Pentactella Verrill, 1876

O'Loughlin, P. Mark, Skarbnik-López, Jessica, Mackenzie, Melanie & VandenSpiegel, Didier, 2015, Sea cucumbers of the Kerguelen Plateau, with descriptions of new genus and species (Echinodermata: Holothuroidea), Memoirs of Museum Victoria 73, pp. 59-93 : 80-81

Pentactella Verrill, 1876

Pentactella Verrill, 1876a: 68 , 69.

Laevocnus O’Loughlin (in O’Loughlin et al., 2014): 46.

Type species. Pentactella laevigata Verrill, 1876a , b (type locality Kerguelen Islands ; initially monotypic) .

Assigned species and occurrences. Pentactella cornuta ( Cherbonnier, 1941) (Patagonia) ; P. intermedia ( Théel, 1886) ( HIMI and Kerguelen Is); P. katrinae (O’Loughlin in O’Loughlin et al., 2014) ( Antarctica, Shag Rock ); P. laevigata ( Verrill, 1876a, b) ( HIMI, Kerguelen Is, Macquarie I.)); P. leachmani (Davey & O’Loughlin in O’Loughlin et al., 2014) (Ross Sea); P. leoninoides ( Mortensen, 1925) ( New Zealand sub-antarctic islands); P. leonina ( Semper, 1867) (Falkland Is) ; L. marionensis ( Théel, 1886) (Marion I.) ; P. perrieri ( Ekman, 1927) (Falkland Is, South Georgia); P. serrata ( Théel, 1886) ( HIMI).

Diagnosis (sensu stricto; based on 14 specimens in HIMI lot NMV F85005). Cucumariinid species; body wall thin, firm, not calcareous; body fusiform with posterior rounded taper but not tail; preserved, relaxed body up to 43 mm long (excluding tentacles); 10 equal dendritic tentacles; tube feet on radii only, radial series cross introvert, radial series on relaxed specimens single, slightly zig-zag, spaced, slightly more numerous on three ventral radii; lacking external or internal anal scales; lacking calcareous ring in all specimen sizes; three long, thin polian vesicles; lacking genital papilla, gonad tubules not branched; two, laterally paired, mid-body, mid-ventral, coelomic brood sacs, with external transverse slit openings, sacs and opening sometimes present; brood juveniles with distinct tentacle crowns may be present in brood sacs, brood juveniles up to 3 mm long. Preserved colour off-white to pale fawn.

Body wall ossicles abundant, oval to elongate, single-layered, perforated plates, typically two large lateral central perforations, typically knobbed centrally, one end of plate tapered and distally spinous, opposite end not tapered, not spinous, plates up to typically 130 µ m long; lacking knobbed buttons that do not have any spinous margin. Tube feet with endplates, diameters up to 320 µ m, tube foot support ossicles curved perfortated plates with outer edge spinous, plate lengths up to 140 µ m. Tentacle ossicles thick, perforated plates, irregularly oval to elongate, plates up to 260 µ m long; thin, irregular, convex, perforated plates, up to 100 µ m across; distally perforate, bent rods, up to 120 µ m long; lacking rosettes.

Remarks. Panning (1949) considered Pentactella Verrill, 1876 to be a junior synonym of Stereoderma Ayres, 1851 . Pawson (1964) followed Panning (1949), reporting Stereoderma laevigata (Verrill, 1876) . Subsequently Panning (1962) referred this species to Pseudocnus Panning, 1949 . Pawson (1968) followed Panning (1962), reporting Pseudocnus laevigatus (Verrill, 1867) . In describing the new genus Laevocnus O’Loughlin (in O’Loughlin et al. 2014) the authors failed to notice that their type species for Laevocnus , Pentactella laevigata Verrill, 1876 , is also the type species for the monotypic Pentactella Verrill, 1876 . Pentactella is here raised out of synonymy with Stereoderma and Pseudocnus , and Laevocnus is an objective synonym of Pentactella .

We recognize variations in morphological form amongst the species assigned to Pentactella . These variations have been included in the diagnosis for Laevocnus (= Pentactella ) in O’Loughlin et al. 2014. The problem of a diagnosis for Pentactella is compounded by our recognition of the consistent presence of some knobbed buttons that lack a spinous end in specimens of Pentactella intermedia ( Théel, 1886) . Based on some supportive genetic data P. intermedia remains assigned to Pentactella . There are to date inadequate genetic data to know what morphological characters are reliable for generic diagnosis. We have thus provided above a sensu stricto diagnosis for Pentactella that is based on one lot of 14 specimens from the southern Kerguelen Plateau ( NMV F85005).

The status of type material for Pentactella laevigata Verrill 1876 is uncertain. USNM holds a single specimen with a label: “ Type, Pentactella laevigata Kidder, Cat. No. 3148, Locality Kerguelen Is, Coll. by Transit of Venus Expedition, Date Dec. 1876, Id. by Verrill”. Obviously Verrill was the taxa author, and not the collector Dr. J. H. Kidder. Verrill (1876) gave a collection date as January 1875. This accords with the date of the US Transit of Venus Expedition during 1874–1875. The label date (Dec. 1876) may refer to the date of description by Verrill. Pawson (1968) noted “this may be the only extant specimen of the original type series”. Verrill provided measurements for only one specimen, and did not indicate more than one type specimen. Pawson (1968) reported on the USNM specimen as a “Co-Type” ( USNM Cat. No. 3148). He judged that this specimen generally matched the description by Verrill (1876). But Pawson noted two anomalies: the presence of a calcareous ring, while Verrill explicitly stated that such plates were absent; and the presence of ventral brood pouches that Verrill did not describe. Our sensu stricto diagnosis above matches the descriptions by Verrill (1876) and Pawson (1968), except that we have never observed calcareous ring plates for this species. The presence of ventral brood pouches is rare. Only two specimens of the lot of 14 that we examined have brood pouches.

O’Loughlin (2009) discussed in detail Pseudocnus intermedia ( Théel, 1886) , Pseudocnus laevigatus (Verrill, 1876) and Pseudocnus marionensis ( Théel, 1886) , the three species subsequently referred to Laevocnus O’Loughlin (in O’Loughlin et al. 2014) (= Pentactella Verrill, 1876 ).

O’Loughlin (2009) noted some misleading captions in Théel (1886), that referred to figures of Cladodactyla crocea ( Lesson, 1830) and Cucumaria laevigata (Verrill, 1876) . This error misled Massin (1992) who reported Cladodactyla crocea croceoides ( Vaney, 1908) from Marion Island, with Cucumaria laevigata as a junior synonym. This variety was referred to the synonymy of Cladodactyla crocea in O’Loughlin et al. 2014. Amongst the many holothuroid specimens collected from the Kerguelen Plateau no specimen of Cladodactyla crocea has been found.