Given the obvious morphological differences described above, we used gene sequences to test the evolutionary relationship between the two strains.
This is not surprising, since early embryogenesis is strongly conserved among dipterans (reviewed in [ 20, 59, 60]; most morphological differences described so far involve extra-embryonic tissues [ 61]).
The morphological differences described statistically above and depicted in Figure 5 are easily visible when inspecting the actual bone structures of the different skulls.
The difference in induction of luminal epithelial cell proliferation in these two rat strains was clearly reflected in the morphological and histological differences described above, as well as in differences in epithelial density measured by quantifying the number of luminal epithelial cells per microscopic field.
They described morphological differences in several organs between aged Agtr1a−/− mice and wild-type controls, such as lower cardiomyocyte size and collagen deposition in the heart, fewer atherosclerotic lesions in the aorta, and fewer lymphoid aggregates in the pancreas of Agtr1a−/− mice17.
Lungs from E17.5 Crem+//−, Crem+/− (Fig. 2D) and Creb1−/−, Crem−/− (Fig. 2E) mice also showed no overt morphological differences to the phenotype described for Creb1−/−, Crem+/+ mice (Fig. 1F).
Previously described morphological differences originally referred to the overall shape of the skull, rounded in N. milleri and more angular in N. anomalus [ 23, 24].
These two taxa were described in 1907 as morphological species and, therefore, the support for their species status comes, not only from the multilocus analysis performed here, but also from previously described morphological differences [ 23– 27].
In 1886 Golgi described the morphological differences that are still used to distinguish two malaria parasite species Plasmodium vivax and Plasmodium malariae.
Morphological differences in GGA4 have been described between different chicken breeds[ 25], and the ancestral bird chromosome 4 (corresponding to GGA4q and APL4, respectively) is also one of the chromosomes most prone to convergent independent fusions in birds (with ancestral chromosome 10) [ 6].
Studies in Europe, Africa, and Australia described the morphological differences of hookworms obtained from dogs and cats, where A. caninum was distinguished from A. tubaeforme and was thought to be host-specific for dogs [ 31, 32].
