Abstract
Paratomy is an asexual reproductive process that occurs in annelids, flatworms and other groups. During this process, anterior structures are formed in the middle of the body, giving rise to segmented organisms, each segment being called a zooid. Once formed, the zooids detach and form new organisms. Using RNAseq of worms prior to zooid formation and with two zooids, we search for genes that are differentially expressed and may be related to the control of this process in the flatworm Stenostomum leucops. Several signaling pathways showed differential expression, including MAPK/ERK, PI3K-Akt, Wnt, TGFb, mTOR, FoxO and others. Forty-five genes were found to be particularly significant because they are differentially expressed and play an important role in the development of other flatworms. These include ERK, MKP, JNK, PI3K, PTEN, β -catenin, FoxO, Sufu, GH and others. The results suggest some similarities in gene regulation between paratomy and regeneration observed in other flatworms after fission or amputation. In worms without zooids, pathways required for cell proliferation, differentiation of cells into multiple cell lineages and determination of the body axis are activated. In worms with 2 zooids, genes involved in cell growth and apoptosis are activated. Activation of genes involved in neoblast proliferation and maintenance appears to occur at both stages.