What is the Difference Between Carapace and Plastron?

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The carapace and plastron are two different parts of the exoskeleton in some animals, such as turtles and tortoises. They serve as protective coverings for the animal's body. Here are the key differences between carapace and plastron:

  • Carapace: This is the dorsal (upper) part of the exoskeleton. It is typically convex in shape and covers the back of the animal. In turtles and tortoises, the carapace is a protective shell covering most vital organs and constitutes the rib cage of the animal.
  • Plastron: This is the ventral (lower) part of the exoskeleton. It is generally flat in shape and covers the underside of the animal. In turtles and tortoises, the plastron is a protective shield that covers the ventral side. A typical plastron is made of nine bones.

In some species of turtles, the males have a concave plastron, while the females have a convex one, which helps them during mating. Additionally, the female plastrons are often lighter in color than the males, which can help identify the sex of the Testudines.

Comparative Table: Carapace vs Plastron

Here is a table comparing the differences between carapace and plastron:

Feature Carapace Plastron
Location Dorsal side of the exoskeleton Ventral side of the exoskeleton
Shape Typically convex Flat, convex, or concave structure
Function Protective exoskeleton Protective shield
Occurrence Found in crustaceans, arachnids, and some vertebrates like turtles and tortoises Found in turtles and tortoises
Structure Made up of fused bones, covering the fused thorax and head region in crustaceans, and carrying the ocularium, eyes, and ozopores in arachnids Constructed from nine bones in turtles and tortoises
Sexual Dimorphism None In some species of turtles, males have concave plastron, while females have convex structure
Pigmentation Can be seen Can be seen, with some differences between sexes in certain species

Both carapace and plastron are bony structures that serve as protective coverings for animals, joining one another along each side of the body. They are made from fused bones and share similar compositions.