Abstract
A new record of lithistid demosponges is reported from a western Sardinian karstic cave. The new specimen matches the trait of the genus Neophrissospongia (Corallistidae) for an ectosomal skeleton of radial dichotriaenes, a choanosomal skeleton as a network of dicranoclone desmas, and streptaster/amphiaster microscleres with short spiny rays bearing blunt tips. The cave-dwelling N. nana nov. sp. diverges from the other species of the genus in diagnostic characters such as the large irregular plate-like growth form, the topographic distribution of inhalant and exhalant apertures, and a smaller size of all spicular types. Moreover it displays an additional rare second type of dichotriaenes with smooth cladomes, shared with other genera of Corallistidae but never reported before for the genus Neophrissospongia. In addition N. nana nov. sp. bears style-like sub-ectosomal spicules shared with N. microstylifer from deep water of New Caledonia. As for the latter trait, a present in-depth analysis of N. nolitangere from the Atlantic Ocean contrasts with previous historical records reporting monaxial spicules as oxeas/anisoxeas. The diagnosis of the genus Neophrissospongia is therefore emended for the growth form and for the micro-traits of dichotriaenes and monaxial sub-ectosomal spicules. Morphological data indicate that the new species is allied to N. nolitangere and N. microstylifer from Eastern Atlantic and New Caledonian deep water, respectively, and confirm the highly disjunct geographic range of the genus Neophrissospongia in the Lusitanian-Macaronesian-Mediterranean area and the Pacific Ocean supporting the relic condition of the genus in the Mediterranean Sea. This discovery stresses the key status of Mediterranean palaeoendemics as possible remnants of an ancient Tethyan fauna and focuses the need to plan conservation measures for these rare cave-dwelling taxa.
Highlights
Among Demospongiae the archaic polyphyletic group of Lithistid is present in Europe and North Africa with a highly diversified Jurassic and Cretaceous fossil palaeofauna but apparently very few living representatives have been recorded in the Mediterranean Sea and this recent fauna is poorly-known
We report here the discovery of the genus Neophrissospongia Pisera & Lévi, 2002 from a shallow water cave in the western Mediterranean with description of a new species based on a comparative analysis of morphological diagnostic traits versus the other species of the genus
The sponge was dissected under a stereomicroscope to observe macro-traits and to obtain representative fragments of the skeleton to be processed by boiling in nitric acid to prepare slides for light microscopy (LM) and stubs for scanning electron microscopy (SEM, ZEISS DSM 962) following standard methods
Summary
Among Demospongiae the archaic polyphyletic group of Lithistid (sensu Pisera and Lévi 2002) is present in Europe and North Africa with a highly diversified Jurassic and Cretaceous fossil palaeofauna but apparently very few living representatives have been recorded in the Mediterranean Sea and this recent fauna is poorly-known. All Mediterranean records refer to genera characterised by a highly disjunct distribution with a spot-like pattern in tropical/subtropical latitudinal ranges of the Atlantic, Indian and western Pacific oceans. These taxonomic and biogeographic patterns suggest the condition of lithistids as remnants of an ancient Tethyan fauna (Reid 1967; Perez et al 2004; Manconi et al 2006; Pisera and Vacelet 2006). We report here the discovery of the genus Neophrissospongia Pisera & Lévi, 2002 from a shallow water cave in the western Mediterranean with description of a new species based on a comparative analysis of morphological diagnostic traits versus the other species of the genus
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