We are in the process of re-starting series of samples with light-traps in western Indian Ocean (Reunion and Madagascar). Until now, invertebrates were considered as “by-catches” and thus not analyzed but we think we are missing some valuable information.
As we do not have time to process the samples when they are fresh (too much work with fish post-larvae), what would be the best way to preserve the invertebrates caught in light-traps (mainly crustacean larvae but also octopuses, worms, etc.).
The aim is to (later) follow the barcoding of life procedures (i.e. taking images, keeping a voucher, etc.). But we hesitate between using ethanol (will make the individuals stiff and difficult to photograph), or freezing the samples (lead to the risk of DNA degradation when samples are sorted out).
Thanks for your ideas and do not hesitate if you are interested getting access to the samples.
try lyophilized or just dry, but you need to take the pictures before, on freshly caught material.
Moi je mets generalement ethanol 96 pour barcoding, pour mes collègues, ça va vite de prendre un petit échantillon. L'animal ensuite n'importe quel moyen classique
Since only a tiny sample is usually sufficient for DNA work, if it is not too time-consuming you could place a pleopod in ethanol and then freeze the rest of the sample for photography.
If you're following the BOL approach, you have already done some sorting of your specimens. The best way is to preserve several specimens in ethanol (the purest the best, and never re-use it) for DNA, several in formaldehyde (I usually used 3 % formaldehyde with sea water) to preserve tissular structures and pigments and take pictures of one or two specimens just after sampling.
I think the first thing to do is to take pictures. Then, for DNA analysis, the sample needs to be preserved in ethanol. For soft-bodied organisms (polychaetes, molluscs etc.) it's better to preserve them in formalin for morphological indetifications. So you can take a tiny piece of the body for DNA (preserved in ethanol) and keep the rest of the body in formalin. For others (arthropods) you can preserve them in ethanol. Hope this is helpful :)
Thanks for all your answers. Our problem will be the lack of time for sorting out, taking pictures, etc. of the invertebrates as fish larvae are our priority. We'll see what's possible to do.
By the way, has any of you an idea of the best setting for pictures of invertebrates?
Oppositely to fish larvae, I think they look better on a dark background (which means different settings for fish and invertebrates...). Life is complicated ;-)
My understanding is 95% ethanol works just fine. I received several shipped fishes that way that I'm submitting to the Biodiversity Institute of Ontario for barcoding. I don't see why invertebrates would be any different. I'm no expert though.
For invertebrate pictures, indeed black background works the best. Your biggest problem will be to find a really dark background. Some dark cloth that you can buy is also pretty hairy and therefore may reflect light in unwanted ways. Unfortunately you'll have to experiment with what you have. It is probably best to have two light sources away from the specimen. In any case you will have to use flash light. I use what I have, which is a ring flash, and it works, but it may not be the best solution. Pictures can be taken from fresh specimens or from formalin-preserved specimens later.
Preserve a tiny bit of tissue in 100% ethanol for barcoding procedures before you do anything else. We also freeze ours, but if not possible on a ship, it should still be ok. For morphological preservation use formaldehyde with sea water to produce formalin. It will not be buffered, but the sea water is better than fresh water for preservation. Once at home, specimens should eventually be washed three times simply with tap water and then stored in 75% ethanol. If you have limited time, you could even wait a few years before placing them into alcohol, if they are in formalin. But for barcoding you should take a small sample before the whole formalin procedure. There are different barcoding protocols for fresh and old specimens, but I believe, for specimens stored in ethanol and then frozen the easier fresh-specimen protocol can be used.
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