Population dynamics of Antarctophthirus microchir (Anoplura: Echinophthiriidae) in pups from South American sea lion, Otaria flavescens, in Northern Patagonia.

M.S. LEONARDI; E.A. CRESPO; B. BERÓN VERA; D.G. VALES; S. AMEGHINO; J.A. RAGA; F.J. AZNAR

Montevideo

Workshop; XIII Reunión de trabajo de Especialistas en Mamíferos Acuáticos de América del Sur y 7º Congreso SOLAMAC.; 2008

Sociedad Latinoamericana de Especialistas en Mamíferos Acuáticos

The marine lifestyle of pinnipeds has imposed fundamental restrictions to the life cycle of their specific lice (family Echinophthiriidae), i.e. transmission and reproduction can only occur on land, particularly during the host’s reproduction period. Logistic reasons, however, have hampered studies on population dynamics for most echinopththiriid species. In this study, we analyzed patters of transmission and changes in population structure of Antarctophthirus microchir based on counts of adults and nymphs from 73 pups of South American sea lion, Otaria flavescens. Sampling was carried out under natural conditions at the rockery of Punta León, Argentina, in 2007. Pups were aged and marked at the beginning of the study, then sampled for lice (the chest and belly only) at different periods throughout the host’s reproductive season. All 1day-old pups were uninfested, but 70% of 2day-old pups were already infected, as were all older pups. Nymph 1 was the only instar with significantly lower numbers in 1-day-old pups, indicating a lower potential for transmission. Clear population trends were observed for each instar. A goodness-of-fit comparison of these trends with projections derived from simple deterministic stage-based population models suggested that (i) the generation time of A. microchir might be about 20 days, meaning that a only single generation could be produced on land; (ii) mother-to-pup transmission during the first 10 days seems to be fundamental to determine population dynamics in pups. We hypothesize that individuals of A. microchir cannot reproduce on pups > 30 days old because they start moulting and going to sea, and both events produce mortality of eggs and, probably, of nymphs 1. Pup hosts might play a central role in the population dynamics of A. microchir because they are the only age group that stays continuously on land enough time for lice to multiply.