Domoic acid-producing algal blooms are increasing in size, frequency, and duration along the eastern Pacific coastline resulting in regular and repeated exposure of marine mammals to the toxin. Because of their prolonged gestation, large numbers of marine mammals are now encountering this excitotoxin in utero, with potential long-term developmental effects. Evidence of developmental neurotoxic effects is accumulating in California sea lions particularly, which serve as an accessible sentinel species for studying the effects of domoic acid exposure in mammals. In biomedical settings, rodent models have revealed some developmental aspects of early domoic acid exposure, including a tendency for gross neurobehavioral changes to emerge after puberty. However, rodents are altricial and have a truncated developmental course. In contrast, marine mammals are precocial and mature slowly. Further, neurobehavioral responses to domoic acid have notable differences between those in adult rodents exposed in vivariums and in free-ranging wildlife. Primate models address some of these gaps, but are limited by practical constraints. There is a clear need to establish an ecologically valid model of brain development and clinical progression of developmental domoic acid exposure in long-lived and precocial mammals. Here we present California sea lions born in wildlife rehabilitation facilities to mothers with documented domoic acid toxicosis as a promising and accessible disease model, and we provide a framework for future research. Hundreds of adult sea lions in rehabilitation centers have already taken part in veterinary assessments and experimental assays of brain and behavior, demonstrating the plausibility of careful and scalable science with these animals. We discuss preliminary work with a juvenile sea lion enrolled in a longitudinal study with repeated clinical, behavioral, and neurobiological assessment, and advocate for cohort-based studies of maternally exposed sea lions.
Background/Objectives: Human-driven environmental change can promote cancer development in wild species, yet the pathophysiology of wildlife cancers remain largely unexplored. Urogenital carcinoma (UGC) in the California sea lion (CSL) (Zalophus californianus) is one of the most common cancer types documented in any wild mammal. The pathogenesis of UGC in CSLs is known to be multifactorial, with links to environmental contaminant exposure and infection by Otarine Herpesvirus-1 (OtHV-1); however, the genomic features of these cancers have not been thoroughly explored. Understanding UGC pathogenesis in the CSL has important implications for the health of humans and other species that share environment and diet. Methods: We leveraged the evolutionary conservation between the domestic dog and CSL genomes to perform cross-species whole-exome sequencing (WES) of CSL UGC tumors and matched normal tissue pairs. We also used PCR and Sanger sequencing to investigate the prevalence of DNA from OtHV-1. Results: Bioinformatic analyses identified shared somatic variants and DNA copy number aberrations in UGC tumor samples, including recurrent exonic single-nucleotide variants in CD274/PD-L1, and recurrent copy number gains in CD274/PD-L1, TNFRSF14, CD200, CDK4, and PLCG2. In an extended cohort of 70 CSLs (tumor, matched normals, and controls), a recurrent C > T single-nucleotide variant in exon 4 of CD274/PD-L1 was identified in 54 of 68 (79.4%) CSLs with diagnosed UGC. OtHV-1 DNA was detected in 67 of 70 individuals (95.8%). Conclusions: These results demonstrate that cross-species exome capture provides a means to identify genomic alterations that may play a role in the molecular pathogenesis of UGC in the CSL and adds to the body of evidence for an association between OtHV-1 and UGC in this species.
Per- and polyfluoroalkyl substances (PFAS) are a class of man-made persistent chemicals that have been detected in both terrestrial and aquatic environments and thus impact humans, household pets, agricultural species, and wildlife. PFAS exposure is linked to a variety of adverse health consequences, including cancer and immune disruption. This study investigates differences in PFAS exposure between California (CSL, n = 69) and Galapagos (GSL, n = 65) sea lion pups and juveniles across various sampling locations within each species' habitat range. Whereas the GSL were all considered healthy, 17 of the 69 CSL were classified as malnourished. Comparing the two species, significantly higher serum concentrations of summed PFAS, perfluorooctanesulfonic acid (PFOS), perfluorononanoic acid (PFNA), and perfluorodecanoic acid (PFDA) were detected in CSL than in GSL. This elevated PFAS exposure in CSL is likely related to historic pollution in their environment and close proximity to the urbanized coastline of Southern California. Within species, malnourished CSL had significantly higher PFNA than healthy CSL pups. GSL pups also tended to have higher PFAS levels than GSL juveniles. Within the Galapagos archipelago, PFAS exposure differed between rookeries, with PFOS exceeding its method reporting limit (0.5 ng/mL) in every sample, including GSL from islands uninhabited by humans. Summed PFAS, PFNA, PFDA, and perfluoroundecanoic acid (PFUnA) were all significantly higher in sea lions sampled on uninhabited than inhabited islands in the Galapagos archipelago. This study is the first comprehensive report of PFAS in CSL and the first archipelago-wide assessment of PFAS in GSL.
Natural infections of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been documented in over 60 animal species, some distantly related. Several marine mammals have been predicted as highly susceptible to SARS-CoV-2 infection based on the homology of their ACE2 receptors to those of humans. To assess potential exposure of marine mammals to SARS-CoV-2, we conducted an opportunistic survey from 2020 to 2025 and tested 1,808 swabs and 378 serum samples from 21 marine mammal species in the United States. All the swabs tested by RT-qPCR were negative, indicating the absence of active infection. A low level of SARS-CoV-2 neutralizing antibodies was detected in three pinniped species, including Phoca vitulina (harbor seal, 13.6%, 95% CI: 5.2-27.4%), Zalophus californianus (California sea lion, 7%, 95% CI: 1.9-17.0%), and Halichoerus grypus (grey seal, 3.7%, 95% CI: 0.5-12.7%). These findings represent the first serological evidence of SARS-CoV-2 exposure in marine mammals in the United States, highlighting the need for continued monitoring of these populations and further research on SARS-CoV-2 transmission dynamics in wildlife.
Free-ranging otariids are routinely captured for data and sample collection. To achieve this, anesthesia may be used to facilitate handling, decrease stress, and improve human and animal safety. Injectable anesthetics are widely used for such endeavors; however, certain disadvantages to this approach warrant further exploration of alternative anesthetic techniques. Inhalant anesthesia, commonly utilized for otariids in a clinical setting, is used more sparingly in the field, with few studies assessing safety and efficacy in free-ranging otariids. During 2016-2020, 175 Guadalupe fur seals were net-captured and anesthetized with isoflurane and oxygen on Guadalupe Island, Mexico, for satellite telemetry attachment and biological sampling. To contribute to the body of knowledge surrounding the use of inhalants in the field, physiologic and anesthetic parameters (time to induction, total oxygen use, heart rate, respiratory rate, time to recovery, and anesthetic depth) were assessed for effects of biometric and logistical factors (pursuit and holding time, sex, age class, body weight, year, oxygen flow rate, and total anesthesia time). This anesthetic technique provided rapid induction and recovery times and rare side effects in Guadalupe fur seals, serving as a practical means of field immobilization for minimally invasive procedures in this imperiled species.
