Role of the median neurosecretory cells in the ovarian development of the blow fly Protophormia terraenovae

Staining with paraldehyde-thionin-paraldehyde-fuchsin labeled 10-14 median neurosecretory cells (MNC) in each hemisphere of the brain of diapause and nondiapause adults of the blow fly, Protophormia terraenovae (Diptera: Call iphoridae). Various surgical operations were performed on the brain-retroce rebral complex of female adults to investigate the role of these cells in o varian development and diapause. Under the diapause-averting conditions of LD 18:6 (18 h light and 6 h darkness) and 25 degrees C, most of the intact and sham-operated females had vitellogenic ovaries, whereas all of the fema les with the MNC completely removed had immature ovaries. The corpus allatu m (CA) was significantly smaller in the MNC-removed females than in the int act and sham-operated ones. After severance of the nervi corporis cardiaci, most of the females had immature ovaries. Even after severance of the card iac recurrent nerve, there were vitellogenic ovaries in about 60 % of the f emales. However, after removal of the corpus cardiacum and hypocerebral gan glion complex (CCHG), no females had vitellogenic ovaries. Under the diapau se-inducing conditions of LD 12:12 and 20 degrees C, most females had immat ure ovaries and the CA was small irrespective of the surgical procedures. T he results indicate that the MNC may secrete an allatotropic factor to stim ulate vitellogenesis. The factor seems to be released to the hemolymph from the CCHG and a part of the aorta.