Unraveling the gut microbiota of Mexican pinnipeds: the dominance of life histories over phylogeny.

Studying how phylogeny influences the composition and functions of microbiotas within animal hosts is essential for gaining insights into the connection between genetics, ecology, and health in the animal kingdom. However, due to limited comprehensive studies, this influence remains unclear for many wild mammals, including Mexican pinnipeds. We employed 16S rRNA gene deep-sequencing to investigate the impact of phylogeny on the gut microbiota of four pinniped species inhabiting Mexican shores: the Pacific harbor seal (Phoca vitulina richardii), the northern elephant seal (Mirounga angustirostris), the California sea lion (Zalophus californianus), and the Guadalupe fur seal (Arctocephalus philippii townsendi). Our results indicated that factors such as diets and shared life histories exerted more influence on microbiota composition than phylogeny alone. Notably, otariid species sharing similar life histories displayed greater microbiota similarity than phocids, which have distinct life histories and fewer microbiota similarities. Furthermore, harbor seals have more microbial similarities with the two otariid species than with elephant seals. Of particular concern, we observed a higher abundance of potentially pathogenic bacteria (e.g., Photobacterium damselae and Clostridium perfringens) in harbor seals and Guadalupe fur seals compared to other pinnipeds. This finding could pose health threats to these species and nearby human populations.IMPORTANCEPinnipeds in Mexico host microbial communities that remain understudied. While several factors can influence microbiota composition, the role of phylogenetic relationships among these pinnipeds remains unclear due to limited knowledge of the microbiota in certain species. This study aimed to fill this gap by characterizing the composition and function of the gut microbiota in the four pinniped species that occur in Mexico. Our analysis reveals that shared diets and life histories contribute to similarities in the composition of gut microbial communities. This study also highlights the potential differences in the metabolic capabilities and adaptations within the gut microbiota of pinnipeds. Understanding how phylogeny impacts microbial communities enhances our insights into the evolutionary dynamics of marine mammals.

Conservation energetics of beluga whales: using resting and swimming metabolism to understand threats to an endangered population.

The balance between energetic costs and acquisition in free-ranging species is essential for survival, and provides important insights regarding the physiological impact of anthropogenic disturbances on wild animals. For marine mammals such as beluga whales (Delphinapterus leucas), the first step in modeling this bioenergetic balance requires an examination of resting and active metabolic demands. Here, we used open-flow respirometry to measure oxygen consumption during surface rest and submerged swimming by trained beluga whales, and compared these measurements with those of a commonly studied odontocete, the Atlantic bottlenose dolphin (Tursiops truncatus). Both resting metabolic rate (3012±126.0 kJ h-1) and total cost of transport (1.4±0.1 J kg-1 m-1) of beluga whales were consistent with predicted values for moderately sized marine mammals in temperate to cold-water environments, including dolphins measured in the present study. By coupling the rate of oxygen consumption during submerged swimming with locomotor metrics from animal-borne accelerometer tags, we developed predictive relationships for assessing energetic costs from swim speed, stroke rate and partial dynamic acceleration. Combining these energetic data with calculated aerobic dive limits for beluga whales (8.8 min), we found that high-speed responses to disturbance markedly reduce the whale's capacity for prolonged submergence, pushing the cetaceans to costly anaerobic performances that require prolonged recovery periods. Together, these species-specific energetic measurements for beluga whales provide two important metrics, gait-related locomotor costs and aerobic capacity limits, for identifying relative levels of physiological vulnerability to anthropogenic disturbances that have become increasingly pervasive in their Arctic habitats.

Endocrine-Disrupting Chemical Exposure Induces Adverse Effects on the Population Dynamics of the Indo-Pacific Humpback Dolphin.

Cetaceans play a pivotal role in maintaining the ecological equilibrium of ocean ecosystems. However, their populations are under global threat from environmental contaminants. Various high levels of endocrine-disrupting chemicals (EDCs) have been detected in cetaceans from the South China Sea, such as the Indo-Pacific humpback dolphins in the Pearl River Estuary (PRE), suggesting potential health risks, while the impacts of endocrine disruptors on the dolphin population remain unclear. This study aims to synthesize the population dynamics of the humpback dolphins in the PRE and their profiles of EDC contaminants from 2005 to 2019, investigating the potential role of EDCs in the population dynamics of humpback dolphins. Our comprehensive analysis indicates a sustained decline in the PRE humpback dolphin population, posing a significant risk of extinction. Variations in sex hormones induced by EDC exposure could potentially impact birth rates, further contributing to the population decline. Anthropogenic activities consistently emerge as the most significant stressor, ranking highest in importance. Conventional EDCs demonstrate more pronounced impacts on the population compared to emerging compounds. Among the conventional pollutants, DDTs take precedence, followed by zinc and chromium. The most impactful emerging EDCs are identified as alkylphenols. Notably, as the profile of EDCs changes, the significance of conventional pollutants may give way to emerging EDCs, presenting a continued challenge to the viability of the humpback dolphin population.

Metabolic Water As a Route for Water Acquisition in Vertebrates Inhabiting Dehydrating Environments.

Vertebrates have expanded their habitats during evolution, which accompanies diversified routes for water acquisition. Water is acquired by oral intake and subsequent absorption by the intestine in terrestrial and marine animals which are subjected to constant dehydration, whereas most water is gained osmotically across body surfaces in freshwater animals. In addition, a significant amount of water, called metabolic water, is produced within the body by the oxidation of hydrogen in organic substrates. The importance of metabolic water production as a strategy for water acquisition has been well documented in desert animals, but its role has attracted little attention in marine animals which also live in a dehydrating environment. In this article, the author has attempted to reevaluate the role of metabolic water production in body fluid regulation in animals inhabiting desiccating environments. Because of the exceptional ability of their kidney, marine mammals are thought to typically gain water by drinking environmental seawater and excreting excess NaCl in the urine. On the other hand, it is established that marine teleosts drink seawater to enable intestinal water and ion absorption, and the excess NaCl is excreted by branchial ionocytes. In addition to the oral route, we suggest through experiments using eels that water production by lipid metabolism is an additional route for water acquisition when they encounter seawater. It seems that metabolic water production contributes to counteract dehydration before mechanisms for water regulation are reversed from excretion in freshwater to acquisition in seawater.

A chromosome-level genome assembly for the dugong (Dugong dugon).

The dugong (Dugong dugon) is a marine mammal widely distributed throughout the Indo-Pacific and the Red Sea, with a Vulnerable conservation status, and little is known about many of the more peripheral populations, some of which are thought to be close to extinction. We present a de novo high-quality genome assembly for the dugong from an individual belonging to the well-monitored Moreton Bay population in Queensland, Australia. Our assembly uses long-read PacBio HiFi sequencing and Omni-C data following the Vertebrate Genome Project pipeline to reach chromosome-level contiguity (24 chromosome-level scaffolds; 3.16 Gbp) and high completeness (97.9% complete BUSCOs). We observed relatively high genome-wide heterozygosity, which likely reflects historical population abundance before the last interglacial period, approximately 125,000 yr ago. Demographic inference suggests that dugong populations began declining as sea levels fell after the last interglacial period, likely a result of population fragmentation and habitat loss due to the exposure of seagrass meadows. We find no evidence for ongoing recent inbreeding in this individual. However, runs of homozygosity indicate some past inbreeding. Our draft genome assembly will enable range-wide assessments of genetic diversity and adaptation, facilitate effective management of dugong populations, and allow comparative genomics analyses including with other sirenians, the oldest marine mammal lineage.

Comparative genomics provides insights into the aquatic adaptations of mammals.

The ancestors of marine mammals once roamed the land and independently committed to an aquatic lifestyle. These macroevolutionary transitions have intrigued scientists for centuries. Here, we generated high-quality genome assemblies of 17 marine mammals (11 cetaceans and six pinnipeds), including eight assemblies at the chromosome level. Incorporating previously published data, we reconstructed the marine mammal phylogeny and population histories and identified numerous idiosyncratic and convergent genomic variations that possibly contributed to the transition from land to water in marine mammal lineages. Genes associated with the formation of blubber (NFIA), vascular development (SEMA3E), and heat production by brown adipose tissue (UCP1) had unique changes that may contribute to marine mammal thermoregulation. We also observed many lineage-specific changes in the marine mammals, including genes associated with deep diving and navigation. Our study advances understanding of the timing, pattern, and molecular changes associated with the evolution of mammalian lineages adapting to aquatic life.

Photobacterium damselae subspecies damselae Pneumonia in Dead, Stranded Bottlenose Dolphin, Eastern Mediterranean Sea.

Photobacterium damselae subspecies damselae, an abundant, generalist marine pathogen, has been reported in various cetaceans worldwide. We report a bottlenose dolphin in the eastern Mediterranean Sea that was found stranded and dead. The dolphin had a severe case of chronic suppurative pneumonia and splenic lymphoid depletion caused by this pathogen.

Holocene deglaciation drove rapid genetic diversification of Atlantic walrus.

Rapid global warming is severely impacting Arctic ecosystems and is predicted to transform the abundance, distribution and genetic diversity of Arctic species, though these linkages are poorly understood. We address this gap in knowledge using palaeogenomics to examine how earlier periods of global warming influenced the genetic diversity of Atlantic walrus (Odobenus rosmarus rosmarus), a species closely associated with sea ice and shallow-water habitats. We analysed 82 ancient and historical Atlantic walrus mitochondrial genomes (mitogenomes), including now-extinct populations in Iceland and the Canadian Maritimes, to reconstruct the Atlantic walrus' response to Arctic deglaciation. Our results demonstrate that the phylogeography and genetic diversity of Atlantic walrus populations was initially shaped by the last glacial maximum (LGM), surviving in distinct glacial refugia, and subsequently expanding rapidly in multiple migration waves during the late Pleistocene and early Holocene. The timing of diversification and establishment of distinct populations corresponds closely with the chronology of the glacial retreat, pointing to a strong link between walrus phylogeography and sea ice. Our results indicate that accelerated ice loss in the modern Arctic may trigger further dispersal events, likely increasing the connectivity of northern stocks while isolating more southerly stocks putatively caught in small pockets of suitable habitat.

Flow cytometric kinetic assay of calcium mobilization in whole blood platelets of bottlenose dolphins (Tursiops truncatus).

Marine mammals may suffer alterations in platelet function and hemostasia due to multiple pathologies, environmental conditions (including stress) or exposure to different contaminants that induce platelet activation. Detecting early alterations in platelet function in these animals could be an especially relevant diagnostic tool in these species because they typically do not show signs of weakness or disease until the pathology is in advanced state, in order to avoid attracting predators in natural conditions. The study of early markers of platelet activation is relevant for the detection, monitoring and therapy of inflammation and hemostasis disorders. Flow cytometry provides a convenient method to evaluate platelet activation by following the kinetics of intracellular Ca2+ , using sensitive fluorescent indicators that can be loaded into intact cells. In order to study intraplatelet Ca2+ mobilization in marine mammals, we have adapted a kinetic assay of human platelet activation to study platelet activation in whole-blood samples of bottlenose dolphins (Tursiops truncatus) using the Ca2+ -sensitive dye Fluo-4AM and a clone of the platelet-specific antibody CD41-PE that recognizes dolphin platelets. This no-wash, no-lyse protocol provides a simple and sensitive tool to assess in vitro the time course and intensity of signal-transduction responses to platelet agonists under near-physiological conditions. The adaptation of this technique to marine mammals represents a methodological advance for basic and clinical veterinary applications but also for general environmental studies on these species.

A regime shift in the Southeast Greenland marine ecosystem.

Two major oceanographic changes have recently propagated through several trophic levels in coastal areas of Southeast Greenland (SEG). Firstly, the amount of drift-ice exported from the Fram Strait and transported with the East Greenland Current (EGC) has decreased significantly over the past two decades, and a main tipping element (summer sea ice) has virtually disappeared since 2003 leading to a regime shift in oceanographic and ecological conditions in the region. The following 20-year period with low or no coastal sea ice is unique in the 200-year history of ice observations in the region, and the regime shift is also obvious in the volume of ice export through the Fram Strait after 2013. In the same period, the temperature of the EGC south of 73.5 N has increased significantly (>2°C) since 1980. Secondly, the warm Irminger Current, which advects warm, saline Atlantic Water into the region, has become warmer since 1990. The lack of pack ice in summer together with a warming ocean generated cascading effects on the ecosystem in SEG that are manifested in a changed fish fauna with an influx of boreal species in the south and the subarctic capelin further north. At higher trophic levels there has been an increase in the abundance of several boreal cetaceans (humpback, fin, killer, and pilot whales and dolphins) that are either new to this area or occur in historically large numbers. It is estimated that the new cetacean species in SEG are responsible for an annual predation level of 700,000 tons of fish. In addition, predation on krill species is estimated at >1,500,000 tons mainly consumed by fin whales. Simultaneously, there has been a reduction in the abundance and catches of narwhals and walruses in SEG and it is suggested that these species have been impacted by the habitat changes.

The roles of brain lipids and polar metabolites in the hypoxia tolerance of deep-diving pinnipeds.

Lipids make up more than half of the human brain's dry weight, yet the composition and function of the brain lipidome is not well characterized. Lipids not only provide the structural basis of cell membranes, but also take part in a wide variety of biochemical processes. In neurodegenerative diseases, lipids can facilitate neuroprotection and serve as diagnostic biomarkers. The study of organisms adapted to extreme environments may prove particularly valuable in understanding mechanisms that protect against stressful conditions and prevent neurodegeneration. The brain of the hooded seal (Cystophora cristata) exhibits a remarkable tolerance to low tissue oxygen levels (hypoxia). While neurons of most terrestrial mammals suffer irreversible damage after only short periods of hypoxia, in vitro experiments show that neurons of the hooded seal display prolonged functional integrity even in severe hypoxia. How the brain lipidome contributes to the hypoxia tolerance of marine mammals has been poorly studied. We performed an untargeted lipidomics analysis, which revealed that lipid species are significantly modulated in marine mammals compared with non-diving mammals. Increased levels of sphingomyelin species may have important implications for efficient signal transduction in the seal brain. Substrate assays also revealed elevated normoxic tissue levels of glucose and lactate, which suggests an enhanced glycolytic capacity. Additionally, concentrations of the neurotransmitters glutamate and glutamine were decreased, which may indicate reduced excitatory synaptic signaling in marine mammals. Analysis of hypoxia-exposed brain tissue suggests that these represent constitutive mechanisms rather than an induced response towards hypoxic conditions.

Paracholeplasma manati sp. nov. isolated from Florida manatees (Trichechus manatus latirostris).

Four novel strains of a member of the genus Paracholeplasma (OakleyT, Holly, Lorelei and Ariel) were isolated from skin of Florida manatees (Trichechus manatus latirostris). These strains were phenotypically and genetically characterized and compared with the known species of the genera Acholeplasma (A.), Alteracholeplasma (Al.), Haploplasma (H.), Paracholeplasma (P.) and Mariniplasma (M.). All the strains produced acid from glucose but did not hydrolyze arginine or urea. All were propagated in ambient air supplemented with 5±1 % CO2 at 35-37 °C using SP4-Z, Columbia and brain-heart infusion medium. Colonies on solid medium showed a typical fried-egg appearance and transmission electron microscopy revealed a typical mycoplasma-like cellular morphology. The results of phylogenetic analyses based on partial 16S rRNA, rpoB, gyrB and parE gene sequences and the whole proteome data indicated that the novel species is a unique species but phylogenetically closely related to Paracholeplasma vituli, Paracholeplasma morum and 'Paracholeplasma brassicae'. The average nucleotide identity and digital DNA-DNA hybridization values between strain OakleyT and the closely related species were significantly lower than the accepted thresholds for describing novel prokaryotic species at the genomic level. On the basis of the genomic, phenotypic and phylogenetic properties, the novel strains represent a novel species of the genus Paracholeplasma, for which the name Paracholeplasma manati sp. nov. with the type strain OakleyT (=NCTC 14352T =DSM 110686T) is proposed. The genomic DNA G+C content and complete draft genome size for the type strain are 38.35 % and 1 873 856 bp, respectively.

Feeding morphology and body size shape resource partitioning in an eared seal community.

Body size and feeding morphology influence how animals partition themselves within communities. We tested the relationships among sex, body size, skull morphology and foraging in sympatric otariids (eared seals) from the eastern North Pacific Ocean, the most diverse otariid community in the world. We recorded skull measurements and stable carbon (δ13C) and nitrogen (δ15N) isotope values (proxies for foraging) from museum specimens in four sympatric species: California sea lions (Zalophus californianus), Steller sea lions (Eumetopias jubatus), northern fur seals (Callorhinus ursinus) and Guadalupe fur seals (Arctocephalus townsendi). Species and sexes had statistical differences in size, skull morphology and foraging significantly affecting the δ13C values. Sea lions had higher δ13C values than fur seals, and males of all species had higher values than females. The δ15N values were correlated with species and feeding morphology; individuals with stronger bite forces had higher δ15N values. We also found a significant community-wide correlation between skull length (indicator of body length), and foraging, with larger individuals having nearshore habitat preferences, and consuming higher trophic level prey than smaller individuals. Still, there was no consistent association between these traits at the intraspecific level, indicating that other factors might account for foraging variability.

Red-list status and extinction risk of the world's whales, dolphins, and porpoises.

To understand the scope and scale of the loss of biodiversity, tools are required that can be applied in a standardized manner to all species globally, spanning realms from land to the open ocean. We used data from the International Union for the Conservation of Nature Red List to provide a synthesis of the conservation status and extinction risk of cetaceans. One in 4 cetacean species (26% of 92 species) was threatened with extinction (i.e., critically endangered, endangered, or vulnerable) and 11% were near threatened. Ten percent of cetacean species were data deficient, and we predicted that 2-3 of these species may also be threatened. The proportion of threatened cetaceans has increased: 15% in 1991, 19% in 2008, and 26% in 2021. The assessed conservation status of 20% of species has worsened from 2008 to 2021, and only 3 moved into categories of lesser threat. Cetacean species with small geographic ranges were more likely to be listed as threatened than those with large ranges, and those that occur in freshwater (100% of species) and coastal (60% of species) habitats were under the greatest threat. Analysis of odontocete species distributions revealed a global hotspot of threatened small cetaceans in Southeast Asia, in an area encompassing the Coral Triangle and extending through nearshore waters of the Bay of Bengal, northern Australia, and Papua New Guinea and into the coastal waters of China. Improved management of fisheries to limit overfishing and reduce bycatch is urgently needed to avoid extinctions or further declines, especially in coastal areas of Asia, Africa, and South America.

Estado en la lista roja y riesgo de extinción de las ballenas, delfines y marsopas del mundo Resumen Para comprender el alcance y la escala de la pérdida de biodiversidad, se necesitan herramientas que puedan aplicarse de forma estandarizada a todas las especies a nivel mundial y que abarquen todos los ámbitos desde la tierra hasta el océano. Utilizamos datos de la Lista Roja de la Unión Internacional para la Conservación de la Naturaleza para proporcionar una síntesis del estado de conservación y el riesgo de extinción de los cetáceos. Una de cada 4 especies de cetáceos (26% de 92 especies) se encuentra amenazada (es decir, en peligro crítico, en peligro o vulnerable) y el 11% de las especies está clasificado como casi amenazada. El 10% de las especies de cetáceos carecía de datos, por lo que predijimos que 2-3 de estas especies también podrían estar amenazadas. La proporción de cetáceos amenazados ha aumentado: 15% en 1991, 19% en 2008 y 26% en 2021. El estado de conservación evaluado del 20% de las especies ha empeorado de 2008 a 2021, pues sólo 3 pasaron a categorías de menor amenaza. Las especies de cetáceos con áreas de distribución geográficas pequeñas tenían más probabilidades de ser catalogadas como amenazadas que aquellas con áreas de distribución extensas, y aquellas que ocurren en hábitats de agua dulce (100% de las especies) y costeros (60% de las especies) eran las que se encontraban bajo mayor amenaza. La superposición de los mapas de distribución de las especies reveló la existencia de puntos calientes de pequeños cetáceos amenazados en el sudeste asiático y en una zona que abarca el Triángulo de Coral y se extiende por las aguas cercanas a la costa de la Bahía de Bengala, el norte de Australia, Papúa Nueva Guinea y las aguas costeras de China. Urge mejorar la gestión de las pesquerías para limitar la sobrepesca y reducir la captura accesoria con el fin de evitar extinciones o mayores descensos, especialmente en las zonas costeras de Asia, África y Sudamérica.

Varying Diet Composition Causes Striking Differences in Legacy and Emerging Contaminant Concentrations in Killer Whales across the North Atlantic.

Lipophilic persistent organic pollutants (POPs) tend to biomagnify in food chains, resulting in higher concentrations in species such as killer whales (Orcinus orca) feeding on marine mammals compared to those consuming fish. Advancements in dietary studies include the use of quantitative fatty acid signature analysis (QFASA) and differentiation of feeding habits within and between populations of North Atlantic (NA) killer whales. This comprehensive study assessed the concentrations of legacy and emerging POPs in 162 killer whales from across the NA. We report significantly higher mean levels of polychlorinated biphenyls (PCBs), organochlorine pesticides, and flame retardants in Western NA killer whales compared to those of Eastern NA conspecifics. Mean ∑PCBs ranged from ∼100 mg/kg lipid weight (lw) in the Western NA (Canadian Arctic, Eastern Canada) to ∼50 mg/kg lw in the mid-NA (Greenland, Iceland) to ∼10 mg/kg lw in the Eastern NA (Norway, Faroe Islands). The observed variations in contaminant levels were strongly correlated with diet composition across locations (inferred from QFASA), emphasizing that diet and not environmental variation in contaminant concentrations among locations is crucial in assessing contaminant-associated health risks in killer whales. These findings highlight the urgency for implementing enhanced measures to safely dispose of POP-contaminated waste, prevent further environmental contamination, and mitigate the release of newer and potentially harmful contaminants.

Spatiotemporal Trends Spanning Three Decades Show Toxic Levels of Chemical Contaminants in Marine Mammals.

Despite their ban and restriction under the 2001 Stockholm Convention, persistent organic pollutants (POPs) are still widespread and pervasive in the environment. Releases of these toxic and bioaccumulative chemicals are ongoing, and their contribution to population declines of marine mammals is of global concern. To safeguard their survival, it is of paramount importance to understand the effectiveness of mitigation measures. Using one of the world's largest marine mammals strandings data sets, we combine published and unpublished data to examine pollutant concentrations in 11 species that stranded along the coast of Great Britain to quantify spatiotemporal trends over three decades and identify species and regions where pollutants pose the greatest threat. We find that although levels of pollutants have decreased overall, there is significant spatial and taxonomic heterogeneity such that pollutants remain a threat to biodiversity in several species and regions. Of individuals sampled within the most recent five years (2014-2018), 48% of individuals exhibited a concentration known to exceed toxic thresholds. Notably, pollutant concentrations are highest in long-lived, apex odontocetes (e.g., killer whales (Orcinus orca), bottlenose dolphins (Tursiops truncatus), and white-beaked dolphins (Lagenorhynchus albirostris)) and were significantly higher in animals that stranded on more industrialized coastlines. At the present concentrations, POPs are likely to be significantly impacting marine mammal health. We conclude that more effective international elimination and mitigation strategies are urgently needed to address this critical issue for the global ocean health.

Identification of Mid-Polar and Polar AhR Agonists in Cetaceans from Korean Coastal Waters: Application of Effect-Directed Analysis with Full-Scan Screening.

Major aryl hydrocarbon receptor (AhR) agonists were identified in extracts of blubber, liver, and muscle from six long-beaked common dolphins (Delphinus capensis) and one fin whale (Balaenoptera physalus) collected from Korean coastal waters using effect-directed analysis. Results of the H4IIE-luc bioassay indicated that the polar fractions of blubber and liver extracts from the fin whale exhibited relatively high AhR-mediated potencies. Based on full-scan screening with high-resolution mass spectrometry, 37 AhR agonist candidates, spanning four use categories: pharmaceuticals, pesticides, cosmetics, and natural products, were selected. Among these, five polar AhR agonists were newly identified through toxicological confirmation. Concentrations of polar AhR agonists in cetaceans were tissue-specific, with extracts of blubber and liver containing greater concentrations than muscle extracts. Polar AhR agonists with great log KOA values (>5) were found to biomagnify in the marine food chain potentially. Polar AhR agonists contributed 8.9% of the observed AhR-mediated potencies in blubber and 49% in liver. Rutaecarpine and alantolactone contributed significantly to the total AhR-mediated potencies of blubber, whereas hydrocortisone was a major AhR contributor in the liver of the fin whale. This study is the first to identify the tissue-specific accumulation of polar AhR agonists in blubber and liver extracts of cetaceans.

A systematic review of the diversity and virulence correlates of metastrongyle lungworms in marine mammals.

Metastrongyle lungworms could be particularly detrimental for diving animals such as marine mammals; however, little is known of the drivers of pathogenic host­parasite relationships in this group. This systematic review analysed the diversity of metastrongyles in marine mammals and the host and parasite traits associated with virulence. There have been at least 40 species of metastrongyles described in 66 species of marine mammals. After penalization for study biases, Halocercus hyperoodoni, Otostrongylus circumlitus, Parafilaroides gymnurus, Halocercus brasiliensis and Stenurus minor were the metastrongyles with the widest host range. Most studies (80.12%, n = 133/166) reported that metastrongyles caused bronchopneumonia, while in the cardiovascular system metastrongyles caused vasculitis in nearly half of the studies (45.45%, n = 5/11) that assessed these tissues. Metastrongyles were associated with otitis in 23.08% (n = 6/26) of the studies. Metastrongyle infection was considered a potential contributory to mortality in 44.78% (n = 90/201) of the studies while 10.45% (n = 21/201) of these studies considered metastrongyles the main cause of death. Metastrongyle species with a wider host range were more likely to induce pathogenic effects. Metastrongyles can cause significant tissue damage and mortality in marine mammals although virulent host­parasite relationships are dominated by a few metastrongyle species with wider host ranges.

Dolphin leukocytes exhibit an attenuated cytokine response and increase heme oxygenase activity upon exposure to lipopolysaccharides.

Cetaceans exhibit physiological adaptations that allowed the transition to aquatic life, including a robust antioxidant defense system that prevents injury from repeated exposure to ischemia/reperfusion events associated with breath-hold diving. The signaling cascades that characterize ischemic inflammation in humans are well characterized. In contrast, cetaceans' molecular and biochemical mechanisms that confer tolerance to inflammatory events are poorly understood. Heme oxygenase (HO) is a cytoprotective protein with anti-inflammatory properties. HO catalyzes the first step in the oxidative degradation of heme. The inducible HO-1 isoform is regulated by various stimuli, including hypoxia, oxidant stress, and inflammatory cytokines. The objective of this study was to compare the response of HO-1 and cytokines to a proinflammatory challenge in leukocytes isolated from humans and bottlenose dolphins (Tursiops truncatus). We measured changes in HO activity, and abundance and expression of interleukin 1 beta (IL-1ß), interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-α), and heme oxygenase 1 (HMOX1) in leukocytes treated with lipopolysaccharide (LPS) for 24 and 48 h. HO activity increased (p < 0.05) in dolphin (48 h) but not human cells. TNF-α expression increased in human (24 h, 48 h), but not dolphin cells following LPS stimulation. LPS-induced cytokine expression was lower in dolphin than in human leukocytes, suggesting a blunted cytokine response in bottlenose dolphin leukocytes treated with LPS. Results suggest species-specific regulation of inflammatory cytokines in leukocytes treated with LPS, which may lead to differential responses to a pro-inflammatory challenge between marine and terrestrial mammals.

The initial steps toward the formation of somatic tissue banks and cell cultures derived from captive Antillean manatee (Trichechus manatus manatus) skin biopsies.

The declining population of the Antillean manatee caused by ecosystem degradation and rising pollution has prompted interest in developing conservation strategies for this species. Given this scenario, somatic tissue banks are important tools for acquiring knowledge about the species, as well as for obtaining somatic cells for biotechnological and ecotoxicological applications. Therefore, we aimed to assess the effects of slow freezing (SF) and solid-surface vitrification (SSV) of the dermis of captive Antillean manatees on the histology and ultrastructure of the tissue and cell viability in culture. While the SSV did not change the dermis thickness, the SF maintained the tissue proliferative potential, assessed by the nucleolar organizer region area, similar to noncryopreserved tissues. Moreover, both techniques reduced the number of fibroblasts and increased the percentage of collagen fibers. Nevertheless, only tissues cryopreserved with SF and noncryopreserved tissues were able to produce cells after in vitro culture. Although SF did not alter cell viability and proliferative activity, cells derived from cryopreserved tissues showed decreased metabolism, altered apoptosis, increased levels of reactive oxygen species, and mitochondrial membrane potential compared to cells from noncryopreserved tissues. In summary, we demonstrated for the first time that Antillean manatee somatic tissues can be cryopreserved by SF, and cells can be obtained after in vitro culture. Improvements in cryopreservation conditions, especially vitrification, of somatic samples are needed to increase the quality of somatic tissue banks in this species.