Worm Breeder's Gazette 11(1): 65
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
We have collected soil from places as near as the institute backyard and as far as the mountains of Peru. From these probes we have isolated different nematode strains and have cultured those which happened (or got used) to grow on our standard agar plates. With the help of Dr. Sudhaus, Berlin, we have characterized them phenotypically. They probably represent 16 different species which all belong to the order 'Rhabditida'. By the criteria of outer inspection one of them appears to be a 'C. elegans', but a cross- fertilization test needs to be done. The adults of all strains are about 1-2 mm long and vary considerably in diameter. Most of them express a life cycle several-fold longer than that of C. elegans, none of them is faster. About half of them are self-fertilizing hermaphrodites. We have analyzed early cell lineages up to the 50- cell stage and have compared them to those of C. elegans. All strains express the typical pattern of nematode cleavage, whereby somatic founder cells (AB,HS,E,C,D) are generated in a series of unequal germline cleavages. In detail, however, variations were found which essentially concern the timing of cell divisions in the germline. Those strains which come closest to C. elegans in speed of developmental events also express the same sequence of early cleavages. In those strains with a slower developmental rhythm, divisions in the germline cells P1- P3 take place relative too early. In general, the following correlation was found: The slower embryogenesis proceeds in a certain strain, the earlier germline cleavages occur in the sequence of dividing blastomeres (see figure below). In our slowest strain (Cephalobus spec. from Peru) P4 is present already in the 6- cell stage, compared to the 24-cell stage in C. elegans. Altered sequence of cleavages leads to early cell patterns different from those in C. elegans. By the 24-cell stage, however, spatial organization of cells has become essentially the same in all strains. Our findings are consistent with the view that germline cells have to cleave within a certain time limit to preserve (or obtain) their specific identity as suggested by the cib-mutants (R. & H. Schnabel, pers. communication). Testing with an antibody against C. elegans P granules, we found that about 50% of the strains showed P granule staining. So far, we have no indication that these results reflect phylogenetic relationships. In no case we detected chromatin diminution. [See Figure 1]