Abstract:
Infective, third, stage E, uncinata juveniles were found in Daphnia pulex, D. magna and Simocephalus vetulus collected from the Field Station Pond at Delta. The parasites were present in the pond from late May to early November, and reached a peak abundance of 108 parasites per 100 D. magna in early August. Laboratory experiments with Daphnia pulex, D. magna, Simocephalus vetulus, Ceriodaphnia reticulata, C. acanthina, Moina macrocopa, Eurycercus lamellatus. Gammarus lacustris. Hyalella azteca, Lynceus brachyurus and Chirocephalopsis bundyi demonstrated that these Delta crustaceans become infected when exposed to E. uncinata eggs. Insect larvae, ostracods, copepods and the cladocerans Alona sp. and Scapholeberis sp. did not become infected. E. uncinata developed to third stage in Daphnia pulex and D. magna in 30 days at 15o C. and in 10 days at 20 - 24o C. Eggs of E. uncinata perished when frozen for 85 days but survived the same period when dried on filter paper at 20 - 24o C. In penned, Delta Mallards, E. uncinata moulted from fourth stage juveniles to adults after 20 days; male worms were sexually mature after 30 days and females were oviposting after 40 days. E. uncinata grew faster and were more successful in one-week old Delta Mallards than in two and three-month old birds. This nematode easily infected mallards, pintails, gadwalls, lesser scaup, common elders and domestic geese, but not shovellers, blue-winged teal, redheads, ruddy ducks and coots. In the definitive host, E. uncinata burrowed under the mucosa of the isthmus, the junction of the proventriculus and gizzard, where granulomas were formed. The number of granulomas was correlated with the number of parasites. E. uncinata survived all winter in mallards kept at the Delta Waterfowl Research Station.
