Structure of the myofibers of the posterior lymph hearts in Xenopus laevis

Amphibians, unlike other vertebrates, do not exhibit passive lymph movement, which is characterized by the transport of lymph through lymph vessels with one-way valves squeezed by surrounding tissues. Instead, amphibians have lymph hearts which actively pump lymph. The lymph hearts provably evolved to facilitate the removal of excess water which enters the permeable skin of amphibians through osmosis. One controversial issue surrounding the lymph heart which has not yet been resolved is the identity of the lymph heart muscle cell type. Based on the literature of previous studies, it is possible that these cells are either a type of modified skeletal muscle, skeletal, or cardiac muscle