Microvascularization and histomorphology of lateral line organs in adult Xenopus laevis.

The microvasculariaztion of the lateral line organs (LLOs) of the adult pipid frog, Xenopus laevis was studied by scanning electron microscopy of vascular corrosion casts (VCCs) and correlative light microscopy of paraplast embedded tissues sections. Scanning electron micrographs of VCCs revealed that each neuromast within the LLO rests on a distinct bowl-like capillary network (vascular bowl). One to three vascular bowls were supplied by an ascending arteriole and drained by a descending venule towards the skin deep dermal vascular network. Blood flow regulation mechanisms in form of intimal cushions were present at the origin of ascending arterioles supplying LLOs, microvenous valves were present at the confluence of deep dermal venules and veins. This together with sprouting and nonsprouting angiogenesis (intussusceptive microvascular growth) found in vascular bowls demonstrate that in adult Xenopus the capillary bed of LLO's still can be adjusted to changing energetic needs.