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How do Crocodylian embryos process yolk? Morphological evidence from the American alligator, Alligator mississippiensis.

Authors
  • Blackburn, Daniel G1
  • Barnes, Madeline S1
  • Reimers, Charles D1
  • Appiah, Farahana A1
  • Lestz, Luisa L1
  • Bonneau, Laurie J1
  • Hanson, Michael2
  • Smith-Paredes, Daniel2
  • Bhullar, Bhart-Anjan2
  • 1 Department of Biology, and Electron Microscopy Center, Trinity College, Hartford, Connecticut, USA.
  • 2 Department of Geology and Geophysics, Yale University, New Haven, Connecticut, USA.
Type
Published Article
Journal
Journal of morphology
Publication Date
Jul 01, 2021
Volume
282
Issue
7
Pages
953–958
Identifiers
DOI: 10.1002/jmor.21252
PMID: 32840899
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

Recent studies have demonstrated a mechanism of embryonic yolk processing in lizards, snakes and turtles that differs markedly from that of birds. In the avian pattern, cells that line the inside of the yolk sac take up products of yolk digestion and deliver nutrients into the vitelline circulation. In contrast, in squamates and turtles, proliferating endodermal cells invade and fill the yolk sac cavity, forming elongated strands of yolk-filled cells that surround small blood vessels. This arrangement provides a means by which yolk material becomes cellularized, digested, and transported for embryonic use. Ultrastructural observations on late-stage Alligator mississippiensis eggs reveal elongated, vascular strands of endodermal cells within the yolk sac cavity. The strands of cells are intermixed with free yolk spheres and clumps of yolk-filled endodermal cells, features that reflect early phases in the yolk-processing pattern. These observations indicate that yolk processing in Alligator is more like the pattern of other reptiles than that of birds. © 2021 Wiley Periodicals LLC.

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