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Australatya striolata (Riffle Shrimp)


fishmosy

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By Fishmosy (Dr. Benjamin Mos) and Northboy

Habitat and Water Conditions

Riffles are so named because they are found in riffles, shallow fast flowing sections of creeks. They occur in easterly flowing creeks from Northern Queensland down to Victoria, Australia. Two famous collecting areas are the Atherton Tablelands in QLD and Never Never Creek, near Bellingen NSW.

Riffles can grow to over 6cm, reports of 8cm is not uncommon. However, these shrimp change sex at around 3.5-4cm from males to females. If you want to breed these shrimp, ensure you have both size ranges.

Breeding

Breeding riffles is fairly easy. The entire lifecycle is carried out in freshwater. BBS or brine shrimp nauplii are a great conditioning food for adults. Eggs are carried by the female and hatch out as miniature adults. Shrimplets take the same food as adults, including brine shrimp nauplii and flake food, as well as grazing on algae/biofilm.

Food

One of the greatest attributes of these shrimp is watching them use their filter feeding feet to catch food items wafting in the current. They may even learn 'feeding time' and take up positions in the tank to grab food drifting by. Riffles also become less timid over time, and are often seen out and about in the aquarium.

Adults are also reported to feed on BBA and cyanobacteria (BGA).

General Notes

Riffles are adaptable to most aquarium conditions as long as extremes are avoided, but require highly oxygenated water, temperatures not exceeding 27 degrees C for long periods of time and are sensitive to phosphates and CO2. Stressed riffles will change colour to bright red or dark blue. However, their natural colouration is highly variable, greens to blues, black and white, and stripes, so colour changes aren't always indicative of problems. Riffles also seem to like hanging out on timber.

Warning: These shrimp can and do climb, so keep tight-fitting lids on your tanks.

You can keep riffles with fish as long as they can't fit in the fishes mouths, although the fish may hassle the shrimp. However, riffles can turn the tables and eat small fry.

Further Information

Riffle Shrimp from the Atherton Tablelands by Bob Kroll in AquariumKeeper Australia Vol 1, Iss 2 (Out of print)

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Below is some water parameters from a creek where riffles are found on the Mid North Coast of NSW, Australia, near Coffs Harbour.

Time of year: Late Spring (Nov, 2012).

Water parameters were as follows:

Temp - 22.5*C

Ammonia - undetectable

Nitrite - undetectable

Nitrate Undetectable

pH 6.8-7.0

Hardness - KH below 10mg/L, - GH 20-40mg/L

Ca - less than 20mg/L

PO4 - undetectable

Other than temperature, these parameters were measured using a Hagen Nutrafin Master test kit.

Here are some pictures from the area.

This is a typical area where riffles can be found, if you are looking in the shallow pool at the bottom of the picture, you won't find them. Look for the riffles like mid photo (enlarged in the second pic), no matter how shallow it may appear, riffles should be there.

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Male and female riffles often congregate in different areas. Here is an area where I found only females. Notice the width of the riffle and the presence of lots of habitat structure (rocks).

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Here is a place that was dominated by males. Notice that there are very few points to access upstream areas. The males were quite dense directly beneath the overflows of the concrete river crossing. Up to 6 riffles under each rock was not uncommon. My theory is that males congregate at these 'choke points' to access females (for breeding) which travel through to access upstream areas. This point was 50m or so downstream of the female habitat. Alternatively females may seek out these areas at moulting time (I have found recently moulted females in these areas).

Another interesting point as to why riffles might not occur in shallow pools was because of the amount of eels in this creek. There was literally one per pool. The large pool above the creek crossing contained one that must have close to 1metre in length.

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Finally another interesting factor I've found in finding riffles is that they seem to prefer the darker rocks (possibly granite, but I'm no geologist) indicated in this picture by blue dots, avoiding the lighter coloured rocks (red dots). In areas where this light coloured rock dominate, I have found no riffles at all, even if it seems like optimal habitat. Maybe it is a camoflague preference?

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Hope you have found this interesting and informative. Best of luck with keeping your riffles.


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  • 1 year later...

By Fishmosy and Northboy

Breeding

Breeding riffles is fairly easy. The entire lifecycle is carried out in freshwater. BBS or brine shrimp nauplii are a great conditioning food for adults. Eggs are carried by the female and hatch out as miniature adults.

Mine do not hatch as miniature adults.  They hatch as planktonic larvae that drift around in the water column.  So far I haven't managed to raise them successfully in fresh water (inc green water) and am thinking a little salt is required.

There is some evidence that the single species of Riffle shrimp may in fact be two species (a northern and a southern) that intergrade - perhaps Fishmosy/northboy's text references the northern and I have the southern. *shrug*.   My Riffles were originally sourced from livefish.com.au so true origin unknown.

 

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Thanks for commenting...... I must have missed this article.... A good read and perhaps it may need a little correction?

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Yes, the above article is in need of an update. Both issues @Grubs has correctly raised have been discussed in other threads regarding riffles, but its worth repeating them here.

1. Larvae of riffles (and other natives) can have two life history modes: the first is where the larvae hatch out and undergo only a couple of developmental stages prior to settling to the bottom. These come from adults in headwater streams (larger eggs so the larvae are more developed when they hatch). I discuss this in more detail in my article on Paratya australiensis. I suppose its misleading to say they hatch out as mini adults, and that should be clarified in the article.
The second life history mode is the one described by Grubs - the larvae hatch out into the plankton and develop through a series of larval stages that may or may not include some time spent in brackish water before heading back upstream to freshwater.  

Grubs: Given what you have said, its highly likely that the riffles you obtained were collected from lowland streams and not headwater streams. I'd highly recommend trying a brackish period much the same as you've had success using for other natives.

2. There is some evidence to suggest that riffles are actually two separate species (northern and southern) but further DNA analysis and taxonomic investigations are required.  @ura may know which stage this investigation is presently at.

@northboy also knows of a population of riffles on the Atherton Tablelands that are reportedly huge, and no males have been found. Is this yet another species of riffle? Why are no males found with the females? Do the males get as big as the females and, if so, does this indicate that these riffles are not sex changers?  A trip to collect some specimens for taxonomic analysis is high on the list of field trips for Bob and I when I can get back to Cairns.

Edited by fishmosy
Fixing links
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Nice wrap up @fishmosy  If I can time it right I'll try some larvae in brackish greenwater (I have a pot of typus cooking now). The scientific literature seems to suggest they have marine larvae more than fresh (though I'm aware of a few people that have had success in fresh water too).  I'd love to see some big-egg direct developers.  If ever you get some from isolated fresh headwaters send me some for comparison :)  though I know Bob has stories of them climbing waterfalls so even headwater populations might still mix with the occasional ocean born mother. The genetics seems to suggest the northern and southern pops are genetically homogeneous (of course they might not have sampled isolated headwaters)  Cook et al 2012

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Thanks Grubs. If I can sample the isolated population, I'll grab some for you. 

Just to preface my following paragraphs: Cryptic species are species that are morphologically identical (i.e. They look exactly the same) to another species but are actually seperate. The best way to tell is DNA analysis. In the below example with Caridina indistincta Clade C, DNA analysis indicates that two species live in the same river in the same areas, yet don't cross breed. One is only found in that river, the other is widespread. The cryptic species would be the one only found in that river. 

Just to clarify with the Cook paper: The genetic analysis indicates that there are two distinct types (northern and southern) but within each of the northern and southern types, their genetics are homogenous. That is, there are no cryptic species within either the southern or northern types. 

This is substantially different from say Caridina indistincta which can be divided into five clades (A-E), however there also appears to be some cryptic species found within some of the clades. Clade C in particular has around five groups within it that each could be a cryptic species. Some are found only in one river system, whereas others are widespread. 

 

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Agreed.  The point I was not making so well (for anyone reading along) was the genetic homogeneity within shrimp species is sometimes interpreted as indirect evidence for a marine larval stage.  Separate populations living in different coastal streams, or upstream and downstream in the same river produce enough larvae that get washed into the ocean to mix the genetics  up and down the coastline over generations (homogenising the gene pool).

The Cook paper suggests that both the northern and southern types each have homogeneous genetics (suggesting both types have enough marine mixing going on within their respective populations).  Yet despite this, there is evidence that populations of Riffle Shrimp exist that have direct developing young (no larval stage).   I'm not a geneticist but I would have thought that this difference in reproductive strategy would give rise to detectable genetic differences.  The difference in reproductive strategies (direct developers vs larval developers) does not appear to be as simple as the northern vs the southern species (because you'd expect less homogeneity in the genetics of the direct developers compared to the larval developers).

Perhaps the direct developers are a third type/species that wasn't included in the Cook et al study (possible if they are in isolated areas only Bob samples), or perhaps the genetic differences between direct developers and indirect developers is such that you wouldn't detect it unless you were looking for it (like I said I'm no geneticist!).... or perhaps they have plasticity where sometimes they can develop right through in the egg (e.g. if the females get enough nutrients to make fat eggs) and other times they have larvae the wash downstream...so its not a genetic difference at all!

*shrug*

20140403_150117.jpg

 

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Lastly - a note for the article concerning Australatya striolata in Victoria.

The natural range for riffle shrimp is from the Victoria to QLD but despite being very common in NSW and QLD they are rare enough at the southern extremity of their range in Victoria to be listed under the Victorian Flora and Fauna Guarantee Act 1988.  According to the legislation you are not allowed to collect them or keep wild caught (from Victoria).  You are allowed to buy them from an Aquarium or keep them if sourced from interstate but you should keep a receipt of purchase as evidence you did not catch them in the wild (I'll be the monkeys uncle if anyone ever asked to see it).

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Agreed.  The point I was not making so well (for anyone reading along) was the genetic homogeneity within shrimp species is sometimes interpreted as indirect evidence for a marine larval stage.  Separate populations living in different coastal streams, or upstream and downstream in the same river produce enough larvae that get washed into the ocean to mix the genetics  up and down the coastline over generations (homogenising the gene pool).

The Cook paper suggests that both the northern and southern types each have homogeneous genetics (suggesting both types have enough marine mixing going on within their respective populations).  Yet despite this, there is evidence that populations of Riffle Shrimp exist that have direct developing young (no larval stage).   I'm not a geneticist but I would have thought that this difference in reproductive strategy would give rise to detectable genetic differences.  The difference in reproductive strategies (direct developers vs larval developers) does not appear to be as simple as the northern vs the southern species (because you'd expect less homogeneity in the genetics of the direct developers compared to the larval developers).

Perhaps the direct developers are a third type/species that wasn't included in the Cook et al study (possible if they are in isolated areas only Bob samples), or perhaps the genetic differences between direct developers and indirect developers is such that you wouldn't detect it unless you were looking for it (like I said I'm no geneticist!).... or perhaps they have plasticity where sometimes they can develop right through in the egg (e.g. if the females get enough nutrients to make fat eggs) and other times they have larvae the wash downstream...so its not a genetic difference at all!

*shrug*

20140403_150117.jpg

 

well said. I'm not a geneticist either so cannot comment. Is it even possible to pick up differences in reproductive strategy using genetics?  I will say this though - most samples collected by scientists are collected from easy to reach locations for obvious practical and logistical reasons. I would suggest it is generally much easier to sample from lowland streams (say near where a road/bridge passes by) verses collecting from headland streams which would tend to be harder to get to. finally I think you are 100% correct when you suggest there is some movement up and down streams that would tend to keep the genetics mixed within streams. 

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