Evidence for the neural crest origin of turtle plastron bones

Area of Science:

• Developmental biology
• Evolutionary biology
• Paleontology

Background:

• Cranial neural crest cells contribute to craniofacial bones in birds, fish, and mammals.
• This has led to the hypothesis that the vertebrate exoskeleton is derived from neural crest ectomesenchyme.
• Turtles (Chelonians) are unique among extant animals for their extensive trunk bony exoskeleton.

Purpose of the Study:

• To investigate the cellular origin of the turtle plastron bones.
• To determine if the turtle plastron shares a neural crest origin with other exoskeleton elements.
• To extend the neural crest hypothesis of exoskeleton formation to include turtles.

Main Methods:

• Analysis of turtle shell bone development.
• Histological staining of plastron bones for specific cell markers (HNK-1 and PDGFRalpha).
• Comparison of turtle plastron development with known neural crest derivatives.

Main Results:

• Turtle shell's carapacial and plastron bones were previously shown to arise from dermal intramembranous ossification.
• Plastron bones stained positively for HNK-1 and PDGFRalpha.
• These markers indicate a neural crest origin for the turtle plastron bones.

Conclusions:

• The turtle plastron bones are likely of neural crest origin.
• This finding supports and extends the hypothesis of neural crest contribution to the vertebrate exoskeleton.
• The study highlights the diverse origins of skeletal elements within vertebrates.