Aedes aegypti (Linnaeus, 1762)

Meyer, Stephanie, Araujo, Thiago Q., Walsh, Elizabeth J., Wallace, Robert L. & Hochberg, Rick, 2023, Integrative microscopy to explore physical and nanomechanical properties of eggshells of diapausing embryos in Rotifera: a proof-of-concept study, Journal of Natural History 57, pp. 1984-2005 : 1993-1994

Phylum Arthropoda :

Aedes aegypti

SEM

The elongate eggs of A. aegypti measured ca 600 µm long (̄x = 596.9 ± 17.1 μm). The posterior and anterior ends tapered into a spindle shape and the centre measured 165 µm in diameter ( Figure 4a ). The textured surface was covered with outer chorionic cells (sensu Mundim-Pombo et al. 2021). Each cell contained a central tubercle and smaller peripheral tubercles ( Figure 4b ). The central tubercles measured ca 7.6 µm in diameter and the peripheral tubercles measured ca 2.1 µm across. The surface of the shell was rugose in regions where tubercles and other ornamentation was absent ( Figure 4c ).

TEM

Not performed in this study. Measurements estimated from Mundim-Pombo et al. (2021) showed an average shell thickness of 1.93 ± 0.63 µm (SD).

AFM

Images of the outer shell layer displayed similar morphologies to those observed in SEM but were less textured. Small bumps on the eggshell measured ~0.79 µm in diameter ( Figure 4d ). The AFM appeared to have taken measurements from the ̍naked̾ region between tubercles or perhaps where tubercles were missing (probably artefactual and due to storage or processing) (see Figure 4a ). An example force–distance curve that displays how Young̾s modulus values were collected for a single spot on one egg is shown in Figure 4e . The Young̾s modulus ranged from 14.09 to 28.61 MPa with an average of 22.54 ± 5.00 MPa (SD) ( Table 1 ). The hardness ranged from 1.78 × 10−2 GPa to 2.75 × 10−2 GPa with an average hardness of 2.28 × 10−2 GPa ± 3.33 × 10−3 GPa (SD) ( Table 2 ).

Figures

Figure 4. Characterisation of the overwintering eggs of Aedes aegypti. a. Scanning Electron Microscopy of an egg. The eggshell is damaged and much of the ornamentation has been artificially removed to expose the shell surface. b. Close-up of the ornamentation of an eggshell. c. Close-up of the surface of the eggshell region without ornamentation. d. Topographic image of the external surface of an eggshell generated with Atomic Force Microscopy. e. Force–distance (FD) curve generated from a single location on an eggshell. Parameters for the position of the location on the eggshell are indicated by the cursor positions (screen shot). Maximum force (MF, green circle) and 20% maximum force (20% MF, orange circle) are indicated on the FD curve. Scale bars: A = 100 µm; B = 53 µm; C = 15 µm.