Another non-obligate symbiosis is known from encrusting bryozoans and hermit crabs that live in a close relationship. The bryozoan colony (Acanthodesia commensale) develops a cirumrotatory growth and offers the crab (Pseudopagurus granulimanus) a helicospiral-tubular extension of its living chamber that initially was situated within a gastropod shell.
What relationship is it considered when the bryozoans and hermit crabs do not live in a close relationship?
{'text': 'non-obligate symbiosis', 'answer_start': 8}