Fig. 4

Lattice types identified in the girdle bands of diatoms. Girdle band structures are labelled as “G” in the source SEM images. Disordered structures lack symmetry, as indicated by the absence of distinct patterns in the Fast Fourier Transform (FFT) analysis. Single pore can be regarded to as potential 1D photonic crystals. Square and hexagonal lattice types may exhibit disordered features, evident as noise in the high-frequency domains of the FFT images. Species with such disordered lattices, here defined as quasi-sPhCs, contain fewer than 15 pores in the z-direction, such as those described in Fig. 3. Species names: (i) Pteroncola sp. UTKSA0078; (ii) Orthoseira dendroteres HK066; (iii) Lambertocellus africana SZCZP74; (iv) Odontella sp.; (v) Coscinodiscus sp.; (vi) Triceratium spinosum UTKSA0420; Trieres mobiliensis.