what could it be?

[Franz Neidl]

Today I found in the marine plancton on the surface of a microscopic red alga a little "forest". A "tree" from the forest was about 200 µm long (high).

I dont know if these are bacteria, fungi or other living organisms.
Somebody can help me?

Obj. 20x, phase contrast.

Franz

[BJ]

Hello Franz,

I am almost certain that these are hairs produced by the seaweed itself. Many red seaweeds produce colourless ("hyaline") hairs. They tend to occur in a zone behind the growing tip. Further back from the tip, they either get worn away or detach.

The uniformity of length and lack of any branching, would I think eliminate the possibility of a fungus. I think the length (200um) would eliminate bacteria. Also, the apparently healthy pigmented aspect of the alga suggests that the filaments are not parasitic.

I do not think that anyone has come up with a definitive function for these hairs - perhaps it varies from species to species. I know that in one case the hairs have been shown to increase nutrient uptake (perhaps functioning a bit like root hairs in plants). Seaweeds with a dense covering of hairs often feel quite slimey.

I find this a very attractive photo. I do not often find phase photos aesthetically pleasing, but in this case I think it works very well.

thanks for sharing,
Brian (PS at long last I have posted a reply to your pm....apologies)