Friday, 19 September 2014

Stars of the shore

Star Ascidians - Botryllus shlosseri 
These amazing creatures are relatively common on Cornish shores but they come in an incredible variety of beautiful colours and forms. Close up photography on our shoresearch surveys this September and over the years have produced some incredible images of these beautiful communal animals whose colours rival any tropical corals.
Gold arrows - found at Hannafore Looe Sept 2014 - Photo Matt Slater
Golden Star ascidian found growing on the stipe of a bushy Cystoceira seaweed, Prisk Cove, Helford September 2014 - photo by Matt Slater

Purple and white -  Marazion night rockpooling 2014 - Photo by Matt Slater

Yellow Star ascidians found at Poleath 2012 Shoresearch - Photo Matt Slater

Sometimes star ascidians carpet overhangs and continue to grow - in this slow motion dripping effect! Photographed at Polzeath during September Shoresearch 2014- Photo Matt Slater

 Star ascidians are colonial sea squirts that live by filtering sea water and removing plankton
Unlike most sea squirts which are solitary creatures star ascidians grow in large colonies in which many individuals (zooids) are joined together in a soft rubbery layer (test) attached rock or seaweed. Look closely at the colony and you will see that 3 - 12 individual squirts are arranged in a circle. Sea squirts are a sack like creature with an inhalent opening through which they draw plankton rich water and an exhalent opening through which filtered water and faeces pass. In the case of a star ascidian each squirt has its own inhalent opening but all of its neighbors share the same communal exhalent opening. Taking communal living to an extreme!

Star ascidian growing on seaweed Hannafore Lagoon 2013 september Shoresearch - Photo Matt Slater
Star ascidians are rubbery and beautiful but they do have their predators! Cowries feed on them by squirting digestive juices into them and then sucking out the juice! Look for cowries in the same habitat as star ascidians - over hanging rocks and boulders on the extreme low shore (only exposed on a spring tide!)
Cowrie, Trivia Monacha, photographed on the shore at Battery Rocks Penzance by Matt Slater

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