Mesothuria milleri Gebruk and Solis-Marin, 2012

Gebruk, Andrey V., Solis-Marin, Francisco A., Billett, David S. M., Rogacheva, Antonina V. & Tyler, Paul A., 2012, Review of the genus Zygothuria Perrier, 1898 and the Atlantic group of species of the genus Mesothuria Ludwig, 1894 (Synallactidae: Holothuroidea) with description of the new species Mesothuria milleri sp. nov., Journal of Natural History 46, pp. 265-348 : 274-283

Mesothuria milleri Gebruk and Solis-Marin sp. nov.

( Figure 4 )

Holothuria verrilli Théel, 1886 – Marenzeller, 1893b: 7–9, pl. 1, fig. 2, pl. 2, fig. 2.

Mesothuria verrilli (Théel, 1886) – Östergren, 1896: 349–351; Perrier, 1902: 307–312, pl. 16, figs. 22–31; Hérouard, 1923: 10–13; Mortensen, 1927: 381–382, fig. 224: 4–5; Grieg, 1921: 4.

Material examined

See Table 3.

Type material

Holotype, NHM 2002.979 (80 mm long), RRS Challenger, St. 51708#2, 13 April 1983, 51 ◦ 31.1 ′ N, 12 ◦ 59.0 ′ W, 1430–1470 m. Paratypes (from the same Challenger station ): NHM 2002.980–981, all measurements are in mm (two specimens, TLmax = 107, TLmin = 83, WWmax = 23, WWmin = 19) ; USNM E18280 (two specimens, TLmax = 149, TLmin = 111, WWmax = 25, WWmin = 20) ; ZMUC (one specimen, TL = 124, WW = 30); ICML-UNAM–5.31.0 (one specimen, TL = 153, WW = 39) .

Museum and No. of Type TL / W (mm) Locality catalogue number specimens material

Date Depth (m)

MNHN 1821 ∗ 1 – – Talisman St. 75, off Sahara , 10-07-1883 25 ◦ 2 ′ — 25 ◦ 1 ′ N , 19 ◦ 11 ′ – 19 ◦ 13 ′ W

MNHN 1911 ∗ 5 – – Talisman St. 81, Golfe de Gascogne , 02-07-1883 23 ◦ 50 ′ N, 19 ◦ 37 ′ W

MNHN 1925 ∗ 1 – – Talisman, St. 141, Golfe de Gascogne , 30-08-1883 45 ◦ 39 ′ N , 6 ◦ 92 ′ W

MNHN 1912 ∗ 6 – – Talisman St. 122, Sud de Fayal , 37 ◦ 35 ′ N, 12-08-1883 31 ◦ 40 ′ W

MNHN 1913 ∗ 7 – – Talisman St. 45, off Morocco, 29 ◦ 8 ′ N, 26-06-1883 14 ◦ 46 ′ W

MNHN 1914 ∗ 4 – – Talisman St. 127, 38 ◦ 38 ′ N, 30 ◦ 41 ′ W 15-08-1883

MNHN 1915 ∗ fragments – – Talisman St. 45, off Morocco, 29 ◦ 8 ′ N, 26-06-1883 14 ◦ 46 ′ W

MNHN 1916 ∗ 2 – – Talisman St. 50 off Morocco, 28 ◦ 35 ′ N, 27-06-1883 15 ◦ 30 ′ W

MNHN 1917 ∗ 1 – – Talisman St. 127, Fayal , 38 ◦ 38 ′ N, 30 ◦ 41 ′ W 15-08-1883

MNHN 1918 ∗ 5 – – Talisman St. 40, 38 ◦ 38 ′ N, 30 ◦ 41 ′ W 31-07-1883

MNHN 1919 ∗ 4 – – Talisman St. 121, 37 ◦ 35 ′ N, 31 ◦ 46 ′ W 12-08-1883

MNHN 1920 ∗ 4 – – Talisman St. 48, 29 ◦ 1 ′ N, 14 ◦ 51 ′ W 26-06-1883

MNHN 1921 ∗ 1 – – Talisman St. 134, NE of Azores , 42 ◦ 19 ′ N, 24-08-1883 23 ◦ 36 ′ W

MNHN 1922 ∗ 1 – – Talisman St. 136 between Azores and 26-08-1883 Europe, 44 ◦ 20 ′ N, 19 ◦ 31 ′ W

MNHN 1923 ∗ 1 – – Talisman St. 136 between Azores and 26-08-1883 Europe, 44 ◦ 20 ′ N, 19 ◦ 31 ′ W

MNHN 1924 ∗ 2 – – Talisman St. 134, N. E of Azores , 24-08-1883 42 ◦ 19 ′ N, 23 ◦ 36 ′ W

2325–2518

1139

1480

1440

1440

1258 1440

975

1275 1910 1442 1180 4010

4255

4255

4010

MNHN 1925 ∗ 5 – – Talisman St. 81, Golfe de Gascogne , 02-07-1883 23 ◦ 50 ′ N, 19 ◦ 37 ′ W

MNHN 1926 ∗ 4 – – Talisman St. 135, 43 ◦ 15 ′ N, 21 ◦ 40 ′ W 25-08-1883

MNHN 1927 ∗ 2 – – Talisman St. 129, Sud Fayal , 38 ◦ 0 ′ N, 16-08-1883 29 ◦ 23 ′ – 29 ◦ 25 ′ W

MNHN 1928 ∗ 3 – – Talisman St. 127, Fayal , 38 ◦ 38 ′ N, 30 ◦ 41 ′ W 15-08-1883

MNHN 1929 ∗ 10 – – Talisman St. 48, off Morocco, 29 ◦ 1 ′ N, 26-06-1883 14 ◦ 51 ′ W

MNHN 1930 ∗ fragments – – Talisman St. 127, Fayal , 38 ◦ 38 ′ N, 30 ◦ 41 ′ W 15-08-1883

MNHN 1931 ∗ 5 – – Talisman St. 127, Fayal, Azores , 38 ◦ 38 ′ N, 15-08-1883 30 ◦ 41 ′ W

MNHN 1932 ∗ 7 – – Talisman St. 121, 37 ◦ 35 ′ N, 31 ◦ 46 ′ W 12-08-1883

MNHN 1933 ∗ 1 – – Talisman St. 15, off Sahara , 33 ◦ 37 ′ N, 13-06-1883 10 ◦ 47 ′ W

MNHN 1934 ∗ 2 – – Talisman St. 121, 37 ◦ 35 ′ N, 31 ◦ 46 ′ W 12-08-1883

MNHN 1935 ∗ 2 – – Talisman St. 127, Fayal, Azores , 38 ◦ 38 ′ N, 15-08-1883 30 ◦ 41 ′ W

MNHN 1936 ∗ fragments – – Talisman St. 17, Coast of Morocco, 14-06-1883 33 ◦ 33 ′ N, 11 ◦ 19 ′ W

MNHN 1937 ∗ 4 – – Talisman St. 122, sud de Fayal, 37 ◦ 35 ′ N, 12-08-1883 31 ◦ 46 ′ W

MNHN 1938 ∗ 1 – – Talisman St. 83, off Sahara , 12-07-1883 22 ◦ 57 ′ – 22 ◦ 55 ′ N , 19 ◦ 51 ′ – 19 ◦ 49 ′ W

NOCS 1 – – RRS Challenger St. 50301 #1, 30-10-1978 56 ◦ 35 ′ – 56 ◦ 30 ′ N , 09 ◦ 38 ′ – 09 ◦ 45 ′ W

NOCS 2 – – RRS Challenger St. 50510 #1, 03-06-1979 51 ◦ 05.3 ′ – 51 ◦ 06.5 ′ N , 13 ◦ 04.5 ′ – 12 ◦ 59.5 ′ W

NOCS 4 – – RRS Challenger St. 50509 #1, 03-06-1979 51 ◦ 14.7 ′ - 51 ◦ 13.5 ′ N , 13 ◦ 16.3 ′ – 13 ◦ 19.2 ′ W

NOCS 1 – – RRS Challenger St. 50517 #1, 07-06-1979 49 ◦ 30.1 ′ – 49 ◦ 27.7 ′ N , 13 ◦ 19.9 ′ – 13 ◦ 17.2 ′ W

1139

4165 2220–2155

275 1180

1275 1275

1442 1425

1442 1275

550

1440

930

1500

1925–1945

1500

1794–1785

(Continued)

Museum and No. of Type TL / W (mm) Locality catalogue number specimens material

Date Depth (m)

NOCS 3 – – RRS Challenger St. 50522 #1, 08-06-1979 49 ◦ 24.0 ′ – 49 ◦ 26.1 ′ N , 11 ◦ 45.4 ′ – 11 ◦ 45.1 ′ W

NOCS 2 – – RRS Challenger St. 50523 #1, 09-06-1979 49 ◦ 31.6 ′ – 48 ◦ 29.0 ′ N , 11 ◦ 23.9 ′ – 11 ◦ 25.9 ′ W

NOCS 7 – – RRS Challenger St. 50611 #1, 08-07-1979 51 ◦ 19.5 ′ – 51 ◦ 15.6 ′ N , 13 ◦ 15.3 ′ – 13 ◦ 20.0 ′ W

NOCS 2 – – Discovery St. 10108 #1, 05-09-1979 49 ◦ 20.6 ′ – 49 ◦ 19.6 ′ N , 12 ◦ 49.2 ′ – 12 ◦ 48.7 ′ W

NOCS 2 – – RRS Challenger St. 50703 #1, 49 ◦ 33 ′ N, 13-10-1979 12 ◦ 34 ′ W

NOCS 1 – – RRS Challenger St. 50713 #1, 51 ◦ 22 ′ N, 20-10-1979 13 ◦ 18 ′ W

NOCS 1 – – RRS Challenger St. 50810 #1, 49 ◦ 34.1 ′ N, 02-07-1980 12 ◦ 41.9 ′ W

NOCS 1 – – RRS Challenger St. 50811 #1, 49 ◦ 38.6 ′ N, 02-08-1980 14 ◦ 34.2 ′ W

NOCS 7 – – RRS Challenger St. 50815 #1, 51 ◦ 36.1 ′ N, 05-08-1980 13 ◦ 04.2 ′ W

NOCS 2 – – RRS Challenger St. 50819 #1, 52 ◦ 04.5 ′ N, 06-08-1980 13 ◦ 29.2 ′ W

NOCS 7 – – RRS Challenger St. 51009 #1, 51 ◦ 34.2 ′ N, 02-05-1981 12 ◦ 54.2 ′ W

NOCS 1 – – RRS Challenger St. 51023 #1, 49 ◦ 30.1 ′ N, 09-05-1981 12 ◦ 10.8 ′ W

NOCS 1 – – RRS Challenger St. 51307 #1, 51 ◦ 26.4 ′ N, 19-02-1982 13 ◦ 01.4 ′ W

1000–965

455–490

1365–1415

1385–1390

1575–1625

1649–1605

1649–1605

4400–4350

1280–1344

512–500

1510–1535

1260–1275

1490–1415

NOCS 1 – – RRS Challenger St. 51314 #1, 49 ◦ 31.8 ′ N, 22-02-1982 12 ◦ 29.1 ′ W

NOCS 2 – – RRS Challenger St. 51318 #1, 49 ◦ 34.1 ′ N, 24-02-1982 12 ◦ 41.9 ′ W

NOCS 1 – – RRS Challenger St. 51403 #2, 25-03-1982 51 ◦ 36.9 ′ – 51 ◦ 36.9 ′ N , 12 ◦ 59.2 ′ – 12 ◦ 59.2 ′ W

NOCS 2 – – RRS Challenger St. 51403 #5, 26-03-1982 49 ◦ 23.7 ′ – 51 ◦ 37.3 ′ N , 11 ◦ 34.2 ′ – 12 ◦ 59.0 ′ W

NOCS 1 – – RRS Challenger St. 51403 #7, 26-03-1982 51 ◦ 36.4 ′ – 51 ◦ 39.2 ′ N , 12 ◦ 59.9 ′ – 12 ◦ 58.8 ′ W

NOCS 2 – – RRS Challenger St. 51420 #1, 02-04-1982 51 ◦ 37.3 ′ – 51 ◦ 36.9 ′ N , 12 ◦ 58.6 ′ – 12 ◦ 58.6 ′ W

NHM 2002.979 1 Holotype – RRS Challenger St. 51708 #2, 13-04-1983 51 ◦ 31.3 ′ – 51 ◦ 31.0 ′ N , 12 ◦ 58.4 ′ – 13 ◦ 0.3 ′ W

NHM 2002.980-981, 2 Paratypes – RRS Challenger St. 51708 #2, 13-04-1983 51 ◦ 31.3 ′ – 51 ◦ 31.0 ′ N , 12 ◦ 58.4 ′ – 13 ◦ 0.3 ′ W

USNM E18280 2 Paratypes – RRS Challenger St. 51708 #2, 13-04-1983 51 ◦ 31.3 ′ – 51 ◦ 31.0 ′ N , 12 ◦ 58.4 ′ – 13 ◦ 0.3 ′ W

ICML-UNAM-5.31.0 2 Paratypes – RRS Challenger St. 51708 #2, 13-04-1983 51 ◦ 31.3 ′ – 51 ◦ 31.0 ′ N , 12 ◦ 58.4 ′ – 13 ◦ 0.3 ′ W

NOCS 1 – – RRS Challenger St. 52204 #1, 16-06-1985 51 ◦ 37.07 ′ – 51 ◦ 37.29 ′ N ,

12 ◦ 59.96 ′ – 13 ◦ 0.01 ′ W

NOCS 5 – – Discovery St. 13919#1, 51 o 08.89 ′ N, 11 o 25-10-2000 03.92 ′ W

SBS, BIOICE 2861 1 – TL88 BIOICE, St. 733, off Iceland, 61.74 ◦ N, 30-08-1995 16.94 ◦ - 16.96 ◦ W

– BIOICE, 3574, off Iceland, 63 ◦ 22 ′ N, 05-09-2003

29 ◦ 55 ′ W

SBS, BIOICE 3070 10 – – BIOICE, St. 305, off Iceland, 62.28 ◦ N, 12-07-1997 15.34 ◦ - 15.33 ◦ W

1455–1425

700

1317–1325

1289–1297

1320–1247

1326–1328

1470–1430

1470–1430

1470–1430

1470–1430

1310–1315

1545

2298–2295

2366

2069–2074

(Continued)

Type locality

North-east Atlantic Ocean, 1430–1470 m.

Diagnosis

Body elongated, cylindrical; skin thick but not wrinkled, except in some large specimens. Maximum known size 200 mm (preserved). Mouth and anus terminal. Pedicels minute, all over body, may be absent on anterior part of ventrum and always concentrated in posterior quarter section of ventrum. Tentacles 19–22, relatively small, often retracted.

Ossicles quadriradiate tables, almost similar on dorsal and ventral side. In holotype disks rounded, 0.07–0.09 mm in diameter, surrounded by single crown of eight marginal holes, rarely nine, equal in size ( Figure 4A,B ). Disks with more narrow holes ( Figure 4C ) common on ventrum, occasionally occur on dorsal side too.

Spire tall, its height approximately equal to disk diameter, built up of four rods and always two transverse beams; terminates in four teeth bearing small spines at tips ( Figure 4F ) (in holotype teeth were smooth, possibly owing to initial preservation in formalin). In tubefeet small terminal plates and abortive tables common.

Radial segments of calcareous ring have processes directed anteriolaterally, resembling ‘wings’ ( Figure 4I ). General outline of radial pieces nearly rectangular.

Some variation in size and form of ossicles between larger and smaller specimens; these data presented in Table 4. The longest specimen from more than 200 examined was 180 mm (preserved). Disk diameter slightly greater in larger,> 100 mm long specimens, than smaller, 30–80 mm long, holothurians. Number of marginal holes increased slightly in larger specimens. No major difference between 110 and 180 mm long specimens. Ossicles in bigger specimens usually more irregular and have lower spire and shorter teeth ( Figure 4D–E,H ). No resorption of ossicles occurs in bigger animals, as occurs in M. verrilli .

Remarks

Owing to the poor original description of M. verrilli , a species common in the Caribbean, this name has been widely used for similar holothurians from the eastern Atlantic. Additional problems arise because of the similar type of ossicles found in the older specimens of two species. However, the difference in ossicles between younger specimens (<100 mm in the preserved state) of the two species is obvious.

In specimens of M. verrilli smaller than 100 mm ossicles have (1) a disk diameter of 0.10–0.12 mm, (2) 10–11 marginal holes, and (3) a low spire, often with only one transverse beam and with squarish outline. Specimens of the same size in M. milleri sp. nov. have (1) a disk about 0.08 mm in diameter, (2) usually eight marginal holes ( Table 4), (3) a more regular, circular outline of the disk, and (4) a relatively tall spire always with two transverse beams. Ossicles diminish in size in the larger specimens (> 200 mm) of M. verrilli . This trend is also known in M. intestinalis ( Östergren 1896) . However, the ossicles become slightly bigger in the larger specimens of M. milleri sp. nov. ( Table 4). In M. verrilli the number of marginal holes decreases from 10–12(14) in specimens about 110 mm long to eight in specimens> 250 mm long, whereas in M. milleri sp. nov. the number increases from eight in 80-mm long specimens to 8–10 in 110-mm long specimens, and remains the same in specimens up to 180 mm long ( Table 4). This

Note: Holotype in bold; several specimens (3–5) of each size class have been examined, except for a single 180 mm long specimen.

is about the maximum size for this species in the preserved state. Finally, in M. verrilli ossicles reach their maximum size in c. 200-mm long specimens and then significantly diminish in the older animals, whereas in M. milleri sp. nov., which is a relatively smaller species, no peak state and consequent regression could be distinguished. The tables are slightly larger in 100-mm animals. These two different trends result, however, in very similar types and sizes of ossicles in both species in specimens> 100 mm long in M. milleri sp. nov. and> 200 mm long in M. verrilli (both preserved state).

Different trends in age variation in M. verrilli and M. milleri sp. nov. help to recognize the latter in the descriptions of Marenzeller, Perrier, Östergren, Hérouard and Mortensen. Hence, Marenzeller indicates the disk diameter 0.07–0.09 mm for a specimen 110 mm long (preserved). Disks that are 0.08 mm in diameter with eight marginal holes are very clearly described as dominant and illustrated by Perrier, who pointed out the similarities between his specimens and those of Hérouard. The description provided by Mortensen (1927) is uncharacteristically poor, but the ossicles he illustrated have a tall spire indicative of M. milleri sp. nov. As a result of confusion of M. verrilli with M. intestinalis , as pointed out by Deichmann (1930), in some earlier publications the latter name was often confused for the specimens with the characters of M. verrilli ( Koehler 1896; Ludwig 1901). Owing to similar types of ossicles in the large specimens of two species, earlier identifications of these holothurians are not always reliable. This is especially true when the illustrations of ossicles and their details, e.g. size, are missing ( Koehler 1896; Ludwig 1901; Grieg 1921). Additionally, age variations of ossicles were not recognized earlier. In the literature the size of the animal to which certain ossicles relate is not given, making some old descriptions of doubtful value. The possibility that both species occur in the west and east Atlantic cannot be excluded.

Relationships

On the basis of morphology, M. milleri sp. nov. is most closely related to M. verrilli . The major differences between the two include (1) ossicles being bigger, given the same size of specimens, in M. verrilli (except in big animals), also in M. verrilli (2) disks with more marginal holes and (3) spire relatively smaller.

Trends in ossicle variation with age. In M. verrilli ossicles grow slightly throughout life, reaching a peak size in c. 200-mm long animals and then diminish significantly. In M. milleri sp. nov. ossicles get slightly bigger in the specimens> 100 mm long.

Distribution

The distribution range is not known with certainty, partly as a result of confusion over the name ‘ verrilli ’ and close similarity between large specimens of M. verrilli and M. milleri sp. nov. As discussed above, a strong case can be made to show that all previous records of M. verrilli in the east Atlantic correspond to M. milleri sp. nov. ( Figure 3 ). This species is widely distributed in the north-north-east Atlantic: off north-west Africa, the Canary Islands ( Perrier 1902; Grieg 1921), the Azores ( Hérouard 1902, 1923; Perrier 1902), the Bay of Biscay ( Koehler 1896; Perrier 1902), the Porcupine Seabight ( Mortensen 1927; plus present material), Goban Spur, Rockall Trough ( Harvey et al. 1988), and off British Isles and Morocco ( Pérez et al. 1984).

Bathymetric range

The bathymetric range of this species is uncertain owing to confusion with other species. A range for specimens described previously as M. verrilli in the north-east Atlantic extends from 550 to 4255 m off the Azores ( Perrier 1902). Perrier, however, was uncertain about two records deeper than 4000 m, the lower limit then being 3018 m off the Azores ( Hérouard 1923). The upper depth limit is also dubious ( Billett 1988). Mortensen (1927) gives a reduced bathymetric range of 990 to 1765 m. In the Porcupine Seabight the species occurs between 1255 and 1794 m, but is most common only between 1430 m and 1530 m (82% of the specimens collected; Billett 1988).

Etymology

The species is named in honour of the Right Reverend John E. Miller ( USA) who has contributed much to our knowledge of sea cucumbers.

Figures

Figure 3. Distribution of Mesothuria verrilli, Mesothuria milleri sp. nov. and Mesothuria intestinalis.

Figure 4. Mesothuria milleri sp. nov. Ossicles (A–H) and segments of calcareous ring (I): (A–E,G–I) from holotype; (F) BIOICE, sample no. 2861 (St. 733). (A–E) disks; (F–H) spires. Scale bars 0.04 mm for A–E; 0.06 mm for F,G.