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Development and Structure of the Chorioallantoic Membrane of the Ostrich, Struthio camelus Egg
Author(s) -
Maina John N,
Willoughby Bronwyn
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.897.1
Subject(s) - struthio , chorioallantoic membrane , incubation , biology , hatching , incubator , yolk , embryo , eggshell , zoology , vitelline membrane , precocial , fowl , andrology , embryogenesis , anatomy , oocyte , food science , biochemistry , microbiology and biotechnology , ecology , medicine
In amniotic eggs, the chorioallantoic membrane (CAM) is formed by fusion of the allantoic‐ and the chorionic membranes. Because in the cleidoic egg the CAM provides O 2 and nutrients to the developing embryo, it is analogous to the placenta of mammals. Since the needs for nutrients and O 2 increase with embryonic development, we speculated that surface area and the vascularization of the CAM should increase with incubation time. The CAM is very instructive model for the study of angiogenetic mechanisms, especially in cancers and other diseases and conditions that affect the hemopoietic system. In birds, the development and structure of CAM has mostly been studied in the domestic fowl ( Gallus gallus variant domesticus ). Here, the CAM of the egg of the ostrich ( Struthio camelus ), the largest extant bird that weighs as much as 150 kg, lays the largest egg that may weigh as much as 1.5 kg, has one of the longest incubation periods of 40–42 days and one having particularly poor hatching success was studied. Seven ostrich eggs were weighed and incubated an Inco Term Incubator under a temperature of 36.3°C and a relative humidity 40%. The eggs were manually rotated at least 3 times a day to avert adhesion of the CAM to the internal shell wall. At days 14, 16, 21, 25 and 28, at least one egg was removed from the incubator, the shell removed and the CAM carefully laid out flat. Its surface area was determined using a quadratic lattice grid with squares of known areas. Tissue samples taken from different regions of the CAM and fixed in 2.5% glutaraldehye buffered in sodium cacodylate (osmolarity 350mOsm; pH 7.4) for light‐ and scanning electron microscopy. The surface area and the vascularity of the CAM increased greatly with the incubation time. The blood capillaries budged towards the inner shell wall. Because of the large size of CAM of the ostrich, it is more convenient to use in study of normal and abnormal vascular development. Its functional design may explain the particularly low hatchability of the ostrich egg. Support or Funding Information National Research Foundation of South Africa