Mesothuria bifurcata Hérouard, 1901

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 : 283-284

Mesothuria bifurcata Hérouard, 1901

( Figure 5 )

Mesothuria bifurcata – Hérouard, 1901: 40; 1906: 4–6, pl. 2, fig. 3; Jangoux and Massin, 1986: 84 (list); O’Loughlin et al., 1994: 553–554; O’Loughlin, 2002: 313, 315.

Mesothuria (Mesothuria) bifurcata – Heding, 1942a: 8, text fig. 7, figs. 1–6.

Material examined

See Table 5.

Type material

Holotype, IRSNB, cat. no. IG 10131, Faubert II, St. 2, 12 May 1898, 71 ◦ 14 ′ S, 89 ◦ 14 ′ W, approximately 800 m (depth estimated from given latitude and longitude by O’Loughlin 2002). Specimen in poor condition. No ossicles were found by O’Loughlin (2002).

Type locality

Western Antarctic , Bellingshausen Sea, depth approximately 800 m.

Diagnosis

After Hérouard (1901) and O’Loughlin (2002): body subcylindrical, rounded anteriorly, slightly tapered posteriorly; flattened dorsoventrally. Mouth ventral, anus posterior. Body wall thick, firm, flexible; up to 20 peltate tentacles. Tubefeet in two rows, in each radius. Lateroventral radius with largest tubefeet. Very small tubefeet scattered dorsally, laterally, few ventrally, absent midventrally. Calcareous ring solid, lacking posterior prolongations, radial plates as high as wide with anterior V-shaped notch, interradial plates at least twice as wide as high. Gonad tubules with multiple branching. Respiratory trees well developed.

Ossicles tables, disk with six holes, column with three arms ending in simple forks, smooth or bearing small spines ( Figure 5A–D ).

Remarks

Mesothuria bifurcata has very characteristic ossicles with bifurcated arms on the spire.

Distribution

Antarctic and north Atlantic ( Figure 6 ).

Bathymetric range

Depth 320–2337 m ( Heding 1942a; O’Loughlin 2002).

Figures

Figure 5. Ossicles of Zygothuria marginata (A–F) and Mesothuria bifurcata (G–J): Mesothuria bifurcata Hérouard, 1901. Ossicles. (A,B) from Heding, 1940; (C,D) specimen from St.10111 #8.

Figure 6. Distribution of a group of Mesothuria and Zygothuria species.