Mutations that produce larvae that are completely stuck in old cuticle, that have rings of unshed cuticle that constrict regions of the body, or that have attached to the tail a train of old cuticle will be described. Such larvae can be detected with a dissecting microscope, permitting a semi-clonal screen. The search for such mutations was begun because a failure to complete molting is an aspect of the phenotype conferred by loss-of-function mutations in
lrp-1 , the product of which resembles mammalian
gp330/megalin, a large member of the LDL receptor family of proteins [Yochem et al., Development 126, 597 (1999)]. It is hoped that new mutations will reveal genes whose products are required for the same process as LRP-1. The mutations also have the potential for increasing our understanding of molting, a process that has not been much studied genetically in nematodes. To date, mutations have defined eight candidate genes. Of particular note are
mlt-3(
sv8) and
mlt-7(
sv16) , both of which closely resemble the
lrp-1 mutant phenotype. Thanks to Simon Tuck, Min Han, and Bob Herman.