Synallactes viridilimus Cherbonnier 1952

Synallactes viridilimus Cherbonnier, 1952

(Table 3, Figs. 8 & 9)

Synallactes viridilimus Cherbonnier, 1952: 473, pl. 35, figs. 1–17, pl. 36, figs. 16–17;? Thandar, 2008: 43, 46–48, fig. 17.

Diagnosis (See Cherbonnier 1952, Solis-Marin 2003)

Material examined. A31395, West Coast Survey 2011, between the Cape Peninsula and Cape Town, 33° 33.67'S, 17° 25.137'E, DemersalTrawl 036-5119, Cruise 270, 584 m, 23/01/2011, Lara Atkinson, 1 spec.

Description. Form subcylindrical, slightly arched dorsally, flattened ventrally. Body wall thick, rough. Live colouration purple, purple to grey in alcohol. Length 250 mm in life, 128 mm in alcohol, preserved mid-body diam. 25 mm. Mouth ventral, anus terminal. Tentacles 20, peltate, encircling mouth with upper semi-circle portion in a single row, lower semi-circle portion in a double row, off-white to yellow in alcohol. Tube feet short, retractile, 1– 5 mm long, in 2–3 longitudinal rows within each ambulacrum, sometimes irregular, distributed in a zigzag formation, from ventral to lateral surface; ambulacra diverge anteriorly but coalesce posteriorly, those of midventral ambulacrum extending to anus but stopping 4 mm short of mouth. Papillae dorsal and dorso-lateral, in five indistinct or zigzag rows, arising from large (1–8 mm) wart-like protruberances, long and slender or reduced; some special papillae surround anus dorsally and mouth mid-dorsally and dorso-laterally.

Specimen eviscerated, major part of gut and respiratory trees lost. Plates of calcareous ring fragile, weakly fused, notched posteriorly, radial plates larger, more deeply notched posteriorly, irregularly undulate anteriorly, interradial plates with triangular anterior projection. Stone canal short (4 mm), madreporite attached to dorsal mesentery. Polian vesicles two, one large, elongate (11 mm), other much smaller (4 mm). Gonad of long, fine branched tubules. Longitudinal muscles broad.

Body wall ossicles comprise tables. Dorsal tables of two types: large (disc diam. 130–340 µm), 3-armed, arms unbranched, with irregular perforated ends; other tables smaller (disc diam.180–330 µm), 3–4 armed, arms dichotomously branched, multilocular, sometimes fused to form an almost complete disc. Spire height of dorsal tables 70–140 µm), ends bifurcate, with or without terminal hole. Ventral tables identical to those of dorsal surface and also of two sizes: small, 3–4 armed, arms unbranched or branched dichotomously with branches sometimes fused to form complete disc (70–140 µm), and others large, 3–4 armed, with dichotomously branched arms which sometimes fuse but never really form a full disc (150–290 µm). Spire of ventral tables 20–90 µm). Anal region with no specialised ossicles.

Tube feet rods large (330–890 µm), straight or curved, spinous, sometimes terminally bifurcate with perforations at one or both ends, sometimes with lateral projections with or without perforations. Papillae ossicles mainly composed of small tables and spinous rods identical to those of tube feet. Tentacle rods of two sizes: small, 110–330 µm, spinous, curved, sometimes bifurcate terminally, with or without a hole at one or both ends; and large, 550–780 µm, also spinous, with 1–4 holes, usually without side projections but with spines at extremities.

Distribution. Known only from the west coast of South Africa, 42– 584 m.

Remarks. The specimen in the current collection is almost identical to that described by Cherbonnier (1952) but differs in texture and consistency of body wall from that described by Thandar (2008). Variations in the external and internal features, including ossicles dimensions are tabulated in Table 3. All three samples originate from the west coast of South Africa, at more or less similar depth and are similar with few variations. The current specimen differs from that described by Thandar (2008) in the presence anal papillae, the number of tentacles and Polian vesicles and the arrangement of tube feet but very close to the type described by Cherbonnier (1952). However, contrary to the type and Thandar’s specimen small tables are absent from the dorsal body wall.

The discs of the large ventral tables of Cherbonnier’s specimen are noticeably smaller than those reported by Thandar and in the current material, although the spire height appears to be similar. The smaller ventral table discs in the current specimen are also larger than those recorded by both the authors, but the spires of the smaller tables are higher. The tentacle and tube feet rods are variable in size but Cherbonnier did not differentiate between large and small rods.

However, ossicle size can vary due to age and individual and local variations. Despite this, the current material is referred to S. viridilimus without any doubt, based on similarities of external and internal features and the resemblance of the ossicles to those of the holotype and Thandar’s (2008) specimens. This species also bears some semblance to the Sub-Antarctic S. challengeri in the appearance of branched cruciform bodies in which the arms also sometimes anastomose forming a complete disc (see Massin 1992). However, in Thandar’s (2008) reexamination of the type of S. challengeri, no small tables with complete discs were observed. There were also no complete discs in cf. S. challengeri described herein. Other differences between these two species include the variation of ossicles found in different body regions, the distribution of tube feet, papillae and the branching of the gonad. Since Thandar’s S. viridilimus differs substantially in the texture and consistency of the body wall it is here doubtfully referred to the synonymy of S. viridilimus.