A model for the prediction of IgG titres in females of the Jackass penguin (Spheniscus demersus) was developed, based on IgG which was maternally transmitted to the yolk of unembryonated eggs produced by these females. However, prediction of the female titre based on the titre of embryonated eggs may be inadequate. Blood samples from 10 S. demersus females and their corresponding embryonated (n = 10) and unembryonated (n = 49) eggs were analysed by indirect ELISA for avian malaria (Plasmodium relictum, P. elongatum) IgG and Aspergillus spp. IgG. There was no correlation between humoral responses to avian malaria and Aspergillus spp. in females or in their eggs. Avian malaria and Aspergillus spp. titres were significantly higher (P < 0.05) in the eggs than in the corresponding females and were significantly correlated (P < 0.01) with the blood titres, r = 0.84, r = 0.89, respectively. No correlation was found between titres of embryo yolk-sac (embryonated eggs) and the blood of their female parent; however, the embryo blood and the corresponding female titres were significantly (P < 0.05) correlated (avian malaria, r = 0.74; Aspergillus spp., r = 0.69). Blood and the corresponding egg-yolk (unembryonated eggs) IgG titres regressed significantly (P < 0.01). Female IgG titre (y) is related to (unembryonated) egg-yolk IgG titre by the significant (P < 0.05) regression y = -0.61 + 1.46X for avian malaria, and y = -0.02 + 0.85X for Aspergillus spp., with +/- 95% prediction limits of +/- 0.15 and +/- 0.12, respectively. This model provides access to serological information on the remote free-ranging Jackass penguins and captive Jackass-penguin colonies without the necessity of stressful blood collection.
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Graczyk et al. (1996) studied this question.
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