SIKES, J.M.*; BELY, A.E.; University of Maryland, College Park; University of Maryland, College Park: Regeneration and asexual reproduction in acoels of the genus Convolutriloba

Acoels in the genus Convolutriloba display remarkably different forms of asexual reproduction and possess amazing capacities for regeneration. While C. hastifera reproduces by simple transverse fission followed by regeneration, the closely related C. longifissura reproduces by two orthogonal divisions, a first one transverse (dividing the worm into an anterior half and a posterior half) and a second one longitudinal (dividing the posterior half further into left and right halves). Yet another species in the genus, the remarkable C. retrogemma, reproduces by forming two posterior buds that have a reversed A/P polarity relative to the parent. We are investigating the evolution and development of these varied modes of reproduction and how they relate to regeneration abilities in this genus, focusing initially on a comparison between C. hastifera and C. longifissura. We find that the products of fission in both species inherit both symbiotic algal cells and pigment globules from the parent individual. Immediately following a fission event, the posterior fragment remains stationary until anterior structures are replaced while the anterior fragment is immediately motile. With respect to regeneration, we find that both C. longifissura and C. hastifera can rapidly regenerate from either transverse or longitudinal cuts, even though only C. longifissura employs its longitudinal regeneration ability for reproduction. After either transverse or longitudinal amputations, pulse-chase BrdU-labeling experiments reveal a temporally dynamic pattern of cell proliferation that suggests an important role for cell migration (possibly of stem cells) during left/right and anterior/posterior regeneration. We are performing similar BrdU studies during fission to infer whether extensive cell migration might also be important during asexual reproduction.