New data on distribution and ecology of the mushroom sponge Artemisina transiens Topsent, 1890 (Porifera) in the Atlantic Iberian margin

Artemisina transiens (Topsent 1890), a mushroom-shaped marine sponge, is poorly documented in the literature. To address this knowledge gap, we conducted a study in northern Portugal, Viana do Castelo (41°50' N; 8°57' W and 41°36' N; 8°57' W), from May 2022 to September 2023, focusing on the distribution, and abundance of mushroom sponge A. transiens , as well as documenting the main species associated to this sponge. A comprehensive literature review established a foundational baseline and identified key habitat preferences. Remote-operated vehicles (ROVs) were deployed for underwater surveys, capturing new insights into the species' presence across varied depths and substrates and revealing significant occurrences in previously unexplored areas. The results showed that A. transiens distribution is influenced by depth and substrate slope, with a preference for low slopes/flat surfaces and depths below 40 m. Detailed spatial analysis using Local Moran's I statistic indicated a non-random distribution of A. transiens , emphasizing its clustering in specific areas likely influenced by local environmental conditions. This study enhances the understanding of mesophotic ecosystems, highlighting the need for targeted conservation efforts and further research to comprehend the complex interactions within these biodiverse but understudied marine environments. • Literature review shows A. transiens distribution solely in the Iberian Peninsula. • Artemisina transiens prefers low slopes and depths bellow 40 m. • Common co-occurring fauna are suspension feeders such as sponges and cnidarians. • Spatial analysis shows cluster patterns and hot-spots near fishing-restricted zones.