Examination of gill vasculature of yellow stingray, Urolophus jamaicensis (Urolophidae), by SEM observations of resin casts

Examination of the gill vasculature of Urolophus jamaicensis confirms struc tural differences in urolophid gill vasculature compared with other elasmob ranchs. Differences include: 1) absence of a septal corpus cavernosum; 2) p resence of a vessel connecting the afferent filament arteries near the tip of each filament; 3) a vessel, possibly an extension of the afferent filame nt artery, that runs along the top of the filament corpus cavernosum which may connect the afferent and efferent filament arteries at the lip of some filaments. Additionally, a constriction indicating the presence of a sphinc ter muscle was noted on the efferent lamellar arteriole in Li. jamaicensis. This structure has not been previously noted in urolophids. The vascular s tructures in Atlantic U. jamaicensis are similar to those previously descri bed in Pacific U. paucimaculatus and U. mucosus.