Pseudostichopus Théel, 1886

O'Loughlin, P. Mark & Ahearn, Cynthia, 2005, A review of pygal-furrowed Synallactidae (Echinodermata: Holothuroidea), with new species from the Antarctic, Atlantic and Pacific oceans, Memoirs of Museum Victoria 62 (2), pp. 147-179 : 168-169

Pseudostichopus Théel, 1886

Table 1, Figure 9

Pseudostichopus Théel, 1886: 169 .— Ludwig, 1894: 38.— Perrier, 1902: 337-338.— Hérouard, 1902: 11.— Fisher, 1907: 691.— Mitsukuri, 1912: 3.— Hérouard, 1923: 21–23.— Ekman, 1925: 32–36.— Ekman, 1926: 451–470, fig. I.— Mortensen, 1927: 386–388.— Deichmann, 1930: 86–87.— Heding, 1940: 356, 358- 360.— Djakonov, 1952: 125.— Imaoka, 1978: 377–378.— Thandar, 1992: 163–164.— Rowe, 1995: 285.— O’Loughlin, 1998: 497.— O'Loughlin, 2002: 304.

Filithuria Koehler and Vaney, 1905: 81–81 .— Heding, 1940: 356–357 (new synonym).

Pseudostichopus (Pseudostichopus) .— Heding, 1940: 357, 360.— Imaoka, 1978: 378.— Thandar, 1992: 164.

Pseudostichopus (Trachostichopus) Heding, 1940: 357 , 361.— Imaoka, 1978: 380 (new synonym).

Plicastichopus Heding, 1940: 357 (nomen nudum).— Heding, 1942: 5–6 (new synonym).

Peristichopus Djakonov, 1952: 125 (new synonym).

Type species. Pseudostichopus mollis Théel, 1886 (subsequent designation by Fisher, 1907).

Other included species. Pseudostichopus aemulatus Solís-Marín and Billett, 2004 ; P. echinatus Thandar, 1992 ; P. elegans ( Koehler and Vaney, 1905) ; P. hyalegerus (Sluiter, 1901) ; P. mollis Théel, 1886 ; P. occultatus Marenzeller, 1893 ; P. papillatus ( Djakonov, 1952) ; P. peripatus (Sluiter, 1901) ; P. profundi Djakonov, 1952 ; P. spiculiferus ( O'Loughlin, 2002) ; P. tuberosus sp. nov..

Diagnosis. Characters of pygal-furrowed Synallactidae (above); prominent appendages (tube feet, papillae) along the paired radii only; longitudinal muscles cylindrical, not flat, narrowly attached to the body wall; gonad tubules not branched, arising in series along the gonoduct, not from a common base; ossicles sometimes present in tube feet and papillae; tentacle ossicles predominantly unbranched rods, rarely rods with ends intertwining and side branches fused to create mesh.

Distribution. Cosmopolitan; 91–5453 m.

Remarks. The larger radial appendages of the species of Pseudostichopus are frequently tapered and variably elongate, extremely so in P. elegans (below), and when distinctly tapered are described in this work as papillae rather than tube feet.

The monotypic genus Filithuria Koehler and Vaney, 1905 was established for F. elegans Koehler and Vaney, 1905 which is assigned here to Pseudostichopus and described in detail below. F. elegans has the diagnostic characters of Pseudostichopus (above), and the dorsolateral radial papillae are distinctively elongate. The dorsolateral appendages in the type species for Pseudostichopus , P. mollis , are moderately elongate and distinctly tapered, and have the appearance of papillae more than tube feet. The length of the dorsolateral papillae is an inadequate single character on which to maintain the monotypic genus Filithuria , which becomes a junior synonym of Pseudostichopus .

Heding (1940) erected the genus Plicastichopus citing as type species the manuscript name Plicastichopus ingolfi . Until he formalised the name in 1942, the genus remained a nomen nudum. O'Loughlin (2002) synonymised P. ingolfi Heding, 1942 with Meseres peripatus (Sluiter) , Plicastichopus Heding, 1942 becoming a junior synonym of Meseres . Meseres peripatus is reassigned below to Pseudostichopus , Plicastichopus now becoming a junior synonym of Pseudostichopus .

Heding (1940) erected the subgenus Trachostichopus (of Pseudostichopus ), with type species Pseudostichopus trachus Sluiter. Rowe (1995) referred trachus to Meseres Ludwig , Pseudostichopus (Trachostichopus) becoming a junior synonym of Meseres . P. trachus is considered below to be a junior synonym of Pseudostichopus mollis , Trachostichopus now becoming a junior synonym of Pseudostichopus .

The monotypic genus Peristichopus was established for Peristichopus papillatus Djakonov, 1952 . Djakonov (1952) characterised the genus by: cylindrical body; ventral mouth, anus; pygal furrow; small tube feet on paired radii; cylindrical longitudinal muscles; unbranched gonad tubules in two bundles; tentacles with rod ossicles, some rod ossicles perianally and in tube feet; and body wall, genital tubules, respiratory trees lacking ossicles. Djakonov (1952) noted that Peristichopus was close to Pseudostichopus , but gave no diagnostic distinctions. Peristichopus papillatus is very close to Pseudostichopus mollis , and no justification is found here for maintaining Peristichopus Djakonov which is a junior synonym of Pseudostichopus Théel.

Figures

Figure 9. Characters of Pseudostichopus. a, drawing of transverse section of mid-body (as in P. mollis); b, cylindrical longitudinal muscles detached from calcareous ring (P. tuberosus sp. nov., NMV F101864, paratype); c, dorsolateral radial papillae (P. elegans, NMV F97447, papillae up to 8 mm long); d, drawing of part of gonad, unbranched tubules, arising separately along gonoduct; e, two series of unbranched gonad tubules along gonoduct (P. mollis, TM H2004); f, gonad (P. tuberosus sp. nov., paratype, USNM 1008333).