Regenerative limbs , moveable stomachs , expansive spawning solutions … Paul Naylor enthuses about a well familiar echinoderm
CRITTERCONFIDENTIAL
A spawning starfish , raised up on its arms and releasing wisps of spawn
Spiny starfish
Marthasterias glacialis
Regenerative limbs , moveable stomachs , expansive spawning solutions … Paul Naylor enthuses about a well familiar echinoderm
This prominent , easily recognisable animal is a common sight in many of the popular diving areas around the UK . It can be found at virtually any depth and in most habitats so it ’ s easy to take for granted but , if you put that ubiquity aside , it ’ s a stunning creature .
I particularly like spiny starfish because various aspects of their form and behaviour
18 are easy to observe and photograph . They can be seen , for example , practising the ‘ squirt and hope ’ mating strategy that is typical of starfish and many other marine animals . Look out for them in elevated positions , such as near the top of a kelp canopy , releasing a cloud or wisps of spawn that drift away in the current . There may well be others doing the same nearby because
Trio of spiny starfish on a shallow reef we can be sure that natural selection has ensured the process is less random and more successful than it might first appear .
Spiny starfish can also be watched ‘ chasing ’ their prey , albeit in slow motion ! With patience and time in shallow water , you can observe the intriguing process as one digs itself down into a sand or gravel seabed to capture a buried clam . The ‘ legions ’ of tube feet under each of the starfish ’ s arms gradually push away the sediment so the predator ’ s mouth comes down close to its victim . Depending on the size of the clam , the starfish can either engulf it whole or force its shell apart and slip that famously protrusible starfish stomach inside .
It is slow going though , and a favourite recent find , along the lines of ‘ here ’ s one I made earlier ’, was a star-shaped crater in a maerl seabed with the starfish that was responsible for it just crawling away . Many empty clam shells strewn over the whole area indicated there had been a lot of similar activity . I have sometimes wondered why clams , admittedly not the word ’ s speediest critters , cannot get away from a predator that is descending down on them so slowly . Is such predation perhaps limited to places