Tropical Fish Forums

[BarebackDreamer]

some of you may remember my elderly cories who constantly spawned. just a few minutes ago I found my female had passed away. how could I preserve her body? I really do not want to just bury her or freeze her. I've had her most of my life. I have put her in the fridge for now.

ETA: I've read that I could put her in a jar of alcohol. is this correct? I've done this with dead spiders but wasn't sure if it would work with a fish.

[UncleWillie]

Alcohol is the way to go - it is safer and more available than the formalin (formaldehyde) alternative. However if you constantly have to kill and preserve fish for museum / ichthyologist collection quality you'd need formalin for sure. If you have some alcohol, drop it in that. Then after a day or so, use fresh alcohol and do a 30/70 water/alcohol solution for long term. Remember this fish will lose color (turn tan, brown) and will be a bit dehydrated. I suggest getting start right away to try to start preserving the fish before any bloating or decomposition.

[BarebackDreamer]

thanks for the fast response. do I need to do anything to her before I put her in it? one place I checked out online said I should poke holes in her so the alcohol gets to all her tissues.

[UncleWillie]

Nah. If you have big fish (+4 inches or very robust fish) then it is a good to split the belly or take a syringe and inject the tissues with alcohol or formalin. I reckon you could poke tiny holes with a needle if you want to - just remember to poke at an angle to go underneath the scales rather than damaging them or removing them.

[monstrosity]

that is weird...
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29 G

[unissuh]

Could try stabbing through the back of the mouth, less noticeable than through the belly region.

When I'm using alcohol I tend to fix samples (admittedly not piscine) in 95% alcohol, not neat. Supposedly the 5% water helps penetration into the tissues. Can also use acetone (nail polish remover) neat, but I think alcohol fixes better in general.

BTW Willie, do you know if the standard % of alcohol used for storing specimens is based on disinfection %, or whether 70% is actually better than 80%? They made a big fuss about switching over to 80% for disinfecting things for "EHS reasons" over here a year or so ago, supposedly works better than 70%. Same time they made >2.5L bottles of alcohol against EHS regs.

PS: Don't worry about it being a bit strange, I have a number of weirder samples sitting on my work desk collected over the years.
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Fishing in the Rivers of Light

[UncleWillie]

Unissuh is right about injecting through the mouth. You can also inject through the vent to keep from damaging the exterior of the fish.

Uni, I know there has been some debate with __% alcohol's ability to disinfect. Some say 95% is not any better at disinfecting than 60%, but other say there is a huge difference. I haven't really looked at particular publications to back up either claim.

One main reason we use 70% is because fish tend to dehydrate in anything much stronger. They will often start to shrivel and become hard (a fishy raisin if you will ). Plus when we preserve fish we aren't really concerned with any zoonosis. It may be a different story if we were working with different or filthy critters that could create a health threat.

We will use ethanol if we need to collect one or two fish for identification later, but we have mostly use formalin now if we are planning long-term storage. It tends to fix fish better (I don't know about other species). I know alcohol seems to do fine long term with aquatic insects and crayfish and such.

[unissuh]

[keithkyli]

Not sure if my background as a BSc and MPhil in Biology could help.

As far as I know, for disinfection, 70% ethanol is the best, because it penetrates bacterial cells better than 95%. The work of ethanol once it enters the cell is to denature proteins and dissolve the lipid cell membrane. At 95% the ethanol may not be able to enter the cell because it is too hydrophobic (=water-resistant). I worked in a biotechnology lab for my MPhil years and I know well about this.

On the other hand I have never heard of people using any concentration of ethanol for long term storage of biological specimens. I have not made nor handled any "macro" (multicellular) specimens, but what I've learned is that formalin is the preferred choice. In addition to being toxic to microorganisms, formalin fixes the proteins and DNA, and that is true concern for keeping a specimen.

I guess you can keep it at 70% ethanol, as people have tried, but I'd like to know from the guys who've done that, do you find the specimen a bit soft or fragile? I have no idea. Thanks.
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Diamond Hill, Hong Kong

[unissuh]

It's good to hear from people in the field. Both Willie and I are in biological science fields too.

I did touch on it earlier, but people have been slowly switching across to 80% ethanol from 70% for disinfection. This apparently works better than 70% & is now the new standard in microbiology and immunology labs (of which I spend a good % of my waking hours in).

As for why ethanol is sometimes used instead of formalin...it has to do with the fixing of the samples and really depends what you want to use the sample for. Formalin is great for tissue structure and use with classical dyes, but usually "overfixes" the sample so that the proteins become hard to deal or unrecognizable at a molecular level. This is most common when one takes sections of tissue for staining via biological means e.g. with antibodies, in situ hybridisation etc. I typically use 95% ethanol to fix sections before doing any of this work (note fixing being different to disinfecting), the 5% water supposedly being helpful to penetrate tissues and/or cells like you say. I don't tend to store samples for this work, rather tend to take and fix therm just before the procedure. Where I use 70% ethanol for storage is typically after fixing with formalin, tissues can be stored in 70% ethanol (and have to be stored in this fashion at least overnight) before being further processed. Once the tissue is fixed, it doesn't tend to degrade when stored in 70% ethanol, not for at least months...can't say I've kept anything longer than about a month in it.
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Fishing in the Rivers of Light