Presence of larval and adult diapauses in a subtropical scarab beetle: graded thermal response for synchronized sexual maturation and reproduction

Abstract The white grub Dasylepida ishigakiensis has a 2‐year life cycle and spends approximately 9 months as a nonfeeding larva, pupa and adult on a subtropical island. Evidence is presented indicating that this beetle has two diapauses that appear to synchronize this long life cycle with the seasons. Larvae exposed to 20, 22.5, 25 and 27.5 °C late in the third (last) stadium pupate rapidly except for some individuals kept at the highest temperature. The latter pupate upon transfer to 22.5 °C, indicating that larval diapause is maintained at high temperature but terminates upon transfer to a lower temperature. Pupal development is directly temperature‐dependent in the range 20–30 °C. Adults develop reproductive organs (i.e. the ovary in females and the seminal vesicles and accessory glands in males) rapidly at 15 and 20 °C, whereas those kept at 25 °C take a long time to do so. Ovarian development is completely suppressed at 30 °C but initiated upon transfer to 20 °C. In the laboratory, males with well‐developed reproductive organs mate even with sexually immature females , whereas females with undeveloped ovaries show no sexual behaviour. Although the two diapauses of this species are thermally regulated (i.e. a characteristic commonly expressed by insects in summer diapause), adults of this beetle emerge from pupae late in the autumn and remain in the soil for 2 months. Adult diapause effectively serves to synchronize the time of sexual maturation with the coldest month of the year.     

Clinical,Pathological, and Etiologic Aspects of Acquired Dermal Melanocytosis

To study the pathogenesis of acquired dermal melanocytosis (ADM), we reviewed the clinical, immunohistochemical, and ultrastructual features of 34 cases (female, 33, and male, 1) of ADM. The patients’ ages at onset ranged from 8 to 51 years and averaged 26.8+12.7 years. There was a positive family history. Gray-brown macules were mostly recognized on the face. Not only active dermal melanocytes but also non-pigmented c-KIT-and TRP-2-positive immature melanocytes were detected in the dermis. Taken together those clinical and histological findings, activation of pre-existing immature melanocytes by sunlight, estrogen, and/or progesterone, and some other factors, may be the most likely mode of the development of ADM. Moreover, using cultured murine neural crest cells as a model of c-KIT-positive immature melanocytes, we confirmed that endothelin-1, which is produced and secreted by keratinocytes after UV-irradiation, affects melanocytes and accelerated melanogenesis.