The symbiotic communities of invertebrates in dead coral gravel on the shallow, warm-temperate coast of the Kii Peninsula in western Japan. New bivalve species and sideswimmer have been found to live communally with the greenish Bonellia spoonworm. Live-in symbionts share the burrows of other organisms in sand and mud on the seabed. However, studies on burrow niches in rigid substrates, such as rocks on the seabed, have been scarce.