Zoological Studies

Vol. 43 No. 4, 2004

Bifurcating Pattern of the Ventral Aorta and Distribution of the Branchial Arteries of Hagfishes (Myxiniformes), with Notes on the Taxonomic Implications

Hin-Kiu Mok1,* and Charmion B. McMillan2

1Institute of Marine Biology, National Sun Yat-sen University, Kaohsiung, Taiwan 804
2Scripps Institution of Oceanography, 0202, University of California, San Diego, CA 09093

Hin-Kiu Mok and Charmion B. McMillan (2004) Intraspecific and interspecific variations in the position of the bifurcation of the ventral aorta, the distribution of the afferent branchial arteries on the ventral aorta, and connections among the efferent branchial arteries, carotid artery, and medial dorsal aorta of hagfishes are reported. Numbers of afferent branchial arteries on the medial section and side branches of the ventral aorta varied to a certain degree within and among species according to where this aorta is bifurcated. Intraspecific variation is considered low, and the presence of interspecific variation makes the related characters valuable for taxonomy. Whether the ventral aorta bifurcates, the distance of the position of bifurcation from the heart, and the number of afferent branchial arteries arising from the medial section of the ventral aorta were applied to identify species and to interpret hagfish phylogenetic interrelationships.

Key words: Circulatory system, Hagfishes, Myxiniformes, Systematics.