Oogenesis, Spermatogenesis, Fertilization and Microfilarial Production of Canine Heartworms

Abstract

In some old dogs infected severely with Dirofilaria immitis, no microfilariae were detected in the peripheral blood, but many eggs containing a degenerative embryo were found in blood collected from the lungs by puncture. The intact female reproductive system was dissected to observe the development of microfilariae from oogonia. Eggs containing atrophic embryo-cells were first discriminated from normal ones in the upper part of the uterus in all mature female worms. By that time normal eggs had developed into the 20-cell stage. The rate of degenerative eggs was much lower in worms obtained from relarively young dogs than in some of those from relatively old dogs.