The Bathyal Holothurians of the New Zealand Region
Mesothuria Ludwig, 1894
Mesothuria Ludwig, 1894
Atlantis Herouard, 1902, Zygothuria Perrier, 1898.
Diagnosis : Gonad comprising only a single tuft. Ventral surface flattened. Tubefeet all over body, or in single or double rows on paired radii. Deposits tables with approximately circular disc bearing large perforations, and a spire composed of three processes united by crossbars.
Type Species: Mesothuria multipes Ludwig.
Remarks: This is a large genus, containing in excess of 25 species, of which several are cosmopolitan in distribution. Deichmann (1930, 1954) is in favour of retaining Zygothuria Perrier (type species Zygothuria lactea (Theel)) as a distinct genus to accommodate the "almost footless" species Z. lactea. Heding (1942) reduced Zygothuria to the status of a subgenus of Mesothuria. It does not now seem necessary to retain Zygothuria, even as a subgeneric name.
Mesothuria lactea (Theel)
Holothuria lactea Theel, 1886a, p. 183; 1886b, p. 6.
Holothuria aspera Bell, 1892, p. 50.
Zygothuria lactea Perrier, 1902, p. 322, Pl. XVII, figs. 1–10; Deichmann, 1930, p. 108, Pl. 8, figs. 8–9; Deichmann, 1954, p. 386.
Zygothuria lactea var. oxysclera Perrier, 1902, p. 323.
Mesothuria lactea Herouard, p. 21, Pl. 1, figs. 17–19; Sluiter, 1910, p. 332; Herouard, 1923, p. 13, Pl. 4, figs. 1–3; Mortensen, 1927, p. 382, fig. 227.
Mesothuria (Zygothuria) lactea lactea Heding, 1940, p. 340, Text-fig. 7 (3); Heding, 1942, p. 9, Text-fig. 9.
Material Examined: None.
Remarks: This species was originally described from specimens collected near New Zealand ("Challenger" Station 169) and near the Azores (Stn. 78), in depths of 1,260 metres and 1,800 metres respectively (Theel, 1886a). Subsequently the species was collected from many localities in the Pacific and Atlantic Oceans, and in the Arctic region. Mesothuria lactea is cosmopolitan, in depths ranging from approximately 700 metres to 5,100 metres.