Lieutier F
Ann Parasitol Hum Comp. 1982;57(4):407-18.
The variations of the weight of the fat body and the ovaries, as well as the length of the maturest oocyte, have been studied in Ips sexdentatus, from the end of the maturation of pre-swarming to the 24th hour after the copulation. In the healthy Insects, the weight of the ovaries and the size of the terminal oocyte grow till the swarming, but decline slightly at the 3rd hour after the copulation; the growth recovers afterwards, at first slow, then very steep after the 12th hour. The fat body declines at the swarming, but grows distinctly at the 6th hour; its weight decreases strongly at the 12th and 18th hour, then grows again considerably at the 24th hour. The variations of the weight of the ovaries (and of the size of the terminal oocyte) may be compared with that of the fat body, if we take into consideration the being of a delay in the "response" of the ovaries. This combined variations might be agreed with important periods of the biology of the bark-beetle: swarming, slow then steep maturation of the ovaries, oviposition. In the Insects parasitized by the Nematodes Parasitaphelenchus sp., P. sexdentati (Fuchs 1937) Rühm 1956, Contortylenchus diplogaster (V. Lins 1890) Rühm 1956, the fat body and the ovaries are always slighter, and the terminal oocyte less developed than in the healthy Insects. Moreover, the fat body of the infected Insects cannot accumulate the indispensable stocks for the maturation of the oocytes, just as these one seem to want that. Therefore the maturation of the oocytes of this Insects is delayed. This delay, by accumulating itself for the successive oocytes, might explain the important reduction of the oviposition in the parasitized Insects. The effect of the Nematodes on the ovaries of Ips sexdentatus might be indirect, the direct effect being related to the fat body or to the blood. On the otherside, the abdominal fat body seems to be more affected by the parasitism than the prothoracic one.
