Skip to content
Login Register

#amphibian eggs

2 public questions tagged with this topic.

amphibian Development-l

The vegetal pole in amphibian eggs contains:

Amphibian eggs exhibit pronounced animal-vegetal polarity that influences cleavage. Animal hemisphere contains little yolk, abundant mitochondria, ribosomes, and divides rapidly into small micromeres that contribute mainly to ectoderm and nervous system. Vegetal hemisphere accumulates dense yolk platelets, glycogen, lipids, and maternal mRNAs such as VegT and Vg1, slowing cleavage and producing large macromeres. Heavy yolk physically hinders contractile ring constriction, lengthening cell cycle vegetally. This gradient creates unequal blastomere sizes, partitions endoderm determinants vegetally, and influences induction of mesoderm via Nodal signaling from vegetal cells to marginal zone.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 2: Vegetal yolk distribution and cleavage retardation.

View Details
amphibian Development-l

Amphibian eggs are classified as:

Amphibian eggs contain moderate amount of yolk unevenly distributed, denser at vegetal pole and sparse at animal pole, a condition classified as mesolecithal or moderately telolecithal. This intermediate yolk content distinguishes them from alecithal mammalian and highly telolecithal avian eggs. Because yolk impedes cytokinesis vegetally, cleavage remains holoblastic but unequal, producing small animal micromeres and large vegetal macromeres. Mesolecithal organization permits blastocoel formation and sets up gradients of maternal mRNAs like VegT, influencing germ layer patterning and gastrulation movements for aquatic development.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 2: Amphibian eggs mesolecithal pattern and yolk distribution.

View Details