CONICET | Buscador de Institutos y Recursos Humanos

Antarctophthirus microchir are lice of pinnipeds. These hosts alternate between two different habitats: the sea, where they feed, and the land, where they reproduce. Therefore, their lice are restricted in their biology, especially because eggs do not develop in the sea. We analysed the population dynamics of A. microchir on South American sea lions. This study was undertaken in Punta León, Argentina, during 2005-2006. Parasite parameters were analysed in 2 locations of the rookery, i.e., a traditional, well-structured breeding area and an expanding area with juveniles and a lax social structure. We examined 94 pups, determined their sex, age, weight and number of lice present. The lice were classified in nymph stages (N1, N2, N3) and adults. Eighty-five percent of the pups were infected. The probability of infection was calculated through a logistic regression, and it only considered the age of the pups. A mixed linear model showed that both age and location were the predicting factors of the number of lice per pup. We observed changes in the population structure with the age of the pup, independently from the location or the year. Based on our results we can conclude that female O. flavescens would infect their newborn pups with N2, N3 and mainly adults. Once on the pups, adult lice would reproduce immediately and N1 would develop from eggs after 10 days. Through day 30, and after successive molts, the number of N2 and N3 would increase. However, the life cycle would be restricted to one reproductive event during the breeding season because pups start getting into the sea once they are about a month old. Therefore, there would not be time enough for the development of a new generation of lice and this would be the reason why we did not see a new appearance of N1.

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