I've got you under my skin: inflammatory response to elephant seal's lice

Abstract

Seals (Phocidae) undergo an annual cycle of moulting that implies hair regeneration, and in the case of southern elephant seals, it also involves the superficial strata of the epidermis. Therefore, surviving the moulting period is crucial for their obligate and permanent ectoparasites. Throughout evolutionary time, sucking lice (Echinophtiriidae) have developed morphological, behavioural and ecological adaptations to cope with the amphibious lifestyle of their hosts. Lepidophthirus macrorhini, the Southern elephant seal louse species, faces the additional challenge of surviving attached to the host during the moulting period. Since lice live on the skin, L. macrorhini has developed a unique survival strategy by piercing the skin of their host, thus keeping them protected from moulting. During fieldwork in Patagonia and Antarctica, skin samples with lice within were collected for histological analysis to assess whether these parasites caused damage to the host. Lice generate an inflammatory process in the host's dermis, and these lesions could alter the normal chemical and mechanical protective properties of the skin facilitating secondary infections. Further studies that analyse the potential pathogens in those skin lesions are necessary to properly assess the real impact of ectoparasites on their host health.

How Did Seal Lice Turn into the Only Truly Marine Insects?

“…Probably, these legs play a sensory role in insects where, according to the literature, eyes are absent [4,19,20]. However, the first pair of legs of L. macrorhini is robust, and the tarsal claws are modified into well-developed hooks [21]. It has been suggested that this species utilizes its claws to perforate the skin and dig into the host epidermis, in order to stay attached during elephant seal molting [21].…”

“…However, the first pair of legs of L. macrorhini is robust, and the tarsal claws are modified into well-developed hooks [21]. It has been suggested that this species utilizes its claws to perforate the skin and dig into the host epidermis, in order to stay attached during elephant seal molting [21]. Regarding the absence of eyes, a series of studies in different species is required to determine the presence of specific structures or pigments capable of detecting light.…”

“…The incapacity of N1 to survive underwater was suggested to be associated with the absence of abdominal scales [20,22,27], which are abundantly present in the tolerant instars. When seal lice emerge in seawater, they experience a reduction in oxygen availability, and a rapid and large drop in temperature (20)(21)(22)(23)(24)(25) °C difference between air and water in summer), as well as an increase in hydrostatic pressure. It has been reported that contact with seawater triggers reflex immobility (akinesis) in A. microchir and in L. macrorhini, which is immediate (in seconds) in the former and requires several minutes in the latter [23,30].…”

High prevalence and low intensity of Echinophthirius horridus infection in seals revealed by high effort sampling

“…The seal louse coevolved with terrestrial ancestors of seals from land into the marine environment millions of years ago 9 , 17 – 19 , hence the seal louse plays an important role as potential vector for a variety of infectious pathogens such as viruses and bacteria 20 , 21 and heartworms ( Acanthocheilonema spirocauda ) 11 , 22 – 24 . Because prevalence and intensity of ectoparasite infection are important biological indicators for predicting host health and inferring evolution 11 , 25 , 26 , precise information on seal louse infection parameters in vulnerable aquatic wildlife are crucial and of parasitological and veterinary relevance 24 , 27 .The seal louse developed biomechanical and physical adaptations for attachment and respiration in the marine environment 15 , 28 , 29 to sustain high pressure, drag forces, and hypoxemia 30 . The sampling of live lice is relevant for experiments on respiration, to investigate feeding and attachment adaptations 29 and reproductive processes in vitro.…”