Living between two worlds: ecological, morphological and physiological adaptations of amphibious licecal

M.S. LEONARDI; E.A. CRESPO; M. FERNÁNDEZ; J.A. RAGA; F.J. AZNAR

Ürgüp

Conferencia; International Conference on Phthiraptera- ICP4; 2010

International Society of Phthirapterists

Among sucking lice, species of the family Echinopthiriidae are peculiar in that they infect hosts with a marine life style, i.e. pinnipeds. This ecological feature imposes important physiological, ecological and behavioral adaptations, particularly for species infecting seals and sea lions, the pelage of which is wet when the animal is submerged. In these cases, lice must be able to breathe underwater and are forced to reproduce only when hosts are on land because the eggs of sucking lice can develop only under aerial conditions. In this talk we will illustrate the adaptive versatility of echinophthriids taking Antarctophthirus microchir on South American sea lions, Otaria flavescens, from Patagonia as a model. All instars of A. microchir except the first present modified scale-shaped setae which are unique among non-echinophthiriid anoplurans. Scales have been proposed to have a respiratory function during immersions, but their precise performance is still discussed. In addition, scales are absent in some echinophthiriid species from seals that must also breathe underwater. Vertical cow-pup transmission is essential for the life cycle of A. microchir because pups are the only age group that stays continuously on land enough time for successful lice reproduction to occur. Indeed, A. microchir has a window of time of just 1 month to reproduce because, afterwards, pups go to sea and start moulting. Therefore, A. microchir, and, by extension, echinophthiriid infecting seals and sea lions with limited periods ashore, might confront a trade-off between generation time and fecundity. Apparently, A. microchir is able to accommodate 2 new generations in one month; a third could be risky, and perhaps the missing of this generation is compensated by the production of larger, more fecund, females. At high latitudes, many species of the Echinopthiriidae face the problem of low temperature, a critical factor for egg development and survival in sucking lice. Other species of Antarctophthirus, e.g. A. ogmorhini and A. callorhini, select body areas with bare skin (fundamental for host termoregulation at high latitudes) to feed and reproduce. However, in the Patagonian summer, A. microchir faces up strong thermal stress by high temperature. Accordingly, instars are mainly found on ventral body areas of the pup. However, gravid females tend to occur also on the dorsal part, and eggs are by far more common on this site. It is possible that, within a tight reproductive schedule of A. microchir, females select microhabitats where high solar radiation and high temperature accelerate egg development.