Microscopy and development of a remarkable pitted quill from the thin-spined porcupine, Chaetomys subspinosus

Abstract

Scanning electron microscopy shows that the quill surface from the thin-spined porcupine (Chaetomys subspinosus (Olfers, 1818)) has several regional cuticular patterns of which the most expansive is highly pitted with 4 μm wide pores leading to pits, which in turn communicate circumferentially via tunnels to neighboring pits. The cell unit of the pitted layer is a hexagonal or pentagonal prism, the “pitted fibrillous cuticular cell” (PFCC), which has a superficial pitted cuticular scale derived part with an underlying part packed with fine fibrils and the nucleus. The scaled part has about six scales, which swell and fuse except where raised cuticular scales from the inner root sheath intervene. This unique and complicated cell soon dies even while below the skin’s surface during its development. The raised scale-bearing cells of the inner root sheath leave their imprints on the PFCC’s surface, thus indicating that the quill’s pitted layer is at one time soft. Histochemistry, energy dispersive X-ray spectrometry, and Fourier transform infrared spectrometry show that the PFCC is keratinous.