Theses and Dissertations

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Defense Date

1997

Document Type

Thesis - NSU Access Only

Degree Name

M.S. Marine Biology

Department

Oceanographic Center

First Advisor

Richard E. Spieler

Second Advisor

Patricia Blackwelder

Third Advisor

Kenneth R. Olson

Abstract

The yellow stingray, Urolophus jamaicensis, is a small, common western Atlantic fish. Although it is abundant in coastal waters from North Carolina to Brazil, very little work has been done on the anatomy of this animal. It has been previously demonstrated in two Pacific congeners that there are several structural differences in urolophid gill vasculature from other elasmobranchs. The gill vasculature of U. jamaicensis was examined in order to investigate the hypothesis that these structural differences may be common to the genus Urolophus. Gross examination of preserved gills using light microscopy confirms that the basic structure of U. jamaicensis' gill arches is similar to that reported from other elasmobranchs. However, scanning electron microscopic examination of Mercox methylmethacrylate casts of the fine gill vasculature confirms several structures not reported in non-urolophid elasmobranchs. The differences include; 1) absence of a septal corpus cavernosum; 2) the presence of a vessel which connects the afferent filament arteries near the tip of each filament; and 3) a vessel, possibly an extension of the afferent filament artery, that runs along the top of the filament corpus cavernosum possibly connecting the afferent and efferent filament arteries at the tip of some filaments. The fine vascular structures identified in U. jamaicensis are very similar to those previously described in U. paucimaculatus and U. mucosus in the western Pacific.

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