The key difference between animal pole and vegetal pole is that the animal pole is a region of the embryo in the developing stage and consists of small cells that divide very rapidly, while the vegetal pole is a region of the embryo in the developing stage that consists of large yolky cells that divide very slowly.
In embryo development biology, the embryo is divided into two regions: the animal pole and the vegetal pole within a blastula. The animal pole gains its name due to its liveliness relative to the slowly developing vegetal pole, and the vegetal pole is named for its inactivity relative to the animal pole.
CONTENTS
1. Overview and Key Difference
2. What is Animal Pole
3. What is Vegetal Pole
4. Similarities – Animal Pole and Vegetal Pole
5. Animal Pole vs Vegetal Pole in Tabular Form
6. Summary – Animal Pole vs Vegetal Pole
What is Animal Pole?
The animal pole is a region or one hemisphere of the embryo in the developing stage and consists of small cells that divide very rapidly. It is the region of the embryo where polar bodies are extruded and receive the sperms. The vegetal pole is the pole that is opposite the animal pole. In the embryo, the animal pole is located above the vegetal pole. The animal pole is thought to be differentiated into the later embryo by itself in some cases.
Figure 01: Animal and Vegetal Pole
The development of the animal-vegetal axis occurs before fertilization. Moreover, sperm entry can occur anywhere in the animal pole. The point of the sperm entry defines the dorsal-ventral axis, while the cells in the region opposite to the sperm entry will eventually form the dorsal part of the body. Furthermore, animal poles are the most active parts of the protoplasm. The animal pole is usually heavily pigmented. This pigmentation difference is evident in species such as frogs (Xenopus laevis). At the animal pole, the cytoplasm appears to be more active. In addition to that, the nucleus is also present at the animal pole.
What is Vegetal Pole?
The vegetal pole is a region of the embryo in the developing stage and consists of large yolky cells that divide very slowly. In the placenta in mammals and chorion birds, the vegetal pole is thought to be differentiated into the extraembryonic membranes. These extra embryonic membranes protect and nourish the developing embryo.
The vegetal pole is not the most active part of the protoplasm. Moreover, the vegetal pole divides slowly. However, it divides into larger blastomeres. The cytoplasm is less active at the vegetal pole. Furthermore, the vegetal pole is unpigmented. It has been identified that the animal pole is normally dark brown while the vegetal pole or hemisphere is only weakly pigmented.
What are the Similarities Between Animal Pole and Vegetal Pole?
- In development biology, the animal pole and the vegetal pole are two regions of the embryo.
- Both poles are within a blastula.
- Both poles are separated by an unpigmented equatorial belt.
- They play important roles in the separation of the dorsal-ventral axis and dorsal part of the body.
What is the Difference Between Animal Pole and Vegetal Pole?
The animal pole is a region of the embryo in the developing stage and consists of small cells that divide very rapidly. Meanwhile, the vegetal pole is a region of the embryo in the developing stage and consists of large yolky cells that divide very slowly. Thus, this is the key difference between animal pole and vegetal pole. Furthermore, the animal pole is thought to be differentiated into a later embryo by itself in some cases, while the vegetal pole is thought to be differentiated into the extraembryonic membranes that protect and nourish the developing embryo.
The below infographic presents the differences between animal pole and vegetal pole in tabular form for side-by-side comparison.
Summary – Animal Pole vs Vegetal Pole
In development biology, the animal pole and the vegetal pole are two regions of the embryo. The animal pole consists of small cells that divide very rapidly. Meanwhile, the vegetal pole consists of large yolky cells that divide very slowly. Besides, the animal pole is highly pigmented, while the vegetal pole is weakly pigmented. Moreover, the animal pole is the most active part of the protoplasm while the vegetal pole is less active. So, this summarizes the difference between animal pole and vegetal pole.
Reference:
1. “Preparatory Events.” Encyclopædia Britannica, Encyclopædia Britannica, Inc..
2. P Darras S; Marikawa Y; Elinson RP ;Lemaire. “Animal and Vegetal Pole Cells of Early Xenopus Embryos Respond Differently to Maternal Dorsal Determinants: Implications for the Patterning of the Organiser.” Development (Cambridge, England), U.S. National Library of Medicine.
Image Courtesy:
1. “Oocyte Poles” By Catcasillas21 – Own work (CC BY 3.0) via Commons Wikimedia