Pseudocnus laevigatus Verrill 1876

Pseudocnus laevigatus (Verrill, 1876)

Figure 2 d insert; table 1.

Distribution. Heard, Kerguelen and Macquarie Islands, littoral to 528 m (Heard I., this work).

Remarks. Pentactella laevigata Verrill, 1876 was described for a single specimen from the Kerguelen Is, and the species later assigned to Pseudocnus Panning, 1949 by Panning (1962). Pawson (1968) discussed a possible “co-type” specimen of Pentactella laevigata (USNM cat. No. 3148), but noted that the presence of conspicuous ventral brood pouches that Verrill did not mention, and presence of a calcareous ring that Verrill reported as absent, cast doubt on the type status of this specimen. The largest illustrated ossicle length from the type in Pawson (1968) is 124 µ m, and average length reported as 110 µ m. These are significantly smaller than reported below (160 and 200 µ m) for Kerguelen specimens.

Pseudocnus laevigatus (Verrill) is the most abundant holothuroid from the Kerguelen Is in the BANZARE collection. Théel (1886) also reported abundant Challenger specimens, and his description of the material, including loss of ossicles with size, also describes the BANZARE specimens. Except that the figures in the first of his two sets (Théel 1886, pl. 3 fig. 5) are a good illustration of the ossicles of Cladodactyla crocea (Lesson). The figures do not match Théel’s second set of figures (pl. 6, fig. 13), and do not match his text. In the 1886 Challenger Report Théel’s description of Cucumaria crocea Lesson from the South Atlantic follows his description of Cucumaria laevigata Verrill. I presume that pl. 3 fig. 5 has been mistakenly placed with C. laevigata instead C. crocea. This presumption is supported by the facts that the only figures for C. crocea (pl. 12 figs 1, 2) are of body form, and Théel’s description of the ossicles of C. crocea clearly refers to pl. 3 fig. 5.

Massin (1992b) was misled by this mistake in his discussion of Marion I. holothuroids, and included the Cucumaria laevigata figures in his synonymy for Cladodactyla crocea croceoides (Vaney). In the extensive sampling of the Kerguelen Is by BANZARE neither Cladodactyla crocea nor Cladodactyla crocea croceoides was found. The species found on the Kerguelen Is that most closely resembles the juvenile specimens described by Massin (1992b) as Cladodactyla crocea croceoides is Staurocucumis liouvillei (Vaney, 1914).

Ekman (1927) distinguished a South American form from the Kerguelen form of Cucumaria laevigata and erected Cucumaria perrieri for the former. Panning (1962) considered the distribution of Pseudocnus laevigatus to be Prince Edward, Crozet, Kerguelen and Heard Islands. Some, if not all, of the Prince Edward and Crozet material may prove to be Pseudocnus marionensis (Théel, 1886) (see below). I would add Macquarie I. to Panning’s distribution, but note that there is morphological evidence that Pseudocnus laevigatus on these islands is probably an allopatric species complex. Maximum body length: Heard 44 mm (this work); Kergulen 130 mm (this work; Théel 1886, 115 mm); Macquarie 15 mm (this work; Pawson 1968, 25 mm). Maximum pear shaped ossicle lengths: Heard 128 µ m (this work); Macquarie 144 µ m (this work; Pawson 1968, average 110 µ m); Kerguelen 200 µ m (this work; Théel 1886, 160 µ m). In this work ventral brood pouches were observed in a few Heard I. specimens (NMV F85005), but not in Kerguelen or Macquarie specimens. The Heard lot of 26 specimens was collected on 28 September from 528 m. Only a few specimens had ventral brood pouches, with eggs and embryos and juveniles at various stages of development. Pawson (1968) did not observe brood pouches in Macquarie specimens.