Sea firs & cystocarps at Ringstead in February

A Post from the Past [2009]

I am continuing today with the theme started in previous Posts, talking about the association of many seashore life-forms with seaweed. The photograph at the top of the page shows what seem to be some sort of plant growing on a piece of kelp; but these fine and delicate ‘stalks’ are actually colonial animals. They are hydroids, or Sea Firs, which belong to the Bryozoa group. You may remember that I previously talked about two encrusting forms of Bryozoa, the sea mat form, in the Post of 10th February 2009.

 In these sea fir colonies, each of the minute cups that appear on alternate sides ascending the stems, contains an individual animal bearing tentacles that it uses to filter the seawater for food particles. The ones in the picture are probably Sertularella polyzonias (Linnaeus). I say ‘probably’ because they are rather degraded and I did not look through a hand lens at them to examine the details of the polyps or cups alternating up the stem. However, their overall appearance tallies with the species description.

On the same stretch of strandline, I also found the piece of red seaweed shown in the photograph below. I am not an Algae specialist, so it may be that someone will advise me on the matter, but I believe this is the Eyelash Weed Calliblepharis ciliata (Hudson) Kutzig. I have been wondering about the identity of the small projections that are scattered across the surface of the frond. They are clearly an integral part of the plant. The nearest suggestion I can make is that they are reproductive bodies of the seaweed, possibly things called cystocarps or even tetrasporangia! I need to investigate this some more.

© Jessica Winder and Jessica’s Nature Blog, 2009