The corn snake yolk sac becomes a solid tissue filled with blood vessels and yolk-rich endodermal cells.

The corn snake yolk sac becomes a solid tissue filled with blood vessels and yolk-rich endodermal cells. Biol Lett. 2014;10(1):20130870 Authors: Elinson RP, Stewart JR Abstract The amniote egg was a key innovation in vertebrate evolution because it supports an independent existence in terrestrial environments. The egg is provisioned with yolk, and development depends on the yolk sac for the mobilization of nutrients. We have examined the yolk sac of the corn snake Pantherophis guttatus by the dissection of living eggs. In contrast to the familiar fluid-filled sac of birds, the corn snake yolk sac invades the yolk mass to become a solid tissue. There is extensive proliferation of yolk-filled endodermal cells, which associate with a meshwork of blood vessels. These novel attributes of the yolk sac of corn snakes compared with birds suggest new pathways for the evolution of the amniote egg. PMID: 24402715 [PubMed - in process]
Source: Biology Letters - Category: Biology Authors: Tags: Biol Lett Source Type: research