Embryonic Patterning: Segmentation
Mesoderm-derived: Somites; Limb Formation
Stage of Development: Embryo
This American alligator embryo, Alligator mississippiensis, is around Stage 8 or 9 and is 8-10 days old. The optic vesicle (ov) is slightly pigmented. The telencephalon (te), diencephalon (di), midbrain (mb) and hindbrain (hb) are present. The four visceral arches are fusing into conglomerate visceral arches (cva). The heart (hr) will develop four chambers, like other Archosaurians, but unlike other reptiles. Below the heart is the liver (l). The forelimbs (fl) and hindlimbs (hl) are elongating. Somites (s) are still being formed anterior to the tailbud (tb) region.
Dr. Ruth Elsey of the Rockefeller Wildlife Refuge in Grand Chenier, Louisiana kindly provided our lab with alligator eggs. I'd like to also acknowledge Dr. Walter Eckalbar who dissected this alligator embryo.
Eckalbar, W.L., Lasku, E., Infante, C.R., Elsey, R.M., Markov, G.J., Allen, A.N., Corneveaux, J.J., Losos, J.B., DeNardo, D.F., Huentelman, M.J., Wilson-Rawls, J., Rawls, A., Kusumi, K. Somitogenesis in the anole lizard and alligator reveals evolutionary convergence and divergence in the amniote segmentation clock. Developmental Biology, 2012, 363:308-319.
Deeming, D.C. Ferguson, M.W.J. Morphometric analysis of embryonic development in Alligator mississippiensis, Crocodylus johnstoni and Crocodylus porosus. Journal of Zoology, 1990, 221:419-439.
Iungman, J. Pina, C.I., Siroski, P. Embryological Development of Caiman latirostris (Crocodylia:Alligatoridae). 2008, Genesis. 46:401-417.