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Studies on the cryopreservation of Dictyocaulus viviparus (Nematoda) third-stage larvae
Published online by Cambridge University Press: 18 November 2009
Abstract
Various cooling (01–5.100 Cmin−1) and warming (2O–6,8OO½Cmin−1) rates, stepped cooling schedules and four cryoprotective additives (dimethyl sulphoxide, methanol, ethanediol and glycerol) were investigated in cryopreservation studies with Dictyocaulus viviparus third-stage larvae. Exsheathment with sodium hypochlorite was essential to achieve significant survival. With uninterrupted cooling, highest survival (30% normally motile) was achieved with rates of 10–70½C min−1. Survival was higher (50–75%) using 1 ½C min−1 to — 10½C followed by plunging into liquid nitrogen. The optimum warming rate was 6,8OO½C min−1. The use of cryoprotectants led to marginally lower survival while varying the suspending media had no significant effect on survival. X-irradiated, exsheathed third-stage larvae cryopreserved by the optimum protocol yielded 38–3 ±4–2% survival. Two calves each infected with 45,000 (15,000 viable) exsheathed, unirradiated, C“ryopreserved third-stage larvae harboured 494 worms (11% infectivity) and 355 worms (0-8%) at necropsy. Numbers of first-stage larvae in the faeces reached 420/G and 105/G respectively 27 days after infection.
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