Synallactes mollis Cherbonnier, 1952

Thandar, Ahmed S. & Rambaran, Ryan, 2015, On some sea cucumbers (Echinodermata: Holothuroidea) from off the south and west coasts of South Africa collected by the South African Environmental and Observation Network (SAEON), Zootaxa 3999 (1), pp. 41-61 : 49-53

Synallactes mollis Cherbonnier, 1952

( Table 2 , Figs. 6 & 7 )

Synallactes mollis Cherbonnier, 1952: 475 –476, Pl. 36, figs. 1–15, 18, 19. Synallactes cf. mollis ; Thandar, 2008: 41 , 43, fig. 16.

Diagnosis (see Cherbonnier 1952, Solis-Marin 2003)

Material examined. A31645, South Coast Survey 2011, off the coast of George, South Africa (34° 35'S, 22° 36'E), Demersal Trawl 066-6546, Cruise 273, 650 m, 30/04/2011, RV Leslie, 8 specs.

Description. Most specimens damaged and/or eviscerated, with tears in the mid-body and anal region; intact specimen sub-cylindrical, ventrally flattened, dorsally arched. Sample length 63–104 mm, width of mid-body 7–16 mm. Tentacles peltate, 16–22, off-white to yellowish-brown, tightly arranged in two circles. Live colouration dark purple to brown, purple to off-white in alcohol. Body wall soft, thin, smooth. Mouth ventral; anus terminal, ventrally directed. Tube feet variable in size, in one mid-ventral and two ventro-lateral bands, decreasing in size posteriorly. Ventro-lateral tube feet in two distinct rows, mid-ventral tube feet in 2–3 rows, scattered at times; ventro-lateral tube feet extend to anterior end, while mid-ventral tube feet stop 3–10 mm before mouth; regions between mid-ventral and ventro-lateral tube feet naked. Papillae dorsal and dorso-lateral, in six rows, arise from much reduced wart-like structures, extending to anal region, descreasing in size posteriorly, longer papillae (2–5 mm) surround mouth dorsally.

Calcareous ring well developed, radial and interradial plates fused. Plates notched posteriorly, radial plates more so; interradial plates with sharp anterior projection; radial plates bifurcate anteriorly. Stone canal 8 mm long, highly coiled, no evidence of distinct madreporite but single, large pore present at terminal end of stone canal (?damaged madreporite). Polian vesicles two, one much larger, saccular, mid-dorsal. Respiratory trees mostly lost, where present left tree more profusely branched, up to third body length. Gonad in two tufts, highly branched. Longitudinal muscles in double bands, yellow.

Body wall ossicles comprise 3–4 armed tables of two sizes, arms of dorsal tables longer (120–140 µm), terminally perforated with 1–2 holes; spire of moderate height (60–100 µm), terminating in two or three projections which are sometimes spinous. Ventral tables more reduced (arms 10–30 µm, spire height 20–40 µm), appearing mostly as crosses, also with 1–2 holes on each arm, spires terminally spinous. Anal region with tables similar to those of dorsal body wall, but bulkier (arms 70–160 µm, spire 70–90 µm), each arm with 1–4 terminal holes, usually one large hole and other smaller ones. Tentacle ossicles comprise small (50–120 µm) to large (230– 270 µm) curved rods, larger ones with spinous outgrowths, smaller ones either smooth or spinous. Tube feet also with rods similar to those of tentacles but larger and more variable in size (290–420 µm) with perforations sometimes occurring at one extremity which can be smooth or spinous, some tube feet rods with marginal projections, some with ornamented ends; end-plates massive, complex network of plates. Papillae with large rods with spinous outgrowths, identical to those of tube feet.

Distribution. Off south and west coast of Western Cape Province, South Africa, 366–1006 m.

Remarks. This species, despite its determination, is described in some detail as it may not be connspecific with Cherbonnier’s (1952) species. Thandar (2008) provides a table comparing several related species of Synallactes . The specimens at hand most closely resemble Cherbonnier’s type and Thandar’s S. cf. mollis , with several differences (see Table 2 ). They resemble Cherbonnier’s type and Thandar’s S. cf. mollis in being subcylindrical with a thin body wall. The depth at which the current specimens were taken (650 m) falls in-between that recorded by Cherbonnier (366 m) and Thandar (1006 m). a bathymetric range endorsed by Solis-Marin (2003) as being characteristic of the Synallactidae family. The length of the current material ranges from 63–104 mm, which falls within the size of Thandar’s specimen (75 mm) but well outside that of Cherbonnier’s S. mollis (220 mm), perhaps representing juvenile material. However, the mid-body width (7–16 mm) is much smaller than that recorded by Thandar (37 mm) and Cherbonnier (50 mm). This can be also be attributed to the juvenility of the material and loss of most internal organs. A double ring of 18 tentacles was recorded for the holotype of S. mollis , while a range of 16–22 is here recorded for the current material. The position of the mouth and anus is identical to that of S. cf. mollis .

S. mollis S. cf. mollis S. mollis spire height not mentioned large 50–110 µm, small 60–100 µm

20–100 µm

Size of ventral body wall tables disc diam large 160 µm, large 110–340 µm, small 30–50 µm

small 80–100 µm 50–110 µm

arm length large 90–130 µm, small large 43–100 µm small 14– 10–30 µm

30–40 µm 43 µm

spire height large 40–90 µm, large 50–70 µm, 20–40 µm

small 30–70 µm small 40–50 µm

While the arrangement of tube feet in one mid-ventral and two ventro-lateral bands is common in all materials, their distributions differ. Thandar described the ventro-lateral tube feet in two zigzag rows, while in the current collection they form almost distinct double rows. Cherbonnier also recorded two longitudinal rows in the ventrolateral radii. While 4–6 rows of tube feet were recorded mid-ventrally for the holotype, Thandar recorded only 3–4 rows. The current collection shows only 2–3 rows of sometimes irregularly distributed mid-ventral tube feet. Thandar noted the extension of the mid-ventral tube feet to the mouth. In the current collection, the ventro-lateral tube feet extend to the mouth but the mid-ventral tube feet stop 3–10 mm short of the mouth. Six rows of papillae occur in all specimens, but their length varies, being much reduced in the current collection. Thandar (2008) reported the absence of oral papillae in his specimen, but in the current collection there are papillae encircling the mouth dorsally and are larger than the dorsal papillae.

Cherbonnier (1952) described the calcareous ring as being well-calcified and massive, with a very irregular form, whereby the distinction between radial and inter-radial plates could only be made through the examination of the muscle attachment points. However, the current specimens display a clear distinction between the interradial plates, with a single anterior projection, and the radial plates which anterior bifurcation. It is noteworthy that Cherbonnier (1952) also recorded two Polian vesicle.

The ossicles of the body wall in all three materials are consistently 3–4 armed tables, larger dorsally, with the arms never fusing to form a complete disc, like they do in S. viridilimus and S. samyni . Both Cherbonnier (1952) and Thandar (2008) recorded the presence of large and small tables in the dorsal body wall, with the smaller ones being rare. In the current collection there are no obvious differences in the size of the tables but a clear difference in size between the dorsal and ventral tables. Therefore table sizes were taken as a collective in each region.

Dorsal table disc mean size in the current collection (90 µm) is much smaller than the mean recorded for the larger tables by Thandar (280 µm) but within the means of his smaller table discs (80 µm) and the large table discs (130 µm) recorded by Cherbonnier. The mean length of the table arms of the current material (130 µm) corresponds well with the mean determined from ossicles from the type (130 µm) and the mean of the smaller table arms recorded by Thandar (166 µm). However, unlike Thandar’s form, the arms never form racquet-like expansions. The dorsal table arms with one or two terminal holes more closely resemble those of the large table arms of the holotype. However, the mean spire height is close to that recorded by Thandar (70 µm), also terminating in three teeth or projections.

The ventral table discs are smaller than those of the large table discs noted by Thandar (mean 180 µm) and the large (mean 160 µm) and small (mean 90 µm) discs illustrated by Cherbonnier, but within the range of the smaller table discs recorded by Thandar (mean 80 µm). The mean arm-length of tables of the current material is close to that of the arms of the small tables (40 µm) but not to that of the larger tables (110 µm) illustrated by Cherbonnier. The spire height is within the range of both Cherbonnier’s and Thandar’s specimens. However, it should be noted that the difference between spire height of the large and small tables is small and their size range tend to overlap. This suggests that all spire heights fall within a general range of 30–80 µm, irrespective of the size of the table or the region from which it was extracted. The presence of thicker tables in the anal region observed in the current collection, was also noted by Cherbonnier (1952).

The small holes at one or both ends of the tentacular rods, noted by Thandar (2008), were not found in the current collection. The tube feet and papillae rods conform to descriptions provided by Cherbonnier (1952) and Thandar (2008), though the mean size of tube feet rods provided by Thandar (510 µm) is 150 µm more than that of the current collection. There are thus many variations in the three forms but due to the general body form and the resemblance of the ossicles to the holotype, the specimens are here assigned to S. mollis and Thandar’s cf. S. mollis is considered a synonym of this species. It is here noted that since all specimens are small the differences may just be age variations. However, this could not be determined with any degree of certainty since in only one specimen from those dissected the gonad is intact but lacks gametes.

Figures

FIGURE 6 Synallactes mollis Cherbonnier, 1952. A 31645. A. Dorsal body wall tables; B. Ventral body wall tables; C. Tentacle rods; D. Tables from anal region; E. Madreporite; F. Calcareous ring; G. Tube feet rods (Figures A, C, D, scale b; figure B, scale a; figure E, scale c; figure F, scale d)

FIGURE 7. Synallactes mollis Cherbonnier, 1952. A 31645. A. Crosses of body wall; B – D. Body wall tables; E. Tube feet rods; F. Tentacle rods; G. Entire specimen (dorsal view); H. Same (ventral view).

Tables

TABLE 2. Distribution records and size variations of ossicles of S. mollis from three different collections.

	Cherbonnier, 1952	Thandar, 2008	Current collection
Length	220 mm	75 mm	82 mm
Depth	366 m	1006 m	650 m
Distribution	west coast of SA	south coast of SA	south coast of SA
Oral papillae	not mentioned	absent	present, 2–5 mm
Length of dorsal papillae	15 mm	10 mm	1–3 mm
Number of tube feet rows in ventro-lateral radii	2	2	2
Number of tube feet rows in mid-ventral radius	4–6	3–4	2–3
Size of dorsal body wall tables disc diam.	large 204–333 µm	large 150–410 µm, small 30–140 µm	20–140 µm
arm length	large 80–190 µm	large 114–250 µm, small 43–64 µm,	120–140 µm