Quills, hairs and.. quiars?

March 2, 2023 Judith Duinkerken

Tenrecs, much like other mammals, have a skin covered in hairs and sometimes quills. But did you know there’s another form of fur that isn’t described as often? During our microscopic study into the structure and pigments in hairs and quills, we quickly discovered the weird wonders of biology when it comes to types of fur. In this post, we will be doing a deep dive into out microscopic study and .. our findings along the way.

The collection of hairs and quills

At the start of our microscopic research into the structural and pigmentational differences in hairs and quills between species in 2019, we started off collecting quills from African pygmy hedgehogs with the idea that we might not be able to cover all of the various species of hedgehogs and tenrecs. After a few weeks, more and more people started paying attention to this project and people started to offer us quills and hairs from their hedgehogs and eventually, also tenrecs. One thing lead to another and within a year of starting this project, we had a range of different species in our collection! Amazing news, because this meant we could actually dive deeper into this project and compare species. We still haven’t gotten all of the species, but with well over 50 species of hedgehogs and tenrecs, we expect to have this project running in another 10 years or maybe even longer. Not because a lack of effort though, but some species are very rarely ever seen in the wild. It’ll be hard to collect hairs and quills from those species.

Tenrec ecaudatus

Within that group of people offering hairs and quills was also blogger Hedgehogs of Asgard, who kindly offered us quills and hairs from her several species of tenrecs. Including those of the Tenrec ecaudatus, or commonly known as the Common Tenrec. A bigger species of tenrecs and the only species within the Tenrec genus of the Tenrecinae subfamily, which has a more bristly fur rather than a full back of quills.

And so we expected mainly hairs and maybe some quills within that sample. Little did we know, we would stumble upon a very strange find. Because yes, Common tenrecs do have hairs on their bellies and they do have some quills on their back in between the thick bristly fur. But we also found something in between the two types: we found thick hairs that resembled quills at a first glance, but were structured like hairs…. Quiars? Haills? We weren’t sure if there was a term for it, so we took to Google to feed our curiosity. Turned out: they were semi-hairs!

Semi-hair (left) and a regular hair (right).

Different terms explained

Reading through the gallery, you might become confused by some of the terms. We get it, it’s a lot to remember and learn, so we’ll explain them to you.

Semi-hair: A hair that resembles both a hair and a quill and presents features of both fur types.
Regular hair: A stereotype hair with a smaller root, a thin cuticle layer, thin cortex and medium sized medulla.
Root: This is where the hair, semi-hair or quill starts.
Follicle bulb: The thickined part of the root that sits in the follicle sack in the skin to keep the hair, semi-hair or quill in place.
Cuticle: The outer layer with dead, overlapping cells that form scales that protect and strengthen the hair, semi-hair or quill.
Cross-section: A section of the fur that has been cut in diameter of the hair, semi-hair or quill. A section that’s cut in the length of a hair, semi-hair or quill is called a longitudinal section.
Medulla: The inner core of a hair, semi-hair and quill.
Cortex: The middle layer between the medulla and the cuticle. It hold the ‘living’ cells as well and holding the pigment of the hair.
Scale cast: A pressed print of a hair, semi-hair or quill, in this case in clear nail polish, dried overnight and then pulled out.
Transitional scaling: Overlapping scales that are not connected in a ring around the hair or semi-hair.
Distant scaling: This means that the space between the scale rings are farther apart.
Dentate scaling: This is the type of scaling which is irregular but still in rings.

The differences

The main differences between a hair and a semi-hair is that semi-hairs are much more stirdier: their medulla is very dense and their cortex is thicker. Semi-hairs are less bendier then regular hairs and they tend to be more pigmented due to the thicker cortex. While the difference between a semi-hair and a quill is also very obvious under the microscope: quills don’t have scales. Quills tend to have dents in the outer cuticle layer, but no scaling. This add to the stirdiness of the quill. But there’s something else. Quills have stacked air pockets, divided by keratine sheets and dreads holding the inside of the quill together. This helps to absorb shocks.