Life begins when the sea lion is ashore: microhabitat use by a louse living on a diving mammal host

Abstract

Among Anoplura, the family Echinophthiriidae includes species that infest pinnipeds and otters. Previous evidence obtained from pinnipeds infested by echinophthiriids, specifically from seals, indicates that flippers are the preferred infestation sites, while lice from fur seals select areas in the pelage. We studied habitat selection of Antarctophthirus microchir on South American sea lion pups (Otaria flavescens Shaw, 1800) from Patagonia, Argentina, during the austral summer of 2009. We found a clear pattern of habitat selection: eggs are laid on the dorsal surface; nymphs 1 hatch there and then migrate to the belly, where they develop into adults and copulate; and then ovigerous females return to the dorsal surface. On the one hand, nymphs 1 are characterised by their low locomotory ability; therefore, the fact that they migrate as soon as they hatch suggests a clear pressure leading to microhabitat restriction. On the other hand, the described pattern of microhabitat selection seems to respond to the physiological requirements of each stage, which vary according to the physiological process considered, e.g. oviposition, morphogenesis, hatching and development. Accordingly, it appears that A. microchir would prefer the host's ventral area for development and copulation and the dorsal area for oviposition. However, the causes of this pattern are not clear, and many factors could be involved. Considering that sea lion pups periodically soak at high tides, and that prolonged immersion and very high humidity are known to be lethal for lice eggs, selecting the dorsal area would be advantageous for oviposition because it dries much faster. Furthermore, because humidity should be retained for longer periods on the ventral surface of the pup, wetter conditions on the sea lion would prevent desiccation of the nymphs in the very arid environment where O. flavescens breeds.

Host correlates of diversification in avian lice

“…A similar phenomenon is also known in, for example, parasite fauna of pinnipeds; seals seem to host a reduced subset of the parasites characteristic to terrestrial carnivores (Aznar et al, 2001). Within their unsaturated parasite communities, seals also harbour lice that are active only during the hosts' short terrestrial phase of life (Leonardi et al, 2012).…”

Uncovering deep mysteries: The underwater life of an amphibious louse

“…Murray and co-workers arrived at a similar conclusion (Murray and Nicholls, 1965; and by Kim (1975) regarding lice on northern fur seals from the absence of N1 in old pups and adult pinnipeds. The incapacity of N1 to survive underwater was suggested to be associated with the absence of abdominal scales (Kim, 1975;Aznar et al, 2009;Leonardi et al, 2012b), which are present over the body of the other instars.…”

“…Conversely, sea lions, phocids, and walruses rely on a blubber layer for insulation and present a wettable pelage (Mostman Liwanag, 2008). As a consequence, echinophthiriids infesting sea lions, phocids and walruses are exposed to real aquatic conditions, and this would result in further morphological, and presumably physiological, adaptations for surviving when the host submerges (Hinton, 1976a;Murray, 1976;Mehlhorn et al, 2002;Leonardi et al, 2012b).…”

“…However, Murray (1976) argued that the scales could not be related to aqua- tic respiration because they have no connection with the tracheal system, i.e. spiracles are free from scales (see Leonardi et al, 2012b). This author suggests then that lice take oxygen directly from water by cutaneous exchange, proposing that scales would provide mechanical protection (Murray, 1976).…”

“…This author suggests then that lice take oxygen directly from water by cutaneous exchange, proposing that scales would provide mechanical protection (Murray, 1976). In A. microchir, scales cover the whole abdomen and are disposed in an imbricated pattern (Leonardi et al, 2012b), an arrangement that could allow the retention of an air film. However, in this species, scales are not particularly disposed around the spiracles (Fig.…”