New family and genus of a Dendrilla-like sponge with characters of Verongiida. Part II. Discovery of chitin in the skeleton of Ernstilla lacunosa

Evolution and multi-functionality of the chitin system in sponges (Porifera) is currently a prime focus in modern experimental zoology including in phylogenetic studies of diverse poriferan taxa. Here, we present the first evidence of chitin in the skeleton of the demosponge originally defined as Dendrilla lacunosa (Porifera: Dendroceratida: Keratosa). The presence of chitin has been clearly confirmed using special Calcofluor white staining, Fourier-transform Infrared (FTIR) and Raman Spectroscopy, electrospray ionization mass spectrometry (ESI-MS), as well as a chitinase digestion assay. This feature is, however, unusual for Keratosa sponges with skeletons usually made of structural protein – spongin, and at the same time is typical for sponges of the Verongiida (subclass Verongimorpha). Consequently, obtained bioanalytical results, together with our findings about distinctive morphological and molecular characters of this Dendrilla-like sponge confirmed the necessity of renaming this organism as a novel species Ernstilla lacunosa in the new family Ernstillidae. This study is the first example of the impact of the reporting of chitin on the systematics of sponges. •We proved that, the skeleton of a representative of the new genus Ernstillidae: Ernstilla lacunosa possesses chitin, and the presence of chitin has been confirmed using various analytical methods.