Why the emphasis on Scotland ? It ’ s because one of the many reasons I love diving around Scotland , including in the beautiful and reliably sheltered sea lochs , is the unusual dominance of echinoderms in terms of their size and abundance .
The largest starfish , and that includes the sunstars which are simply starfish with a lot more arms than the standard five , are all seen more readily around Scotland than off the southern coasts of England .
Most interestingly , they can be seen in action hunting their prey which , in many cases , is other echinoderms . The Common Sunstar ( Crossaster papposus ), for example , can envelop and devour Common Starfish ( Asterias rubens ), a real case of the ‘ biter bit ’ because the latter uses its own force and persistence to consume molluscs such as mussels and clams .
The Purple Sunstar ( Solaster endeca ), a species completely absent in the south , is the only animal I have seen eating large sea cucumbers , apparently its favourite prey . Both sunstars will capture brittlestars if they get the chance but these spindly relatives of theirs are nifty movers across the seabed and can ‘ out-run ’ them . A sunstar within a bed of brittlestars will often have an empty space around it as the brittlestars have sensed their approach and crawled out of the danger zone .
Purple Sunstar in hunting mode , with the tube feet on its leading arms extended
Large Seven-armed Starfish ( Luidia ciliaris ), yet another species seen more in the north , are a greater threat as they can move surprisingly quickly . Their tube feet are tipped with little knobs ( rather than the suckers on other starfish ) so act as ‘ running spikes ’ when they pursue the brittlestars that are fleeing for their lives .
Dense carpets of brittlestars themselves can occur around most of Britain but I find them a much more common sight within shallow diving depths in sea lochs . Presumably this is because while there are currents to bring them suspended food , there is also much better shelter from swells and surf .
Even an echinoderm which is abundant in
the south , the Spiny Starfish Marthasterias glacialis , seems to be bigger in sea lochs – and I have seen some memorable monsters there .
As a final bonus and aside from these large and impressive predators , further colourful echinoderms are much more common or only found around Scotland , including the Red Cushion Star ( Porania pulvillus ), the Celtic Feather Star ( Leptometra celtica ) and the Pinkspotted Sea Cucumber ( Psolus phantapus ). A joy to behold . �
Paul ’ s photos and video clips capturing UK marine life stories are on Instagram @ paulnaylormarinephoto
The striking Pink-spotted Sea Cucumber , a species with very limited distribution
This monster of a spiny starfish spawning in Loch Torridon was 80 cm across
The attractive large Red Cushion Star
Seven-armed Starfish moving rapidly across the seabed and seeking prey
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