An unusual spine-bearing Pinnularia species from the Antarctic Livingston Island (South Shetland Islands)

A new spine-bearing Pinnularia species, Pinnularia gemella sp. nov., is described from a sediment core taken on the Antarctic Livingston Island (South Shetland Islands, southern Atlantic Ocean). The morphology of this species was examined using scanning electron microscopy. The species is easily recognizable by the presence of a continuous row of small, spathulate spines on one side of the valve. Using these interlocking spines, the species forms small colonies with the frustules lying in juxtaposition. The morphology and colonial form of the new species is compared to all other spine-bearing species such as P. sofia Van de Vijver & Le Cohu andlor colonial species such as P. cardinaliculus (A. Schmidt) Cleve. The ecology of the new species is derived from the ecological preferences of the associated flora.