reported from Australia.

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Plate 4

Plate 4

A, E, Ophiuraster symmetricus sp. nov; A, adoral and E, aboral aspect. B, C, D, Ophiomastus admiral sp. nov.; B, laeral aspect of arm; C, aboral and D, adoral aspects. F, H, I, Ophiacantha yaldwyni sp. nov.; F, aboral aspect; I, adoral aspect; H, spinules from upper side of disc. G, L, Ophiacantha abyssicola otagoensis var. nov.; G, aboral aspect of arm-joint; L adoral aspect. J. K, Ophiacantha rosea Lyman; J, jaw-region and K, spinules from up per surface of disc.

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Ophiacantha abyssicola G. O. Sars var. otagoensis var. nov. Plate 4, Figs. G, L, holotype.

Diagnosis: Differing from the typical form in having transversely rhombic oral shields, which lack the distal lobe.

Holotype: In the Portobello Marine Station, Otago.

Material Examined: 3 specimens from 275 fathoms, Canyon A off Otago Heads, Alert Station 54.13, E. Batham.

Remarks: The difference in the oral shields is the only significant one I can observe in the material, when it is compared with Mortensen's (1928) account of the North Atlantic form. It does not seem sufficient for establishing a new species, even though the geographical separation is that of the globe itself; for, as is now becoming increasingly evident, deep-sea ophiuroids tend to have very widespread distribution patterns.

Since the species has not hitherto been taken in the Pacific, it is desirable to list the features that have influenced me in assigning the Otago material as O. abyssicola, and these are illustrated in Figs. G, L. The dorsal arm-plates have the form that Mortensen (1928) calls "cup-shaped": the ventral plates are very broad; the disc is finely granulated above and laterally, but the plates are naked on the lower surface; there is a single round tentacle-scale; three oral papillae, of which the outer one is somewhat widened; the disc diameter is ca. 5 mm.

Ophiacantha vepratica Lyman
  • Lyman, T. 1882. Challenger Ophiuroidea, p. 182, Pl. 13.

Material Examined: Two individuals, one from 300 fathoms, the other from 260 fathoms, from Stations 5 and 52 respectively of the Chatham Islands 1954 Expedition.

The holotype was taken by the Challenger at Station 171, in 600 fathoms off the Kermadec Islands. The presence of the species in New Zealand waters was therefore to be expected.

Ophiacantha vilis Mortensen
  • Mortensen, Th. 1924. Vid. Medd. dansk naturh. For., 77, p. 114, Fig. 7.

Material Examined: Six specimens from the following stations: 600 fathoms. Cook Strait, VUZ Station 75, 1 specimen; 400 fathoms, NE of Mayor Island, Bay of Plenty, Dominion Museum Station B.S.210, 1 specimen; 200–300 fathoms, Cook Strait, VUZ Station 51, 4 specimens.

The holotype was from Cook Strait, 200 fathoms (Mortensen, 1924).