Polymastia tenax

Polymastia tenax is a sponge species found in the Western Central Atlantic, particularly around Belize and the Caribbean. It is characterized by its reddish groups of large papillae that encircle tall membranous oscules. These structures often fill crevices or grow among coral branches, providing a tough consistency that contracts upon contact. This species is sessile, meaning it remains fixed in one place, typically in tropical waters. Divers may encounter Polymastia tenax in shallow waters, as 90% of recorded occurrences are at depths shallower than 40 meters, with most being even shallower than 30 meters. The sponge's unique appearance makes it distinguishable from other species, especially with its ability to contract its papillae when touched. It is harmless to humans and does not pose any threats. In terms of reproduction, Polymastia tenax is hermaphroditic, like other members of the class Demospongiae. The life cycle begins with the zygote developing into a free-swimming parenchymella larva, which eventually settles on a substrate to grow into a young sponge. Currently, there is no evaluation of its conservation status by the IUCN.