Ophioplinthus undetermined

Ophioplinthus sp. juvenile

Fig. 3F–H

Material examined. MD 50 DC34, MNHN IE.2009.1619 (1).

Remarks. The 4 mm dd specimen is a juvenile which makes identification problematic. It has the classic Ophioplinthus characters of reduced DAPs (Fig. 3G), fragmented oral shield and small inconspicuous tube feet (Fig. 3H). It has the second oral tentacle pore well outside of the jaw slit, two spiniform tentacle scales on the first arm segment and one on the next two, thereafter none (Fig. 3H). The tentacle pores become progressively inconspicuous down the arm. The dorsal disc is dominated by the six primary plates, two interradial scales and some small intercalary scales. There are small DAPs on the first two segments free of the disc. The surface of the LAPs appears to be beaded. There is one, rarely two, short arm spines. DNA barcode evidence indicates that there are numerous cryptic species of Ophioplinthus in the Southern Ocean (O’Hara et al. 2013). The problem of identification is compounded by the presence of either a hydroid (Hydractinia) or sponge (Iophon) that grows (parasitically?) on some lineages, altering the growth of the external plates.