Cucumella triperforata, Thandar, Ahmed & Arumugam, Preyan, 2011
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publication ID |
https://doi.org/ 10.5281/zenodo.204574 |
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DOI |
https://doi.org/10.5281/zenodo.3505025 |
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persistent identifier |
https://treatment.plazi.org/id/1145847B-FFB8-FF8C-6BD4-FD91F51E79D0 |
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treatment provided by |
Plazi |
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scientific name |
Cucumella triperforata |
| status |
sp. nov. |
Cucumella triperforata n. sp.
Diagnosis. Small, U- to barrel-shaped dactylochirotid holothuroid with few sparsely distributed tube feet and 12 unequal tentacles with one or two conspicuously larger than the others. Calcareous ring simple, no posterior bifurcations/prolongations to radial plates. Body wall ossicles exclusively tables with trilobed, trilocular, smooth disc, and a solid spire of three fused pillars diverging in 2-(3) non-denticulate processes/teeth. Plates absent.
Etymology. The specific name is with reference to the exclusive trilocular table discs which characterize this species.
Material examined. Holotype, SAM-A28114, off Port St. Johns-East London area, South Africa, 32° 28.6' S, 28° 58.8' E, R.V. ‘Meiring Naude’, St. SM 226, 24.vi.1979, 710– 775 m, Ƥ. Paratypes, SAM-A28115, same data as holotype, 7 spec (2 dissected).
Description of holotype. Specimen ( Figure 1 View FIGURE 1 D) small, female, distinctly U-shaped, length 9 mm along ventral surface, breadth across mid-body 2.5 mm. Preserved colouration off-white. Posterior end much narrower than anterior. Mouth and anus terminal, the latter surrounded by five unequal radial papillae of which two are conspicuously larger than the rest. Tentacles 12 ( Figure 1 View FIGURE 1 F), finger-shaped (digitate), retracted, of three sizes, two large (longer one 2 mm, coiled), two of medium size and eight very small. Tube feet scarce, only 15 located in the middle of the bulbous part of body, in three rows on the ventral ambulacra, none dorsally or at extreme anterior or posterior ends. Largest tube foot 0.15 mm; suckers reduced. Skin soft, thin, densely packed with ossicles clearly visible through stereoscope, table spires project well out of body wall rendering it rough to the touch.
Calcareous ring ( Figure 1 View FIGURE 1 C) low, simple, without posterior processes/bifurcations to radial plates, radial and interradial plates of more or less equal size; anterior projections of radial plates bifid, posterior margin deeply concave; interradial plates triangular, each with blunt anterior projection and slightly concave posterior margin. Stone canal ( Figure 1 View FIGURE 1 E) short, madreporite as rounded structure located in posterior concavity of mid-dorsal interradial plate of calcareous ring. Polian vesicle single, comprising a long narrow neck ending in a bulbous sac. Respiratory trees as simple sacs, unbranched, right tree smaller than left, not as bulbous; tiny projections on right tree perhaps indicate aborted branches. Longitudinal muscles as single strands, almost thread-like; retractor muscles thread-like. Ovary as two sac-like organs, one on each side of dorsal mesentery. Both sacs distended with mature and developing oocytes (90–425 µm, mean 236 µm), mature oocytes with thick enveloping capsule. An elongated structure, perhaps representing a developing juvenile, found lying in one ovarian sac.
Ossicles of body wall exclusively tables with trilocular disc ( Figure 1 View FIGURE 1 A, 3A) and a spire of moderate height ( Figure 1 View FIGURE 1 B), of fused pillars, ending in 2-(3) smooth, diverging processes or teeth, spire sometimes reduced to a knob on surface of disc; posterior tables smaller ( Figure 2 View FIGURE 2 B, 3B). Ossicles of tube feet similar to those of body wall but with reduced spires; delicate, reduced end-plates in tube feet. Ossicles of tentacles ( Figure 2 View FIGURE 2 A) comprise slightly knobbed rods, with usually a large perforation at one or both ends. Anal papillae densely packed with simple or C-shaped rods, often perforated at ends ( Figure 2 View FIGURE 2 D).
Description of dissected paratypes. Of the two paratypes dissected, largest one is U-shaped, measuring 10 mm along ventrum and 6 mm along dorsum; the other is slightly barrel-shaped, possibly due to contraction, measuring 6 mm along ventral surface. In larger paratype calcareous ring better calcified than that of holotype and not covered by hardened mesentery but gonad immature, lacking gametes. Smaller paratype mature with the ovary containing eggs with thick enveloping membrane. In same, Polian vesicles two, of more or less equal length, one with a long neck ending in a bulbous sac, the other saccular; madreporite bean-shaped, stone canal short; respiratory trees arising independently from cloaca, sac-like, with left one slightly larger, as in holotype; retractor muscles threadlike, arising from longitudinal bands at anterior third of body. Ossicles of both paratypes as in holotype (60– 108 µm; mean 88.0 µm). End-plates of tube feet unbroken ( Figure 2 View FIGURE 2 C). Anal papillae with dense accumulation of rods (42–99 µm, mean 61.4 µm), rendering them as rigid as anal teeth.
Description of other paratypes. Specimens similar in texture and colour to holotype. Tube feet few, ventral ones better developed, dorsal ones shorter, often reduced to suckers. Number of tube feet of left dorsal ambulacrum vary from 1–4 and that of the right dorsal ambulacrum 0–3, while that of the left ventral ambulacrum 4–7, right ventral ambulacrum 4–8 and mid-ventral ambulacrum 4–5. In at least one paratype two anal papillae are much longer than rest and project well out from the body. No differences in ossicles were detected in male and female specimens.
Distribution. Known only from type locality.
Habitat. Not recorded.
Remarks. In the presence of 12 tentacles, the new family approaches some members of the family Vaneyellidae , whereas the unequal tentacles suggest a relationship with the family Ypsilothuriidae . However, both these families are characterized by possessing only plates in the body wall. The new species, on the other hand, possesses only tables in the body wall. Although members of the family Rhopalodinidae do possess tables, they are of a different form and nearly always accompanied by plates. Furthermore, this family is unique in having both the mouth and anus opening on the tip of a long proboscis-like structure. A closer relationship is here proposed with the Vaneyellidae on the bases of body form as well as the form of the calcareous ring of C. triplex . According to Heding & Panning (1954) the calcareous ring of C. triplex resembles that of Mitsukuriella Heding & Panning, 1954 and Vaneyella Heding & Panning, 1954 currently classified in the Vaneyellidae within the Dactylochirotida. However, if the new species was included within Vaneyellidae it would have necessitated a drastic amendment of its diagnosis. Such a step would be inadmissible as Vaneyellidae is well characterized by only plates in the body wall or by a plated skeleton.
The rigidity of the anal papillae is here perceived to be a transient feature in their future transformation into teeth. In one paratype there appears an oocyte apparently sub-divided into two cells. This perhaps indicates intraovarian development, but this is by no means certain. However, the peculiarity of the “juvenile” like structure lying in one ovarian sac of the holotype may support this speculation.
The body wall ossicles of C. triperforata comprising only tables with a trilobed, trilocular disc and a solid spire ending in 2-(3) diverging processes/teeth bear a striking resemblance to those of the molpadid, Cherbonniera utriculus Sibuet, 1974 ( Figure 4 View FIGURE 4 C), so common in the very deep waters of the north and west Atlantic Ocean (see Pawson et al. 2001). However, ordinal differences between the taxa readily separate them. The body wall ossicles of Ch. utriculus are also exclusively tables with trilobed, trilocular disc (120–165 µm, mean 156.8 µm) ( Figure 4 View FIGURE 4 A), a spire of moderate height (58–140 µm, mean 104.25 µm), of three, mostly fused pillars ending in an undivided tip (80%) or in three diverging processes (20 %) ( Figure 4 View FIGURE 4 B). The tail ossicles are of similar form but slightly smaller (60–120 µm, mean 92.75 µm); with undivided (30%) or 3-toothed (70%) spire tip; height of spire (50–105 µm, mean 73.35 µm). However, we report here for the first time that the tips or diverging processes of the table spires in this species are finely denticulate/spinulated, very unlike those of the new species which are always smooth. These denticulations, confirmed in every specimen examined, including the type material, are perhaps an adaptation for increased traction necessary for locomotion in a soft substrate. The higher concentration of the three-pronged spires in the tail tables perhaps supports this speculation. The similarity in the form of the ossicles of the two species is perhaps indicative of parallel evolution and convergence consequent upon a similar mode of life, since both species are U-shaped and perhaps live buried in the sediment.
Ch. utriculus , in addition, has peculiar, table-like rods of varying shapes, each with a perforated base and a 1–3 toothed ‘spire’, in the peristome and/or collar surrounding the tentacles ( Figure 4 View FIGURE 4 D). Such deposits have also not been reported before for the species and may be precursors of tables. However, no such transformation of the ossicles was noticed in the body wall of all specimens examined and hence it is likely that these peculiar deposits are characteristic of the peristome/collar.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.