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

LEONARDI, MARÍA SOLEDAD; CRESPO, JOSÉ E.; SOTO, FLORENCIA ANABELLA; LAZZARI, CLAUDIO R.

Insects

Nickolas G. Kavallieratos

Año: 2021 vol. 13

Insects are the most evolutionarily and ecologically successful group of living animals,being present in almost all possible mainland habitats; however, they are virtually absent in theocean, which constitutes more than 99% of the Earth?s biosphere. Only a few insect species canbe found in the sea but they remain at the surface, in salt marshes, estuaries, or shallow waters.Remarkably, a group of 13 species manages to endure long immersion periods in the open sea, aswell as deep dives, i.e., seal lice. Sucking lice (Phthiraptera: Anoplura) are ectoparasites of mammals,living while attached to the hosts? skin, into their fur, or among their hairs. Among them, the familyEchinophthiriidae is peculiar because it infests amphibious hosts, such as pinnipeds and otters, whomake deep dives and spend from weeks to months in the open sea. During the evolutionary transitionof pinnipeds from land to the ocean, echinophthiriid lice had to manage the gradual change to anamphibian lifestyle along with their hosts, some of which may spend more than 80% of the timesubmerged and performing extreme dives, some beyond 2000 m under the surface. These obligateand permanent ectoparasites have adapted to cope with hypoxia, high salinity, low temperature, and,in particular, conditions of huge hydrostatic pressures. We will discuss some of these adaptationsallowing seal lice to cope with their hosts? amphibious habits and how they can help us understandwhy insects are so rare in the ocean