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Nematology, 2000, Vol. 2(1), 71-79 Symposium The demise of the Platonic worm

Summary: Nematology, 2000, Vol. 2(1), 71-79 Symposium
The demise of the Platonic worm
Ricardo B.R. AZEVEDO 1,*
, Ana CUNHA 1, Scott W. EMMONS 2 and Armand M. LEROI 1
1 Department of Biology, Imperial College, Silwood Park, Ascot, Berkshire SL5 7PY, UK
2 Department of Molecular Genetics, Albert Einstein College of Medicine, Bronx, NY 10461, USA
Presented at the symposium `Biodiversity in the phylum Nematoda', Gent, Belgium, 17 September 1999
Summary ­ Nematodes are generally considered to have an adult cell number that does not vary among wildtype individuals as a
consequence of invariant cell lineages (eutely). However, there is extensive evidence that at least some cell lineages can be variable
in nematodes. In a comparative study of 13 free-living nematode species, we have shown that the adult epidermis of most species
contained variable numbers of nuclei and that this variance was positively correlated with mean epidermal nuclear number. Here we
present simulations of the lateral seam cell lineages of four species and show that variance in cell number is in uenced by lineage
topology, as well as by the frequency of lineage variants. We show that the epidermal variability of Panagrellus redivivus cannot
be accounted for by the complexity of its lineage, but requires higher levels of lineage variability than are found in Caenorhabditis
elegans, Oscheius myriophila and Rhabditella octopleura. Our ndings suggest that many nematodes may have tissues composed of
indeterminate numbers of cells formed from variable lineages and, as such, resemble other metazoans.
Résumé ­ Le décès du ver platonique ­ Les nématodes sont généralement considérés comme ayant un nombre de cellules invariable
chez les individus de type sauvage, conséquence d'un lignage cellulaire xe (eutélie). Cependant, il est d'évidence qu'au moins certains
des lignages cellulaires peuvent varier chez les nématodes. Dans une étude comparative portant sur 13 espèces de nématodes libres,
nous avions montré que l'épiderme de la plupart de ces espèces comportait un nombre variable de noyaux et que cette variabilité était


Source: Azevedo, Ricardo - Department of Biology and Biochemistry, University of Houston


Collections: Biology and Medicine; Environmental Sciences and Ecology