Abstract
Heavy-ion micro-beams are extremely useful radio-surgical tools for studying bio-function and differentiation of various cells and tissues in insects. A spot irradiation to the cellular blastoderm stage eggs of the silkworm, Bombyx mori, brought about various abnormal embryos including deletion, duplication, and fusion. The location of the defects within the cuticle pattern induced on the resultant embryos correlated closely to the site of irradiation. Based on this correlation, a fate map of the Bombyx mori egg at the cellular blastoderm stage was established. Position-related cell fate and plasticity of the cell differentiation process were revealed with local irradiation of heavy ions. Locally targeted irradiation of heavy-ion beams of silkworm larva had no deleterious effects on survival, but induces marked functional disruption of the irradiated tissues or organs. For example, in instances where larval epidermis was locally irradiated with heavy-ions, scale development did not occur to various degrees in the irradiated area of the adult moths depending on the dose of irradiation. One of body-shape mutants of Bombyx mori, Knobbed, is characterized by the appearance of dermal protuberances (knobs) on the crescent and star-spot larval markings. To clarify the mechanism of Knob formation, we investigated the effects of heavy-ions on the corresponding epidermal cells of newly hatched larvae and found that the knob protuberances disappeared after the local irradiation.
