Aggregated Nipple Sponge

Polymastia pachymastia

The Aggregated Nipple Sponge, scientifically known as Polymastia pachymastia, inhabits the intertidal and subtidal zones of the north Pacific Ocean, stretching from the Aleutian Islands to Southern California. This sponge typically appears in shades of white or dark yellow, with a size range from 2.5 cm to as large as 1 meter in diameter. Its surface is smooth, and the base is often covered by debris. In turbulent waters, it takes on a folded appearance, while in calmer areas, it develops distinct nipple-like projections. These hollow, cone-shaped papillae can reach up to 2 cm in height and are generally shorter and less pointed compared to other species in the Polymastia genus, aiding in identification. The Aggregated Nipple Sponge is found at depths of up to 55 meters, with 32% of sightings occurring at depths shallower than 40 meters. Reproduction involves the release of small, swimming larvae known as amphiblastula, which eventually settle and grow into adult sponges. This sponge is hermaphroditic, a common trait among members of the class Demospongiae. Divers may encounter this sponge encrusting rocky surfaces or partially concealed by debris. It is more likely to be found in sheltered areas where its nipple-like extensions are more evident.