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"Sea Lions"
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Meet the sea lion
\"Playful sea lions are among the most popular and entertaining zoo animals. This book introduces kids to these fascinating marine mammals and explores their watery lives.\"--Publisher web site.
Book
Mass mortality event in South American sea lions (Otaria flavescens) correlated to highly pathogenic avian influenza (HPAI) H5N1 outbreak in Chile
In Chile, since January 2023, a sudden and pronounced increase in strandings and mortality has been observed among South American (SA) sea lions (Otaria flavescens), prompting significant concern. Simultaneously, an outbreak of highly pathogenic avian influenza H5N1 (HPAIV H5N1) in avian species has emerged since December 2022. To investigate the cause of this unexpected mortality, we conducted a comprehensive epidemiological and pathologic study. One hundred sixty-nine SA sea lions were sampled to ascertain their HPAIV H5N1 status, and long-term stranding trends from 2009 to 2023 were analyzed. In addition, two animals were necropsied. Remarkably, a significant surge in SA sea lion strandings was observed initiating in January 2023 and peaking in June 2023, with a count of 4,545 stranded and deceased animals. Notably, this surge in mortality correlates geographically with HPAIV outbreaks affecting wild birds. Among 168 sampled SA sea lions, 34 (20%) tested positive for Influenza A virus, and 21 confirmed for HPAIV H5N1 2.3.4.4b clade in tracheal/rectal swab pools. Clinical and pathological evaluations of the two necropsied stranded sea lions revealed prevalent neurological and respiratory signs, including disorientation, tremors, ataxia, and paralysis, as well as acute dyspnea, tachypnea, profuse nasal secretion, and abdominal breathing. The lesions identified in necropsied animals aligned with observed clinical signs. Detection of the virus via immunohistochemistry (IHC) and real-time PCR in the brain and lungs affirmed the findings. The findings provide evidence between the mass mortality occurrences in SA sea lions and HPAIV, strongly indicating a causal relationship. Further studies are needed to better understand the pathogenesis and transmission.
Journal Article
Divergent allele advantage at MHC-DRB through direct and maternal genotypic effects and its consequences for allele pool composition and mating
It is still debated whether main individual fitness differences in natural populations can be attributed to genome-wide effects or to particular loci of outstanding functional importance such as the major histocompatibility complex (MHC). In a long-term monitoring project on Galápagos sea lions (Zalophus wollebaeki), we collected comprehensive fitness and mating data for a total of 506 individuals. Controlling for genome-wide inbreeding, we find strong associations between the MHC locus and nearly all fitness traits. The effect was mainly attributable to MHC sequence divergence and could be decomposed into contributions of own and maternal genotypes. In consequence, the population seems to have evolved a pool of highly divergent alleles conveying near-optimal MHC divergence even by random mating. Our results demonstrate that a single locus can significantly contribute to fitness in the wild and provide conclusive evidence for the ‘divergent allele advantage’ hypothesis, a special form of balancing selection with interesting evolutionary implications.
Journal Article
Marine mammals harbor unique microbiotas shaped by and yet distinct from the sea
Marine mammals play crucial ecological roles in the oceans, but little is known about their microbiotas. Here we study the bacterial communities in 337 samples from 5 body sites in 48 healthy dolphins and 18 healthy sea lions, as well as those of adjacent seawater and other hosts. The bacterial taxonomic compositions are distinct from those of other mammals, dietary fish and seawater, are highly diverse and vary according to body site and host species. Dolphins harbour 30 bacterial phyla, with 25 of them in the mouth, several abundant but poorly characterized Tenericutes species in gastric fluid and a surprisingly paucity of Bacteroidetes in distal gut. About 70% of near-full length bacterial 16S ribosomal RNA sequences from dolphins are unique. Host habitat, diet and phylogeny all contribute to variation in marine mammal distal gut microbiota composition. Our findings help elucidate the factors structuring marine mammal microbiotas and may enhance monitoring of marine mammal health.
Little is known about the microbiota of marine mammals, despite the crucial ecological roles played by these animals. Here, Bik
et al
. describe the bacterial communities associated with various body sites in dolphins and sea lions, as well as the microbiota of their dietary fish and adjacent seawater.
Journal Article
Dokdo sea lion Zalophus japonicus genome reveals its evolutionary trajectory before extinction
Background
The Dokdo sea lion (
Zalophus japonicus
), commonly referred to as Gangchi in Korea and the Japanese sea lion internationally, was endemic to the Northwest Pacific before its extinction in the 1950s. However, its origins, speciation, and genetic diversity remain poorly understood.
Results
To address this, we sequenced DNA from 16
Z. japonicus
bone fragments, obtained from Dokdo and Ulleungdo islands in Korea. Our genome-wide SNP analyses reveal
Z. japonicus
as the earliest diverged species within its genus, redefining its evolutionary relationship with the California (
Z. californianus
) and Galapagos (
Z. wollebaeki
) sea lions. Our research further elucidates the phylogeny of
Z. japonicus
, shedding light on the complexity of the genetic isolation process within its genus that was prompted by the geographic isolation of the three populations of
Zalophus
ancestral stock. Conversely, the genetic signature of the Dokdo sea lion genome can be modeled as an evolutionary pathway involving gene flow from Otariidae species with shared range. In addition, we discovered that the population decline of
Z. japonicus
started already over 100,000 years ago; however,
Z. japonicus
genome maintained a relatively high heterozygosity despite nearing extinction.
Conclusions
Our genome-scale analysis sheds light on the phylogeny of
Z. japonicus
, the evolutionary pathways underlying its speciation, and its genetic diversity before extinction. Broadly, we elucidate
Zalophus
gene flow complexity and genetic diversities among extant species. Furthermore, this study offers retrospective genomic insights into the extinction process of a carnivorous marine mammal, information that could aid conservation efforts for extant Otariidae species.
Journal Article
The sea lion
\"When a baby sea lion's mother leaves him at the lighthouse, the lighthouse family enjoys caring for him until she returns\"-- Provided by publisher.
Book
Do as I do imitation in a steller sea lion Eumetopias jubatus
The present study explored whether a well-socialized Steller sea lion named Hama could reproduce similar actions with human demonstrations using the “Do as I do” (DAID) paradigm. Hama had learned 50 types of behaviors, but her social learning ability was unknown. In Study 1, we trained Hama to produce simultaneous DAID responses. After introducing the DAID training, we conducted four tests to confirm Hama’s acquisition of demonstrator-matching behavior. We found that Hama successfully acquired the action-matching ability for human actions, not only with three trained actions but also with six out of seven untrained actions (see Test 1 and Test 2). Moreover, Hama’s DAID performance was stable regardless of the familiarity of human demonstrators (see Test 1 and Test 2). Hama successfully performed two completely novel body actions that were not included in her prior learning repertoire, but failed to replicate actions involving object manipulation (see Test 3). She showed no response in control trials without demonstrations, providing partial evidence for negative control (see Test 4). In Study 2, we introduced Hama to performing non-simultaneous DAID responses, which involved suppressing immediate simultaneous actions following the demonstrator and then reproducing the actions upon the verbal cue “Go.” She accurately performed the DAID response even when she delayed her response until the demonstrator’s demonstration was completed (Test 5). Importantly, she reproduced the action accurately when visual contact between the demonstrator and herself was blocked after the demonstration, eliminating the Clever Hans effect as a potential influence on her simultaneous DAID response (Test 6). However, she could not reproduce small or untrained actions (Test 7). These results suggest that Hama may be able to accurately map human action sequences in body-oriented actions to some extent. This study provides the first evidence of motor imitation ability in captive pinnipeds.
Journal Article