Amphiura (Amphiura) correcta Koehler, 1907

Mills, V. Sadie & O'Hara, Timothy D., 2013, Ophiuroids (Echinodermata; Ophiuroidea) of biogenic habitats on the continental shelf of New Zealand, Zootaxa 3613 (5), pp. 401-444 : 411-413

Amphiura (Amphiura) correcta Koehler, 1907

( Fig. 5 )

Amphiura correcta Koehler, 1907b: 300 –301, pl. 12(30–31).—Clark, H.L., 1915a: 225.—Clark, A.M., 1970: 21–22, fig. 4a–b.—McKnight, 1993a: 175, 187.—McKnight, 1993b: 193–194, 199.

Amphiura norae Benham, 1909: 104 –105, pl. 10(1–3).—Clark, H.L., 1915a: 235.—Mortensen, 1924: 140.—Fell, 1953:

101.—Fell, 1958: 26–27.—Fell, 1960b: 68.—McKnight, 1967a: 310 [synonymised by Clark, A.M., 1970]. Amphiura abernethyi Fell, 1951: 1 –3, figs. 1–4.—Fell, 1952: 16 [synonymised by Clark, A.M., 1970]. Hemilepis norae .—Pawson, 1969: 47–49, fig. 1.

Material Examined. Bay of Islands. TAN0906/33, NIWA 54894 (1). TAN0906/42, NIWA 55001 (1); NIWA 54999 (2). TAN0906/50, NIWA 55075 (1). TAN0906/205, NIWA 77803 (1). East Coast North Island. TAN1108/ 203, NIWA 75265 (3). Marlborough Sounds. TAN1105/147, NIWA 73855 (12). West Coast North Island. TAN1105/74, NIWA 73603 (1).

Comparative Material. Amphioplus ctenacantha Baker, 1977 : NZOI/E118, Chatham Rise, 43° 15´S, 176° 0´W, 496 m, 13/10/1964, identified by McKnight (1967a) as Amphiura joubini , NIWA 77869 (1). VUZ /87, Cook Strait, 400 fathoms, 732 m, identified by Fell (1958) as Amphiodia destinata , NIWA 68502 (1). Amphiura cf. joubini ,: NMNZ/BS 545, Kaikoura Canyon, 42° 29´S, 173° 37´E, 1006–1097 m, 18/3/1976, identified by Baker (1977) as Amphiura (Amphiura) lanceolata , NMNZ Ech2279 (1). Amphiura correcta Koehler, 1907 : NMNZ/BS 209, off Mayor Island, Bay of Plenty, 37° 20.5´S, 176° 26.5´E, 493 m, 27/5/1957, identified by Fell (1958) as Amphiodia destinata , NMNZ Ech671 (1). Amphiura lanceolata Lyman, 1879 : Challenger/169, off NE North Island, 37° 34´S, 179° 22´E, 1302 m, 10/7/1874, holotype, BMNH 1882.12.23.371 (1).

Description. Disc to 14 mm diameter, arms at least 10 times dd. Disc incised interradially, covered with plates dorsally, primaries a little larger than other plates, about 20 scales from centre to interradial margin, scales smaller marginally. Radial shields 2.5 to 5 times as long as wide, proximally divergent separated by 1–4 series of plates. Plates on the ventral disc surface restricted to a band along the disc margin and a few rows along the genital slits, otherwise naked except for a few scattered plates, gonads visible. Oral shields spear-head shaped, longer than wide, slightly lobed distally, adorals meet interradially but separated radially. Oral papilla wide, extending along the adoral shield, either consistently low, or forming one or two peaks, the proximal peak generally taller, sometimes as high as the papilla is long. Buccal scale small, pointed and often hidden by the large distal oral papilla. Dorsal arm plates two times as wide as long, with a slightly angled distal margin, just contiguous. Ventral arm plates roughly pentagonal, with a straight to convex distal edge, straight sides and produced proximally, narrowly contiguous. Up to five arm spines, becoming four after a few segments, the second lowest longest, 1.5 segments long, often curved distally at the tip. The middle proximal spines have a long slender sinuous hyaline point. Two tentacles scales, one each on the lateral and ventral arm plates.

Distribution. New Zealand (0–1490 m).

Remarks. The new specimens largely match the figures and notes of the type drawn by A.M. Clark (1970) with the addition that the distal oral papilla is often produced into one or two peaks and the proximal arm spines usually possess a long slender hyaline tip. This species is known to be variable morphologically, in particular the radial shields are known to elongate and separate with growth (Pawson 1969) leading to a series of names being used.

There are a number of similar amphiurid species recorded from New Zealand with two tentacle scales, naked areas of the ventral disc surface, and arm spines terminating in thorns, which has led to erroneous identifications. The Antarctic species Amphiura joubini Koehler, 1912 has been recorded twice from New Zealand (Fell 1958 as A. destinata ; McKnight 1967). Specimens from the Ross Sea differ from A. correcta in having up to six arm spines, the lower spines (in particular the second lowest) with a bent tip, pointing proximally for the first few segments and then distally near the disc margin. The spines at the turnover have two thorns pointing in both directions. There are 1–2 oral papillae, either cylindrical and elongate, or with a slightly swollen base. The buccal scale is long and prominent. The ventral disc is mostly scaled, only naked or with few scales near the oral shield. The dorsal disc scales have minutely spinose rims. Fell's (1958) specimens from the Bay of Plenty are in fact A. correcta with oral papillae produced into two peaks, while the specimens from Cook Strait and McKnight's (1967) specimen from the Chatham Rise appear to be Amphioplus ctenacantha Baker, 1977 .

There are numerous specimens in the NIWA collections which are very similar to A. ctenacantha differing only in having a single rather than two pointed distal oral papillae on most jaws. But these specimens can be distinguished from A. correcta in having narrower dorsal arm plates (to 1.5 times as wide as long) and up to six arm spines, the second lowest having a truncate tip with one or two thorns projecting sideways, and lacking the long pointed hyaline arm spine tips on proximal segments. This species will be treated in full in a future manuscript.

Amphiura lanceolata Lyman, 1879 was described from a small 5 mm dd specimen off north-eastern New Zealand in 1300 m. This specimen is similar to A. correcta in having large naked areas ventrally, an incised disc, two tentacle scales, and five slender tapering arm spines. A re-examination of the type shows that it differs from A. correcta in having a tall conical blunt hollow distal oral papilla, roughly rectangular ventral arm plates, longer than wide, with concave sides, and arm spines that may be very slightly curved but lack a hyaline tip or terminal thorns. A second specimen was recorded by Baker (1977) but this specimen differs from the type in having a mostly scaled ventral disc and arm spines like A. joubini , although it lacks the spinose rim to the dorsal disc plates and probably represents a new species.

The New Zealand species Amphiura rosea Farquhar, 1894 , A. aster Farquhar, 1901 , Amphiura amokurae Mortensen, 1924 and Amphioplus cipus Baker, 1977 also have two tentacle scales but a fully scaled ventral disc. The relationship between some Amphiura and Amphioplus species requires review. Both A. ctenacantha and A. cipus can have 1 or 2 spiniform distal oral papillae on the oral plate, frequently varying even on the same animal.

Figures

FIGURE 5. Amphiura (Amphiura) correcta Koehler, 1907 (NIWA 55075, TAN 0906 / 50) showing live colour and morphological features. A: dorsal side of whole animal, scale bar = 5 mm, b: close-up of ventral side with labels indicating sharp hyaline-tipped arm spines (as), widened distal oral papillae (dop), naked ventral disc (vd) and paired tentacle scales (ts)., c: close-up of fully scaled dorsal disc.