Photomicrograph from a healthy example of elkhorn coral side-by-side with elkhorn coral found with multifocal tissue loss

(A) Photomicrograph from a healthy example of elkhorn coral (Acropora palmata). Tall columnar epidermis (E), gastrodermis (g), skeletal space (s), gastrovascular cavity (gvc), and calicodermis (white arrowhead). H&E stain. (B) Photomicrograph from elkhorn coral found with multifocal tissue loss in the Dominican Republic. Epidermis (E) and gastrodermis (g) are atrophic and surface body wall is thin. Epidermis is ulcerated, exposing skeleton (s). Simple squamous calicodermis (white arrowheads) has an area of transition (black arrowhead) into columnar epidermis. H&E stain.