Cryptoplax

Schwabe, Enrico, Sirenko, Boris I. & Seeto, Johnson, 2008, A checklist of Polyplacophora (Mollusca) from the Fiji islands, Zootaxa 1777, pp. 1-52 : 31

Cryptoplax sp.

( Figures 8A, B )

Fiji records: Cryptoplax striata ; Bergenhayn 1930a: 23.

Remarks: The specimen Bergenhayn mentioned from Fiji, Viti Levu, Namuka [17°59’S 178°36’E] that was collected at 15 June 1917 during the Sixten Bocks Expedition 1917–18 is deposited in the SMNH (87439 [old no. 639]) and measures 13 mm. Based on the available picture alone, the species can not be attributed with certainty to a living representative of the genus Cryptoplax . Comparison with the 46.1 mm long holotype of Cryptoplax striata (Lamarck, 1819) (MNHN 6081) shows differences in the valve sculpture. That is why we report here the species as Cryptoplax sp. only.

While Bergenhayn’s specimen has narrow, granulated radial ribs in the pleurolateral areas, the holotype shows solid, smooth radial ribs. Unfortunately we never saw juvenile specimens of Cryptoplax striata , which according to Gowlett-Holmes (2001) is a strictly Australian species, so that we are unable to say whether the tegmental differences reflect growth stages only, or warrant a specific separation. The granulated radial ribs in Bergenhayn’s specimen show similarities to the sculpture of the following fossil species. The juveniles of this species also differ from those of its Fijian congeners. Small specimens of C. elioti have a much finer tegmentum sculpture, lacking radial ribs in the head valve. Juveniles of Cryptoplax larvaeformis were not found in the material from Fiji, but numerous specimens are available for comparision from New Caledonia (Schwabe et al. [unpublished data]). It was found that juveniles of C. larvaeformis tend to lose the contact between the valves when they grow to about 10 mm body length. These small specimens were generally redish with dark spotted posterior valve margins and the tegmentum has a finer sculpture, while Bergenhayn’s specimen has throughout white valves. Thus we consider the illustrated specimen different from C. elioti and C. larvaeformis .

Figures

FIGURE 8. A – B, Cryptoplax sp., SMNH 87439 (photo: Purba Pal / SMNH, © All rights reserved), Viti Levu, Namuka [17 ° 59 ’ S 178 ° 36 ’ E], dorsal view. A, complete specimen. B, detail of the intermediate valves. C – F, Choneplax littlerorum Sirenko, 2003. C, “ Acanthochitona sp. ”, ZSM Mol 20061626: Fiji, Viti Levu, Laucala Bay, west side of the Nukumbutho channel of the fringing reef opposite the USP, 18 ° 10.899 ' S 178 ° 27.971 ' E, dorsal view. D, same specimen as in fig. C, but alive, photo taken through the microscope. E, “ Notoplax sp. ”, ZISP: Fiji, Vekai Island [17 ° 34 ’ S 178 ° 49 ’ W], Callisto St. 94, dorsal view. F, Choneplax littlerorum Sirenko, 2003, ZSM Mol 20062136: Fiji, Viti Levu, Laucala Bay, west side of the Nukumbutho channel of the fringing reef opposite the USP, 18 ° 10.899 ' S 178 ° 27.971 ' E, ventral view of a tail valve, sl indicates the position of the incisions [slits]. Scale bars A 2 mm, B – E 1 mm, F 100 µm.