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Myotomal myogenesis in Triturus vulgaris L. (Urodela) with special reference to the role of mesenchymal cells

100%

Daczewska M., Kielbowna L.

Folia Biologica

2000

vol. 48

issue 1-2

37-42

Two stages can be distinguished in the differentiation of myotomal muscle fibres in Triturus vulgaris. In the first stage only synchronously differentiating myotomal cells are engaged; in the second stage mesenchymal cells also take part in the process. Myotomal cells (primary myoblasts) fuse to form 2-3 nucleate myotubes. Only in the caudal part of the embryo mononucleate myotubes persist. The mononucleate myotubes, like polynucleate ones, occupy the whole length of the myotome. The differentiation of myotubes is accompanied by vitellolysis. At further development stages mesenchymal cells enter the intermyotomal fissure, after which they migrate to the myotomes, between the myotubes. The cells that remain in the intermyotomal fissures retain their fibroblastic potential (they synthesise collagen). Their daughter cells adjoining the myotubes acquire myogenic abilities. Their myoblastic potential is evidenced by their ability to fuse with the myotube. Fusion of secondary myoblasts (of mesenchymal origin) with the myotube results in further growth of the myotubes. In T. vulgaris myotomal myotubes and muscle fibres developing from them are of myotomal-mesenchymal origin.

Genetic differentiation of the two subspecies of the smooth newt inhabiting Romania, Triturus vulgaris vulgaris and T. v. ampelensis (Urodela, Salamandridae) as revealed by enzyme electrophoresis

88%

Rafinski J., Cog_lniceanu D., Babik W.

Folia Biologica

2001

vol. 49

issue 3-4

239-245

Starch gel electrophoresis was applied to quantify genetic variation and divergence in samples from Romanian populations of the nominal form of the smooth newt Triturus vulgaris and those of the endemic Romanian subspecies T. v. ampelensis, a population from a parapatric area was additionally included. All the samples had similar levels of genetic variation measured by the mean heterozygosity, proportion of polymorphic loci, and mean number of alleles per locus. T. v. ampelensis samples were genetically clearly different from the nominal form samples, the mean genetic distance between the two subspecies was being estimated as DN = 0.114. No fixed differences in allele composition between the two subspecies were found, although some of the alleles were found either exclusively in the nominal form (Aat-1 a) or in T. v. ampelensis (Mpi a). Other alleles at these loci together with Mdh-1 differed markedly in frequency. The population from the parapatric area was intermediate in allelic composition, but grouped together with the T. v. ampelensis samples in a maximum likelihood tree (99.7% bootstrap support for this grouping). The data indicate that the two subspecies interbreed in a parapatric zone. The molecular clock applied to electrophoretic data indicates that these two forms split during the Pleistocene.

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2 Folia Biologica

1 2001

1 2000

1 Babik W.

1 Cog_lniceanu D.

1 Daczewska M.

1 Kielbowna L.

1 Rafinski J.

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Myotomal myogenesis in Triturus vulgaris L. (Urodela) with special reference to the role of mesenchymal cells

Genetic differentiation of the two subspecies of the smooth newt inhabiting Romania, Triturus vulgaris vulgaris and T. v. ampelensis (Urodela, Salamandridae) as revealed by enzyme electrophoresis