Psolidium pseudopulcherrimum, Thandar, 2008

Thandar, Ahmed S., 2008, Additions to the holothuroid fauna of the southern African temperate faunistic provinces, with descriptions of new species, Zootaxa 1697 (1), pp. 1-57 : 36-39

Psolidium pseudopulcherrimum n. sp.

Figure 14

Diagnosis A small species, up to 10 mm long; sole well-defined. Body invested in imbricating scales, 10-12 scales between mouth and anus. Mouth surrounded by scales (?valves) similar to those of body wall, anus by anal teeth/papillae. Dorsal podia inconspicuous, ventral podia in a single row on each side of sole, odd ambulacrum naked, except for the anterior-most and posterior-most podium. Polian vesicle single. Species broodprotecting, with paired coelomic brood pouches. Dorsal scales up to 775 µm, simple, always made up of a single layer of calcareous material, rarely with few or more faintly developed knobs; ventral scales 158-383 µm, simpler than those of dorsal body wall. Baskets 35-55 µm. Podial, introvert and tentacle deposits as in P. pulcherrimum .

Etymology

The species is so named because of its superficial resemblance to the previous species, P. pulcherrimum .

Material examined

Holotype, SAM-A28019, UCT Ecol. Surv., Still Bay Shelf Transect , St. SST 12, 35 o 22' S, 22 o 31' E, 20.vi. 1972, 200 m. Paratype, SAM-A28020, same data as holotype, one specimen .

Type locality Still Bay , WCP, 200 m.

Description of holotype

Specimen small, 9 mm long, 3.5 mm broad in mid-body, distinctly psolid-like, sole well-defined, 6 mm long. Colour uniformly white. 10-12 scales between mouth and anus, nine scales laterally on each side anteriorly and seven posteriorly. Mouth dorsal, surrounded by scales (?valves) similar to those of body wall; anus also dorsal, encircled by anal teeth/papillae. Dorsal podia not detected, ventral podia in a single row on each side of sole, about eight on right and about 10 on left ventral ambulacrum, odd ambulacrum naked except for the anterior-most and posterior-most podium.

Internal anatomy similar to that of preceding species except trees not bright yellow and right respiratory tree longer than left, reaching mid-body, left tree confined to posterior third of body. Gonad (ovary) developed as two tufts of short tubules, three on each side of mesentery. Brood pouches internal, paired, right pouch with 10 brood-embryos, left one with eight.

Body wall invested in imbricating scales covered by superficial layer of baskets ( Figure 14C ) similar but slightly smaller (35-55 µm, mean 48 µm) than those of preceding species. Scales of dorsal and ventral body wall different from those of preceding species. Dorsal scales ( Figure 14A ) ca. 775 µm, simple, always made up of a single layer of calcareous material, margins smooth, rarely with few faintly developed knobs; ventral scales ( Figure 14B ) small, 158-383 µm (mean 255 µm), simpler than those of dorsal body wall and the corresponding ones of the preceding species. Podial, tentacle and introvert deposits as in preceding species. Podial deposits ( Figure 14D, E ) 53-170 µm (mean 103 µm) with 3-6 holes and up to six faint knobs; end-plates ca. 165 µm. Tentacle rods 92-298 µm (mean 159 µm), with 3-7 holes; tentacle plates 45-90 µm (mean 67 µm) with 3-12 holes ( Figure 14F ); introvert rods 208-435 µm long, with 4-7 holes ( Figure 14G ).

Description of paratype

Specimen small, twice as long as broad, 6.5 x 3 mm, sole 3.5 mm long. About 8-9 scales between mouth and anus, about seven scales laterally on each side. Sole distinct, displaced posteriorly, six scales between mouth and sole. Marginal podia 7-8, of unequal length, suckers well developed; odd ambulacrum without podia except one at each end of sole. Several pores present on sole but definitely not indicative of retracted podia, may represent pores of brood pouches. Imbricatng plates ( Figure 14H, I ) larger than those of holotype but with better developed knobs; podial deposits ( Figure 14K, L ) and end-plates ( Figure 14J ) similar to those of holotype.

Distribution Type locality only.

Remarks

On first observation the two specimens were thought to represent the preceding species. However, on closer examination they were found to differ from it in the presence of a fewer number of scales between mouth and anus, a distinct sole, the naked odd ambulacrum and imbricating plates made up of a single layer of calcareous material. The new species also differs from other nominal species of Psolidium in the same way as P. pulcherrimum . Although both the brood-protecting species are closely related, they are definitely not conspecific, despite their sympatry.

Figures

FIGURE 14. Psolidium pseudopulcherrimum sp. nov. A-G. Holotype, SAM-A28019. A. Fragmented scale from dorsal body wall; B. plates from ventral body wall; C. baskets from ventral body wall; D. rods from ventral podia; E. plates from ventral podia; F. rods and plates from tentacles; G. rods from introvert. H-L. Paratype, SAM-A28020, H. scales from dorsal body wall; I scales from ventral body wall; J. reduced end-plate from ventral podium; K. knobbed plates from ventral podia; L smooth plate from ventral podium. A & H scale a; B-G & I-L scale b.