Fig. 9. Fate mapping the yolk sac and amniotic mesoderm with AlexaFluor594-conjugated Concanavalin A. Allantoises in D-I are from conceptuses that had been cultured for 20-24 hours and exposed on the same film to compare relative intensities of allantoic fluorescence within the same experiment. Embryo stages before and after culture in D-I are separated by a `/'. All panels contain gross microscopic views. (A-B) Posterior region of a LHF-stage conceptus in brightfield (A) and viewed by fluorescence after (B) labeling the exocoelomic cavity (x) with AlexaFluor ConA. (C) The allantois (al) has been removed from A to show complete superficial ConA labeling by fluorescence. (D,E) Cultured conceptus (4/12) in brightfield before (D) and in corresponding fluorescence (E). That most of the label is in the allantois and not the chorion was revealed by cutting the allantois away from the chorion and re-examining it (not shown). (F,G) Brightfield (F) and corresponding fluorescent (G) regenerated control allantois (EHF/9) in which the exocoelom had been labeled after removal of the allantois, thereby marking the posteriormost level of the streak. Arrowheads provide examples of very small individually labeled cells and patches of positive cells arranged in a lateral line spanning proximal to distal, typical of all six such `pre-labeled' allantoic regenerates. (H,I) Brightfield (H) and corresponding fluorescent (I) images of an allantoic regenerate (2/11) (al-r) that contains two very small positive cells (arrowheads) in the distal region. Scale bar in I: 100 µm (C-I); 400 µm (A,B).