The premise that lower vertebrate embryos not only survive but continue to develop after the removal of their heart speaks against the widely accepted concept that the heart is the primary source of blood movement. This is validated by heart ablation and flow reversal studies where embryo hearts were explanted, turned 180°, and re-implanted. The hearts continued to contract against the direction of blood flow. A further example is the genetic mutants of Mexican salamander larvae which survive up to 2 weeks with morphologically normal, but functionally non-beating hearts. Various avian, mammalian, and zebrafish mutants have been described which collectively demonstrate related phenomena.
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