Examination of Gill Vasculature of Yellow Stingray, Urolophus jamaicensis (Urolophidae), by SEM Observations of Resin Casts

<p> Examination of the gill vasculature of <em> Urolophus jamaicensis </em> confirms structural differences in urolophid gill vasculature compared with other elasmobranchs. Differences include: 1) absence of a septal <em> corpus cavernosum; </em> 2) presence of a vessel conneaing the afferent filament arteries near the tip of each filament; 3) a vessel, possibly an extension of the afferent filament artery, that runs along the top of the filament <em> corpus cavernosum </em> which may connect the afferent and efferent filament arteries at the tip of some filaments. Additionally, a constriction indicating the presence of a sphincter muscle was noted on the efferent lamellar ar&hyphen;teriole in <em> U. jamaicensis. </em> This structure has not been previously noted in urolophids. The vascular structures in Atlantic <em> U. jamaicensis </em> are similar to those previously described in Pacific <em> U. paucimaculatus </em> and <em> U. mucosus. </em></p>