Euryrhynchus amazoniensis

[josu2]

I thought I'd share this unusual (to aquarists) shrimp that I have been keeping for a few months. My keeping of it to this point has been almost entirely seat of pants, with near-zero previous testimonials that give any detail of longevity, behavior, etc.

 

I started my journey to finding this shrimp when building a South American biotope aquarium, more specifically targeting a Colombian/Venezuelan llanos Orinoco tributary stream biotope. I realized that there are not any regularly traded South American shrimp species, though there is no deficiency of shrimps in the region. I started looking into which species were at least irregularly traded and found Euryrhynchus amazoniensis as one of those. Still, I could not find any US sellers/sellers willing to ship to USA.

 

 

By chance, I found a seller who had several shrimps which were labeled something to the effect of Macrobrachium sp. "Peruvian zebra". I checked against some of the identifying characteristics (and distribution information, confirming E. amazoniensis is in Peru among other places, especially Brazil/Rio Negro) laid out in the literature and felt comfortable this was a Euryrhynchus sp. rather than Macrobrachium and given E. amazoniensis's status as a previously traded aquarium shrimp, I figure that's what I've got. By the time I got to this point, I was no longer interested in adding this species to my community biotope—indeed, I do not believe you'd find it in the llanos—but felt like it was a really cool species and one that if I was lucky enough I might be able to distribute to fellow aquarists. Scientific literature indicates that its reproduction is similar to the familiar Neos and Caridina, with no larval stage and no need for brackish/marine water. Pictures may not accurately portray the size of the shrimp...even including the length of the arms, they do not even reach 2" long.

 

 

Unfortunately, I have not been able to simulate its native habitat as well as I wished. Their small tank has Caribsea's Floramax planted tank substrate, which despite the bag's promises is not inert and in fact buffers the water into at least the upper 7s of the pH. I have not been able to get the TDS levels any lower than the upper 100s, though I often allow it to get higher (but I conduct water changes to keep below 300). These shrimps are native to igapos which have extremely low, at or near 0 TDS in the wild. E. amazoniensis is among the select few that can survive in these habitats year round. Stomach analyses indicate that they feed on small crustaceans, not unlike many small tetras and the like we keep in our aquariums. Researchers in the 1970s/1980s found captive specimens unwilling to take the lion's share of foods offered nor did they observe much activity at all.

 

Indeed, these are secretive fellows. I have 8 of them and when having a friend check on the tank (just 5 gallons!) in the week or so following purchase, my friend reported seeing none of them in the several hours she spent around the tank. I've had far better luck, but they certainly are shy and prefer being under some sort of cover at virtually any time that they aren't actively grabbing at food. I have furnished them with a manmade cave decoration that is the centerpiece of the tank and it is the hub of their activity, though they are truly remarkable at disappearing within it even when I shine a light inside.

 

 

I can put frozen spirulina brine shrimp or similar in the tank, though, and before long I usually see 3-6 moving about, sensing the food around. The signature move is to take the largest chunk of food they can grab with their claws and then retreat backwards so fast you'd think they were possessed. Other times, particularly in the case of the females and younger/smaller males, they feel comfortable eating out in the open. I have gotten the biggest male as well as a female or two to take frozen live food from my planting tongs, so they are not exactly in mortal fear of the unknown.

 

I see occasional sparring, but it is never violent...more like slapping or light pinching with the claws. Two had apparently lost and then regrown their "big" arms before I purchased them, though, so this suggests they can probably hurt one another. I would guess their aggression may be a little bit like dwarf crayfish, which can often coexist peacefully but sometimes turn ugly.

 

 

Given their ability to hide, I've not much entertained the idea of changing out their tank's substrate or moving to a bigger and better setup. The thought of catching even just one or two of them sounds nightmarish to me. In rescaping the tank, I had removed their large cave and their couple pieces of driftwood...yet saw not one of them! When spooked, they can really disappear. I had resigned to them being a neat curiosity more than anything else due to my inability to replicate their natural habitat, but lo and behold just days ago I discovered a berried female! Perhaps they are more comfortable than I give credit for. Truly remarkable that they can adapt to such a different set of conditions...it could be the case that they are more broadly distributed in the wild than previously thought. Even those describing the species scientifically suggest that they are not at all easy to find in the wild and probably wouldn't be found by accident too often.

 

 

Anyways, this is probably information overload but I figure if anyone would appreciate this interesting experience it would be the good folks at the Shrimp Spot.

[Soothing Shrimp]

Awesome shrimp to read about.  Thank you soooo much for putting all this information together and sharing it with us.

 

So, in your opinion, these shrimp would be able to live in pure ro without remin?

[Vpier]

Cool shrimp. Since they are S.American I would start by using RO and remineralizer like SS GH+ or SL-Aqua Blue Diamond and ADA Amazonia.  The Orinoco is soft and acidic so I would start out by keeping them in the lower end of caridina water parameters.

[Shrimple minded]

Thanks Josu, really interesting. Keep us updated, can't wait to see more.

Sent from my iPhone using Tapatalk

[josu2]

Awesome shrimp to read about.  Thank you soooo much for putting all this information together and sharing it with us.

 

So, in your opinion, these shrimp would be able to live in pure ro without remin?

 

Certainly something close to it, I would think. Collections from multiple sites reported in the early 1980s say that the conductivity was less than that of rainwater, the numbers cited translate to <13 TDS and from 3.8-6.0 pH. Their habitats are characterized by seasonal flooding, but I can't quite grasp what differences it would make for water params...but it clearly brings new fauna, though throughout the year they seem to eat miniscule detrivore crustaceans.

 

Cool shrimp. Since they are S.American I would start by using RO and remineralizer like SS GH+ or SL-Aqua Blue Diamond and ADA Amazonia.  The Orinoco is soft and acidic so I would start out by keeping them in the lower end of caridina water parameters.

 

At some point in the future, I'll have to replace the substrate and/or move them to a new tank to accommodate this, which was my goal all along until I ran into these problems derived from substrate. For now, I'm going to leave things as they are because I don't want to stress my gravid female into dropping her eggs.

 

[Soothing Shrimp]

This may help you josu2 http://www.crusta-fauna.org/shrimp-index/euryrhynchus-amazoniensis/

[josu2]

Got a butt-side view of the berried female.

 

[josu2]

So on Feb. 6th, I I decided to set these guys up in a new tank. They were in a tank that I didn't particularly like because its viewing angles were poor and their cherry shrimp tankmates—the adults, at least—were dying one by one due to incomplete/failed molts. Cherries went to my snail tank and these guys got their own digs for the time being. I was worried about catching them but ultimately it wasn't too bad.

 

I initially kept them in conditions very similar to what you see in scientific articles that describe their habitat, about 40ppm TDS and pH ~5. Even though they seemed perfectly happy in those conditions, which is amazing, I decided to bring up the TDS to the 125 range and the pH more around 6. I think I will add a softwater Caridina shrimp at some point to add more visual interest to the tank and am kicking around the idea of some Boraras brigittae. I generally remineralize with Seachem Replenish, in part because I still am skeptical of buying a pricey shrimp-specific product.

 

The substrate is an inert black sand, which offers me more control over params. There are several torn up Catappa leaves in the tank for hiding places and to better simulate their natural habitats. There is some christmas moss tied to cholla and covering the sponge filter where they do some hiding as well. I have a little bit of corkscrew val growing, but it is generally speaking not as densely planted as I usually do. Several pieces of driftwood seem to be where they do their most hiding, using up every conceivable crevice.

 

Anyway, I got some new pictures during the process of setting up the tank. I kept them in two sets of four while switching everything over. I have to say I almost never had seen those brilliant blue males until that night, I'm thinking they must have matured considerably under my care. I'm surprised one is still so small. In the month since I've taken these pictures, a second (and possibly third, hard to say when they are never all out at once) female has become berried. I've not seen any evidence of shrimplets, but again they are very secretive and it is still within the plausible timeframe that the original berried female could still be carrying eggs (~4-5 weeks).

 

[Vpier]

where and who did you get them from? cool shrimp

[Soothing Shrimp]

Are the offspring low order or high?

[Shrimple minded]

"Scientific literature indicates that its reproduction is similar to the familiar Neos and Caridina, with no larval stage and no need for brackish/marine water."

[Pokeshrimp]

Very cool. Can't wait to see how they behave with their new tank mates.

[Soothing Shrimp]

Thanks Shrimple.  I must have missed that part.

[josu2]

Thought I'd throw in an update.

Yesterday I saw one of the big, handsome red-colored males lying dead in the front of the tank. I didn't see any obvious explanations. At the time I saw him, he must not have been long dead since he had yet to really turn white like many who keep common dwarf shrimp would recognize. He did do that eventually, though. No signs of a failed molt—it would be fascinating to know what kinds of things would interfere with molting in a creature that can inhabit <10 TDS waters, though.

I did have a minor crisis after seeing this, worrying that maybe others had died but not in the open. I have not changed the water in some time, given that I don't want to add my own tap water to this very soft water tank. I did do a 25% WC after removing the body, though. My tap water is about 150 TDS right now, the tank water was around 120, it was worth what little risk there is in modestly hardening the water to remove any possible harmful component in the water column. I will probably do another 25% WC with RO water later in the week. Before the WC, pH was between 5.7 and 6.0, ammonia was 0, nitrites were 0, nitrates were 0. A note on the nitrates–the entire surface of the tank is covered in dwarf water lettuce. I've added nitrates as fertilizer to this tank and it still measured out at 0 (Seachem test kit), so this is just a case of hungry plants.

The shrimp had been in my care for over 4 months and arrived at this adult size. It could be the case that it had reached a natural end to its lifespan, the length of which is unclear from my research but we know with most dwarf shrimps that 2 years would be regarded as a relative maximum and 1 year maybe more of a norm. I can't know how old it was when I got it.

I was deliberately a little disruptive with my water change because I wanted to get the other shrimps to show themselves as a way to reassure myself that they didn't all die on me for some reason unknown. By the time I got to sleep, I saw at least 3 of them (possibly 4, but the two times I saw a big pair of claws come out to grab food I didn't get a great look at the whole body). One of the males, who I noticed weeks ago had lost one of his large claws, has an abnormality on his remaining one. It looks like a hole! I couldn't get a good picture of it, but it looks like a tiny hole in the chunky segment just before the pincers. This shrimp is by far the most gregarious, I see it walking around the tank more than any of the others. Its loss of an arm/claw is odd, but I should note that I had one totally missing a big claw like this when I got them and by the time I moved them to the new tank, it was impossible to tell which of them it was because it had apparently grown back so well. I wonder if this fellow lost a fight and if that is what caused the hole in the remaining arm as well.

Another note–nothing to report on shrimplets. About a week ago, I saw the first berried female, apparently still berried. At this point, my hopes aren't super high and it could be the case that she's actually dropped eggs and become berried again in the almost two months since I first saw her berried. I put some food near her hiding place yesterday and she didn't come out to get it, but that's not all that abnormal. There was at least another berried female, but with the place it hides I see it far less frequently under normal circumstances. There are now chili rasboras in the tank, 15mm micro-fish. They could potentially harm newborns, but I doubt they'd be able to find enough to decimate the population. I'll just have to keep an eye out...

[oem]

First time I caught this thread.  Really interesting shrimp and an equally interesting quest to understand their particulars and eventually breeding them.  You really have some amazing projects going on.  Thank you for a different side of our hobby.

[josu2]

These guys are really something. I can't tell you how many times I've felt like I was getting nothing out of their tank, questioned whether many were even alive or were healthy...but then they draw me back in.

 

The other night, I saw...something. There are some pest snails in their tank, plus the chili rasboras, and a not small share of detritus from catappa leaves and such. I felt like it was moving slowly and deliberately. Never got a good look at it. Then a few days later, I saw something that sure looked like a shrimplet. I felt 95% sure, but it was SO small. Tonight I did a water change and yes, shrimplets. I've seen at least 4, but knowing this species, there are always more than you see at one time. I cannot for the life of me figure out how old they would be. It has to have been at least 3 weeks, if not more like 6 weeks, since I've seen a 100% certain pregnant adult. And at that point, we're looking at a ~2 month or up to 3 month gestation period. Maybe there was another hatching in the middle that didn't work out, I don't know.

 

I don't have any pictures of these guys yet, but they're barely bigger than the very smallest RCS shrimplets that I've been able to glimpse with my naked eye (mind you, I'm not extensively experienced with RCS, so I don't necessarily have a trained eye for these things). While these have no larval stage, I do wonder if they start out much smaller. Whatever the case, it's very encouraging to see the cycle of life in progress.

[Soothing Shrimp]

Awesome!

[josu2]

Decided to grab some pics and videos after a water change yesterday.

 

Two babies:

 

 

 

My estimate, based on taking photos of them with a dime nearby, is that the largest babies are about 8mm long now. I dug up some old studies with captive breeding of these and in those cases they were born at 3.5-5mm, so that checks out. This does suggest that they are very slow growers, though!

Here's a video of the guy in the first picture (sorry for all the refocusing, my camera does not like trying to focus on such a tiny subject):

 

And here's an adult grabbing some seaweed I added. I put this in for the neos I have in there, but the Euryrhynchus go nuts for it. I suspect that while their wild diet doesn't involve algae, the tiny crustaceans they eat have themselves eaten algae and plant material, so their captive diet probably needs some of these vegetarian components.

 

[ohmiko]

Any new updates on this? Would love to try some but dont know what water parameters and such  I read through this and i'm just a little confused

[josu2]

My little tank of these guys is still going strong. They seem to breed continuously much like caridina/neos, though I think at a bit slower pace and smaller numbers of eggs. I would guess that there are at least 30 of them in the tank right now. I don't have a good way to know if any of them are from the original group I purchased. I rarely see any dead ones, but I do know that in general they like to pull any dead animals in the tank into a hiding spot for later consumption.

 

I believe I have seen photos from Chris Lukhaup of a berried female, so I know I'm not the first to breed in captivity. With that said, almost all reports I can find online describe failures to keep these shrimps alive for long, let alone breeding them. There are some differences in my care compared to that many of these other keepers who struggled. The most consistent one: temperature. I don't know exactly where this came from, but most other accounts of keeping these shrimps involve matter-of-fact claims that the shrimps need very warm water, >80F. I can't find any published scientific basis for this claim (though that would be true of most fish and shrimp we keep in the hobby). What I can find is a published description of the collection sites for a study of this and a couple other species:

 

Quote

The water is poor in minerals (conductivity below 10 microsiemens), acid (pH 4.3-4.7) and relatively cool the year round (this at least in the middle and upper course; 24-25 C). Owing to its extreme mineral poverty there are virtually no water plants with the exception of some microscopic algae (Conjugatophyta, Diatomeae) which are invariably found within submersed litter. The food chains start essentially with decom- posing fungi and with detritivores; the fauna is therefore associated with submerged litter that accumulates in certain meanders, in small recesses in the banks and in the mouths and beds of affluent streams.

 

This is from:

 

Walker, I., & Ferreira, M. de N. (1985). On the population dynamics and ecology of the shrimp species (Crustacea, Decapoda, Natantia) in the Central Amazonian river Tarumã-Mirim. Oecologia, 66, 264–270.

 

So the water in the habitats used for collections in this study are barely tropical in temperature. The tank I keep them in ranges from 76-78, depending on ambient conditions and the efficiency of the heater. It could be a coincidence that I've had such success at this temperature and others have struggled at higher temperatures.

 

On the other hand, my conditions differ in significant ways from their natural habitat. I've begun using just the water from my tap, which has about 150ppm TDS, 5-6 dGH, 2-3 dKH, and settles at about 6.5 pH. Nitrates are always undetectable in this tank due to some dwarf water lettuce and moss. In fact, the tank water has fewer nitrates than my tap, which has 5-10ppm depending on the amount of runoff from the farms outside my city. But I found it difficult to maintain conditions using acid buffers and the like and I am not investing in an RO system (and I don't like the accumulation of empty distilled water jugs when I try to replenish with those). Importantly, the shrimps never seemed to mind one way or another when I did these things. Maybe they have their limitations in terms of the amount of water hardness and pH, but my tap doesn't push it.

The article I cited also mentions in passing that for part of the year, their habitat can be somewhat turbid and with a fair amount of water flow (but not quite hillstream conditions). For my part, they just have a sponge filter, so very little flow whatsoever. They've even survived a few days when my cat chewed through the airline tubing when I was on vacation, thus stopping the filter entirely. My take on the shrimps is that they are very hardy since they have survived much of my experimentation and mistakes. Maybe there's something essential that once satisfied, leaves you with a tough fish. I'm reminded of otos in that way; if you can keep your otos over a month or so, you'll have happy and healthy otos that are indestructible for years.

 

I would estimate that about 50% of the surface area of the bottom of this tank has driftwood on it or just over it. The shrimps spend most of their time hiding in and under the wood. They also go into the moss and under leaves I have in there. I do wonder if other keepers have provided so much cover. It often means that I can look at the tank and see no shrimps, but honestly I no longer have to spend much time looking before I see one or two. After a water change or after tossing some ground up flake food in there, I often see several, sometimes more than 10 at a time. I think they're quite funny, really, with some of the crankiness (and harmlessness) that dwarf crayfish have.

 

FWIW, I tend to feed mostly ground up New Life Spectrum community flake on the basis of gut analyses showing they seem to be aufwuchs eaters with some preference for tiny crustaceans and insect larvae. They also like frozen brine shrimp quite a bit as I believe I posted long ago. But they take pretty much whatever I put in there. I also think they may be killing some bladder snails, but I can't prove it. What I can say is there are usually several empty bladder snail shells on the substrate and I have on several occasions seen a shrimp eating out of one of the shells. Surely they would eat a dead one if they came across it, so I can't say for sure whether the bladder snails starve to death and then are eaten or if they are actually killed by the shrimps.

 

Soon I am planning to put them in a bit larger tank, which would have the side effect of letting me get a grip on how many there are. If I could be confident that I have plenty, I would think about selling some to someone serious about providing for them.

 

[William]

has anyone nailed down a source for these shrimp?