The Blood Vascular Architecture of the Salamander External Gill: A Scanning Electron Microscopic study of Corrosion Casts

Abstract

The blood vascular architecture in three-paired external gills of salamander tadpoles, Hynobius dunni Tago, was demonstrated with special reference to metamorphosis by scanning electron microscopy of vascular corrosion casts. In the fully developed gill, each of the three-paired afferent branchial arteries gave off secondary afferent filament arterioles. The afferent filament arteriole drained toward the efferent filament arteriole, forming the loop at the posterior extremity of the gill filament. The branched capillaries from the afferent filament arteriole formed two plates of respiratory capillary networks with irregular honeycomb-shaped meshes. In addition, there were non-respiratory shunts as bypass of the blood circulation between the afferent and efferent branchial arteries without branching filament arterioles. Furthermore, the deep venous plexus and subepithelial capillary plexus were seen around each efferent branchial artery. The filament central venule in the central part of the filament merged into the venous plexus. Nutritive capillaries branched from efferent branchial arteries also drained toward the venous plexus. Such general vascular architecture is simpler than that of the fish. During metamorphosis, the pattern of the vascular distribution, especially filament net capillaries became irregular, and then markedly tortuous or convoluted blood vessels occurred in the absorbing gill. At the metamorphic climax, the capillary network practically disappeared in the remnant of the gill but the bypass shunt as a non-respiratory artery remained almost unchanged.

Cardiovascular shunting in vertebrates: a practical integration of competing hypotheses

“…Presumably, all developmental stages experience intracardiac shunting within their anatomically undivided ventricle, like embryonic non-crocodilian reptiles. Shunts allowing bypass of the gills have been both morphologically and physiologically identified in the aquatic larval stages of several anurans and salamanders (Malvin, 1985;Malvin & Dail, 1986;Malvin & Heisler, 1988;Kato & Kurihara, 1989;Minnich, Bartel, & Lametschwandtner, 2002).…”

Regression of blood vessels in the ventral velum of Xenopus laevis Daudin during metamorphosis: light microscopic and transmission electron microscopic study

“…The reported shortening of capillaries might occur by shrinkage of the endothelium and\or by a 'shedding' of endothelial cells into the vessel lumen. Furthermore, the structural alterations of endothelial cells may well explain the wrinkled, tortuous appearance of vessels of involuting tissue (Kato & Kurihara, 1989 ;Carretero et al 1995 ;Aichhorn & Lametschwandtner, 1996) as well as the narrowings in cast lumina (Carretero et al 1995 ;Aichhorn & Lametschwandtner, 1996). The endothelial cell detachment present in regressing velar capillaries results in an increased leakiness of the vessel wall that explains the presence of small globular extravasations at these sites when such a vessel is cast with diluted Mercox.…”

Intussusceptive microvascular growth in the lung of larval Xenopus laevis Daudin: a light microscope, transmission electron microscope and SEM study of microvascular corrosion casts

“…Generally, during metamorphosis oxygen uptake in the lungs increases, but decreases in gills and skin (Burggren and West 1982). Development, anatomy and physiology of larval respiratory organs have been thoroughly studied (Nieuwkoop and Faber 1967;Fox 1984;Burggren and Just 1992), but surprisingly little is known on the microvascular anatomy (Smith and Campbell 1976;Smith and Rapson 1977;McIndoe and Smith 1984a,b;Kato and Kurihara 1989;Aichhorn and Lametschwandtner 1996).…”