Laboratory culture of the free-living stages of Neomesomermis flumenalis, a mermithid nematode parasite of Newfoundland blackflies (Diptera: Simuliidae)

Laboratory methods were developed for culturing the free-living stages of Neomesomermis flumenalis, a mermithid parasite of simuliids, especially Simulium venustum Say and the complex of Prosimulium mixtum Syme & Davies and P. fuscum Syme & Davies, from simuliid larvae collected in the field in Newfoundland. The best results were obtained by placing 50 pairs of nematodes under xenic conditions in 500-ml containers containing about 450 ml wet sand. With this method, 78.6% of the females introduced to culture reproduced. The influence of factors such as microorganisms, substrate, container volume and sterility on culturing the mermithid is discussed. Differences were noted in the development of N. flumenalis from winter-breeding Prosimulium hosts and those from summer-breeding Simulium. Parasites from Simulium developed nearly twice as fast as those from Prosimulium at 10 deg C. Studies showed that Simulium parasites were better adapted for higher temperatures (20 deg C) but were more poorly adapted to lower ones (5 deg C) than parasites from Prosimulium. The differences noted suggest that there are two physiological strains of the same species, one developing in Simulium spp. and the other in Prosimulium spp..