Worm Breeder's Gazette 5(1): 28
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 begun to examine the postembryonic cell lineages of Panagrellus redivivus. We hope to correlate morphological and physiological differences between P. redivivus and C. elegans with lineage differences. P. redivivus is dioecious and larger than C. elegans. Females have a one-armed gonad, directed anteriorly from the vulva, and a post-vulva 'uterine sac.' Females do not lay eggs but do release L1's. In general, development in the two species is similar; L1's are essentially identical, except in size. So far we have found several lineage differences. In the C. elegans hermaphrodite, a single mesoblast (M) divides in the L1 to generate 14 body muscles, 2 coelomocytes, and 2 sex myoblasts (SM). The SM's each undergo three rounds of division in the L3 to generate 8 sex muscles per side. In the M cell lineage of the P. redivivus female, there is a programmed cell death of an anterior daughter in each muscle quadrant (i.e., of M. draa, M.dlaa, M.vraa, and M.vlaa), so that only 8 body muscles, 2 coelomocytes, and 2 SM's are generated in the L1. Each SM undergoes 3 rounds of division in the L3, except that SM.aa dies, so that only 6 progeny are generated per side. Four of these six nuclei lie anterior to the center of vulval symmetry, suggesting that the two anterior- most cells may be uterine muscles and the other four may be vulva muscles. The M lineage cell deaths seen in P. redivivus are striking in two ways: a) there are no postembryonic mesodermal cell deaths in C. elegans and b) most C. elegans cell deaths are of posterior daughters. The M cell lineage in the Panagrellus male gives rise to four SM's (2 dorsal, 2 ventral) on each side, as compared with three ( 2 dorsal 1 ventral) on each side in C. elegans. The female vulva is formed from four ventral hypodermal precursors, instead of from three as in C. elegans. There is a second round of intestinal nuclei divisions during L3 lethargus in P. redivivus, as well as several additional rounds of division in the lateral hypodermis; both may be related to the larger size of P. redivivus.