August 20, 2017

The botanical buffet...

If you follow this blog over the past few years, you've probably noticed that we cover pretty much every aspect of the use of botanicals in our aquariums...Like, probably more than anyone ever has or cared too, lol. However, once as aspect of botanicals that we haven't really given much attention to is discussing them in the context of food.

Yup, eating them! Or, perhaps more specifically, serving some substenance either from them directly, or from the living materials they recruit while underwater.

It's long been known that many species of fishes, particularly Panaque/Panaqolus and some Hypostomus/Cochliodon love the stuff. These species are equipped with teeth specifically 'designed' to gouge wood. And there's probably another odd one or two that consume it as well. Now, you should be aware that wood 'eaters' don't eat the wood per se, they consume it as by product of their overall feeding strategy.

(The "business end" of Panaque nigrolineatus by Neale Monks, used under CC BY-SA 3.0)

In fact, some recent scientific studies have corroborated digestive enzyme activity profiles and gastrointestinal fermentation levels in the fishes’ GI tracts, suggesting that the "wood-eating catfishes" are not true xylivores such as beavers and termites, but rather, are detritivores like so many other fishes from the family Loricariidae.

In fact, the conclusion of one study indicated that "..the fishes’ whole digestive strategy ranging from intake, to passage rate, digestive enzyme activities, gastrointestinal fermentation, and decreasing surface area in the distal intestine suggests that these fishes are geared for the digestion and assimilation of soluble components of their detrital diet. However, the wood-eating catfishes do take macroscopic detritus (i.e., woody debris) and reduce it to <1 mm in diameter, which likely has significant consequences for carbon cycling in their environment. Given that much of the Amazonian basin is unstudied, and much of it is under threat of deforestation (leading to more wood in waterways), the wood-eating catfishes may play a crucial role in the dynamics of the Amazonian ecosystem, and certainly in the reduction of coarse woody debris."

(German DP. Inside the guts of wood-eating catfishes: can they digest wood? Journal of Comparative Physiology B, Biochemical, Systemic, and Environmental Physiology. 2009;179(8):1011-1023. doi:10.1007/s00360-009-0381-1.)

Interesting, right?

And it has some implication for how we keep these fishes in our botanical-style aquariums, right? I mean, we have no shortage of pics of your Plecos tearing into various botanicals, ranging from leaves to seed pods, like the "Teardrop Pods", "Savu Pods", etc. So, based on the study above, it would suggest that at least part of the pods do form a part of the diet of these fishes, and in the process of consuming them, the fishes are helping enrich the aquarium habitat.

Now, the botanicals themselves may not be "the whole meal" for many fishes, but the biofilms, algal threads, and other biocover which grow on them do provide foraging for many fishes. A number of us have noticed a wide-ranging variety of fishes, from Barbs to characin to cichlids, feeding actively on the materials on the materials which are "recruited" by submerged botanicals.

This type of activity has led me to postulate that the use of botanicals can perform a definite "feeding support function" for a wide variety of fishes.

further, I have this hunch that it might be an interesting experiment to utilize botanicals as part of a more "natural" fry rearing system for a number of different types of fishes. The fact that they seem to "actively recruit" biocover and microfauna as they break down indicates to me that they might be a nice way to provide some supplemental natural foraging for fry. Now, I'd be cautious about utilizing large number of botanicals in unfiltered or minimally-filtered rearing containers, as the possibility of the CO2 levels rising (or conversely, oxygen levels being depleted) as the botanicals break down en masse exists.

Rather, I see utilizing a "field" of botanicals in a more established, well-filtered natural system, containing a fine, shallow bed of sand or other substrate; perhaps even some floating plants as well. Based on some of the observations I've made, as well as some of yours- of fry foraging and seemingly actively feeding off of the life forms in the botanicals- I think this could be a legitimate and very efficient way to supplement the feeding of a variety of fish fry, particularly those which would benefit from a continuous source of food.

And of course, there's shrimp.

I almost don't need to touch on what has been known for decades- that many of the ornamental shrimp hobbyists know and love tend to consume leaves and other botanical items. Again, it's probably a function of them utilizing materials attached to or contained within the structures of the botanicals, but they seem to do a great job at breaking down botanicals in our aquariums, don't they?

I feel that one of the most incredible benefits of utilizing natural materials in our aquariums is that they truly bring out the natural behaviors of our fishes- whether it's rasping at a piece of driftwood, eating biofilms off of the surfaces of a few seed pods, sheltering in plants, or sifting through a field of decomposing cattapa leaves for crustaceans. Even if the foraging activities yield relatively minimal nutritional benefit for our "wood eating" (or more appropriately, "wood-processing) fishes and fry, I think just having some of these materials available to perform their natural functions is invaluable to them.