Hi all,
We did have quite a long thread about these papers after Dr German's work was published. I've also had some correspondence with Donovan German, originally this was because I was sceptical and there were some experimental details that I wanted clarified from the
Panaque papers. (Specifically why he used a
Quercus sp. as his wood food source, when Nelson's study had found that
Panaque nigrolineatus fed on palm "wood" belonging to
Scheelea phalerata). He was very informative and helpful (he actually observed
Panaques feeding on a very wide range of trees) and later correspondence covered other aspects of his work (he is interested in the biological degradation of lignin and my research career started (and largely finished shortly afterwards) working on Spent Mushroom Compost).
Dr Germans summary:
"So, just to summarize what I think these fish are doing… the wood-eating catfishes dig into decaying wood and efficiently digest wood degradation products that environmental microbes are making available as they degrade wood. The fish also have elevated digestive enzyme activities (e.g., N-acetyl-b-D-glucosaminidase) suggestive that they digest fungi within the wood matrix. Thus, they likely get “energy” from the degraded wood. The stable isotopic signatures (carbon and nitrogen) of wild-caught wood-eating catfishes certainly suggest that they get their protein from fungi and amorphous detritus, and we find periphyton and amorphous detritus in their guts (in addition to the wood; see the “inside the guts” paper where I do a detailed gut content analysis of wild-caught fish). Basically, the fish have to get their nitrogen from somewhere other than the wood detritus (there isn’t much N in wood anyway). The fish certainly ingest wood, they just don’t use the same “pathway” to obtain energy from it as a termite. Rather than harbouring an endosymbiotic community, they let the microbes in the environment do the work for them. This may be a function of living in an aquatic environment."
Dr German is still doing some "fish work":
German, D. & Bittong, R. (2009)
"Digestive enzyme activities and gastrointestinal fermentation in wood-eating catfishes".
Journal of Comparative Physiology B 179: 1025-1042
<
http://pd.bio.uci.edu/ee/dgerman/images ... _print.pdf>
German, D.
et al (2010)
"Feast to famine: The effects of food quality and quantity on the gut structure and function of a detritivorous catfish (Teleostei: Loricariidae)." Comparative Biochemistry and Physiology, Part A 155 (2010) 281–293.
available from: <
http://pd.bio.uci.edu/ee/dgerman/images ... _print.pdf>.
As MatsP said most of Donovan's papers are available from his pages at: <
http://pd.bio.uci.edu/ee/dgerman/> and they are well worth a read.
Hope that helps.
cheers Darrel