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Native Texas Freshwater Micro-Crabs


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#1 JohnnyMorales

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Posted 11 April 2016 - 04:38 PM

I was just wondering if there is any interest among people in Central Texas to go out and try and collect some.

 

For the record, the specific information on this critter while available, can be contradictory, due to the different ways even the researchers will describe it's needs.

 

The most thorough information I've found indicates that this is a recent freshwater adapter, and differs from closely related brackish water relatives only in that it can reproduce in fresh water.

 

Still biologists in Texas won't declare it a separate species, even though this crab has been found to REPRODUCE with extreme success in water with a salt content of  .04ppb which is considered fresh by all measures.

 

It lives on the Brazos watershed, and is common in a couple of lakes on that river. How much salt is in that river varies by location, but the lake these guys can be found in is very fresh, and is just outside Waco.

 

I have a feeling why some state biologists insist on calling it the gulf coast mud crab (dwarf about one inch max - the one in the pic is smaller just 20 mm) is to avoid having to protect it in any way.

 

 

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#2 Betta132

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Posted 11 April 2016 - 07:13 PM

Very interesting. I might be interested in helping- where would this be? If I can come, I'll bring a bunch of bottle traps we can use for them, especially given their size. 

What would be the aim in collecting them? Just for observation and inspection purposes, or in order to possibly bring some back and attempt to keep them in aquaria? I wouldn't think it would be too much of a challenge, most crabs are pretty easy to keep in halfway decent water. 

I wonder if we could get them declared a separate species if we managed to find some teeny-tiny ones that were clearly babies? 



#3 zooxanthellae

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Posted 11 April 2016 - 10:05 PM

Being able to reproduce in freshwater, although interesting, does not on its own warrant a new species declaration. There are a number of amphidromous species (Macrobrachium comes to mind) which are well known for doing this. Last year we discovered an amphidromous goby that we believe may be breeding in a freshwater pond, should we automatically declare this a new species? Look into the "biological species concept", it might help explain.

 

 

giphy.gif



#4 JohnnyMorales

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Posted 11 April 2016 - 10:08 PM

Very interesting. I might be interested in helping- where would this be? If I can come, I'll bring a bunch of bottle traps we can use for them, especially given their size. 

What would be the aim in collecting them? Just for observation and inspection purposes, or in order to possibly bring some back and attempt to keep them in aquaria? I wouldn't think it would be too much of a challenge, most crabs are pretty easy to keep in halfway decent water. 

I wonder if we could get them declared a separate species if we managed to find some teeny-tiny ones that were clearly babies? 

I want to keep them as pets and see how easy they are to raise with the long term goal of perhaps introducing them to the aquarium hobby overall.

 

Considering how many people seem to be interested in the Thai micro crab, which is about the same size, I imagine if people knew about these critters, they'd go for it.

 

It's right outside of Waco, in a lake that was originally created to cool a now gone power plant, called tradinghouse creek reservoir.

 

It's location is http://www.bing.com/...=en&FORM=HDRSC4

 

Oh there is no need to find proof they reproduce. I only know that from reading reports from a few different researchers from Texas universities who stated they had discovered large numbers of baby crabs much to their surprise, because they all thought it required access to brackish or salt water for the larvae to successfully develop.

 

Here is a link to a brief report from one retired researcher from Tarlton State up near Brownwood, or thereabouts, from years ago.

 

http://www.tarleton....th/MudCrab.html



#5 JohnnyMorales

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Posted 11 April 2016 - 10:22 PM

Being able to reproduce in freshwater, although interesting, does not on its own warrant a new species declaration. There are a number of amphidromous species (Macrobrachium comes to mind) which are well known for doing this. Last year we discovered an amphidromous goby that we believe may be breeding in a freshwater pond, should we automatically declare this a new species? Look into the "biological species concept", it might help explain.

 

 

giphy.gif

I don't make the rules for that.

 

What I'm going by is the scientific use of the term, which includes designating a species based on having a unique trait not shared by other members of the same species as well as living in as an isolated population.

 

On both counts they qualify.

 

As for your Goby example. Are you assuming this about all the members of that species wherever it is found, or just that pond? If this proves to be the case for this gobi, and not just those in that pond, then no it would not be a new species. All you did was discover an ability ALL the members of the current species share.

 

Also Breeding and developing to adulthood are two different things.

 

Believing vs. proved is also a key distinction.

 

Have you found populations of various ages from the egg stage to adult in the pond in question?

 

Texas researchers already proved this to be the case with isolated populations of this crab going up the Brazos river 100s of miles in several different locations isolated by major dams.

 

 In this case, there are no other cases on the books of these crabs breeding in fresh water across its range in the Gulf of Mexico drainage.

 

 

This larvae of this crab hatch and develop in fresh water without there ever being a need for more brackish water as is often the case with long arm shrimp, especially the one found rarely now in the Rio Grand.

 

If you disagree then your disagreement is with the scientific community and its moving target in regard to what is or isn't a species.

 

And while I appreciate your effort to educate me in regard to the term, judging from your doubts from how I used the term, it's you who needs some brushing up ;)


Edited by JohnnyMorales, 11 April 2016 - 10:31 PM.


#6 zooxanthellae

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Posted 12 April 2016 - 09:56 AM

"What I'm going by is the scientific use of the term, which includes designating a species based on having a unique trait not shared by other members of the same species as well as living in as an isolated population."

 

I think you will find that there is no universally agreed upon definition of a species. This is why I recommended reading up on the biological species concept (as well as other species concepts). It really will help shed some light on this for you.  

 

"As for your Goby example. Are you assuming this about all the members of that species wherever it is found, or just that pond? If this proves to be the case for this gobi, and not just those in that pond, then no it would not be a new species. All you did was discover an ability ALL the members of the current species share."

 

You should read:

 

OCCURRENCE, REPRODUCTION, AND POPULATION GENETICS OF THE ESTUARINE MUD CRAB, RHITHROPANOPEUS HARRISII (GOULD) (DECAPODA, PANOPIDAE) IN TEXAS FRESHWATER RESERVOIRS

TERRENCE BOYLE JR., DONALD KEITH and RUSSELL PFAU
Crustaceana
Vol. 83, No. 4 (April 2010), pp. 493-505
 
There are a few ideas about how these crabs managed to colonize different fw habitats. One of the authors conclusions is that it has possibly happened multiple times based on a dozen different haplotypes found in the area. If his is true, it means that fw colonization is an ability of the species at large (although not necessarily to every population).
 
Forget about the goby though, that was just hyperbole. If you can't access that paper, pm me. 
 
 " In this case, there are no other cases on the books of these crabs breeding in fresh water across its range in the Gulf of Mexico drainage"
 
Yes there are, granted in the same area of texas though. Researchers aren't sure whether the other fw populations are related via a founding population that spread to other fw habitats, or if they represent other colonization efforts. 
 
"This larvae of this crab hatch and develop in fresh water without there ever being a need for more brackish water as is often the case with long arm shrimp, especially the one found rarely now in the Rio Grand."
 
There are populations of euryhaline macrobrachium species known to reproduce in purely fw habitats. Admittedly, I know of no other crabs that do this. 
The take away message here is that this is not a new species of animal, it is an r-selected, euryhaline species that can withstand many different habitats, and may have recently adapted to fw. Whether or not the coastal population can adapt to full fw regularly is unknown at this time. 
 


#7 gerald

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Posted 12 April 2016 - 10:02 AM

Johnny, different populations within a species may have different behaviors and tolerances, some of which may be genetically fixed at birth and some of which are acquired during the animal's life, due to genes being activated or inactivated by environmental cues.  A longear sunfish taken from a cool spring-fed stream population and released in a warm coastal plain stream might not have the heat tolerance of longears (same species) that were born there.  There's more to deciding when a population should be called a new species than just identifying a unique characteristic and isolation.  Speaking of which, do you know whether these freshwater-breeding mud crabs are really isolated from their tidal-water cousins, and for how long?  There might be a good bit of genetic exchange between the coastal and inland "populations".  And even if there isn't, the inland pop may not have been isolated long enough to have changed significantly.  One other thought -- there may be something about the chemistry, plankton community, predators,or other ecological factors at this site that allows mud crab larvae to survive here better than in other freshwater sites.

 

"Taxonomy is the diaper used to organize the mess of evolution into discrete packages" - Mike Sandel

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"Taxonomy is the diaper used to organize the mess of evolution into discrete packages" - M.Sandel


#8 Betta132

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Posted 13 April 2016 - 06:46 PM

I'm pretty sure that for something to be considered a species, it has to be no longer genetically compatible with the other version- either they try to reproduce and fail, or the result is a sterile hybrid. Not sure how one would test that with two variations of critter whose larvae require different conditions to survive, though. 



#9 9darlingcalvi

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Posted 13 April 2016 - 07:13 PM

Give them a standardized reading, history and science test?

#10 gerald

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Posted 13 April 2016 - 08:52 PM

I'm pretty sure that for something to be considered a species, it has to be no longer genetically compatible with the other version- either they try to reproduce and fail, or the result is a sterile hybrid. Not sure how one would test that with two variations of critter whose larvae require different conditions to survive, though. 

 

That traditional "species concept" has pretty much blown out the window too.  Lots of distinct species can interbreed and yield fertile offspring (in captivity), but for whatever ecological reasons, they either dont interbreed much in nature (behavioral isolating mechanisms, like color, season, habitat) or the hybrid offspring fizzle out after a generation or two.  It may just be that the hybrids cant compete as well; not that they're genetically incompatible.  A change in the environment might even give the hybrids an advantage, in some cases.  Species concepts really are a "mess" - there's no solid definition that works for every case.   Back to mud crabs, I'm guessing the "freshwater" ones can probably still reproduce in their ancestors' estuarine/brackish habitat too.


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"Taxonomy is the diaper used to organize the mess of evolution into discrete packages" - M.Sandel


#11 JohnnyMorales

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Posted 17 April 2016 - 11:21 PM

I'm pretty sure that for something to be considered a species, it has to be no longer genetically compatible with the other version- either they try to reproduce and fail, or the result is a sterile hybrid. Not sure how one would test that with two variations of critter whose larvae require different conditions to survive, though. 

No that's not true. All the sunfish species and crayfish species that readily hybridize and produce fertile and sometimes more viral offspring make it clear that is not a basis for species.

 

To be considered a species, you need a researcher or researchers committed to making it so.

 

Species has taken on a political meaning that has ruined it in science.

 

The political context that ruined it as scientific word is due to it being a defining term in the "endangered species act". Both sides in conflicts over preservation vs development have found ways to use it to their advantage.

 

Some environmentalists have seized on the word and used it as a cudgel to stop development wherever they think it needs to be stopped.

 

Creating new species based on incredibly minimal differences between say two fish coming from different tributaries of the same river for example to build a case that a damn should not be built for example.

 

I've read several articles about endangered species of crayfish in tributaries of the Tennessee river describing identical critters as species deserving special protection lest they disappear. About the only basis for them being called a species was that they came from populations too far away to enable easy breeding between the two. THAT'S IT.

 

OF COURSE there has been push back from interests often on the state level to stymie their efforts.

 

And that is where this mud crab comes in..

 

It is NOT in the interest of Texas regulators to have this creature be declared a species.

 

If it is, it would be a rather unusual and rare one, and almost immediately gain similar status to a lot of pup fish in the nation.

 

The end result is land owners would not be able to do whatever they want with their land without first making sure they are not destroying these guys.

 

The article that picture came from was a brief on the habit of the crab of clogging intake pipes for houses near the lake where it lives.

 

The implied solution which would be extermination would be severely hindered if this crab were declared a separate species.


Edited by JohnnyMorales, 17 April 2016 - 11:23 PM.


#12 JohnnyMorales

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Posted 17 April 2016 - 11:29 PM

 

That traditional "species concept" has pretty much blown out the window too.  Lots of distinct species can interbreed and yield fertile offspring (in captivity), but for whatever ecological reasons, they either dont interbreed much in nature (behavioral isolating mechanisms, like color, season, habitat) or the hybrid offspring fizzle out after a generation or two.  It may just be that the hybrids cant compete as well; not that they're genetically incompatible.  A change in the environment might even give the hybrids an advantage, in some cases.  Species concepts really are a "mess" - there's no solid definition that works for every case.   Back to mud crabs, I'm guessing the "freshwater" ones can probably still reproduce in their ancestors' estuarine/brackish habitat too.

 

I'd say you're guessing, but not based on any data ;)

 

They are completely cut off from their estuarine habitat in the freshest water they can reproduce in Tradinghouse Creek reservoir and on lakes further up on the Brazos they are cut off by enormous damns.

 

Is it possible sure, but nobody has bothered to do a study, and nobody will.

 

If breeding in saltwater proved to be problematic, then it would be hard to deny this was a new species, and having a new, freshwater crab in a limited habitat is the absolute last thing Texas regulators want to contend with. Thus their insistence on calling a crab they have only ever collected in freshwater lakes an estuarine crab.

 

It's nice to read one response from someone who realizes just how unscientific the term species has become.


Edited by JohnnyMorales, 17 April 2016 - 11:31 PM.


#13 Moontanman

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Posted 17 April 2016 - 11:30 PM

I was just wondering if there is any interest among people in Central Texas to go out and try and collect some.

 

For the record, the specific information on this critter while available, can be contradictory, due to the different ways even the researchers will describe it's needs.

 

The most thorough information I've found indicates that this is a recent freshwater adapter, and differs from closely related brackish water relatives only in that it can reproduce in fresh water.

 

Still biologists in Texas won't declare it a separate species, even though this crab has been found to REPRODUCE with extreme success in water with a salt content of  .04ppb which is considered fresh by all measures.

 

It lives on the Brazos watershed, and is common in a couple of lakes on that river. How much salt is in that river varies by location, but the lake these guys can be found in is very fresh, and is just outside Waco.

 

I have a feeling why some state biologists insist on calling it the gulf coast mud crab (dwarf about one inch max - the one in the pic is smaller just 20 mm) is to avoid having to protect it in any way.

 

 

 

 

If you get some I would love to try breeding them, I have bred crayfish and shrimp, crabs look like a good challenge...


Michael

Life is the poetry of the universe
Love is the poetry of life

#14 Moontanman

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Posted 17 April 2016 - 11:37 PM

The species thing is interesting, I know there is a guy on aquabid who from time to time sells hog chokers he says he catches in a land locked lake in Florida, I've often wondered if they are a different species..  


Michael

Life is the poetry of the universe
Love is the poetry of life

#15 JohnnyMorales

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Posted 17 April 2016 - 11:38 PM

 

Johnny, different populations within a species may have different behaviors and tolerances, some of which may be genetically fixed at birth and some of which are acquired during the animal's life, due to genes being activated or inactivated by environmental cues.  A longear sunfish taken from a cool spring-fed stream population and released in a warm coastal plain stream might not have the heat tolerance of longears (same species) that were born there.  There's more to deciding when a population should be called a new species than just identifying a unique characteristic and isolation.  Speaking of which, do you know whether these freshwater-breeding mud crabs are really isolated from their tidal-water cousins, and for how long?  There might be a good bit of genetic exchange between the coastal and inland "populations".  And even if there isn't, the inland pop may not have been isolated long enough to have changed significantly.  One other thought -- there may be something about the chemistry, plankton community, predators,or other ecological factors at this site that allows mud crab larvae to survive here better than in other freshwater sites.

 

"Taxonomy is the diaper used to organize the mess of evolution into discrete packages" - Mike Sandel

 

 

You seem to think I'm assuming about the critter, when I'm paraphrasing the researcher's own findings. Based on what I read, they did not feel your assumptions were held up by their findings. They had the same assumptions re how isolated they were.

 

You can google the species name and add the qualifier site:.tamu.edu to get only results from the Texas university system.

 

The only addition I made is that considering what has qualified other species for species status, this mud crab certainly qualifies. Hell based on what is described it probably qualifies for genus level designation.



#16 JohnnyMorales

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Posted 17 April 2016 - 11:42 PM

Give them a standardized reading, history and science test?

They did, but it was in saltwaterese and they didn't understand.



#17 JohnnyMorales

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Posted 18 April 2016 - 12:01 AM

 

"What I'm going by is the scientific use of the term, which includes designating a species based on having a unique trait not shared by other members of the same species as well as living in as an isolated population."

 

I think you will find that there is no universally agreed upon definition of a species. This is why I recommended reading up on the biological species concept (as well as other species concepts). It really will help shed some light on this for you.  

 

"As for your Goby example. Are you assuming this about all the members of that species wherever it is found, or just that pond? If this proves to be the case for this gobi, and not just those in that pond, then no it would not be a new species. All you did was discover an ability ALL the members of the current species share."

 

You should read:

 

OCCURRENCE, REPRODUCTION, AND POPULATION GENETICS OF THE ESTUARINE MUD CRAB, RHITHROPANOPEUS HARRISII (GOULD) (DECAPODA, PANOPIDAE) IN TEXAS FRESHWATER RESERVOIRS

TERRENCE BOYLE JR., DONALD KEITH and RUSSELL PFAU
Crustaceana
Vol. 83, No. 4 (April 2010), pp. 493-505
 
There are a few ideas about how these crabs managed to colonize different fw habitats. One of the authors conclusions is that it has possibly happened multiple times based on a dozen different haplotypes found in the area. If his is true, it means that fw colonization is an ability of the species at large (although not necessarily to every population).
 
Forget about the goby though, that was just hyperbole. If you can't access that paper, pm me. 
 
 " In this case, there are no other cases on the books of these crabs breeding in fresh water across its range in the Gulf of Mexico drainage"
 
Yes there are, granted in the same area of texas though. Researchers aren't sure whether the other fw populations are related via a founding population that spread to other fw habitats, or if they represent other colonization efforts. 
 
"This larvae of this crab hatch and develop in fresh water without there ever being a need for more brackish water as is often the case with long arm shrimp, especially the one found rarely now in the Rio Grand."
 
There are populations of euryhaline macrobrachium species known to reproduce in purely fw habitats. Admittedly, I know of no other crabs that do this. 
The take away message here is that this is not a new species of animal, it is an r-selected, euryhaline species that can withstand many different habitats, and may have recently adapted to fw. Whether or not the coastal population can adapt to full fw regularly is unknown at this time. 
 

 

I did read that paper a while back.. I apparently came away with different point of view.

 

The conclusion you sight and think scientific is an ASSUMPTION to explain away the need for species status.

 

It could also be that along the Brazos various populations have been isolated for eons.

 

Since you know about that paper no doubt you know about the 50s paper that found barnacles AND CRABS in Salt Water springs 6 or 800 miles up the Brazos river. A tiny population that quickly exterminated as a result of efforts to isolate the salt water flow into the Brazos in order to freshen up the water.

 

The results of the work can still be seen today on Google maps.

 

That research speculated that the barnacles could have been a refuge population from the time when that part of Texas was part of the mid-continental seaway.

 

The most important thing however was that he found crabs, tiny crabs in a saltwater spring with absolutely NO access to the ocean.

 

The real problem with your whole original comment is the implied belief that species is a hard and fast scientific term, used judiciously and wisely based on hard parameters making manipulation of its use difficult.

 

That's simply not true.

 

You can argue it's not a species, but you would be no more right than I, because most of what makes a species these days is subjective, and the most important thing is to have researchers interested in making something a species.

 

Texas as a state is loathe to find a new species, especially one that might immediately qualify for protection under the endangered species act. To that end, research always couches potential findings pointing in that direction to obscure that fact.

 

Now you can choose to believe that in super pro-development Texas where fracking wastes is routinely injected underground potentially polluting groundwater resources is a state that would NOT do that, and believe that Texas researchers who receive funding from the state at state institutions are able to work to protect potentially new species whenever they find them, but considering the paucity of new species of consequence found in a region the size fo Texas ....

 

And since you know about that research, you must also know of research that refers to it as an invasive removing it from any protective category  making the case for the state to exterminate it as they see fit wherever it is found to be an annoyance


Edited by JohnnyMorales, 18 April 2016 - 12:07 AM.




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