Photomicrographs from little brown bats, one with square-eared anomaly, found dead in Montana, USA.

Photomicrographs from an unaffected Little Brown Bat (M. lucifugus; A-B) and Little Brown Bat found dead in Montana, USA with the square-eared anomaly (C-E). Periodic Acid Schiff-Hematoxylin. (A) Pinna of an unaffected Little Brown Bat showing the epidermis (e and arrow), dermis (d) and central elastic cartilage plate (c). (B) Higher magnification of the pinna showing the large number of melanocytes in the stratum basale (arrowhead), the dermis with adnexa (d), and central basophilic elastic cartilage plate composed of chondrocytes (caret) in lacunae (arrow) surrounded by the perichondrium (p). (C) Pinna of a Little Brown Bat with square-eared anomaly showing lightly pigmented epidermis (e and arrow), dermis with no evident collagen fibers and reduced adnexa (d), low numbers of adipocytes (arrow), and eosinophilic elastic collagen plate (c). (D) Higher magnification of the epidermis and dermis showing low numbers of melanocytes in the epidermis (arrowhead) and eosinophilic, amorphous material (edema fluid, asterisk) in the dermis along with low numbers of mononuclear inflammatory cells (arrow). (E) Higher magnification of the eosinophilic elastic cartilage plate showing empty lacunae (arrow) or lacunae with degenerating chondrocytes with vacuolated cytoplasm (arrowhead).