Ophiuroglypha irrorata

Ophiuroglypha irrorata (Lyman, 1878), unresolved species complex

Ophioglypha irrorata Lyman, 1878: 73, pl. 4 figs 106–108.

Ophioglypha orbiculata Lyman, 1878: 74, pl. 4 figs 103–105.

Ophioglypha loveni Lyman, 1878: 80, pl. 4 figs 109–111.

Ophioglypha involuta Koehler, 1897: 295, pl. 6 figs 16–18.

Ophioglypha tumulosa Lütken & Mortensen, 1899: 120, pl. 1 figs 9–13.

Ophioglypha concreta Koehler, 1901: 228, figs. 6–8.

Ophioglypha integra Koehler, 1908: 146.

Ophioglypha figurata Koehler, 1908: 251; Paterson 1985: 123.

Ophiura (Ophiuroglypha) irrorata var. polyacantha Mortensen, 1933: 87–88.

Ophiuroglypha irrorata — Hertz 1927: 29

Ophiura (Ophiuroglypha) irrorata irrorata — Paterson 1985: 123

Ophiura (Ophiuroglypha) irrorata concreta — Paterson 1985: 125

Ophiura (Ophiuroglypha) irrorata polyacantha — Paterson 1985: 124

Ophiuroglypha irrorata irrorata — O’Hara et al. 2018: 10 (transfer of genus)

Ophiuroglypha irrorata loveni — O’Hara et al. 2018: 10 (transfer of genus)

Ophiuroglypha irrorata polyacantha — O’Hara et al. 2018: 10 (transfer of genus)

Figure 3C, D

Material examined

O. irrorata irrorata

MAKASSAR STRAIT • 4 specimens; 03°56’S, 118°26’E; 1990–2000 m; 24 Aug. 1951; Galathea II stn. 453; greenish clay; NHMD-868357.

SUNDA TRENCH • 1 specimen; 09°49’S, 114°13’E; 3810–3840 m; 11 Sep. 1951; Galathea II stn. 474; NHMD- 868309.

GREAT AUSTRALIAN BIGHT • 1 specimen; 37°28’S, 138°55’E; 1320–1360 m; 05 Dec 1951; Galathea II stn. 554; Globigerina ooze; NHMD-868423.

TASMAN SEA • 11 specimens; 44°18’S, 166°46’E; 3580–3830 m; 17 Jan. 1952; Galathea II stn. 607; NHMD- 868425.

KERMADEC TRENCH • 1 specimen; 36°07’S, 178°32’E; 5230–5340 m; 23 Feb. 1952; Galathea II stn. 661; pumice in abundance; NHMD-868411 • 10 specimens; 36°31’S, 178°38’E; 4410 m; 24 Feb. 1952; Galathea II stn. 663; brown sandy clay with pumice; NHMD-868421.

EAST PACIFIC OCEAN • 100 specimens; off Nicaragua; 09°23’N, 089°32’W; 3570 m; 06 may 1952; Galathea II stn. 716; dark, muddish, clay; NHMD-868307, NHMD-868314.

O. irrorata concreta

EAST ATLANTIC OCEAN • 2 specimens; West Africa, Bight of Bonny Islands, Principe; 01°42’N, 007°51’E; 2550 m; 30 Nov. 1950; Galathea II stn. 52; muddy clay; NHMD-867142 • 1 specimen; off Angola; 08°49’S, 011°10’E; 2690 m; 11 Dec. 1950; Galathea II stn. 99; yellowish clay; NHMD-867404.

INDIAN OCEAN • 9 specimens; Mozambique Channel, N of Madagascar, S of Mayotte; 14°20’S, 045°09’E; 3390–3530 m; 17 Feb 1951; Galathea II stn. 217; clay, Globigerina ooze; NHMD-867146 • 125 specimens; off Kenya; 03°23’S, 044°04’E; 3960–3980 m; 13 Mar. 1951; Galathea II stn.238; Globigerina ooze; NHMD-305715, NHMD-867376 • 24 specimens; Sri Lanka; 03°38’N, 078°15’E; 3310 m; 10 Apr. 1951; Galathea II stn. 281; Globigerina ooze; NHMD-867212 • 50 specimens; off Sri Lanka; 05°32’N, 078°41’E; 4040 m; 11 Apr. 1951; Galathea II stn. 282; blackish mud; NHMD-305707.

Remarks

The most recent molecular phylogeny (Christodoulou et al. 2019) suggests that O. irrorata and its currently accept- ed subspecies O. irrorata concreta, O. irrorata loveni, and possibly O. irrorata polyacantha, may be a polyphyletic species complex containing multiple species. They are differentiated in the dorsal disc scaling, arm spine numbers and placement, and dimensions of the oral shield (Paterson 1985). In addition to the subspecies, at least six nominal species are currently considered conspecific with the nominal O. irrorata (Paterson 1985; Stöhr et al. 2020), which suggests that morphological species differences (e.g., disc plating, dimensions of oral shields, margin of disc shape sharp or not, number and shape of arm spines, shape of radial shields, shape, size and position of tentacle scales) may have been interpreted as intraspecific variability. Among the species currently synonymised with O. irrorata, O. figurata differs in the arm comb not being visible in dorsal view and may be a valid species, whereas the arm combs continue across the arm in Ophiura clemens (Koehler, 1904), Ophiuroglypha jejuna (Lyman, 1878) and Ophiura monostoecha H.L. Clark, 1911. All of these and Ophiuroglypha verrucosa McKnight, 2003, Ophiura albata (Lyman, 1878), Ophiura lenticularis (Koehler, 1908), Ophiura mimaria (Koehler, 1908), should be considered in a future revision of O. irrorata, due to the presence of an enlarged distal tentacle scale, but a complete revision of the genus Ophiura Lamarck, 1801 may also be necessary.

Among the Galathea II material we found specimens in the Atlantic and Indian Oceans that concur morphologically with O. irrorata concreta, and in the Indo-Pacific and Pacific Oceans we found O. irrorata irrorata (Tables 1, 2). These two subspecies differ mainly in the placement of their three arm spines, equidistant in O. irrorata irrorata and with the dorsalmost spine at a wide distance from the two ventral spines in O. irrorata concreta. Olbers et al. (2019) assigned South African specimens to O. irrorata irrorata, despite the fact that they had the spine configuration of O. irrorata concreta. The type locality of O. irrorata is South Africa (Lyman 1878), O. concreta originated from Cape Verde (Koehler 1901), which suggests that all South African material should belong to the original nominal species and should have its spine arrangement. Paterson (1985) mentioned the occasional occurrence of the dorsal spine being separated from the others in O. irrorata irrorata, but considered O. irrorata concreta valid, based on its separated spines. Pending a study of more material from South Africa and re-examination of the type material, we suspect that the spine arrangement may be variable and not species specific. These confusing findings question the identity and taxonomic status of both O. irrorata and O. concreta.

A uniting feature for all species in this group is an enlarged distal tentacle scale on the proximal arms (Paterson 1985), which is shared also with Ophiura (Ophiura) scomba Paterson, 1985, supporting its placement close to O. irrorata on the molecular phylogeny (Christodoulou et al. 2019). Likewise, Ophiura ossiculata (Koehler, 1908) and Ophiura plana (Lütken & Mortensen, 1899) possess a large distal tentacle scale, and were treated as members of the O. irrorata group of species by Paterson (1985). Hence, we propose to transfer O. ossiculata, O. plana and O. scomba to Ophiuroglypha. Galathea specimens from Nicaragua, here identified as O. irrorata, may instead belong to O. plana , but are morphologically indistinguishable and molecular data are not available. Previously considered a member of the genus Ophiura in the family Ophiuridae, the Ophiuroglypha irrorata group was recently transferred to the family Ophiopyrgidae, and the subgenus Ophiuroglypha was raised to generic rank (as intended by Hertz 1927), based on molecular data (O’Hara et al. 2017, 2018). One of the main characteristics of Ophiuroglypha is the presence of a small hook-shaped spine on the distal arms (Hertz 1927; Mortensen 1933), a character that is shared with Ophiura robusta (Ayres, 1852), as was recently shown (Thuy & Stöhr 2011), but that species is placed close to Ophiura albida Forbes, 1839 by molecular data (Christodoulou et al. 2019). Hence, we consider hooks to be homoplaseous.