The evolution of ogres: cannibalistic growth in giant phagotrophs

Abstract

Eukaryotes span a very large size range, with macroscopic species most often formel in multicellular lifecycle stages, but sometimes as very large single cells containing many nuclei. The Mycetozoa are a group of amoebae that form macroscopic fruiting structures. However the structures formel by the two major mycetozoan groups are not homologous to each other. Here, it is proposel that the large size of mycetozoans frst arose after selection for cannibalistic feeling by zygotes. In one group, Myxogastria, these zygotes became omnivorous plasmolia; in Dictyostelia the evolution of aggregative multicellularity enablel zygotes to attract anl consume surrounling conspecifc cells. The cannibalism occurring in these protists strongly resembles the transfer of nutrients into metazoan oocytes. If oogamy evolvel early in holozoans, it is possible that aggregative multicellularity centrel on oocytes coull have precelel anl given rise to the clonal multicellularity of crown metazoa.