Phylum Rotifera:

Brachionus plicatilis

SEM

Diapausing embryos were ovoid and measured ca 134 µm in diameter (̄x = 134.0 ± 4.0 μm). The outer surface was composed of numerous smooth ridges and wrinkles, creating an overall rough surface (Figure 2a,b).

TEM

The shell consisted of a thick apical layer and a thin basal layer. Average shell thickness was 2.30 ± 0.22 µm (SD). The outer layer, termed the alveolar layer by Munuswamy et al. (1996), had a wavy texture (Figure 2c,d). Electron density was highest at the topmost and bottom portions of the alveolar layer, otherwise it had a similar electron density throughout its thickness and contained many ̍empty̾ pockets that were interconnected through electron-dense bridges. The basal layer [s1 of Munuswamy et al. (1996)] had an amorphous appearance that consisted of an electron lucent zone and a more electron-opaque zone below it (Figure 2d). Thin fibres were present throughout both zones.

AFM

Topography of the outer shell showed rugosity and similar attributes to those in SEM, but with fewer details (Figure 2e). An example force–distance curve that displays how Young̾s modulus values were collected for a single spot on one egg is shown in Figure 2f. The Young̾s modulus ranged from 12.24 to 19.85 MPa with an average of 15.81 ± 2.49 MPa (SD) (Table 1). Hardness values ranged from 1.14 × 10−2 to 5.31 × 10−2 GPa with an average hardness of 1.853 × 10−2 ±1.23 × 10−2 GPa (Table 2).