New observations on two umbraculid molluscs: Tylodina perversa (Umbraculida: Tylodinidae) and Umbraculum umbraculum (Umbraculida, Umbraculidae) along the central‑eastern coast of Sicily

The present note aims to provide detailed information on the biology and ecology of two marine heterobranch species belonging to the order Umbraculida: Umbraculum umbraculum and Tylodina perversa. The observations were carried out through scuba dives from 2017 to May 2022 in 5 sites located along the central-eastern coast of Sicily. For each species, information on the morphology, abundance, bathymetric range, substrates and habitats, seasonality, and further remarks were here provided. Through this research, it was noted that along the central-eastern coast of Sicily, T. perversa has never been found on sponges of the genus Aplysina, its prey so far documented, but always on algal substrates. Regarding U. umbraculum, it was observed that it counts among the sponges of its diet also the poriferan C. crambe. Moreover, through this study, it was documented for the first time the breeding activity of U. umbraculum, never reported in detail.