Figure 3. Dimorphic development of Daphnia magna.

Eggs induced to become males were obtained from D. magna. After injection of the synthesized dsRNA, sexually dimorphic phenotypes were examined at the fifth or sixth instar except first antennae (third instar). The first two columns represent normal male and female phenotypes, respectively. The third and fourth columns represent phenotypes of individuals injected with #1-dsRNA of dsx1 and dsx2, respectively. (A): Lateral view of the head. Arrowheads indicate the first antennae. (B): First thoracic limb. Dotted line shows the outline of the stout chitinized hook. A female-type long filament corresponding to the hook is labeled with an asterisk. (C): Gonad. Daphnids were embedded in paraffin and sectioned, following by standard hematoxylin and eosin staining. Dorsal is left, ventral is right. Dotted circled lines show gonads at both sides of a gut. T and O indicate testis and ovary, respectively. Arrowheads indicate large lipid droplets lying among the eosinophilic yolk granules. Arrows indicate lumens into which the mature spermatozoa are released. (D): Gene expression profile of Dsx1 and Dsx2 in embryos injected with dsRNA of Dsx1 (left panel) and in dsRNA of Dsx2 (right panel). The MalE gene from E. coli was used as a control gene. Bars in (A), (B) and (C) indicate 200, 100, 50 µm, respectively.