picked up a fragment of tentacle from one of the many snakelocks. Its stings then activated when I swapped to my snorkel at the end of the dive!
The snakelocks is unusual in that, unlike most other sea anemones, it cannot retract its tentacles into its body when it has stopped feeding; and this may be a key factor in making it such a popular home for other species. Foremost among these lodgers are symbiotic single-celled algae that live within the anemone’ s tissues. The algae get a safe place to live and some of the chemicals they need while‘ paying rent’ by providing carbohydrate nutrition produced from their photosynthesis back to the host anemone. Their presence is the reason why snakelocks anemones generally live in well-lit places on the top of reefs rather than in shaded overhangs. Moreover, we now know that snakelocks anemones can track the sun by pointing their tentacles towards it. An observant researcher spotted snakelocks in an aquarium all pointing their tentacles at a window but losing this response when the shutters were closed. Studies then found equivalent behaviour in the laboratory and natural habitats.
Two distinctive crustaceans also lodge with snakelocks anemones. The most abundant and easiest to see is the small
Two Inachus crabs sheltering under a snakelocks anemone. Two crabs do not always co-habit so willingly!
Very small, bright green Snakelocks Anemones in a shore pool
The top of a kelp canopy can be a popular location for the light-loving snakelocks and usually sponge-covered Leach’ s spider crab, Inachus phalangium( other Inachus species may do the same). The crabs get protection by hiding around the base of the anemone beneath the curtain of tentacles, or actually sitting amid the tentacles. They show some fascinating behaviour; I have spent happy hours watching these little crabs argue over the best spot under an anemone, grabbing at passing gobies or searching for sponges to enhance their camouflage. Apparently, if you find one away from its home anemone, it may be
a male on the way to a location which he has learnt harbours females.
The snakelocks anemone shrimp Periclimenes sagittifer is rarer and much harder to spot among the anemone’ s tentacles but a delight when you do, thanks to its exotic appearance. First recorded on the mainland British coast at Swanage Pier by Seasearch volunteers in 2007, its distribution is slowly spreading around the south-west. Whether either crustacean benefits the anemone with a cleaning or some other function in return for protection seems to be uncertain. �
Very small, bright green Snakelocks Anemones in a shore pool
Snakelocks anemone shrimp at home under Swanage Pier
Paul’ s photos and video clips capturing UK marine life stories are on Instagram @ paulnaylormarinephoto
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