Psolidium Ludwig

O’Loughlin, P. Mark & Ahearn, Cynthia, 2008, Australian species of Psolidium Ludwig (Echinodermata: Holothuroidea: Psolidae), Memoirs of Museum Victoria 65, pp. 1-22 : 4-8

Key to Australian species of Psolidium Ludwig

1. Dorsal and lateral scales with vertical spires/pillars (not lumps) 2

— Dorsal and lateral scales lacking spires/pillars; some species with surface lumps on the scales 3

2. Dorsal and lateral scales each covered with slightly bulbous pillars; lacking mid-ventral radial series of tube feet; “thorn” ossicles present in body wall P. parmatus ( Sluiter, 1901) (NW Australia slope)

— Dorsal and lateral scales with predominantly single digitiform spires; mid-ventral radial series of tube feet present; lacking “thorn” ossicles in body wall P. spinuliferus (H. L. Clark, 1938) (N and W Australia)

3. “Thorn” ossicles present in body wall; live and preserved colour “black” P. nigrescens H. L. Clark, 1938 (central New South Wales)

— Body wall lacking “thorn” ossicles; live and preserved colour not “black” 4

4. Body wall with cupped crosses and/or cups 5

— Body wall lacking cupped crosses and/or cups 11

5. Cupped crosses and/or cups in sole of 2 ranges of size 6

— Cupped crosses and/or cups in sole of 1 range of size 7

6. Rosettes present in dorsal body wall and tentacles; smaller cupped crosses and cups up to 32 μ m long; sole with irregular thick perforated plates, knobbed on surface and margin P. marshae sp. nov. (SW Australia)

— Rosettes absent from dorsal body wall and tentacles; smaller cupped crosses and cups up to 24 μ m long; sole with smooth perforated plates P. minutus (H. L. Clark, 1938) (E Tasman Sea)

7. Dorsal and lateral cups shallow, completely covered by fine spinelets, including the cross; lacking mid-ventral radial series of tube feet P. mccallumae sp. nov. (Western Australia slope)

— Dorsal and lateral cups and cupped crosses not shallow; spinelets on rim of cup or distally on branches of cupped cross, not on cross; mid-ventral radial series of tube feet present 8

8. Body wall with predominantly cups, fewer cupped crosses 9

— Body wall with predominantly cupped crosses, fewer cups 10

9. Knobbed plates in sole; tentacle rosettes small, up to 40 μ m long; body rounded ventrally in transverse section P. berentsae sp. nov. (NE Queensland)

— Perforated plates in sole predominantly smooth; tentacle rosettes large, up to 80 μ m long; body flat ventrally P. laperousazi sp. nov. (SE Australia)

10. Knobbed perforated plates in sole; irregular perforated plates in tentacles P. hutchingsae sp. nov. (N New South Wales)

— Perforated plates in sole predominantly smooth; tentacles lack irregular perforated plates P. ravum Hickman, 1962 (SE Australia)

11. Lacking series of mid-ventral radial tube feet; dorsal and lateral tube feet inconspicuous in mid-body; dorsal and lateral scales coarsely granuliform P. granuliferum H. L. Clark, 1938 (southern Australia)

— Mid-ventral radial tube feet present as scattered series; dorsal and lateral tube feet conspicuous in mid-body; dorsal and lateral scales finely granuliform P. karenae sp. nov. (South Australia)

Psolidium Ludwig

Figures 1e , 2d , 4 b-d, 5e, 8f

Psolidium Ludwig, 1886: 9 .— Mortensen, 1927: 413.— Deichmann, 1941: 141-143.— Deichmann, 1947: 336.— Lambert, 1996: 21.

Diagnosis. Dendrochirotid holothuroids; small, up to 40 mm long; mid-body arched dorsally in transverse section, flat ventrally; dorsal and lateral body covered with imbricating scales, usually macroscopically conspicuous, sometimes obscured by integument, scales irregular in size and arrangement; scales decreasing in size ventro-laterally, orally and anally; lacking large oral valves; extensible oral cone, anterior or anterior-dorsal or dorsal orientation; extensible anal cone, posterior or posterior-dorsal or dorsal orientation; tube feet dorsally and laterally in mid-body, pass through scales.

Sole distinct, oval to elongate; discrete margin created by junction of small imbricating ventro-lateral scales with thin-walled, usually calcareous sole that lacks scales; peripheral band of tube feet, may be discontinuous across the inter-radii anteriorly and posteriorly; peripheral tube feet frequently of 2 sizes, those of outer series smaller; mid-ventral radial series of tube feet present or absent.

Calcareous ring solid, plates sub-rectangular, radial and interradial plates with tapered anterior projections; radial plates with deep notch posteriorly, interradial plates with shallow concave indentation posteriorly; 10 dendritic tentacles, ventral 2 smaller.

Dorsal and lateral ossicles: multi-layered or single-layered perforated plates (scales), always some with tube foot canals; integument covering scales may have cupped crosses, cups, “thorn” ossicles (irregular branched rods pointed distally), buttons, perforated plates and rosettes; tube foot small endplates, and tube foot support ossicles that are irregular rods and plates, bent and curved, variably perforated.

Sole ossicles: inter-radii with small to large single-layered perforated plates (rarely with multi-layering), smooth to variably knobbed and thickened, sometimes with cupped crosses, cups, thorn ossicles and rosettes; radii with additional tube foot ossicles, large endplates and tube foot support ossicles that are irregular rods and plates, bent and curved, variably perforated.

Tentacle ossicles: rods variably perforated, thick to thin, long to short, straight or bent, flat or curved; dendritic tentacle branch endplates are small, irregular in shape, cupped, with a few large perforations and irregular margin; perforated plates may be present; densely branched rosettes may be present.

Type species. Psolidium dorsipes Ludwig, 1886 .

Australianspecies. Psolidiumberentsae sp.nov., P.granuliferum H. L. Clark, 1938 , P. hutchingsae sp. nov., P. karenae sp. nov., P. laperousazi sp. nov., P. marshae sp. nov., P. mccallumae sp. nov., P. minutus (H. L. Clark, 1938) , P. nigrescens H. L. Clark, 1938 , P. parmatus ( Sluiter, 1901) , P. ravum Hickman, 1962 , and P. spinuliferus (H. L. Clark, 1938) .

Remarks. The descriptive term “thorn” ossicles is used for the body wall ossicles in the form of irregular short branched rods that are pointed distally. They occur in Psolidium nigrescens H. L. Clark and P. parmatus Sluiter. H. L. Clark (1938) referred to them as “triradiate particles/spicules”. Sluiter (1901) did not report their presence. The type of P. parmatus was examined by one of us (PMO), and their presence noted.

Pawson and Valentine (1981) reported that their Atlantic species Psolidium prostratum lacked endplates in the dorsal tube feet. Thandar (2006) described Psolidium multipes from South Africa, and among characteristic Psolidium features reported that the sole was not distinct from the dorsum, the ventral tube feet were in radial series, and there were multi-layered ossicles in the sole. These characters are atypical of Psolidium , but may indicate juvenile form.

The Australian species of Psolidium are distinguished from each other in the key. The key indicates three morphological groupings of Australian Psolidium species: P. parmatus and P. spinuliferus and with their vertical pillars/ spires on dorsal and lateral scales; species with cupped crosses and cups (as for the type species P. dorsipes ); and species lacking cupped crosses and cups.

Figures

Figure 1. Photos of live specimens of Psolidium Ludwig, 1886 (a–d, in situ by K.Gowlett-Holmes; e, in aquarium by L.Altoff):a, P. granuliferum H. L. Clark, 1938, Port Davey, Tasmania (14 mm long preserved; SAM K2174, PK0259); b, P. karenae sp. nov., Yorke Peninsula, South Australia (17 mm long preserved; holotype SAM K2177, PK0105); c, P. laperousazi sp. nov., Kangaroo I, South Australia (13 mm long preserved; paratype SAM K2179, PK0253); d, P. marshae sp. nov., Kangaroo I (10 mm long preserved; SAM K2173, PK0273); e, P. ravum Hickman, 1962, Portland, Victoria (17 mm long preserved; NMV F125379).

Figure 2. Photos of preserved specimens of Psolidium Ludwig, 1886 (a, c–d by L. Altoff; b, e–f by S. Hinkley and D. Maric): a, P. berentsae sp. nov., Lizard I, Queensland (lateral view; 12 mm long; holotype AM J24098); b, P. granuliferum H. L. Clark, 1938, Smokey Bay, South Australia (dorso-lateral view, with mouth left; 19 mm long; SAM K2176); c–d, P. hutchingsae sp. nov., Split Solitary I, New South Wales (20 mm long; holotype AM J24107); c, dorso-lateral view; d, 10 tentacles, with 2 small ventral ones bottom; e, P. karenae sp. nov., Adelaide (lateral view, mouth left; 20 mm long; paratype SAM K2185); f, P. laperousazi sp. nov., D’Entrecasteaux Channel, Tasmania (dorso-lateral view, mouth right; 18 mm long; paratype SAM K2339).

Figure 4. a, P. spinuliferus (H. L. Clark, 1938), Darwin (lateral view; 10 mm long; AM J24096; photo by L. Altoff); b, generalised form of radial (left) and interradial plates of the calcareous ring of Psolidium species (drawing by M. O’Loughlin); c–d, drawings of sole showing distribution of tube feet (by D. Maric); c, P. granuliferum H. L. Clark, 1938 (SAM K2176); d, P. karenae sp. nov. (SAM K2188).