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. 2020 Mar 18;9(3):744. doi: 10.3390/cells9030744

Figure 4.

Figure 4

Common centriole models in germ cells of Hexapoda. Cross sections of centrioles and axonemes in (A,B) Campodea (Diplura), (C,D) Allacma (Collembola), and (E,F) Drosophila (Diptera). Low Hexapoda have centrioles with doublet microtubules (C) and axonemes without accessory tubules (D). Insect spermatocytes usually show centrioles with triplet microtubules (A,E) and axonemes with distinct accessory tubules (B,F) derived by the proliferation of the C-tubules (inset B, arrowhead). Longitudinal sections of centrioles in growing primary spermatocytes of the coleopteran Adalia (G) and the dipteran Drosophila (H) showing their different length: both the centrioles and the cilium-like regions (CLR) will grow further during prophase progression to reach their full length in mature primary spermatocytes but their different dimensions do not change. The cartwheel (brackets) extends along the length of the centriole in Adalia, whereas it is restricted to the proximal region of the centriole in Drosophila. The daughter centriole (d) is orthogonal to the basal region of the mother (m). Bars: A–F, 100 nm; G,H, 200 nm.