Sherman, R.L.*; Sulikowski, J.; R.E. Spieler: Similarities and differences in fine gill vasculature among batiod elasmobranchs

Classic studies of gill vasculature indicate the gross anatomy of elasmobranch gills is similar in most species, and in general, resembles that of teleosts. Recent studies of fine gill structure of several species of batoid elasmobranchs (Order: Rajiformes), however, have reported previously undescribed fine structural differences including; the presence, in Urolophus jamaicensis, U. mucosus, U. paucimaculatus, Rhinoptera bonasus, Dasyatis americana and D. sabina (Suborder: Myliobatoidei), of; 1) a tip channel, possibly an extension of the afferent filament artery that runs along the distal end of the filament corpus cavernosum; and 2) a vascular arcade, a vessel serially connecting afferent filament arteries of individual hemibranchs near the tip of the gill filaments. Using light and scanning electron microscopy we examined the fine gill structure of Raja erinacea, R. ocellata and R. radiata (Suborder: Rajoidei). Contrary to previous reports which suggested that these structures might be unique to Myliobatids, results of this study indicate the presence of a similar vascular arcade and tip channel in Rajoidei. However, differences were found in the gross structure of the ventral aorta and afferent branchial arteries between the suborders. Additional research is necessary to further elucidate the adaptive significance, if any, of these morphological differences between closely related groups of Rajiform fishes.