On the trail of the Amazonian Shrimp...

It seems that the longer you're in this hobby, the deeper you dive into geeky, highly specific little tangents, right? And of course, myself being a prototypical fish geek, am hardly immune from such little jaunts. My obsession with blackwater, botanical-style aquariums keeps me searching for all sorts of bits of information from Nature that can give me a new angle to explore...

It's often taken me into some interesting- if not silty and tannin-stained- directions! 

Obviously, you know by now that I'm just a bit partial to the environmental niches, species, and diversity of the Amazon region. The number of cool aquarium species found in this region alone could keep the most ardent fish geek busy for several lifetimes, and the remarkable diversity of biotopes found in the region is an aquarst's dream come true!

We are all aware of the many species of fishes found in the hobby that hail from this region. However, we don't hear much about the invertebrate life from Amazonia, particularly from a hobby perspective, do we? At least, I haven't- and I certainly haven't heard much about them in the hobby at all.

However, there ARE shrimps which live in this region.  Like, where the hell have they been hiding (literally) from the hobby for so long, and why?

Let's cut to the chase.

It all starts in leaf litter, of course.

I was perusing (as I frequently do) some scholarly articles on Amazonian stream leaf litter ecology and diversity, when I kept stumbling on mentions of  various types of shrimp found in the litter beds.

Yeah. Shrimp. 

There are a few species of shrimp that are found in the Amazon region, and they may or may not be suitable for aquariums...

However,  I find it rather fascinating that we've been taking fishes from this region for the hobby for decades, with almost nothing heard from the invert side...wierd...at least, it is to me. I have seen some vague references in hobby literature and sites to the genus Macrobrachium, but have not seen them for sale currently during my (admittedly) limited hobby research on them.

Well, part of it is most likely because they are not all that sexy looking. They're pretty much like, clear. Let's be honest- clear shrimp are not what many enthusiasts are looking for, particularly when you have new morphs of crazy-colorful Neocaradina and such coming from Asia (and domestic breeders, of course) by the bagful almost weekly.

Nonetheless, the genus Pseudopalaemon (P. amazonensis, in particular) and Macrobrachium are quite interesting, in that they inhabit many of the same streams and the niches that you'll find some of our favorite fish species, such as Apistogramma and various species of characins.

Now, unlike a lot of shrimp found in the Americas, these species complete their entire life cycle in freshwater environments- in particular, the blackwater leaf-litter niches of Amazonian streams. 

Well, I'm kind of intrigued...

And it seems a bit at odds with what we know about the composition of Amazonian blackwater and some of the environmental requirements for crustaceans, right? Black waters typically are rather acidic than the typically more neutral white waters. The major difference is the concentrations of magnesium, sodium, potassium, and calcium. Those ions are very low in black waters. And of course, this lack of ions has some ecological implications, right? Certain organisms, like snails and mullosks, need more calcium than is available in blackwater systems; in fact, they need a lot of calcium to build their shells, and they're are not really abundant in blackwaters.

Makes sense, right?

And this little tidbit from a research paper I stumbled on by Michael Goulding and Efrem J. G. Ferreira:

"There are two families of freshwater shrimp in the Amazon. Palaemonidae contains four genera and 14 species (Kensley and Walker, 1982). Sergestidae is represented by only one genus, and it has two or three species. Over 50 species of Amazonian fishes have been reported to eat shrimp..."

So, yeah, there are fishes which eat shrimp in the region, so there must be a fair number of shrimp, right? In fact, it's thought that Sorubim lima, a fish common to the Amazonian region, is a shrimp feeding specialist!

 According to at least one scholarly article I found that mentioned these shrimp (in conjunction with a study on the overall leaf litter communities of Amazon streams) discussed the differing feeding habits of the two genera in question here. Pseudopalaemon tend to feed predominantly on algal growth, whereas the Macrobrachium species tend to feed on leaf litter detritus and its associated fungi (Henderson and Walker, 1986).

Studies cite a ph range of 4.3-4.7 in the areas in which shrimp have been described! And the conclusion of one study in these habitats was that, "...collections over four years in the habitat of submerged litter show that shrimps are abundant the year round...."

The study I found surveyed the fishes and inverts of the leaf litter communities of the Tarumazinho, a small blackwater tributary of the Rio Negro. P. chryseus and P. amazonensis were the most abundant of their genus found in the study, and M. natteri and M. inpa were the most abundant of theirs. 

And the common denominator here- Leaf litter.

So, yeah...leaf litter beds are so freaking compelling to me as aquatic habitats for aquarium representation that it's not even funny!

I find it compelling and interesting to think about shrimps from the Amazonia region. It would be pretty cool to be able to keep and breed these animals (obviously, to avoid decimating valuable role-playing wild populations with unchecked, non-sustainable collection) in aquariums.

Not only would they be more "biotope specific" for many of the aquaria we tend to keep- they would be fascinating and well-adapted to leaf litter type aquaria. And we're all pretty experienced at playing with this stuff, aren't we?

It's interesting to me to find out about animals that might be overlooked in the hobby. I admit that my knowledge of shrimp in general tends to be far less than my knowledge of fishes, yet I am very intrigued by these species and the potential for them to be aquarium residents!

Obviously, wanting to have animals for our hobby that are important in the natural environment carries some ethical implications, and if they are not suited for removal from these precious communities, then the use of more commonly available captive-propagated shrimp, such as the Amano Shrimp (Caridina multidentata) would make a fine facsimile substitute for these enigmatic inverts in our aquaria.

(Image by Atulbhats, used under CC BY-S.A. 4.0)

Of course, I fully expect some shrimp enthusiast to tell me that, "These shrimp from The Amazon are found like EVERYWHERE man! What rock have you been sleeping under...?"

You know, something like that.

Maybe not, yet I am certainly not the only one who's thought about these guys before. I have seen some references to propagated Macrobrachium before...They're out there still, I'll bet.

Somewhere. Maybe?

It's certainly fun to ponder, nonetheless. Right?

Just another example of the many interesting little "backroads" we can travel as we explore this amazing, addictive, and fascinating hobby.

I like those backroads, myself. You never know what you might find out there!

Stay resourceful. Stay curious. Stay intrigued. Stay diligent...

And Stay Wet.

Scott Fellman

Tannin Aquatics

 

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