A study on lungfish, bony fish and cartilaginous fish has a great deal to offer in understanding development of legs for life on land. Lungfish are ancient ancestors of tetrapods - four legged animals. Walking on their fins and breathing air, lungfish bravely moved onto the land.
Research has relied on bones preserved as fossils, but muscles cannot be "saved" in this way. A fetus shows ancient stages in a creatures development. This is why a human fetus seems to be reptile-like in its early stages. Examining muscle development of modern lungfish is very informative. Tests were also done on cartilaginous fish such as sharks and ordinary fish.
Embryos of cartilaginous and bony fish were genetically altered to promote growth of precursor pelvic fins that in lungfish became legs. Engineered cells were made to emit red and green light. The study on muscles highlighted the fact that bony fish evolved legs while cartilaginous fish did not. Pelvic muscles of bony fish are a transitory stage between cartilaginous fish and land animals.
Research has relied on bones preserved as fossils, but muscles cannot be "saved" in this way. A fetus shows ancient stages in a creatures development. This is why a human fetus seems to be reptile-like in its early stages. Examining muscle development of modern lungfish is very informative. Tests were also done on cartilaginous fish such as sharks and ordinary fish.
Embryos of cartilaginous and bony fish were genetically altered to promote growth of precursor pelvic fins that in lungfish became legs. Engineered cells were made to emit red and green light. The study on muscles highlighted the fact that bony fish evolved legs while cartilaginous fish did not. Pelvic muscles of bony fish are a transitory stage between cartilaginous fish and land animals.
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Biology