Nuphela troglophila sp. nov., an aerophilous diatom (Bacillariophyta) from the Bossea cave (NW Italy), with notes on its ecology.

Abstract: Nupela troglophila sp. nov. is described from epilithic and epiphytic samples collected around the artificial lighting system in the Bossea cave, SW Alps (NW Italy). The morphological features of the new species are described and documented through light microscopy and scanning electron microscopy analysis. A comparison with morphologically similar taxa is provided. Nupela troglophila belongs to the group of the small, elliptical–lanceolate species of the genus Nupela. The key feature that distinguishes it from all the other taxa belonging to this genus is the shape of the distal raphe fissures, always laying on the valvar surface, strongly deflected on the same side, but never reaching the valve mantle. The ecological preferences of the most abundant diatom species are explored through the ecological optimum calculation and the Outlying Mean Index (OMI) analysis. Within the Bossea cave, N. troglophila seems to prefer humid and warm sites. The highest abundance was reached on wet walls characterized by low light conditions. Nupela troglophila was generally associated with Humidophila pyrenaica that showed the same pattern of distribution in the cave and similar relative abundance. On the contrary, N. troglophila showed its lowest densities when Humidophila contenta was abundant. Until now, N. troglophila has been recorded only in the type locality