Psolidium pulcherrimum, Thandar, 2008
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publication ID |
https://doi.org/ 10.11646/zootaxa.1697.1.1 |
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persistent identifier |
https://treatment.plazi.org/id/DE2087C7-F500-8765-A0AD-F3E596A85ACA |
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treatment provided by |
Felipe |
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scientific name |
Psolidium pulcherrimum |
| status |
sp. nov. |
Psolidium pulcherrimum View in CoL sp. nov.
Figure 13 View FIGURE 13
Diagnosis
A small species, holotype (mature female) 11 mm, invested in imbricating scales, up to 20 scales between mouth and anus; mouth bordered by smaller scales (?valves), anus by papillae/teeth. Ventral surface sole-like but distinct sole absent. Dorsal podia usually inconspicuous, ventral podia restricted to ambulacra in single rows, including those in odd ambulacrum. Tentacles dendritic, 10, mid-ventral two reduced. Polian vesicle single. Respiratory trees bright yellow. Females brood-protecting with a pair of coelomic pouches. Scales heavily-knobbed, multi-layered, dorsally 600-960 µm, ventrally 405-605 µm. Baskets cup-like with a spinose rim. Ventral body wall, in addition, with slightly elongate, 205-365 µm, finely-knobbed plates. Podial deposits as small, smooth, perforated plates. Introvert with rods. Tentacle stalk with rods; branches with smooth, perforated plates.
Etymology The specific name refers to the beautiful form of the body from Latin (pulcherrimum-most beautiful).
Material examined
Holotype (female), SAM-A28017, UCT Ecol. Surv., Still Bay Shelf Transect , St. SST 12, 35 o 22' S, 22 o 31' E, 20.vi. 1972, 200 m. Paratypes, SAM-A28018, same data as holotype, 5 spec.
Type locality Still Bay , WCP, 200 m.
Description of holotype
Female, 11 mm long, 5 mm wide in mid-body. Dorsal surface well arched, covered with imbricating scales which also extend laterally; over 20 scales between mouth and anus, about 20 scales laterally on each side. Mouth sub-dorsal, opened, bordered by scales smaller than those of dorsal surface, no distinct valves; anus completely concealed by scales. Ventral surface flattened, sole-like, but distinct sole absent. Dorsal podia not discernable, ventral podia well developed, restricted to ambulacra in single irregular rows, including those of odd ambulacrum. Tentacles dendritic, 10, mid-ventral two reduced. Colour uniformly white, podia slightly yellowish.
Calcareous ring ( Figure 13L View FIGURE 13 ) simple, both radial and interradial plates sculptured, of more or less same length, anterior projection of radial plates thicker that that of interradial plates, bifid anteriorly and with depression for retractor muscle; interradial plates triangular; posterior margin of ring undulating. Polian vesicle single, ventral, elongated; stone canal short, free, madreporite four-lobed ( Figure 13M View FIGURE 13 ). Respiratory trees short, of equal length, confined to posterior third of body, arising independently from reduced cloaca, each only terminally branched; branches yellow, resembling fat bodies of toads, about 10 on the right and six on the left, with the largest branch of latter bearing a couple of diverticula. Gonad (ovary) located in mid-body, comprising two tufts of short unbranched tubules at various stages of maturity; immature tubules short, pyriform; mature tubules elongate, full of eggs in various stages of development. Species brood-protecting, a pair of internal brood pouches clearly visible in mid-ventral coelom, containing brood-embryos (ca. 0.8 mm) or juvenile (ca. 1 mm), right sac with four juvenile and five brood-embryos, left one with four juvenile and three brood-embryos; each sac apparently opening independently on mid-ventral ambulacrum through a deeply folded/pleated structure, external opening(s) not detected. Longitudinal muscles unpaired, thin; retractors thickened distally, just before insertion on calcareous ring.
Scales covered by external layer of deep cup-like baskets. Dorsal baskets ( Figure 13B View FIGURE 13 ) and ventral baskets ( Figure 13G View FIGURE 13 ) more or less identical, dorsal 40-60 µm (mean 51 µm), ventral 46-65 µm (mean 53 µm), usually complete, cup-like, with smooth, cross-shaped base, a spinose rim and usually 4-(6) basal holes. Dorsal scales ( Figure 13A View FIGURE 13 ) large, 600-960 µm (mean 814 µm), heavily-knobbed, composed usually of two layers of calcareous material, round to slightly oval, with numerous (21-36) holes; developing plates ( Figure 13C View FIGURE 13 ) smooth, with irregular margins and fewer holes. Ventral scales ( Figure 13D, E View FIGURE 13 ) round to irregular, heavily-knobbed, similar to but smaller than dorsal scales, 405-605 µm (mean 406 µm); ventral deposits also include slightly elongate, 205-365 µm (mean 271 µm), less-perforate (4-10 holes), faintly-knobbed plates ( Figure 13F View FIGURE 13 ), usually localized at base of podia. Podial deposits comprise smaller plates with irregular margins, few perforations and with or without minute knobs ( Figure 13I View FIGURE 13 ). End-plates large to reduced, up to 360 µm, with irregularly scattered holes, larger medially. Introvert with rods of irregular shapes with few perforations along length and small, usually marginally localized, knobs ( Figure 13H View FIGURE 13 ). Tentacle stalk and main branches include rods, 95-275 µm (mean 164 µm), similar to those of introvert, smooth to slightly knobbed ( Figure 13J View FIGURE 13 ); tentacle branches with smooth, delicate, perforated plates of various sizes, 53-120 µm (mean 84 µm) and with varying number of holes ( Figure 13K View FIGURE 13 ). Retractor muscle devoid of spicules.
Body wall of brood-embryos with numerous cross-shaped deposits ( Figure 13N View FIGURE 13 ), representing early stage of development of scales/plates, and other peculiar, delicate, lattice-like or reticulated bodies ( Figure 13O View FIGURE 13 ). Those of juvenile comprise similar deposits as well as a few developing cups/baskets ( Figure 13P View FIGURE 13 ).
Description of paratypes
Size range 6-10 mm; colour and podia distribution as in holotype, number of scales between mouth and anus variable (12-20), depending on stage of maturity. In four paratypes ventral surface sole-like, but no distinct sole, in remaining one distinct sole evident, perhaps an artefact of preservation. In only two paratypes (including one with sole) anus discernable, anal teeth and/or papillae present. In only two paratypes, including the one with sole, dorsal podia discernable, emitting from between scales. In dissected paratype (mature, male) no brood pouches detected, hence species dioecious.
Distribution Type locality only.
Remarks
The presence of a plated skeleton, dorsal podia (at least in some paratypes), and the sole-like ventral surface with well-developed marginal podia, places the species clearly in Psolidium . However, the barrel-shaped body form, single row of podia in each ventral ambulacrum, the large heavily-knobbed dorsal plates of the Pseudocnella or Pentacta type, accompanied by deep cup-like baskets, sets this species apart from all nominal species of the genus. Only few species of Psolidium have been described with a single row of marginal podia but in none this feature exists in combination with baskets and heavily-knobbed plates. Hence, relating this species to others in the genus is problematical at this stage. Thandar (1999, 2006) described other southern African psolids with a single row of marginal podia but these lack the deep cup-shaped baskets and heavilyknobbed plates characteristic of the new species. Other remarkable features include its brooding habit, recorded for only a few species of Psolidium , and the peculiar nature (colour and form) of its respiratory trees.
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