Flagellar structure and assembly of the eight flagella. Each of the eight axonemes are nucleated by basal bodies located in the cytoplasm between the two nuclei (see schematic in A). Each axoneme also extends through the cytoplasm and is compartmentalized into a membrane-bound flagellum at the flagellar pores (fp). Yet each flagellar pair (AF, anterior; VF, ventral; CF, caudal; PF, posteriolateral) has different lengths in both the cytoplasmic and the membrane-bound regions (B). Flagellar assembly and length maintenance are generally achieved by intraflagellar transport (IFT) powered by MT motors. In Giardia, IFT particles assemble on cytoplasmic portions, accumulate at flagellar pores (fp) and are actively trafficked by IFT on membrane-bound portions as illustrated (see C, D) using a marker of IFT trains (mNG-tagged IFT81, green; MTs, magenta).