I've received this link to a video from a lady. The creature was found on a beach in Tenby, Wales. It looks to me as if a clam was growing some tumor. Any ideas, please?
Hi, easy to suggest it's a sponge as it is very sponge like in appearance - but look closer - the surface of it, as seen quite well on the second and last photos is of a surface covered in tiny circular structures. These are polyps, and together they form a colony as we see here. This is Alcyonium digitatum - aka - "Dead Man's Fingers".
Sponges, being very simple multicellular animals, draw water internally through the whole surface of the sponge into the body cavity and exhaust it through large exhalent tunnels on the surface.
Dead Man's Fingers feed quite differently. When alive and undisturbed in water the fleshy lobes will be covered in what appear to be fine coral polyps. These polyps in appearance look like tiny sea anemones over the surface of the colony. These polyps wave their tentacles in the water current catching food and pass it to the mouth in the centre of each polyp.
When disturbed, or out of the water, the tentacles of each individual polyp are retracted and give the appearance of fleshy lobes, or as the name suggests, dead man's fingers.
Alcyonium digitatum is in fact a soft coral. This colony is obviously a lighter coloured one, but they can range from a creamy white, through yellow to orange. The lobes can be as much as 20cm long, but usually less. Like most corals they are actually quite long lived.