Sterbai Corydoras can commit venom water bath deaths if stressed??

[GaryE]

My understanding, possibly flawed because I last read a paper on it years ago, is that the venom isn't so much a weapon as a warning chemical for the other Corys in the group. It's a chemical signal that happens to be venomous in tiny fish bags. It's the chemical equivalent of a Cory shouting "Incoming predator!!!!" It might also inconvenience a predator in open flowing water, and make it question its choices in life. But it is not a huge quantity of venom in the normal run of things.

I always tell people to proceed as if their Corys have it, because there are so many newly found species comng into the hobby, and so little research into which species have this 'problem' and which don't. The early research has certainly increased the price of newly found wild Corys because they are now shipped differently, in a costlier way.

 

[DoubleDutch]

Moved my Sterbai today. No casualties !

 

[TwoTankAmin]

According to the researchers it is definitely a defese mechanism. Now I will admit I am a bit prejudiced because I know Dr. Eric Thomas.
https://liberalarts.pacific.edu/campus-directory/eric-thomas

I know him from his fish keeping and breeding skills. He is ranked #2 on Planetcatfish's "Breeder Board."

The paper I linked was basically organized by Eric. I also checked and he also worked with this from duplicareus. He is quite certain this is a defense mechanism. It is sort of like squid ink. The idea is it is a coctail of things that will put off an agressor and hopefully provide the opportunity to escape. In a fish bag it doesn't dilute as it does in the wild. It is then it becomes deadly. Handling is know to elicit the of release the exccetions.

 

[DoubleDutch]

According to the researchers it is definitely a defese mechanism. Now I will admit I am a bit prejudiced because I know Dr. Eric Thomas.
https://liberalarts.pacific.edu/campus-directory/eric-thomas

I know him from his fish keeping and breeding skills. He is ranked #2 on Planetcatfish's "Breeder Board."

The paper I linked was basically organized by Eric. I also checked and he also worked with this from duplicareus. He is quite certain this is a defense mechanism. It is sort of like squid ink. The idea is it is a coctail of things that will put off an agressor and hopefully provide the opportunity to escape. In a fish bag it doesn't dilute as it does in the wild. It is then it becomes deadly. Handling is know to elicit the of release the exccetions.

Not any doubt isn't anything else than the defensesystem you're mentioning.

 

[TwoTankAmin]

Not as far as the researchers were concerned. I would be happy to shoot Eric an email or PM and ask him if you like.

If you read the paper you will discover that what the sterbai excretes is not a single chemical, it is a complex mix. You will read this

Corydoras Defenses
All species in the Corydoras genus contain two thick sets of bony plates found along the side of the fish that give it protection along with several spines that it has on their body(4). The armored plates are a passive mechanism of defense. The spines can be found on the leading edge of all fins, except the caudal fin (tail), in each pectoral fin, in the adipose tissue on their body, and the largest in front of their dorsal fin(5). The poison is thought to be found in a gland next to barbs on the pectoral spine and is thought to flow down the spine, allowing the poison to potentially be absorbed into the predator through physical damage from the spines and or gills. The spines and toxin are a more active method of defense. The toxin appears to come out of an opening that is found just under the pectoral fin on either side of the fish.

Apparently, the toxic wins up in the attacker via the spines. So I am doubting the idea I offered that is is like squid ink. However, This may also be the case. Clearly, the stress of handling is enough to cause the fish to emit the toxin. This would imply that is it is not being introduced into a predator via the spines, that is must have some effect in the immediate area of the cory. Before it dissipates due to he volume and movement of the water, it may very well put off a predator. I do not believe they tested for this.

When evovling this defense mechanism in these fish, nature never accounted for the fish being caught, bagged by and shipped to fish keeping hobbyists.

One last observation, the research not only investigated the toxins secreted but also the skin and tissues of the fish that might be involved.

I have personally experienced self-poisoning with sterbai, but I have handled other corys both as purchases and occasionally shipping and I have not seen the self-poisoning in the few other species with which I have worked. I would guess that, at best, I have kept fewer than 10 different cory species over the years. Only the sterbai showed the self poisoning.

 

[GaryE]

It's anecdotal, but I know from hanging around with importers that the good ones take this very seriously. The wholesalers in South America do too. "High end" Corys don't usually even have names, let alone research into the status of their venom production. So there is a tendency to err on the side of caution. I got my last lot of Corys shipped single packed, without my asking for that.
I bought 3 species a few months ago at a new specialized store in my old city, and the seller wouldn't single bag. That was reasonable, as they were brevirostris, CW 123 and concolor - not the most expensive, and he had a store to run. Since I had a 10 hour drive, I had brought enough containers to isolate my planned purchase of 2 species. I repacked once I got back to where I was staying, and all did well. The species (CW 123)that I didn't have containers for was rough to start with, and needed a few weeks of tlc to rebound, but I doubt that was venom related. They were just beaten up by transport to the store, and I took a gamble because I thought they'd turn out well. They did.
I figure we plan for the venom to be there, but wait for the research to tell us what's up species by species, as with all things.

 

[Boundava]

I found out the hard way about the Cory stress toxins. I knew that Cory's did this but completely forgot in the stress of moving. I had taken down a 75 gallon tank that had over 20 albino annaeus, about four green annaeus, two pepper cory that were over 11 years old, and half a dozen panda cory. I moved from one house to another and stupidly put all the corys together on one container along with rainbowfish, rasboras and tetras. They weren't in a bucket-they were in a bin the equivalent size of 30 gallons for the trip. The stress was from the drive and it was enough to make all the corys release stress toxins and by the time I got to the new house all the tetra were dead and the majority of the Cory were dead as well.

This is why most reputable sellers ship their Cory's in groups of threes instead of putting the whole batch in one bag.

I'm not sure if the dwarf varieties do this but I knew the regular size ones are prone for doing this, and no I did not have any sterbai in the mixed Cory group when I moved.

 

[DoubleDutch]

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.catfishstudygroup.org/pdf/journal/2008_2.pdf&ved=2ahUKEwi159Hb5dv-AhUx_rsIHT78AuwQFnoECB0QAQ&usg=AOvVaw3enufEZ6hPPk4g2os6hI5i

Can you download this PDF ?

 

[Byron]

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.catfishstudygroup.org/pdf/journal/2008_2.pdf&ved=2ahUKEwi159Hb5dv-AhUx_rsIHT78AuwQFnoECB0QAQ&usg=AOvVaw3enufEZ6hPPk4g2os6hI5i

Can you download this PDF ?

Thank you for this. It confirms my recollection from Ian that the toxin is applicable to most if not all species, not just C. sterbai.