Effect of host age, sex and life stage on the prevalence and abundance of sucking lice on Weddell seal in the Antarctic Peninsula

Abstract

Through evolutionary time, seal lice have developed morphological, behavioral, and ecological adaptations to cope with the amphibious lifestyle of their hosts in a coevolutionary process. Consequently, the dynamics of lice populations are determined by seals behavior. We aim to study the effects of host sex, age class, year, and sampling location, on the prevalence and mean abundance of Antarctophthirus carlinii, on Weddell seals (WS) Leptonychotes wedelli. The study was conducted at two sites in the Antarctic Peninsula, namely, Marambio/Seymour Island (MI) and the Danco Coast (DC).We collected lice from 71 WS: 33 from MI, during the reproductive season, and 38 from DC, during the molting season, between 2014 and 2017. According to our analyses, host age class and sex were the variables that affected prevalence levels of lice on WS. Whereas, age class, year, site, and sex affected lice mean abundance. Juveniles presented higher prevalence and mean abundance than adults, possibly acting as reservoirs for lice as they move through different colonies until they reach reproductive age. Concurrently, seals during molting season were more infested. Unlike nursing, during the molting season seals spend much time ashore forming mixed groups that favor both egg development and lice transmission.

Tell me who you go with and I will tell you what you do: Antarctic seal lice behave differently

“…Our main conclusion is that A. lobodontis, from crabeater seals, and A. carlinii, from Weddell seals have different reproductive strategies. Although we did not have information on the reproductive season of crabeater seals, our results con rm that A. lobodontis would reproduce at least during the molting season of the seals, whereas the reproduction of A. carlinii would occur mainly during the reproductive season of seals (Soto et al 2022). As we will discuss, these differences may be related to their host's habitat use and foraging behavior.…”

“…However, as WS dives deeper and longer than CS (91 m for 11.5 min; (Costa et al 2010)), lice would have less time to reproduce or at least to successfully hatch eggs. As we described in a previous study (Soto et al 2022), the main way of transmission of A. carlinii should be from female seals to their pups. We also observed that adult A. carlinii were more likely to be transmitted than nymphs and females more likely than males, the same pattern described for A. microchir from sea lions [6].…”

“…When comparing age classes, juveniles of both species had higher prevalence and abundance than adults. From previous studies, we know that these parameters depend mainly on the age class of the hosts (Soto et al 2020(Soto et al , 2022, with juveniles being more abundant than adults. This pattern may also be related to the diving behavior of the host.…”

“…1) which includes eggs, nymphs (three instars) and adults (female or male) (Murray and Nicholls 1965;Kim 1971). Vertical transmission, from female seals to their pups, appears to be the main way of transmission in seal lice ; Leonardi et al 2013;Soto et al 2022).…”