Several techniques have been described to highlight growth rings in ray fish.

The following three techniques are based on alizarin S affinity for calcium (Du Buit, 1977):

"1 - Fixation of vertebral bodies by formalin at 10% for 48 h. Treatment with potash at 5% for 15 to 60 minutes; potash at 2% + alizarin for 24 to 48 hours; potash at 2% for 15 to 60 minutes; potash at 2% + glycerin for 24 to 48 hours. Storage in glycerine for 24 to 48 hours. Conservation in glycerine.

2 - Fixation of vertebral bodies to alcohol at 95 ° for 48 to 96 h. Treatment with potash at 1% for 24 to 48 hours; 1% potash + alizarin for 24 hours; 1% potash + glycerine (50 + 50). Conservation in glycerine..

3 - Treatment with sodium hydroxide at 0-2% for 24 h. Staining with sodium hydroxide + alizarin (9 + 1) for 24 to 72 hours; washing with running water for 15 min; Differentiation with oxygen water at 3% for 24 to 72 hours". Conservation in alcohol at 70 °.

In addition to vertebrae, other fish bones show growth rings as well; depending on the species, you may consider to use the otoliths or the operculum.

Hello,

For muscle digestion e.g. fixed in formaldehyde solution i have tried the solution of saturated borax (alternatively KOH) and trypsin. You need to leave bones in solution in the room temperature or slightly higher. Leave them for several days (up to several weeks). Depending on the biomass of muscles you need to have check daily decomposition of tissue. Before this, dont forgot soak the samples in pure water to wash out of fixator.

All the best.

How said Ronald, other fish structures also show growth rings (vertebral bodies, otoliths, operculum, cleithrum, fin rays, scales etc.).

For maceration you can try to use hot water (only don't make a fish soup!).

Hadeel,

First, I think there is a little confusion concerning which fish group you are referring to when you say rayfish. If you are referring to the ray-finned fishes (Actinopterygii) then Dr. Fricke makes a good point. There are many other, and probably better, structures that you can utilize for aging than vertebrae depending on the species, with otoliths being the standard for many species. If instead you are referring to a species of ray (Batoidea), as I suspect you are, then the answer is quite different, as they don't have the majority of these structures and when they do they may not be useful in aging. For the batoids, as with sharks, you have to clean most of the tissue off of the vertebral centra by hand, scraping away the muscle and cutting off the accessory cartilages (neural and haemal arches) with a scalpel or razor blade, until you are left with pretty clean centra. The centra can then be placed in a mild solution to help dissolve the remaining clinging soft tissue. I have never used potassium hydroxide. We use sodium hypochlorite solution (bleach), but we generally only leave them in the solution for anywhere from 5 to 30 minutes as most of the tissue has been removed previously. I am attaching a paper with the general methods we employ (Driggers et al., 2004) as well as a very general chapter on the aging on chondrichthyan fishes (Cailliet and Goldman, 2004). Obviously you will need to make adjustments depending on the species you are dealing with. Hope this helps. If I can be of any further assistance please feel free to send me a private message and we can discuss this further.

Christian