From predator to plant in one gulp

[Pulsar]

A fascinating article (original paper here). A summary:

The story of a predator that, upon eating a certain food, suddenly becomes a peaceful plant. Sort of.

A working definition for symbiosis is two or more species that live and interact. Mutualism means that each derives a certain benefit from the other, or at most causing no harm to each other. Sometimes the mutualistic symbionts have practically fused into a single functional organism. For example, the Portuguese Man o' War is a colony of four different organisms which form a composite jellyfish; none of the individuals can exist in a free-living form.

The endosymbiotic hypothesis maintains that eukaryotes evolved from symbiotic interactions between bacteria. There is plenty of evidence for that in chloroplasts and mitochondria: they have their own DNA; their membranes, their DNA, their ribosomes all resemble those of bacteria. Over time, the mitochondria / chloroplasts (M/C) have lost most of their genomic material to the host: many of the proteins needed to construct an M/C are not encoded in the M/C but in the host's nucleus, and transported to the M/C. This is probably as intimately connected as two organisms can get, before you cannot tell that they were two separate organisms before they fused into an organism and an organelle.

Two researchers have shown a striking example of endosymbiosis forming now: in 2005 Noriko Okamoto an Isao Inouye reported on a unicellular organism called Hatena. Hatena ("enigma" in Japanese) leads a curious life cycle. Hatena is a single-cell organism, swimming around in the water, using a little feeding apparatus to eat cells and organic material smaller than itself. At some point, it would feed on another unicellular algae, the Nephroselmis. Once Hatena swallows Nephroselmis, it does not digest it. Rather, Nephrosolmis makes a rather comfortable home inside Hatena. Actually, the algae starts growing inside Hatena: it grows to about 10 times its original size, filling up most of Hatena. The alga also seems to lose most of its own organelles, except for the chloroplast. The chloroplast actually grows bigger.

Hatena changes too as a result. Before ingesting the alga, it has a rather complex "mouth", or feeding apparatus. After ingesting the algae, this mouth disappears. Instead, it is replaced by an eyespot from the algae. The eyespot is a light sensing organelle, a very primitive eye that guides algae to light sources. In this case, it also guides the host, Hatena, to light. Hatena has obvioulsy stopped feeding, and least through its mouth. It is now swimming to the light, letting the alga photosynthesize its food for both of them.

Hatena reproduces by binary fission. So once it splits itself, what happens to the symbiotic alga? Well, one daughter cell gets the alga, and the other gets ot be a predator.. at least until it eats another alga. So here we are, looking at a fascinating evolutionary snapshot: two creatures, they can live apart or together. One is not quite an organelle yet, but definitely on its way.

Evolution caught in the act!

 

[Sando]

Wow, that's amazing!

 

[Aught3]

That's quite cool - they're well on their way to forming a new class of plant-like things :?

 

[e2iPi]

Does this count as one "kind" turning into another "kind"?

Just a thought

-1

 

[Sleazy]

Does this count as one "kind" turning into another "kind"?

Just a thought

-1

No, it's more like 2 "kinds" living together out of wedlock after one "kind" munches on the other. As they're living together in sin, one "kind" cooks food for the two of them, while the other "kind" sits its fat ass in the sun soaking in the rays. And if the unholy union produces a child, that child is basically deprived of food and kicked to the curb to fend for itself until it manages to munch on a sugar-daddy like it's momma did.


Sorry. It's 1:00AM here, best I could do.

 

[e2iPi]

No, it's more like 2 "kinds" living together out of wedlock after one "kind" munches on the other. As they're living together in sin, one "kind" cooks food for the two of them, while the other "kind" sits its fat ass in the sun soaking in the rays. And if the unholy union produces a child, that child is basically deprived of food and kicked to the curb to fend for itself until it manages to munch on a sugar-daddy like it's momma did.

Oh, so we have found the evolutionary roots of modern civilization. Cool.

 

[Sleazy]

Oh, so we have found the evolutionary roots of modern civilization. Cool.

More like the evolutionary advantage of learning to swallow.

 

[GoodKat]

More like the evolutionary advantage of learning to swallow.

hahaha, swallow

 

[Sando]

More like the evolutionary advantage of learning to swallow.

Haha, good one!

That's pretty much the evolution of white trash, by the way.

 

[MtheoryGuy]

The most fascinating thing I have heard for a very long while.

 

[Skitz]

Interesting post Pulsar. It reminded me of something I read a few months back about a photosynthetic sea slug. The sea slug Elysia chlorotica acquires chloroplasts by eating the algae Vaucheria litorea. It then 'steals' the genes required to sustain the chloroplasts from the algal genome and incorporates them into its own genome. The presence of the algal gene in slug germ cells suggests that the ability to support chloroplasts may be heritable.

Ref:
Rumphoa M.E, Worfula J.M, Leeb J, Kannana K, Tylerc M.S, Bhattacharyad D, Moustafad A & Manharte J.R (2008) Horizontal gene transfer of the algal nuclear gene psbO to the photosynthetic sea slug Elysia chlorotica. PNAS 105: 17867-17871.

 

[Pulsar]

It reminded me of something I read a few months back about a photosynthetic sea slug. The sea slug Elysia chlorotica acquires chloroplasts by eating the algae Vaucheria litorea. It then 'steals' the genes required to sustain the chloroplasts from the algal genome and incorporates them into its own genome. The presence of the algal gene in slug germ cells suggests that the ability to support chloroplasts may be heritable.

Amazing. You learn something new everyday...

 

[EvilLiberal]

I wander what changes would be made to clasifications if said algae were to become extinct in its free living form, existing only within 'hatena'.
If anyone here is knowledgeble upon the subject, let us know - would it be classified as part of hatena, despite not being herreditory, or would such a reclassification have to wait until it was able to split along with its host?