A novel fracturing device to observe the gut contents of copepod nauplii using a scanning electron microscope

We introduce a novel fracturing device of high accuracy for scanning electron microscopy for the identification of in situ food items in copepod nauplii. The device requires a very small amount of water and sample, which is frozen on the device. The ice is then physically fractured with the included sample, and sublimated to dry. Copepod nauplii of Acartia steueri were fractured with arbitrary cross‐sections using this device, and their digestive tracts were observed. Cyanobacteria, diatoms, bacteria, and flagellates were observed in the guts. Elemental analysis of a fecal pellet in the hind gut of a copepod nauplius detected silicon. The accuracy of the device was tested and distribution of fracturing errors showed a normal distribution; the cumulative frequency between −50 μm and 50 μm was 0.81. The accuracy indicates that the device can be widely applied to other microscopic organisms such as barnacle nauplii, starfish larvae, and sea urchin larvae.