the dinoflagellate Warnowia (with an eye-organelle !)

Franz Neidl · Post by **Franz Neidl** » Fri Nov 04, 2011 3:39 am

I am not very happy about the photographic quality of my picture, but the organism Warnowia sp. is extremly interesting under the aspect of evolution. (I hope to find him again in the plankton and to take an other picture). It is an unicellular flagellate with an eye-organelle and has even a lense (see the 2 pictures) !
I mesured 3 Warnowia cells: they were 105µm, 80µm and 92µm long.

Franz

Charles Krebs · Post by **Charles Krebs** » Fri Nov 04, 2011 12:26 pm

Nice Franz!

You should have also linked to one of your posts from last year (some good info there):
http://www.photomacrography.net/forum/v ... php?t=9854

Mitch640 · Post by **Mitch640** » Fri Nov 04, 2011 4:26 pm

What a find. Very nice couple of shots Franz.

I thought an eye needed a brain to work?

Cactusdave · Post by **Cactusdave** » Sat Nov 05, 2011 1:19 am

Remarkable creature. That second shot is great.

rjlittlefield · Post by **rjlittlefield** » Sat Nov 05, 2011 1:40 am

Mitch640 wrote:I thought an eye needed a brain to work?

Hard to say what the thing even does. Quoting from "Microstructure of algae", page 186:

The protruding ocelloid may have a function in phototaxis, but additionally may even be used as an eye to see prey. Taylor has proposed that the ocelloid could act as a "rangefinder" during phagotrophy. However, he also points out that the ocelloid in several species faces away from the ingestive apparatus.

--Rik

Franz Neidl · Post by **Franz Neidl** » Sat Nov 05, 2011 2:35 am

About the intelligent remark from Mitch :

"I thought an eye needed a brain to work?"

W. Gehring (2005) says in his article "New Perspectives on Eye Development and the Evolution of Eyes and Photoreceptors" (this article is speaking also about Warnowia):

"Nevertheless, we have proposed that the eye came first in evolution (Gehring and Ikeo 1999). The sensory organs are gathering information, whereas the brain is an information processing organ, similar to a computer. If no information is acquired, there is no need for an elaborate information-processing organ. As more information is acquired by the eyes and other sensory organs, the brain evolves in parallel to process this information and transmitt it to the effector organs, like the muscles.................. Therefore, I consider it likely that the eyes evolved first, before the brain" p.180

http://jhered.oxfordjournals.org/content/96/3/171.full

Franz

Mitch640 · Post by **Mitch640** » Sat Nov 05, 2011 2:47 am

Thanks Rik and Franz. Maybe there is a brain analog in that cell somewhere. He must have a use for the eye to have bothered developing it, and it must find it useful or it would devolve it, as so many other bugs have done. Even if it's only to see which direction the light is from, doesn't that take computing power?

It's all so amazing to find these things in single celled animals.

Wim van Egmond · Post by **Wim van Egmond** » Sat Nov 05, 2011 2:48 am

It is an amazing find, Franz, I have never seen it. I don't think it is strange to have an eye without a brain. A light receptor only has to trigger a response. I guess it does not have to be a brain that coordinates the procedure. The function of such an eye could be to avoid predation, or detect food. Or perhaps phototaxis.

Wim

Cactusdave · Post by **Cactusdave** » Sat Nov 05, 2011 4:30 am

I tried to find out a little more about this remarkable dinoflagellate. It seems that the 'eye' most probably derives from a chloroplast in evolutionary terms and that its superficial resemblance to the metazoan eye is a classic case of convergent evolution rather than an indication of relatedness.

Quote:

The ontogenesis of the organelle might help in unraveling its evolutionary origin. Greuet (1977) found that the retinoid/pigment cup complex (all within the same membranous compartment) dedifferentiated to the point that they appeared to derive from a chloroplast during binary fission in warnowiids. These observations suggested that the warnowiids were able to transform a chloroplast into a complex organelle that is morphologically convergent with the metazoan eye. The origin of the chloroplast in the heterotrophic warnowiids is itself uncertain. However, dinoﬂagellates have a remarkable facility to acquire and replace chloroplasts from diverse microalgal groups (Saldarriaga et al. 2001), and even non-photosynthetic dinoflagellates have plastid genes (Sa´nchez-Puerta et al. 2007). Kleptoplastidy in dinoﬂagellates may be the origin of this high diversity of plastids through secondary or tertiary endosymbiosis (Koike et al. 2005).

From :
J. Eukaryot. Microbiol., 56(5), 2009 pp. 440–44
http://www.obs-vlfr.fr/LOV/aquaparadox/ ... omez09.pdf

I love the word 'Kleptoplastidy',

I think it means one species stealing cell organelles like chloroplasts or mitochondria from another species, presumably by engulfing or fusing with them.

René · Post by **René** » Sat Nov 05, 2011 4:33 am

Many algae have simple light-sensitive spots, a direct link towards the flagella is the straightforward choice. Now this thingy takes it many steps further. The black cup-shaped structure is lined with recycled thylakoids, ensuring that light detection is from a far more precise direction. The lens looks impressive, is however not much more then a vesicle with protein fluid, enough of those around in any cell for evolution to decide that it is a very useful adaption, making light detection even more precise, presumably also in depth.

So the crux question is: what for?

I suspect it is for detection of food. Nematodinium has nematocysts that are used for harpooning his food. And although no-one ever has seen it using it eye for this task, I can quite easily see how this would work. Something flashes past the dino's eye, and a harpoon is fired off. No elaborate brain necessary for this.

Nonetheless: WOW.

Best wishes, René