When you think of the preservation of animals, you may imagine taxidermied animals, skinned, stuffed and sewn, glass eyes staring back at you, furs, feathers and leathers. You may imagine the bleached white bones of an animal, wires and glue tying each bone together to form a skeleton. However, something that is often forgotten are the diaphonised specimens. Here at Tāmaki Paenga Hira, we are fortunate enough to have several diaphonised shore skinks (Oligosoma smithi) in our collection, with their records having been enhanced as part of the IDEA project. These have undergone a clearing and staining technique called diaphonisation, which makes the animal translucent and, with the use of dyes, the animal’s bones and cartilage are stained. This process creates beautiful specimens of vibrant reds, pinks, blues and purples.

Firstly, this process involves preparing the animal by removing the organs and the skin of animals with furs or feathers. The animal is then soaked in a trypsin soup (trypsin being a digestive enzyme) that causes it to break down casein, a colour-creating protein, leading to a completely translucent animal. Different dyes that are attracted to certain substances, such as collagen and cartilage (e.g., alizarin red and alician blue, respectively), are used to stain the bones and cartilage, leaving the animals appearing in shades of red/pink and blue. Once completed, the diaphonised specimen is then preserved in glycerin. The skinks here have been dyed with alizarin red and so the skeleton appears in reds and pinks.

This process allows for the ability to identify bone and cartilage structures as found internally without displacing them. It is especially valuable for smaller organisms that are at risk of damage when dissecting, with bones that are small and fragile making it difficult to clean them and prepare articulated skeletons. The soft-bodies of reptiles and amphibians allow them to be a particularly good animal to diaphonise, as they are often difficult to dissect and taxidermise due to their delicate skin. While larger animals with their thick skins and large surface area would require too many chemicals and too much time.

These beautiful specimens allow us to appreciate biology, bringing to life the skeletal and cartilaginous structures of animals clearly in a particularly visually appealing way. Diaphonisation has been particularly useful for taxonomic, developmental and toxicology studies, such as for anatomical mutations and for understanding how chemical pollutants affect growth and development. However, with the advancements in imaging technology, diaphonisation is becoming less common within scientific fields. This leaves the thought of what value do diaphonised specimens hold now?

Though diaphonisation may be becoming less common within the field of science with the development of better imaging techniques, it is still sometimes used over these newer imaging techniques due to cheaper costs and being particularly useful in distinguishing bone from cartilage, which can be hard to detect with many imaging techniques. Additionally, It is also finding new life in the hands of artists that appreciate their visual beauty and the rich diversity of anatomical structures formed in nature.