Vascular architecture of the carotid labyrinth in larval and adult Xenopus laevis – Histomorphology and scanning electron microscopy of vascular corrosion casts

In Xenopus laevis Daudin the anlage of the carotid labyrinth, a baroand chemoreceptor, appears in early premetamorphosis (NF stage 53) as a swelling of the third aortic arch at the point where the common carotid artery gives off the external carotid artery. A conspicuous accumulation of melanocytes preceeds the formation of the labyrinth maze which starts to grow at the end of metamorphic climax (NF stage 64) and continues so through juvenile age. In adult animals the carotid labyrinth displays a spherical to ovoid shape, has an average length of 1.4 mm, a width of about 0.8 mm and a height of about 0.4 mm. The maze vessels form by sprouting angiogenesis from the common carotid artery and the internal carotid artery. Scanning electron microscopy of vascular corrosion casts reveals that size, overall shape, surface morphology and vascular patterns of the carotid labyrinth vary greatly between individuals, whereby intussusceptive microvascular growth (= nonsprouting angiogenesis) and its facets model and contribute to the maturation of the labyrinth’s final vascular patterns.