Morphology of Juvenile Crabs

The general anatomical structures of the juvenile crab were observed under the stereomicroscope (Olympus, Tokyo, Japan). Scanning electron microscope (SEM) (Hitachi, Tokyo, Japan) was used to obtain micrographs of juvenile crabs. The juvenile crabs’ samples were prepared by the standard process described by Zhu et al. [40 (link)]. The samples for observation were prepared through ethanol gradient dehydration and tert-butyl alcohol replacement. After being frozen for 20 h at −20 °C, the samples were dried for 24 h in the Martin Christ Alpha 1—4LD plus freeze dryer (Martin Christ, Osterode am Harz, Germany) before being sprayed with gold by a Hitachi E-1010 ion sputtering device (Hitachi, Japan). The length of male penis was obtained by the software Image J and converted according to the scale of SEM images.