RESUMO
Despite the incredible success of insects in colonizing almost every habitat, they remain virtually absent in one major environment--the open sea. A variety of hypotheses have been raised to explain why just a few insect species are present in the ocean, but none of them appears to be fully explanatory. Lice belonging to the family Echinophthiriidae are ectoparasites on different species of pinnipeds and river otters, i.e. they have amphibious hosts, who regularly perform long excursions into the open sea reaching depths of hundreds of meters (thousands of feets). Consequently, lice must be able to support not only changes in their surrounding media, but also extreme variations in hydrostatic pressure as well as breathing in a low oxygen atmosphere. In order to shed some light on the way lice can survive during the diving excursions of their hosts, we have performed a series of experiments to test the survival capability of different instars of Antarctophthirus microchir (Phthiraptera: Anoplura) from South American sea lions Otaria flavescens, when submerged into seawater. These experiments were aimed at analyzing: (a) immersion tolerance along the louse life; (b) lice's ability to obtain oxygen from seawater; (c) physiological responses and mechanisms involved in survival underwater. Our experiments showed that the forms present in non-diving pups--i.e. eggs and first-instar nymphs--were unable to tolerate immersion in water, while following instars and adults, all usually found in diving hosts, supported it very well. Furthermore, as long as the level of oxygen dissolved in water was higher, the lice survival capability underwater increased, and the recovery period after returning to air declined. These results are discussed in relation to host ecology, host exploitation and lice functional morphology.
Assuntos
Anoplura/fisiologia , Leões-Marinhos/parasitologia , Animais , Anoplura/crescimento & desenvolvimento , Argentina , Mergulho , Ecossistema , Feminino , Masculino , Ninfa/fisiologia , Óvulo/fisiologia , Oxigênio/análise , Água do Mar/análise , TemperaturaRESUMO
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.
Assuntos
Anoplura/fisiologia , Comportamento Animal/fisiologia , Ecossistema , Leões-Marinhos/parasitologia , Animais , Anoplura/crescimento & desenvolvimento , Argentina , Copulação , Mergulho , Feminino , Estágios do Ciclo de Vida , Locomoção , Masculino , Ninfa , Oviposição , Leões-Marinhos/crescimento & desenvolvimento , Água do MarRESUMO
Two species of Phthiraptera, Bovicola caprae (Ischnocera: Bovicolidae) and Solenopotes binipilosus (Anoplura: Linognathidae), and one species of mite, Psoroptes ovis (Acari: Psoroptidae), were recorded on huemul (Hippocamelus bisulcus) in Chile. The sucking louse S. binipilosus and the mite P. ovis are reported for the first time from this host.