Small Calcareous Cup

Sycon ciliatum

Sycon ciliatum, commonly known as the Small Calcareous Cup, is a calcareous sponge that divers may encounter along the coasts of Europe, from Scandinavia to Portugal. This species often grows singly or in small clusters, anchored to a substrate by a single holdfast. It is characterized by a greyish-white, spindle-shaped body. Its surface appears furry due to fine papillae, and the osculum at its tip is fringed with delicate spicules. Divers can distinguish it from similar species like Sycon raphanus by noting that its choanocyte chambers are not fused together but remain distinct. This sponge thrives in temperate coastal waters, often found low on the shore or in the neritic zone. It prefers habitats with minimal wave action, such as areas among seaweed, under stones, or in rock pools. Most occurrences are recorded at depths shallower than 40 meters, with a significant number found at less than 30 meters. Reproductively, Sycon ciliatum is hermaphroditic, producing free-swimming larvae that eventually settle and grow into new sponges. Divers exploring suitable habitats might spot this species nestled among seaweed or clinging to rocks. Its conservation status is currently not evaluated by the IUCN, and it poses no known threat to humans.