Exploring the association between the arrow crab Stenorhynchus lanceolatus (Brullé, 1837) and the sea anemone Telmatactis cricoides (Duchassaing, 1850) in the Canary Islands

Symbiotic relationships are common in marine ecosystems, especially between cnidarians and crustaceans. This study explored the association of the arrow crab Stenorhynchus lanceolatus with different hosts in the Canary Islands, focusing on the relationship with the sea anemone Telmatactis cricoides . Field surveys and laboratory experiments were conducted to assess crab preference among potential hosts (anemones and sea urchins), association rates and behaviours of crabs interacting with the anemone. Field results revealed similar prevalence on anemones and sea urchins, and that most crabs associated to the anemone were solitary females. However, under laboratory conditions, sea urchins were observed to be preferred as hosts, but association with anemones were more stable in time, although its colonization period was slower, likely due to their toxicity and lack of environmental cues. Additionally, crab intraspecific competition seemed to favour the association with the anemone. This study showed the mutualistic and facultative nature of the relationship between S. lanceolatus and T. cricoides, advancing our understanding of benthic ecosystems dynamics . • S. lanceolatus establish facultative mutualistic relationships with the anemone T. cricoides . • The arrow crab associates at similar rates to anemones and sea urchins. • In the laboratory, sea urchins were preferred hosts and associations with anemones slow and stable. • Juvenile and female crabs can share anemone but not pairs of males due to territorial behavior. • Crab intraspecific competition favor the association with anemones despite its toxicity.