SNAKE YOLK-SAC AS A SITE FOR IN-VIVO ORGAN INCUBATION - A NEW METHOD IN THE RESEARCH OF SNAKE EMBRYO DEVELOPMENT

The snake embryo yolk sac served as a culture medium for the developme nt of isolated reptilian organs. Isolated upper jaws of Natrix tessell ata and Vipera palaestinae embryos at the early stages of jaw organoge nesis were implanted into the yolk, close to the yolk sac blood vessel s of Natl ix tessellata embryos in order to determine natural conditio ns for long-term incubation of organ culture. Tissues were incubated i n the yolk for approximately 1 month until 1 day before host embryo ha tching. Histological inspection showed full morphological differentiat ion of all tissues including scales, bones, teeth, glands, and connect ive tissue. The biochemical marker phosphodiesterase showed the typica l developmental pattern in the main oral gland, Duvernoy's gland, and was comparable to the same gland in the host embryo. Vipera implants d eveloped almost normally, except for differentiation of the skin which remained in the stage of one to two cell undifferentiated layers. Nat rix was chosen for these experiments owing to the special chemical com position of its yolk that allows the penetration of blood vessels. Thi s characteristic is probably crucial for the success of angiogenesis, which in turn is an essential condition for tissue survival. The abili ty of the yolk to support normal differentiation of isolated organs pr ovides a valuable tool for the long-term incubation experiments that a re indispensable in order to achieve maximal tissue differentiation. ( C) 1994 Wiley-Liss, Inc.