Explain the difference between enterocoely and schizocoely in animal gastrulation. What animals exhibit these developmental patterns? Draw a picture of each to aid in your answer. What is meant by the term, “secondary schizocoely” and what makes it secondary?
The Correct Answer and Explanation is :
Enterocoely vs. Schizocoely in Animal Gastrulation
Enterocoely and schizocoely are two different mechanisms through which the mesoderm (a primary tissue layer) forms during the early development of animals. These processes occur during gastrulation, a crucial phase of embryonic development when the three primary germ layers—ectoderm, mesoderm, and endoderm—are established.
- Enterocoely:
- In enterocoely, the mesoderm forms from outpocketings of the archenteron (the primitive gut), which eventually pinch off to form the mesoderm. These outpocketings are termed mesodermal pouches.
- The mesodermal tissue then develops into structures such as muscles, circulatory system, and internal organs.
- Example animals: Chordates (like vertebrates) and Echinoderms (such as sea stars) exhibit enterocoely.
- Schizocoely:
- In schizocoely, the mesoderm forms by splitting of the mesodermal tissue. A solid band of mesoderm forms first, and then this band splits to form coelomic cavities (body cavities).
- Example animals: Protostomes (like annelids, mollusks, and arthropods) typically undergo schizocoely.
Secondary Schizocoely
- Secondary schizocoely refers to a type of mesodermal formation that happens in some deuterostomes. Initially, the mesoderm may form differently (via enterocoely), but later splits and forms coelomic cavities, making it a secondary process.
- This type of schizocoely contrasts with the primary schizocoely seen in protostomes, which forms the mesoderm directly by splitting.
Developmental Diagram
Enterocoely:
In enterocoely, mesoderm arises from the outpocketing of the archenteron:
Schizocoely:
In schizocoely, mesoderm forms by splitting from a solid block of mesoderm:
Summary
The key difference lies in the origin of the mesoderm: enterocoely forms from pouches of the gut, while schizocoely results from the splitting of a solid mesodermal block. The term secondary schizocoely refers to the secondary development of mesoderm through splitting, following initial enterocoely. This occurs in deuterostomes like echinoderms and chordates, marking a divergence from the simpler schizocoely process seen in protostomes.