Life begins when the host is ashore: habitat use by a louse infecting a diving mammal.

LEONARDI, M.S., E.A. CRESPO, P. MATEU, J.A. RAGA & F.J. AZNAR.

Melbourne, Australia

Congreso; THE XIITH INTERNATIONAL CONGRESS OF PARASITOLOGY (ICOPA); 2010

Sucking lice (Anoplura) infect a wide variety of mammalian hosts, being adapted to use their pelage as an environment. Host-related physiological, behavioural and ecological factors, in particular temperature, relative humidity, light, grooming and rain, are key factors determining patterns of habitat selection by lice on the host’s body surface. Lice from pinnipeds (fam. Echinophthiriidae) are adapted to survive alternating between an aquatic and a terrestrial environment, particularly in hosts whose pelage soaks during immersion. Previous evidence obtained from echinophthiriids infecting pinnipeds from high latitudes indicates that flippers are the preferred site because to host’ thermoregulatory behavior in a cold climate. We studied the habitat selection by Antarctophthirus microchir on pups of South American sea lion, Otaria flavescens, from Patagonia, during the austral summer of 3 consecutive years, and found a contrasting pattern: the nymphal instars 1-3, adult males and preovigerous females occurred mostly on the ventral surface of the body, particularly on the belly; the pattern was most apparent in more advanced stages. In contrast, ovigerous females, and eggs, were significantly more abundant on the dorsal surface. Accordingly, A. microchir would prefer the ventral area for development and copulation, and the dorsal area for ovoposition. Skin temperatures did not significantly differ between ventral and dorsal areas. Selection of ventral areas could result from negative phototropism coupled with a need for humid conditions. However, the dorsal area would provide better conditions for egg development: long hair and increased exposure to solar radiation, which create a temperature gradient ranging from 41.1 º C at the hair tip to 34 º C on the skin. More importantly, sea lion pups periodically soak at high tides. Since prolonged immersion or very high humidity are known to be lethal for lice eggs, selecting the dorsal would be advantageous because its dries much faster.