Ultrastructure of Hagfish Blood Leucocytes
Ostracoderms were the first fishes to emerge from the primordial ooze during the Devonian and Silurian periods of the Paleozoic era, over 400 million years ago. These ancient armoured fishes are now extinct, but their direct decendents, hagfishes and lampreys, still persist throughout much of the aquatic world. Hagfishes are Agnathan cyclostomes and possess numerous primitive physiologic and morphologic traits. Phylogenetically they are considered to be the lowest living vertebrate. Because of their pre-historic lineage and primitive characteristics, hagfishes probably represent an important stage in the early evolution of advanced fishes and higher vertebrates. An evaluation of their immunologic repertoire may elucidate the early development of immune responsiveness of higher vertebrates. Futhermore, hagfishes which are notochordates represent an important transition between the protochrodates and the true vertebrates may possess immunologic mechanisms common to both groups.
KeywordsHigh Vertebrate Small Lymphocyte Glycogen Granule Golgi Vesicle Secondary Lysosome
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