so, it seems that some true spiders may actually be omnivorous!

[sezra]

I'm currently writing a paper for uni, and stumbled across this. Im not sure if its common knowledge as I've only been at uni for about 5 weeks, but I thought it was interesting enough to share.

Abstract
Orb-weaving spiders (Araneidae) are commonly regarded as generalist insect predators but resources provided by
plants such as pollen may be an important dietary supplementation. Their webs snare insect prey, but can also trap
aerial plankton like pollen and fungal spores. When recycling their orb webs, the spiders may therefore also feed on
adhering pollen grains or fungal spores via extraoral digestion. In this study we measured stable isotope ratios in the
bodies of two araneid species (Aculepeira ceropegia and Araneus diadematus), their potential prey and pollen to
determine the relative contribution of pollen to their diet. We found that about 25% of juvenile orb-weaving spiders’
diet consisted of pollen, the other 75% of flying insects, mainly small dipterans and hymenopterans. The pollen grains
in our study were too large to be taken up accidentally by the spiders and had first to be digested extraorally by
enzymes in an active act of consumption. Therefore, pollen can be seen as a substantial component of the spiders’
diet. This finding suggests that these spiders need to be classified as omnivores rather than pure carnivores.

its a very brief explanation of the results, bu its interesting none the less.

 

[Biollantefan54]

Should they not be classified as carnivores because they are unintentionally eating the pollen and fungal spores?

 

[coppercab]

Thank you for the lovely peice of information I had no idea

 

[sezra]

Should they not be classified as carnivores because they are unintentionally eating the pollen and fungal spores?

no because some of the pollen spores are too big for them to eat.

"The pollen grains in our study were too large to be taken up accidentally by the spiders and had first to be digested extraorally by
enzymes in an active act of consumption. Therefore, pollen can be seen as a substantial component of the spiders’
diet."

The study also showed that young spiders benefit the most as they are too small to tackle large prey. by eating their webs they can effectively live on pollen spores alone. I could post the whole journal here but its massive. I only have access to it through my uni account which sadly requires my username and password. This info should be available to anyone who is interested.

 

[Biollantefan54]

Ok, so they are purposefully eating it than...hmm, well that's pretty interesting lol!

 

[Spepper]

Bagheera kiplingi has a diet over 90% herbivorous. I wrote half a post about it in my blog. (The other half was on the genus Portia.)

 

[The Snark]

Nowhere in the world will you more clearly encounter evolution demonstrated than in the diet of animals. From herbivorous spiders to recessive canines in humans, examples are everywhere. The animal kingdom is in constant flux as it adapts and re-adapts to changes in environment. The alimentary canal is capable of undergoing a complete change in it's biology within a single generation in response to the environmental changes and subsequent foods available.

If you get a white paper cranked out, how about posting where we can find it?

 

[kellakk]

I found the paper. Good find, pretty interesting. It's on PLOS One so it's actually free to the public. Enjoy: http://www.plosone.org/article/info:doi/10.1371/journal.pone.0082637

 

[sezra]

yup, thats the one. didnt realise it was on other sites.