Figure 2: Deep ulcerative lesion of the caudal peduncle provoked by F. psychrophilum in a rainbow trout (Oncorhynchus mykiss).
From: Complete genome sequence of the fish pathogen Flavobacterium psychrophilum

Skin and muscle tissues have been destroyed, exposing the spinal cord. In the course of 'cold-water disease' of adult salmonid fish, such necrotic lesions typically occur around the adipose ('peduncle disease') or dorsal ('saddleback disease') fins, on the gills and on the flank. Scale is in centimeters.