Gaseous Requirements for Postparasitic Development of Romanomermis culicivorax

The development of postparasitic stages of Romanomermis culicivorax was studied under various concentrations of oxygen and carhon dioxide. The nematode developed poorly if only nitrogen was supplied; only one-third molted and all died eventually. In the presence of 5% CO - 95% N, development was normal; most nematodes molted and oviposited with respective mean developmental times of 32 and 50 d. Addition of 0.2% O stimulated development; molting and oviposition commenced at days 18 and 41, respectively. There was an additional stimulation of development by increasing amounts of O up to 1%, but concentrations greater than 1% produced no additional stimulation. Carbon dioxide was required for development after exsheathment under anaerobic conditions or O concentrations less than 1%. Oxygen or CO were not required for embryological development or egg hatch. It is suggested that post-parasitic stages function as facultative anaerobes.