Amphiura (Amphiura) magellanica Ljungman, 1867

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 : 414-415

Amphiura (Amphiura) magellanica Ljungman, 1867

Amphiura magellanica Ljungman, 1867: 320 .—Lyman, 1882: 143.—Koehler, 1908: 271, pl.11(104).—Koehler, 1914: 65.—Clark, H.L., 1915a: 228.—Mortensen, 1924: 132–134, fig. 14, 15a.—Mortensen, 1936: 266–267.—Mortensen, 1952: 16–17.—Fell, 1952: 14.—Fell, 1953: 101.—Fell, 1960b: 68.—Madsen, 1967: 129.— Baker & Devaney, 1981: 175.—McKnight, 1984: 144.—McKnight, 1993b: 194, 199.—O'Hara, 1999: 200, pl. 3d–e.

Monamphiura magellanica .—Bernasconi, 1965: 149–150, pl. 1(3–4).—McKnight, 1967a: 311.—Castillo-Alarcón, 1968: 33–34, fig. L.

Amphiura (Amphiura) magellanica .—Rowe & Gates, 1995: 349.

Material Examined. Bay of Islands. TAN0906/96, NIWA 77794 (7). TAN0906/105, NIWA 77792 (2). TAN0906/ 170, NIWA 56995 (2). TAN0906/235, NIWA 77777 (1). East Coast North Island. TAN1108/179, NIWA 77771 (100). TAN1108/197, NIWA 77779 (4). Far North. TAN0906/152, NIWA 77793 (1). Otago. TAN1108/148, NIWA 77619 (2); NIWA 77778 (4). Stewart Island. TAN1108/77, NIWA 77780 (1). Three Kings Islands. TAN1105/35, NIWA 77776 (6).

Comparative Material. Amphiura argentea Lyman, 1879 : Challenger/171, Kermadec Islands, 28° 33´S, 177° 50´W, 1116 m, 15/7/1874, holotype, BMNH 1882.12.23.373 (1).

Diagnosis. Disc finely scaled dorsally and ventrally. 6–7 arm spines, reducing to five by mid-arm. Ventralmost arm spine elongated and downward projecting on mid arm segments. Single, large, leaf-like tentacle scale.

Description. See Mortensen (1924).

Distribution. New Zealand (5–1080 m), Macquarie Ridge (15–1400 m), south-eastern Australia (163–1200 m), South America (1–419 m), Gough Island (1–140 m).

Remarks. Mortensen (1924) distinguished this species from the closely similar Amphiura spinipes by its slightly more robust appearance. The arm spines of A. spinipes are more slender and the dorsal arm plates and radial shields are more elongated and narrow. These slight morphological differences are confirmed by life history characters; A. magellanica has larger eggs (0.2 vs. 0.1 mm diameter) and is viviparous. While these differences are real and indicate separate species, it can be very difficult to identify individual specimens. Since the distinguishing characters are relative in nature, a range of specimens are required to determine which are more slender than the others, and animals do not always carry mature eggs or juveniles.

The situation is further confused by the likely presence of additional cryptic species that also have elongated ventral arm spines. Mortensen (1924) recorded an undescribed species with elongated ventral arm spines from the Hauraki Gulf. The 4 mm dd holotype (and only known specimen) of Amphiura argentea Lyman, 1879 from the Kermadec Ridge has a single oval tentacle scale, short radial shields (twice as long as wide, 1/8 dd in length), and a flat rounded distal oral papilla. There are six stout blunt arm spines at the arm base, which can be slightly bent and/ or have a thorn on one side of the apex. By the 17th segment the ventral arm spine is much lengthened, two segments in length, and slightly curved. Distally, the four arm spines are more slender, but the lowest is still twice as long as the other spines, 1.5–2 arm segments in length. The arm spines are not equally elongated as described and shown by Lyman (1879, 1882).

Amphiura latisquama (Mortensen, 1924) n. comb.

Amphiura eugeniae var latisquama Mortensen, 1924: 142 –144, fig. 21.

Amphioplus longirima Fell, 1952: 18 –19, figs. 8–10.—Fell, 1958: 28.—McKnight, 1967a: 312 [new synonymy].

Amphiura eugeniae .—McKnight, 1967a: 310 (in part) [Non Amphiura eugeniae Ljungman A V, 1867 ].

Material Examined. West Coast North Island. TAN1105/80, NIWA 77866 (1). TAN1105/88, NIWA 77867 (1). Comparative Material. Amphiura latisquama (Mortensen, 1924) : K7/73/41, Bass Strait, east of North Point, Flinders Island, 39° 44.5´S, 148° 49´E, 421 m, 24/11/1973, MV F52682 (1). SLOPE/32, South of Point Hicks, 38° 21.9´S, 149° 20´E to 38° 21.4´S, 149° 20.9´E, 1000 m, 23/7/1986, MV F93211 (1). SLOPE/48, Off Freycinet Peninsula, 41° 57.5´S, 148° 37.9´E, 400 m, 27/7/1986, MV F93214 (6). SS 04/04/82, Banks Strait, 40° 38.42´S, 148° 47.27´E, 168 m, 25/4/2004, MV F 101722 (1). SS10/2005/44, Albany, 35° 26.046´S, 118° 21´E to 35° 26.244´S, 118° 21.06´E, 900–915 m, 25/11/2005, MV F 112620 (1).

Description. Disc to 9.5 mm dd, arms at least 7 times dd. Disc petaloid, incised interradially and notched radially, fully scaled dorsally and ventrally, disc plates to 0.2 mm wide, smaller interradially and ventrally, primaries evident but not prominent, radial shields 1/5–1/6 dd, 3–4 times as long as wide, rounded to crescent shaped, proximally divergent. Oral shields spear-head shaped, widest distally, 2 times as long as wide, slightly lobed distally, adoral shields just separated or meeting interradially, separated radially by first ventral arm plate. Two (rarely 1 or 3) distal oral papillae, inner largest, rounded or triangular, flattened, on adoral plate. Outer papilla small to rudimentary, either adjacent to the inner one on the adoral shield, or shifted distally to lie over the second oral tentacle pore and leaving a small diastema. Dorsal arm plates 2–3 times as wide as long, rounded quadrangular, slightly produced proximally, just contiguous. Ventral arm plates 1.5–2 times as wide as long, quadrangular, often with a concave distal and convex proximal edge, contiguous. Up to 5 arm spines basally on larger specimens, reducing to 4 then 3 distally. All spines cylindrical with a blunt rounded tip, 2nd lowest longest and thickest, sometimes slightly capitate, to 1.5 segments. Two tentacle scales, one on each of the ventral and lateral arm plate. Small specimens (<5 mm dd) with 4 then 3 arm spines, all less than a segment in length, and narrower ventral arm plates, just wider than long. Female gonads with eggs 0.1 mm diameter, viviparity not observed.

Distribution. New Zealand (230–1153 m), southern Australia (168–1608 m), Lord Howe Rise (650 m).

Remarks. The new material is very similar to the single damaged specimen from an unknown New Zealand location described by Mortensen (1924) as Amphiura eugeniae var latisquama , which we recognise as a distinct species. The magellanic A. eugeniae Ljungman, 1867 differs in having narrower ventral arm plates, longer than wide, and its viviparous reproductive habit (Mortensen 1924; 1936). The species Amphiura antarctica Studer, 1876 from Kerguelen and surrounding subantarctic islands, sometimes treated as a subspecies of A. eugeniae , differs in lacking the small distal oral papilla (Mortensen, 1924; 1936).

This species could be assigned to the subgenus Amphioplus (Unioplus) on the basis of its oral papillae, with two distal papillae, a buccal scale and pair of infradental papillae (A.M. Clark 1970). However, its obvious relationship with A. antarctica , which lacks a small distal papilla, casts doubt on the utility of these subgeneric distinctions. Consequently, it is retained in Amphiura until a more comprehensive revision is carried out.

The nominal species Amphioplus longirima Fell, 1952 is a synonym of A. latisquama . The 5 mm dd type, collected from 300 m on the Chatham Rise, is apparently lost, but the type description and figures are very similar to smaller specimens examined for this study, having slightly shorter and less numerous arm spines than the type specimen of A. latisquama . Amphiura latisquama is herein also reported from the upper slope across southern Australia for the first time. The New Zealand species Amphioplus pegasus Baker, 1977 has similar oral papillae but only one tentacle scale and three arm spines.