Functional histology of quill erection in the porcupine, Erethizon dorsatum

Abstract

The histology of the porcupine's skin and subcutis is described. The functional relationships of the thoracic skin during elevation of the quills involve a smooth arrector muscle attached to quill sets, one set behind the other, with the muscle at a slant usually from a single root tip of one set to the distal part of the follicles in the caudal set. Stretched elastin returns the quills to their resting position. There is a low-resistance pathway for the tilting quill roots through loose connective tissue and fat until a collagenous strand attached to the quill set stops further tilt. The lumbosacral region (rosette) has a two-layered arrector, but it attaches to only its own quill set and inserts into the dermis. Both regions have a varied and complicated system of transverse and oblique muscles associated with the roots in a set. (The occurrence of obliques is variable in the thoracic region.) A hypothesis is presented concerning the mechanism of quill detachment from the porcupine after the quill is rammed into a predator. This involves the shearing of the conical root tip along its adherent follicular cells and a stopping device (spool) to prevent the root from self-stabbing.

Phylogenetic Relationships of New World Porcupines (Rodentia, Erethizontidae): Implications for Taxonomy, Morphological Evolution, and Biogeography

“…Functional analyses of porcupine quill erection (Chapman and Roze, 1997) suggest that these defensive spines can only be erected to an angle of about 90° from the underlying dermal surface, so fully erected quills on a flat skull can only stick straight up. Nasofrontal sinus inflation increases the cranial surface area for quill deployment and allows erected quills to point anteriorly and laterally ( fig.…”

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

“…The histochemical and chemical properties of quills as well as the associated piloerector muscles and dermal components of the skin have been studied in detail in Erethizon (Chapman and Roze 1997;Roze 2002;Cho et al 2012). Quills from Erethizon have recurved barbs anchoring the quill in the predator; also, there is a facilitated release mechanism separating the basal end of the impaled quill from the porcupine (Chapman and Roze 1997;Roze 2002). Surprisingly, barbs facilitate tissue penetration and have inspired the design of less traumatic hypodermic needles (Cho et al 2012).…”

When quills kill: the defense strategy of the crested porcupine Hystrix cristata L., 1758

“…Quills are modified hairs that characterize the body of echidnas, hedgehogs, tenrecs, and New World and Old World porcupines (Zherebtsova 2000). These structures are coated with thick plates of keratin, which makes them similar to spines, and are embedded in the skin musculature (Chapman andRoze 1997, Zherebtsova 2000). Old world porcupine species included in the subgenus Hystrix (Hystrix cristata Linnaeus 1858; Hystrix indica Kerr, 1872; Hystrix africaeaustralis Peters, 1852) present the most complex and dense quill armor (Mohr 1965).…”