Observation on oogenesis and egg shell formation in Haemonchus contortus (Nematoda)

The process of oogenesis and egg shell formation in Haemonchus contortus, a blood sucking nematode parasite of small ruminants was studied. In the germinative zone, the oogonia having prominent nuclei and clear cytoplasm, divide mitotically and are arranged around a central anucleate tube like rachis which is not directly connected to the oogonia by their cytoplasmic extensions but sends out various branches in inter-oogonial spaces. In the growth zone of the ovary, the primary and secondary oocytes attain a substantial increase in size. This region of ovary is tightly coiled around the intestine suggesting trans-membrane flow of nutrients from the gut to the gonads. The secondary hexagonal shaped oocytes detach from the rachis and pass through the narrow oviduct and enter into seminal receptaculum. The process of fertilization initiates egg shell formation. The layers of the egg shell being an indiscernible vitelline layer, a chitinous layer and an outer uterine layer. Uterine lipids and proteins contribute to the formation of outer layer of egg shell which gets coated by acid mucopolysaccharides in the last portion of the uterus. The ova lying in the proximal part of the uterus have already completed the first segmentation division before their expulsion.