Abstract Through evolutionary time, seal lice have developed morphological, behavioral, and ecological adaptations to cope with the amphibious lifestyle of their hosts in a co-evolutionary 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.

RESUMEN La foca leopardo (Hydrurga leptonyx) es una especie poco estudiada a nivel genético. Con el fin de realizar la primera evaluación de la diversidad genética de esta especie en la costa de Danco (Península Antártica), se secuenció 423 pb de la Región Control del ADN mitocondrial (ADNmt-CR) de 13 muestras de sangre colectadas en la Base Primavera (62º15’S, 58º39’W) durante el verano austral 2011-2012. Los resultados mostraron una alta diversidad de haplotipos (h = 0.99), con varios haplotipos divergentes. Nuestros hallazgos genéticos sugieren que las focas leopardo de la costa de Danco podrían representar diferentes filogrupos; sin embargo, es necesario incluir más marcadores genéticos para confirmar esta hipótesis.

ABSTRACT The leopard seal (Hydrurga leptonyx) is a genetically low-studied species. In order to conduct the first genetic diversity assessment of this species in Danco Coast (Antarctic Peninsula), 423 bp of the mitochondrial DNA Control Region (mtDNA-CR) was sequenced from 13 blood samples collected in Primavera Base (62º15’S, 58º39’W) during the 2011-2012 austral summer. Our results showed high haplotype diversity (h = 0.99), with various divergent haplotypes. Our findings suggest that leopard seals in the Danco Coast could represent different phylogroups; however, including more genetic markers are needed to confirm this hypothesis.

ABSTRACT We studied the diet of non-breeding male Antarctic fur Seals Arctocephalus gazella (Peters, 1875) at two different localities of the South Shetland Islands: Stranger Point, King George Island/Isla 25 de Mayo and Duthoit Point, Nelson Island, by the analysis of 65 faecal samples collected in February 2012. Overall, Antarctic krill Euphausia superba (Dana, 1850) and fish were the main prey taxa followed by penguins and cephalopods. Myctophids were dominant among fish; Gymnoscopelus nicholsi (Gilbert, 1911) was the most important prey species at both sampling sites, followed by Electrona antarctica (Gunther, 1878) at Stranger Point and by the nototheniid Pleuragramma antarctica (Boulenger, 1902) at Duthoit Point. The relative similarity found in the dietary composition of fur seals from both locations suggest they might have been sharing common feeding areas. Our results were compared with those reported in the literature for different localities of the South Shetland Islands and the Scotia Sea region. The absence of formerly harvested demersal notothenioid species in the diet of fur seals may reflect the negative impact that commercial fisheries had on some fish populations and supports the importance of implementing long-term monitoring studies on the feeding habits of A. gazella in the area.

RESUMEN Se estudió la dieta de ejemplares macho no reproductivos de lobo fino antártico, Arctocephalus gazella (Peters, 1875) en dos localidades de las Islas Shetland del Sur: Cabo Funes/Punta Stranger, Isla 25 de Mayo / Isla Rey Jorge y Punta Duthoit, Isla Nelson; por medio del análisis de 65 muestras de materia fecal colectadas en Febrero de 2012. En general, el krill antártico Euphausia superba (Dana, 1850) y los peces fueron los taxa presa más consumidos, seguidos por pingüinos y cefalópodos. Entre los peces, los mictófidos fueron dominantes; Gymnoscopelus nicholsi (Gilbert, 1911) fue la especie más importante en ambos apostaderos, seguido por Electrona antarctica (Gunther, 1878) en Punta Stranger y por el nototénido Pleuragramma antarctica (Boulenger, 1902) en Punta Duthoit. La similitud hallada en la composición dietaria de los agrupamientos de lobo estudiados sugiere áreas de alimentación en común. Nuestros resultados fueron comparados con aquellos reportados en la literatura para diferentes localidades de las Islas Shetland del Sur y la región del Mar de Scotia. La ausencia de especies de nototenoideos demersales históricamente diezmadas en la dieta del lobo fino podría estar reflejando el impacto negativo que las pesquerías comerciales han tenido sobre algunas poblaciones de peces y enfatizar la necesidad de realizar un monitoreo a largo plazo de los hábitos alimentarios de A. gazella en el archipiélago de las Islas Shetland del Sur.

The aim of the present study was to enhance the knowledge of the feeding habits of the juvenile component of the population of Southern elephant seals [Mirounga leonina (Linnaeus, 1758)] from Isla 25 de Mayo, South Shetland Islands, age class whose diet information is scarce. A total of 60 individuals were stomach lavaged in the spring - summer seasons of three consecutive years (2003, 2004 and 2005) of which 53.3 % (n = 32) presented food remnants. The Antarctic glacial squid Psychroteuthis glacialis Thiele, 1921 was the dominant prey taxon in terms of frequency of occurrence (68.7%), numerical abundance (60.1%) and biomass (51.5%), contributing 84.1% to the total relative importance index. Other squid prey species of importance were Slosarczykovia circumantartica Lipinski, 2001 in terms of occurrence (37.5%) and numerical abundance (14%) and Moroteuthis knipovitchi Filippova, 1972 in terms of biomass (16%). All identified cephalopod prey taxa are distributed south of the Antarctic Polar Front, except for the squid Martialia hyadesi Rochebrune & Mabille, 1889 which has a circumpolar distribution associated to the Polar Frontal Zone. No significant differences in the sizes of P. glacialis preyed upon by elephant seals were found between sexes and years. However, significant interannual differences were found in the taxonomical composition of their diet. This would be associated with temporal changes in food availability at the foraging areas of seals, which in turn may have been influenced by changes in oceanographic conditions as a result of the El Niño Southern Oscillation (ENSO) phenomenon that occurred during part of the study period. Furthermore, a differential response of males and females to this temporal variation was observed, with the former being also associated to a predation on octopods. This would suggest a sexual segregation in foraging habits of this species from the early stages of its life cycle.

El objetivo del presente estudio fue el de incrementar el conocimiento de los hábitos alimentarios del componente juvenil de la población de elefantes marinos del sur [Mirounga leonina (Linnaeus, 1758)] de Isla 25 de Mayo, Islas Shetland del Sur, clase de edad cuya dieta es poco conocida . Un total de 60 ejemplares fueron sometidos a técnicas de lavaje estomacal durante primavera - verano de tres años consecutivos (2003, 2004 y 2005) de los cuales el 53,3 % (n = 32) presentaba restos alimentarios. El calamar antártico Psychroteuthis glacialis Thiele, 1921 fue el taxón presa dominante en términos de frecuencia de ocurrencia (68,7%), abundancia numérica (60,1%) y biomasa (51,5%), contribuyendo en un 84,1% al índice de importancia relativa total. Otros calamares presa de importancia fueron Slosarczykovia circumantartica Lipinski, 2001, en términos de ocurrencia (37,5%) y de abundancia numérica (14%), y Moroteuthis knipovitchi Filippova, 1972 en términos de biomasa (16%). Todos los taxa presa identificados se distribuyen al sur del Frente Polar Antártico, a excepción de Martialia hyadesi Rochebrune & Mabille, 1889, especie que presenta una distribución subantártica asociada a la Zona del Frente Polar. No hubo diferencias significativas intergenéricas ni interanuales en los tamaños de P. glacialis predados por los elefantes marinos. Sin embargo, se encontraron diferencias interanuales significativas en la composición taxonómica de la dieta. Esto estaría asociado a los cambios temporales en la disponibilidad de alimento en las áreas de forrajeo de los elefantes, que a su vez pudieron estar influenciados por las variaciones en las condiciones oceanográficas, como resultado de la Oscilación Austral del Niño (ENSO) que se produjo durante parte del período de estudio. Por otra parte, se observó cierta respuesta diferencial de machos y hembras a esta variación temporal, estando los primeros asociados a una predación sobre octópodos. Esto sugiere una segregación sexual en los hábitos de forrajeo de esta especie desde etapas tempranas de su ciclo de vida.