A New Method to Examine the Oberhautchen of Lizard Skin
Scanning electron microscopy (SEM) is a powerful tool used in the study of lizard skin morphology and has allowed researchers to gain insight into the intricate structure of complex epidermal layers, an interesting part of which is the outer layer or oberhautchen. Methods involved in the preparation of samples for SEM are invasive and usually involve killing and preserving specimens. Here we present a new, simple, highly accurate method for the examination of living lizard epidermis using polyvinylsiloxane impression material and epoxy resin to create molds. We created molds of live Oedura castelnaui (Squamata: Diplodactylidae) using two different types of epoxy resin to compare their efficacy. Viscosity was the important factor determining whether there were artifacts in the mold, and the resin that created fewest artifacts was Epirez 123® (ITW Polymers & Fluids). We used Epirez 123® to create molds of Phyllurus ossa, P. amnicola, and Nephrurus levis (Squamata: Carphodactylidae), which all have ornate oberhautchen. We visually compared these with published images of hair sensors of congeners, and found that our method compared very favorably. Thus, this method can produce exceptional quality reproductions of complex microornamentations within the oberhautchen of living lizards.Abstract
Molds of dorsal scales from live Oedura castelnaui using two different epoxy resins. (A) Mold made using DEVCON 2-TON®. Portions of the mold, created by large air bubbles (LB), have been ripped out while making the positive replicas of the study surface. Smaller air bubbles (SB) are also produced at the same time but not removed from the mold. Scale bar 500 µm. (B) Mold made using Epirez 123®. No air bubbles are present nor have any portions of the scale been removed due to air bubbles being trapped. Scale bar 500 µm. (C) DEVCON 2-TON® produces microscopic air bubbles (MB) present all over the scale. Three hair sensors (HS) are located at the posterior end of the scale as well as many lenticular sense organs (LSO). Scratches seen on the scale are superficial and occur due to rubbing on cage substrate. Scale bar 50 µm. (D) Epirez 123® greatly reduces the number of microscopic air bubbles. Three hair sensors are located at the posterior end of the scale as well as many lenticular sense organs all over the scale. Scale bar 100 µm.
Molds produced of species with ornate oberhautchen. (A) Phyllurus ossa dorsal spine with hair sensors (HS) at the peak. The rest of the spine is bumpy, and each bump is covered in spinules. Scale bar 100 µm. (B) Deep furrows (F) split dorsal scales in Phyllurus ossa, which each have one or two hair sensors, bumps covered in spinules, and spinulate areas with larger, thicker spinules (TS). Very few microscopic air bubbles (MB) can be found on the scales. Scale bar 50 µm. (C) A hair sensor in Phyllurus ossa which appears to be slightly raised above the scale because of a surrounding moat (MO). It has one thick bristle (BR) that has rows of small barbs, and is surrounded by very short spinules. Scale bar 5 µm. (D) Spinules to the right of the image project towards the microscope, whereas those to the left are on a flatter portion of the scale. Breaks between the two areas are outlines of the clear layer (CL) of the previous skin generation in Phyllurus ossa. Scale bar 1 µm. (E) Phyllurus amnicola has a slightly raised hair sensor surrounded by a wide moat. Bristle is barbed and surrounded by sparse spinules. Scale bar 5 µm. (F) Hair sensor from Nephrurus levis with four bottlebrush-shaped bristles. Some spinules surround the bristles and the hair sensor is surrounded by a shallow moat. Scale bar 5 µm.
Contributor Notes
Associate Editor: M. J. Lannoo.