Practice question

Small micromeres are four cells produced alongside large micromeres at fourth cleavage, residing at extreme vegetal pole as tiny population. Unlike large micromeres that become skeletogenic primary mesenchyme, small micromeres ingress later, divide very slowly, and retain high levels of conserved germline multipotency factors Vasa, Nanos and Piwi. Lineage tracing with vital dyes shows descendants populate left and right coelomic pouches and later contribute predominantly to primordial germ cells of adult rudiment after metamorphosis. They are non-skeletogenic and preserve pluripotency programs. Thus fate is germline maintenance rather than larval skeleton or ectoderm, supporting adult body plan reproduction.