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Philcoxia: a new CP genus from Brazil


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#1 Fernando Rivadavia

 
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Posted 10 January 2012 - 01:57 AM

Hello everyone,

Proof is accumulating in favor of carnivory in the genus Philcoxia, a very rare genus from Brazil with only 3 species and maybe 4-6 total populations known.

Researchers in Brazil have been cultivating P.minensis for several years and their experiments show that nematodes are captured and digested by the sticky underground leaves.

However, some friends & I who have seen this plant in the wild are not in full agreement that carnivory is the function of Philcoxia's sticky leaves. But if it is carnivorous, I doubt Philcoxia belongs in the inner circle of full carnivores as described in Juniper, Joels, & Daniel's carnivorous syndrome. It would need something to attract the nematodes.

Anyway, see below two links regarding this publication. I'm sure we'll be seeing a lot more about this in the coming days. The 1st link is extremely important, not only because it's in Nature, but because I was able to sneak my name into Nature for the first time! :)

http://www.nature.co...erground-1.9757

http://www.newscient...orms-found.html


Best wishes,
Fernando


P.S. Moderators, you'll probably have to change the name of this section to include Philcoxia. ;)
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#2 Marcel van den Broek

 
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Posted 10 January 2012 - 16:16 PM

The 1st link is extremely important, not only because it's in Nature, but because I was able to sneak my name into Nature for the first time! :)

http://www.nature.co...erground-1.9757

http://www.newscient...orms-found.html


Best wishes,
Fernando


And the ICPS too :Laie_99:
Anyway, thanks for the info :thanks:

#3 Ruben Resendiz

 
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Posted 10 January 2012 - 17:37 PM

Hi Fernando

I read the documents, Amazing simply amazing and thanks for the documents.

but I want to see you plublication about this gender someday.

RR

#4 Daniel O.

 
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Posted 10 January 2012 - 20:04 PM

Hi Fernando,

wow, really very interesting.
Are these plants widespread in nature?

Best regards,

Dani

#5 Greg Allan

 
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Posted 11 January 2012 - 19:03 PM

Hi Fernando,

This is very interesting news- thanks for posting. Why do you have continuting doubts as to the carnivory of the genus? Also, whilst we're on the topic of carnivory, do you know anything about the production of proteases and the diigestive processes of Byblis (other than B filifolia, which I believe has been found to produce proteases and B liniflora which has been found to produce phosphatases. This article http://www.carnivoro...v38n3p75_82.pdf appears to indicate (at p81) that Byblis liniflora produces proteases, but I cannot be sure as I am not a scientist and I do not understand all of the terminology.

BTW, if anyone wants to find out about about the genus Philcoxia generally, get a copy of Stewart McPherson's CPs of the World vol 2!

Cheers,

Greg

#6 Andreas Fleischmann

 
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Posted 11 January 2012 - 23:46 PM

Hello,

Fernando probably still is not convinced because he did not ready the article carefully enough? ;) Enzyme activity in the glands + nutrient uptake from the prey directly! That's the best proof for carnivory one can get. There is not doubt that Philcoxia is as carnivorous as Pinguicula is, for example.

Daniel, the three species of Philcoxia are very rare, and each species is currently known only from a very small area (or even just a single population). And all of them are threatened by human mining activity, as the dry sand plains where they grow are exploited.

Andreas

#7 Fernando Rivadavia

 
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Posted 12 January 2012 - 04:04 AM

Hey everyone,

I had a long chat with Andreas this afternoon and he pretty much convinced me that Philcoxia is carnivorous after all. ;) Not surprising I guess, since he was the one who suggested some of those experiments for carnivory used by the authors of that paper...

I'm just still a little puzzled by a few details though, such as: is there something that attracts the nematodes to the leaves or are they just crawling around and get caught accidentally?

Also, how are the nematodes trapped and killed (considering there doesn't seem to be much mucilage on the leaves)? Did any of you see the size of the nematodes relative to the glands in figure 3??? That's gotta be some pretty sticky glue to hold those guys in place! Or maybe the sand grains stuck to the leaves act as magnifying glasses that fry the nematodes? Hahahaha! Dang, I should've saved that one for April Fool's...

Anyway, when I visited P.minensis in September 2011 (at the height of the dry season), the habitat was really dry and the sand really soft and loose around the leaves. I don't know much about nematode ecology, but I really have a hard time imagining any small critters like that surviving in such sterile conditions like hot dry loose sand. Maybe they come up from deeper layers during the cool winter nights? That would be quite a daily migration though -- and to feed on what?

Andreas pointed out to me that nematodes are not actually slimy worms, but more closely related to insects and that they even have a chitinous cuticle. Thus, the nematodes "skeletons" observed on leaves of the herbarium specimens of flowering plants (collected during the dry season) may actually have been sitting on those leaves for several months, having been trapped and killed during the wet season (yes, Philcoxia leaves seem to be long-lasting, although small and fragile).

So maybe Philcoxia is carnivorous only during the rainy season, when nematode prey crawl up from deeper layers to feed on whatever is growing on the humid sandy surface?

Another question is: why does Philcoxia have a thin layer of sand on the leaves? The sand grains seem to be sticking to the glands, but is this accidental? Does the sand accidentally stick to glands that evolved to trap nematodes? Or is it the other way around? Maybe the glands first evolved to hold sand on top of the leaves, allowing enough sunlight through the translucent sand grains for photosynthesis, but not too much that it would burn the fragile leaves in the open mini deserts they grow in. An unexpected side effect could be that the glands trapped nematodes as well as sand grains... and this eventually allowed Philcoxia to also evolve the capability of digesting the trapped prey and absorbing the nutrients. Maybe Philcoxia even evolved a way to attract more prey to the leaves, secreting some tasty substance from the glands, turning them into deadly nematode lollipops! :)


Best Wishes to all,
Fernando Rivadavia


P.S. Moderators, this means that Philcoxia, if fully carnivorous, may need it's own section in this forum! :) Well, we still need to find proof of prey attraction... But it definitely needs to have its name included in this section.

Edited by Fernando Rivadavia, 12 January 2012 - 04:43 AM.


#8 Andreas Fleischmann

 
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Posted 12 January 2012 - 12:04 PM

Hello all,

I had a long chat with Andreas this afternoon and he pretty much convinced me that Philcoxia is carnivorous after all. ;)

Well, your "afternoon" was past midnight for me, thus please excluse if I'm a bit sleepy in this reply ;)

I think we can draw a lot of parallels between the carnivorous nature of Philcoxia and certain zoophagous ("carnivorous" is only applied to flowering plants) soil fungi which catch nematodes with sticky dropplets of glue secreted from the hyphae (probalby few of you are aware that Pleurotus and a few related genera - the oyster mushrooms, - are nematode catching "carnivorous" fungi at least during part of their life stages). Other CP fungi even catch nematodes with actively constricting rings formed by their hyphae (snap traps like in the VFT!). But in all these cases, the nematodes are not killed, but just trapped by the carnivorous traps, and will get slowly digested when still alive.
The same might be true for Philcoxia. Why does it have to "kill" its prey? It only needs to digest it. Same is true for our other CPs. The killing is just a side effect of the beginning digestion (however simplifies digestion in some species of course) of the prey.

I'm not sure if there is actually an attraction of prey to the Philcoxia leave, or if these ABUNDANTLY present soil animals are not just caught by chance. Nematodes are the most abundantly present group of soil life (only outnumbered by bacteria and protozoa), and there is apparently no type of soil where they do not exist. From very wet and submerged to dry desert soils - nematodes are there. Moisture might be an attractant in the dry soils, which is probably used by Philcoxia?
On the other hand, most of the soil interspace microfauna (which is very rich! "Sand" is not sterile and dead - there is a rich microfauna livving inbetween the sand grains, where microdroplets of moisture will condensate for at least a short time of the year) cannot will follow the evaporation water current in the soil, i.e. it is permanently brought from the deeper soil layers to the top. Nematodes can detect light, to actively avoid getting to close to the top of the soil, getting exposed to the surface. And that's - to my understanding- the most likely reason why Philcoxia leaves are burried undergroud: otherwise they would not be able to catch anthying living in the soil. A co-effect (or maybe the primary reason for the subsoil leaves) is that they are protected against the sun radiation, which is extreme in these white quartzitic sands. Several other small plants inhabting sand plain habitats (eg. Genlisea, Utricularia) have their leaves a few mm to a few cm below the soil surface, too. The quartz is like glas, thus the leaves are protected under a thin but still translucent layer - a subsoil greenhouse ;)

At least for me, Philcoxia does not remain a "mysterious, doubtufll carnivore" anymore, but it clearly and evidently is a true carnivorous plant - just like Drosera or Pinguicula are, too.

Just my two cents ;)

All the best,

Andreas

#9 Fernando Rivadavia

 
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Posted 12 January 2012 - 17:12 PM

Andreas,

Thanks for the extra info!

I agree that killing is just a side effect. But looking at fig.3 in that paper, I still have a hard time imagining that the small sparse glands can hold a nematode. Either the glue is really bad-ass, or the nematode is a real pussy - or both. :)

The same might be true for Philcoxia. Why does it have to "kill" its prey? It only needs to digest it. Same is true for our other CPs. The killing is just a side effect of the beginning digestion (however simplifies digestion in some species of course) of the prey.

As I wrote to you just now, if nematodes are truly present in the dry sand of Philcoxia habitats, then maybe they don't even need to waste efforts attracting prey. They could simply act like ant lions, which sit and wait for the prey to come to them.

If humidity is the attractant, then that means that Philcoxia possibly feeds mostly at night when dew is deposited on the soil surface.

Either way, I would be very interested in carrying out a study at a Philcoxia habitat, collecting the upper 1-2cm of sand, adding some water, then looking at it under a microscope to see what is crawling about.

Another study that I think my brain needs to see to believe, is a test of how strong the mucilage on the leaves is. Maybe the Brazilian authors of this latest paper (who have plants in cultivation) would be able to do this, adding live nematodes to the leaves under a microscope to see how well the glands perform at trapping their prey.

As for leaves being "buried underground", I do think there is a bit of exaggeration here. The leaves are really at the soil surface and have only a monolayer of sand grains partially covering the leaves. At least that's what it seemed to me. It sounds good in the paper and all, but I don't think it's all truthful and I see a myth being born.


Thanks for the discussions!
Fernando

#10 jeff 1

 
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Posted 15 January 2012 - 15:12 PM

Bonjour

may be the same phenomen to the Capsella bursa-pastoris 'seeds .


nevertheless here 2 documents from philcoxia with a carnivory test in the second


'a new genus of scrophulariaceae with three new species from eastern brazil '

'Rediscovery and Phylogenetic Placement of Philcoxia minensis
(Plantaginaceae), with a Test of Carnivory'


thank ANDREAS :thumbsup: but they were presented on the web for a long time grace to other sites, but remain cautious.



jeff

Edited by jeff 1, 16 January 2012 - 10:26 AM.


#11 Rkitko

 
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Posted 15 January 2012 - 15:55 PM

Fernando and Andreas,

An interesting conversation. I agree some study on the attractant or lure, if any, would be great. The paper was a great addition to the evidence of carnivory, but I'm still left with questions.

In the paper, they measured nitrogen and phosphorous content of the Philcoxia plants per mg of dry weight and compared it to neighboring noncarnivorous plants. From the higher content found in Philcoxia relative to the other plants, they conclude that this is evidence of a benefit from carnivory. I'm not convinced that's a good comparison. I'd rather see nitrogen and phosphorous content comparisons among fed versus unfed Philcoxia. The authors did note that they're continuing the studies and will be gathering data on photosynthetic rates as a measure of benefit from carnivory. That may be more convincing.

More worrisome to me, however, is the assumption of digestion by action of the plant alone. Couldn't surface microbes, given 48 hr, be doing some of the mineralization of prey? Once mineralized, foliar absorption of the nitrogen is no problem for any plant. Out of my own curiosities, I wonder which species of bacteria are inhabiting the surface of the leaves.

Still, all very interesting and certainly top-notch work published in PNAS. I look forward to more evidence on the plant's carnivory.

#12 Andreas Fleischmann

 
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Posted 15 January 2012 - 16:19 PM

Hello,

More worrisome to me, however, is the assumption of digestion by action of the plant alone. Couldn't surface microbes, given 48 hr, be doing some of the mineralization of prey? Once mineralized, foliar absorption of the nitrogen is no problem for any plant. Out of my own curiosities, I wonder which species of bacteria are inhabiting the surface of the leaves.


Of course this can be the case, as in ANY carnivorous plant. If you will make microbal digestion a criterium to exclude pants from being considered as carnivores, the list of genera treated in this forum here would decrease a lot ;).
However, regarding this enzyme test presented for Philcoxia: if the digestion of the nematodes would indeed by carried out by bacteria, one would not expect to find such a high percentage of nitrogen isotopes in the plant tissue after just a few (- 48) hours. The nitrogen would first be incorporated by the bacteria, and although these have a fast metabolism, one would not find such a high amount of the isotopes from the prey in the plant's tissue, but more in the bacteria.
Regarding such a "digestive mutualism", involving a thrid partner taking over the role of digestive enzymes, I would recommend the articles published on carnivory in Roridula. The tests finding out that Roridula indeed is a true carnivorous plant (although lacking own enzymes) was performed exactly the same way as done with Philcoxia now.
For a carnivorous plant it does not matter at all WHO exactly is doing the digestive part - as long as the plant has developed special structures to attract and catch prey, and special (morphological and ecophysiological) adaptations to absorb and utilize the nutrients released from the prey - it can be called a carnivorous plant. And this is the difference between Philcoxia and tomatoes or Petunia, eg.
Finally, you would not doubt calling a cow a "herbivore", would you? Although the digestion of its vegetarian diet is almost entirely performed by microbes and bacteria.

All the best,

Andreas

PS: Dear Jeff, are you aware that the PDF article you link here hosted on your webpage is actually copyright protected? Although it is nice of course that you would like to share this document with others, I fear that Kew Publishing is still the copyright owner of this publication.

#13 Fernando Rivadavia

 
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Posted 15 January 2012 - 21:24 PM

Finally, you would not doubt calling a cow a "herbivore", would you? Although the digestion of its vegetarian diet is almost entirely performed by microbes and bacteria.


Very good point Andreas!!!

Another thing that still bothers me is their claim that Philcoxia has a simple root system. As far down as I could dig, it did look like there was a single root going deep down into the sand. But I was not able to evaluate if it all of a sudden branches multiple times once it reaches more humid soils below. I wonder if they were able to investigate this in cultivation?



F