Scanning Microscopy


The secondary blood vessel system of the segmental arteries and of the dorsal aorta of the teleost fish Blennius pavo and Zosterisessor ophiocephalus are examined by light microscopy, transmission electron microscopy and by scanning electron microscopy of appropriately processed tissue and of vascular corrosion casts. Dorsal, lateral and ventral segmental arteries and the caudal portions of the dorsal aorta have a secondary vessel system. The secondary vessels are formed by capillaries which arise from the proximal portions of the segmental arteries and from the caudal parts of the dorsal aorta. In Z. ophiocephalus these capillaries are strongly dilated at their origin, in B. pavo they are less dilated, but more intensively coiled. The secondary vessels establish veins which run parallel to the corresponding primary arteries. At the ultrastructural level the secondary vessels consist of a thin endothelium and a longitudinal and a transversal orientated layer of collagen fibres. Secondary veins lack a basal membrane. A possible function of the secondary vessel system of B. pavo and Z. ophiocephalus as a modified drainage system is discussed.

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