of collaborations with other organisms. The relatively large encrusting sponge Lissodendoryx colombiensis is most common on rocky surfaces, but has extended its range into seagrass meadows by letting itself be surrounded or overgrown by seagrass sponges, which are distasteful to the local starfish and therefore protect Lissodendoryx against them; in return the seagrass sponges get higher positions away from the sea-floor sediment. Shrimps of the genus Synalpheus form colonies in sponges, and each shrimp species inhabits a different sponge species, making Synalpheus one of the most diverse crustacean genera. Specifically, Synalpheus regalis utilizes the sponge not only as a food source, but also as a defense against other shrimp and predators. As many as 16,000 individuals inhabit a single loggerhead sponge, feeding off the larger particles that collect on the sponge as it filters the ocean to feed itself. Other crustaceans such as hermit crabs commonly have a specific species of sponge, Pseudospongosorites, grow on them as both the sponge and crab occupy gastropod shells until the crab and sponge outgrow the shell, eventually resulting in the crab using the sponge's body as protection instead of the shell until the crab finds a suitable replacement shell. Sponge loop Most sponges are detritivores which filter organic debris particles and microscopic life forms from ocean water. In particular, sponges occupy an important role as detritivores in coral reef food webs by recycling detritus to higher trophic levels. The hypothesis has been made that coral reef sponges facilitate the transfer of coral-derived organic matter to their associated detritivores via the production of sponge detritus, as shown in the diagram. Several sponge species are able to convert coral-derived DOM into sponge detritus, and transfer organic matter produced by corals further up the reef food web. Corals release organic matter as both dissolved and particulate mucus, as well as cellular material such as expelled Symbiodinium. Organic matter could be transferred from corals to sponges by all these pathways, but DOM likely makes up the largest fraction, as the majority (56 to 80%) of coral mucus dissolves in the water column, and coral loss of fixed carbon due to expulsion of Symbiodinium is typically negligible (0.01%) compared with mucus release (up to ~40%). Coral-derived organic matter could also be indirectly transferred to sponges via bacteria, which can also consume coral mucus. Sponge holobiont Besides a one to one symbiotic relationship, it is possible for a host