Zalophus

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Daniel P Costa - One of the best experts on this subject based on the ideXlab platform.

  • ddt in endangered galapagos sea lions Zalophus wollebaeki
    Marine Pollution Bulletin, 2011
    Co-Authors: Juan Jose Alava, Stella Villegasamtmann, Daniel P Costa, Sandie Salazar, Peter S Ross, Michael G Ikonomou, Marilyn Cruz, Gustavo Jimenezuzcategui, Cory Dubetz, Peter Howorth
    Abstract:

    0-DDE Health risk abstract We characterize for the first time the presence of DDT and its metabolites in tropical Galapagos sea lions (Zalophus wolleabeki). P DDT concentrations in Galapagos sea lion pups sampled in 2005 and 2008 ranged from 16 to 3070 lg/kg lipid. Concentrations of P DDT in pups in 2008 averaged 525 lg/kg lipid and were 1.9 times higher than that (281 lg/kg lipid) detected in pups in 2005. These concentrations are lower than those reported in many pinnipeds elsewhere, comparable to those in Hawaiian monk seals, and higher than those in southern elephant seals. The health risk characterization showed that 1% of the male pups exceeded the p,p 0-DDE toxic effect concentration associated with anti-androgenic effects reported in rats. The findings provide preliminary guidance on the relationship between DDT use and ecological impacts, serving as a reference point against which possible future impact of tropical DDT use can be assessed.

  • low synchrony in the breeding cycle of galapagos sea lions revealed by seasonal progesterone concentrations
    Journal of Mammalogy, 2009
    Co-Authors: Stella Villegasamtmann, Stephen N Atkinson, Daniel P Costa
    Abstract:

    Abstract Mammalian reproductive biology is modified consistently across pinnipeds to achieve a synchronous and seasonal reproductive pattern. This synchrony relies on an embryonic diapause and ensures optimal conditions for offspring survival. Behavioral observations on Galapagos sea lions (Zalophus wollebaeki) indicate little synchrony and variable breeding seasons, making this species unique among otariids. We studied the reproductive physiology of wild female Galapagos sea lions in 2 months in contrasting seasons, March 2005 (n  =  11) and August 2006 (n  =  12) by examining progesterone and estrogen concentrations in serum and plasma. We provide physiological evidence for remarkably low synchrony and minor seasonality in the breeding cycle of Galapagos sea lions. Specifically, we found females in intermediate or advanced pregnancy during both seasons, as determined by high progesterone concentrations coupled with physical examination. Possible causes for this low synchrony are absence of strong photop...

  • maneuverability by the sea lion Zalophus californianus turning performance of an unstable body design
    The Journal of Experimental Biology, 2003
    Co-Authors: Frank E Fish, Jenifer Hurley, Daniel P Costa
    Abstract:

    SUMMARY Maneuverability is critical to the performance of fast-swimming marine mammals that use rapid turns to catch prey. Overhead video recordings were analyzed for two sea lions ( Zalophus californianus ) turning in the horizontal plane. Unpowered turns were executed by body flexion in conjunction with use of the pectoral and pelvic flippers, which were used as control surfaces. A 90° bank angle was used in the turns to vertically orient the control surfaces. Turning radius was dependent on body mass and swimming velocity. Relative minimum radii were 9-17% of body length and were equivalent for pinnipeds and cetaceans. However, Zalophus had smaller turning radii at higher speeds than cetaceans. Rate of turn was inversely related to turn radius. The highest turn rate observed in Zalophus was 690 degrees s -1 . Centripetal acceleration measured up to 5.1 g for Zalophus . Comparison with other marine mammals indicates that Zalophus has a morphology that enhances instability, thus providing enhanced turning performance. Enhanced turning performance is necessary for sea lions to forage after highly elusive prey in structurally complex environments.

  • maneuverability by the sea lion Zalophus californianus turning performance of an unstable body design
    The Journal of Experimental Biology, 2003
    Co-Authors: Frank E Fish, Jenifer Hurley, Daniel P Costa
    Abstract:

    SUMMARY Maneuverability is critical to the performance of fast-swimming marine mammals that use rapid turns to catch prey. Overhead video recordings were analyzed for two sea lions ( Zalophus californianus ) turning in the horizontal plane. Unpowered turns were executed by body flexion in conjunction with use of the pectoral and pelvic flippers, which were used as control surfaces. A 90° bank angle was used in the turns to vertically orient the control surfaces. Turning radius was dependent on body mass and swimming velocity. Relative minimum radii were 9-17% of body length and were equivalent for pinnipeds and cetaceans. However, Zalophus had smaller turning radii at higher speeds than cetaceans. Rate of turn was inversely related to turn radius. The highest turn rate observed in Zalophus was 690 degrees s -1 . Centripetal acceleration measured up to 5.1 g for Zalophus . Comparison with other marine mammals indicates that Zalophus has a morphology that enhances instability, thus providing enhanced turning performance. Enhanced turning performance is necessary for sea lions to forage after highly elusive prey in structurally complex environments.

Jochen B W Wolf - One of the best experts on this subject based on the ideXlab platform.

  • tracing early stages of species differentiation ecological morphological and genetic divergence of galapagos sea lion populations
    BMC Evolutionary Biology, 2008
    Co-Authors: Jochen B W Wolf, Sylvia Brunner, Fritz Trillmich, Chris Harrod, Sandie Salazar, Diethard Tautz
    Abstract:

    Background Oceans are high gene flow environments that are traditionally believed to hamper the build-up of genetic divergence. Despite this, divergence appears to occur occasionally at surprisingly small scales. The Galapagos archipelago provides an ideal opportunity to examine the evolutionary processes of local divergence in an isolated marine environment. Galapagos sea lions (Zalophus wollebaeki) are top predators in this unique setting and have an essentially unlimited dispersal capacity across the entire species range. In theory, this should oppose any genetic differentiation.

  • Galápagos and Californian sea lions are separate species: Genetic analysis of the genus Zalophus and its implications for conservation management
    Frontiers in Zoology, 2007
    Co-Authors: Jochen B W Wolf, Diethard Tautz, Fritz Trillmich
    Abstract:

    Background Accurate formal taxonomic designations are thought to be of critical importance for the conservation of endangered taxa. The Galápagos sea lion (GSL), being appreciated as a key element of the Galápagos marine ecosystem, has lately been listed as 'vulnerable' by the IUCN. To date there is, however, hardly any scientific evidence, whether it constitutes a separate entity from its abundant Californian neighbour (CSL). In this paper, we delineate the taxonomic relationships within the genus Zalophus being comprised of the Galápagos sea lion, the Californian sea lion and the already extinct Japanese sea lion (JSL). Results Using a set of different phylogenetic reconstruction approaches, we find support for monophyly of all three taxa without evidence of reticulation events. Molecular clock estimates place time to common ancestry of the Galápagos sea lion and the Californian sea lion at about 2.3 ± 0.5 mya. Genetic separation is further suggested by diagnostic SNPs in the mitochondrial and nuclear genome. Microsatellite markers confirm this trend, showing numerous private alleles at most of the 25 investigated loci. Microsatellite-based estimates of genetic differentiation between the Galápagos sea lion and the Californian sea lion indicate significant genetic differentiation. Gene diversity is 14% lower in the Galápagos sea lion than in the Californian sea lion, but there is no evidence for recent bottleneck events in the Galápagos sea lion. Conclusion Based on molecular evidence we build a case for classifying the Galápagos sea lion ( Zalophus wollebaeki ), the Californian sea lion ( Zalophus californianus ) and the Japanese sea lion ( Zalophus japonicus ) as true species. As morphological characters do not necessarily fully reflect the rapid divergence on the molecular level, the study can be considered as a test case for deriving species status from molecular evidence. We further use the results to discuss the role of genetics in conservation policy for an organism that already is under the general protection of the habitat it lives in.

  • ten novel dinucleotide microsatellite loci cloned from the galapagos sea lion Zalophus californianus wollebaeki are polymorphic in other pinniped species
    Molecular Ecology Notes, 2006
    Co-Authors: Joseph I Hoffman, Jochen B W Wolf
    Abstract:

    We isolated and characterized 10 novel dinucleotide microsatellite loci from the Galapagos sea lion (Zalophus californianus wollebaeki) and tested their amplification utility in four further otariid species (Zalophus californianus californianus, Arctocephalus gazella, Arctocephalus australis and Eumetopias jubatus) and three phocid species (Hydrurga leptonyx, Halichoerus grypus and Phoca vitulina). All of the loci amplified polymorphic polymerase chain reaction (PCR) products in at least three species other than the Galapagos sea lion. These markers will be useful for studies of pinniped mating systems, genetic structure and genetic diversity.

Frances M. D. Gulland - One of the best experts on this subject based on the ideXlab platform.

  • Isolation of a novel adenovirus from California sea lions Zalophus californianus.
    Diseases of Aquatic Organisms, 2011
    Co-Authors: Tracey Goldstein, Kathleen M. Colegrove, M. Hanson, Frances M. D. Gulland
    Abstract:

    Viral hepatitis associated with adenoviral infection has been reported in California sea lions Zalophus californianus admitted to rehabilitation centers along the California coast since the 1970s. Canine adenovirus 1 (CAdV-1) causes viral hepatitis in dogs and infects a number of wildlife species. Attempts to isolate the virus from previous sea lion hepatitis cases were unsuccessful, but as the hepatitis had morphologic features resembling canine infectious hepatitis, and since the virus has a wide host range, it was thought that perhaps the etiologic agent was CAdV-1. Here, we identify a novel adenovirus in 2 stranded California sea lions and associate the infection with viral hepatitis and endothelial cell infection. Phylogenetic analysis confirmed the classification of the sea lion adeno - virus in the Mastadenovirus genus with the most similarity to tree shrew adenovirus 1 (TSAdV-1, 77%). However, as the sea lion adenovirus appeared to be equally distant from the other Mastadeno - virus species based on phylogenetic analysis, results indicate that it represents an independent lineage and species. Although sequences from this novel virus, otarine adenovirus 1 (OtAdV-1), show some similarity to CAdV-1 and 2, it is clearly distinct and likely the cause of the viral hepatitis in the stranded California sea lions.

  • antemortem diagnosis of a ventricular septal defect in a california sea lion Zalophus californianus
    Diseases of Aquatic Organisms, 2011
    Co-Authors: Sophie Dennison, Terry R Spraker, Nicola Pussini, W. Van Bonn, Marjorie Boor, James Adams, Frances M. D. Gulland
    Abstract:

    A yearling California sea lion Zalophus californianus stranded in poor body condition, and on physical examination a heart murmur was audible bilaterally. The sea lion was diagnosed with a left-to-right shunting membranous ventricular septal defect (VSD) using B-mode, color-flow Doppler and continuous-wave Doppler echocardiography. A left-to-right intracardiac shunting lesion was confirmed during cardiac angiographic computed tomography. The VSD defect was verified during the necropsy examination. On histologic examination concurrent mild multifocal myocarditis with focal mild ventricular free-wall myocardial necrosis were identified. A specific cause for the myocarditis and myocardial necrosis was not found, and association with the VSD and resultant myocardial dysfunction was presumed. This is the first report of the antemortem diagnosis of a VSD in a marine mammal and the first report of a VSD in a California sea lion.

  • immunomodulatory effects upon in vitro exposure of california sea lion and southern sea otter peripheral blood leukocytes to domoic acid
    Journal of Wildlife Diseases, 2010
    Co-Authors: Milton Levin, Frances M. D. Gulland, David A. Jessup, Dhanashree Joshi, Andrew Draghi, Sylvain De Guise
    Abstract:

    During red tide bloom events, the marine diatom Pseudo-nitzschia produces the toxin domoic acid (DA), which has been associated with stranding and mortality events involving California sea lions (Zalophus californianus) and southern sea otters (Enhydra lutris). In addition to these well-documented DA-induced neurotoxic events, there is increasing concern that DA may exert chronic effects, such as immunomodulation, which may potentially increase an individual's susceptibility to a number of opportunistic infections following nonlethal exposure. We investigated the effects of DA on innate (phagocytosis and respiratory burst) and adaptive (mitogen-induced lymphocyte proliferation) immune functions with the use of peripheral blood leukocytes collected from healthy California sea lions and southern sea otters upon in vitro exposure to 0 (unexposed control), 0.0001, 0.001, 0.01, 0.1, 1.0, 10, and 100 μM DA. Domoic acid did not significantly modulate phagocytosis or respiratory burst in either species. For Calif...

  • pathological features of amyloidosis in stranded california sea lions Zalophus californianus
    Journal of Comparative Pathology, 2009
    Co-Authors: Kathleen M. Colegrove, Frances M. D. Gulland, Diane K Naydan, K Harr, Linda J. Lowenstine
    Abstract:

    Amyloidosis was diagnosed in 26 stranded adult California sea lions between 1983 and 2006 by retrospective case analysis. The kidneys (92.3% of animals), blood vessels (80.7%) and thyroid glands (65.4%) were most commonly affected. Macroscopically, affected kidneys were swollen, with pale tan cortices and loss of corticomedullary differentiation. Amyloid deposits in the kidney were located in the glomeruli, blood vessels, and peritubular interstitium, most prominently in the outer stripe of the medulla. The amyloid deposits were identified as type amyloid A (AA) by potassium permanganate staining and immunolabelling with antibodies against AA protein. Concurrent diseases, including inflammatory processes and genital carcinoma, were common in affected animals. Serum amyloid A concentrations were high (>1200 microg/ml) in six of seven affected sea lions, while the median value in clinically healthy animals was <10 microg/ml. These findings suggest that renal amyloidosis contributes to morbidity and mortality in stranded adult California sea lions.

  • seasonal changes in circulating progesterone and estrogen concentrations in the california sea lion Zalophus californianus
    Journal of Mammalogy, 2007
    Co-Authors: Denise J Greig, Frances M. D. Gulland, Kendall L Mashburn, Matthew Rutishauser, Terrie M Williams, Shannon Atkinson
    Abstract:

    Abstract The measurement of circulating reproductive hormone levels provides a relatively noninvasive method for assessing reproductive status. We assessed seasonal changes in concentrations of progesterone and total estrogens from serum samples collected from live stranded (n = 199) and captive (n = 5) California sea lions (Zalophus californianus). Progesterone concentrations increased in the fall (September–November) in both pregnant and nonpregnant animals, with no significant difference associated with pregnancy. Progesterone concentrations were greater in pregnant animals in the spring (February–April) than in nonpregnant animals. Circulating estrogen concentrations in captive, nonpregnant sea lions increased in July and November, correlating with periods of estrus and implantation. These data provide a baseline for studying reproduction in California sea lions.

David Auriolesgamboa - One of the best experts on this subject based on the ideXlab platform.

  • serum cortisol in california sea lion pups Zalophus californianus californianus
    Animal Welfare, 2010
    Co-Authors: David Auriolesgamboa, C Pederneraromano, R A Valdez, Dulce Maria Brousset, M C Romano, F Galindo
    Abstract:

    Marine ecosystems are exposed to a wide variety of factors that may produce disturbances in their structure and functioning. The Gulf of California supports fisheries, tourism, intensive agriculture, mining, and more recently, shrimp aquaculture. Under such conditions, animals are forced to cope with several changes in their environment that can contribute to animal welfare problems. Serum cortisol level analysis may be a particularly useful means of assessing the physiological status of mammals potentially affected by increasing human activity in the Gulf of California, such as the California sea lion (Zalophus californianus californianus). In this study, we report for the first time the serum cortisol concentration of free-living, wild California sea lion pups. The analysis was performed in eleven rookeries along the Gulf of California. Two consecutive blood samples (S1 and S2) were obtained from 56 sea lion pups following a capture, handling and anaesthesia regime, and cortisol was measured by radioimmunoassay. Female pups showed higher serum cortisol than males in the first sample. In males, the second sample was significantly higher than the first. Cortisol levels in the two samples of both sexes combined differed between the Southern and Midriff-region rookeries. This information could be useful to assess welfare in wild populations of sea lions and to determine anthropogenic factors in the Gulf of California that may contribute to stress and reduced welfare.

  • survival rates of the california sea lion Zalophus californianus in mexico
    Journal of Mammalogy, 2008
    Co-Authors: Claudia J Hernandezcamacho, David Auriolesgamboa, Jeffrey L Laake, Leah Gerber
    Abstract:

    California sea lions (Zalophus californianus) in the Gulf of California have declined by 20% over the past 2 decades. The lack of data on life-history parameters for this species has limited the development of demographic models to assess the status of this population. We estimated age- and sex-specific annual survival probabilities for California sea lions using resighting data on 5 pup cohorts from 1981 to 2006. We modeled apparent survival and resighting probability using age-class, sex, and time as potential explanatory variables. Apparent survival rates varied for different age- and sex-classes. Only survival of pups varied by year (from 0.556 to 0.998). Survival was the same for immature males and females (0.90), but differed by sex for young (males = 0.90, females = 0.97) and old (males = 0.75, females = 0.91) adults. Resighting probabilities varied by time, age-class, and sex. Resighting probabilities were higher for females than for males, and lowest for juveniles. The survival estimates presented here provide practical insight into understanding age- and sex-specific survival rates for California sea lions.

  • using carbon and nitrogen isotope values to investigate maternal strategies in northeast pacific otariids
    Marine Mammal Science, 2006
    Co-Authors: Seth D Newsome, Paul L Koch, Mike A Etnier, David Auriolesgamboa
    Abstract:

    We examine the utility of stable carbon and nitrogen isotope variations to characterize the length of the nursing/lactation period and age at weaning for two northern Pacific otariid species, the northern fur seal (Callorhinus ursinus) and California sea lion (Zalophus californianus). We used two sampling strategies to measure ontogenetic trends in isotope value, and compared our results to observational data on the reproductive strategies used by these otariids. For Zalophus, we found evidence for 15 N enrichment and 13 C-depletion in bone collagen representing the first and second year of growth, which is consistent with the ∼12‐14-mo weaning age in this population after a suitable turnover rate for bone collagen is considered. Analysis of individual tooth annuli from a different suite of Zalophus specimens suggests that half of the individuals were weaned at ∼12 mo of age, and half were dependent on milk for a portion of their second year. For Callorhinus, bone collagen for age classes that contain pre-weaned individuals were 15 N-enriched, but values were significantly lower in specimens between 6 and 20 mo of age. These 15 N-enriched values, presumably acquired during nursing between 0 and 4 mo of age in Callorhinus, were not present in specimens older than 12 mo of age. Thus complete bone collagen turnover in young-of-the-year occurs in 8‐10 mo. 15 N enrichment is evident in the first annulus of female Callorhinus individuals, but is not detectable in males. Analyses of Callorhinus tooth annuli show no ontogenetic trends in � 13 C values. Our study indicates that nitrogen, and in some cases carbon, isotopes can be used to assess reproductive strategies in marine mammals. When coupled with accurate age estimates based on bone growth regressions, this isotopic technique can be applied to historical or fossil otariids to gain insight into the flexibility of maternal strategies within and across species.

  • spatial and temporal variation in the diet of the california sea lion Zalophus californianus in the gulf of california mexico
    2004
    Co-Authors: Francisco Javier Garciarodriguez, David Auriolesgamboa
    Abstract:

    The population of the California sea lion (Zalophus californianus), in the Gulf of California numbers approximately 23,000 individuals, 82% of which inhabit the northern region of the gulf above latitude 28° (AuriolesGamboa and Zavala-Gonzalez, 1994). In this region are found the most important reproductive areas and the highest pup production of the Gulf. Aurioles-Gamboa and Zavala-Gonzalez (1994) suggested that the high concentration of animals in this region is related to high abundance of pelagic fi sh such as Pacifi c sardine (Sardinops caeruleus) (also known as South American pilchard, FAO), Pacifi c mackerel (Scomber japonicus), Pacific thread herring (Opisthonema libertate), and anchoveta (Cetengraulis mysticetus)

  • sex differences in body size and body condition of california sea lion Zalophus californianus pups from the gulf of california
    Marine Mammal Science, 2001
    Co-Authors: Sebastian P Luque, David Auriolesgamboa
    Abstract:

    The Gulf of California harbors about 15% of the total California sea lion (Zalophus californianus californianus) population. We studied pup morphometrics from eight Gulf of California rookeries during the 1996 and 1997 reproductive seasons to describe sex differences in body size and body condition indices. Newborn pup body size was not different from previous reports. Male pups were heavier and larger than female pups in terms of all linear dimensions. Morphometric relationships, however, showed that males were 3%-4% denser, and that after removing the effects of length, they were about 2% heavier than females. Sculp depth adjusted for length was 12% larger in female than in male pups. Our data provide further evidence that male otariid pups may allocate a larger fraction of milk energy to muscular and skeletal growth compared to female pups.

Terry R Spraker - One of the best experts on this subject based on the ideXlab platform.

  • complex virome in a mesenteric lymph node from a californian sea lion Zalophus californianus with polyserositis and steatitis
    Viruses, 2020
    Co-Authors: Eda Altan, Terry R Spraker, Martha A Delaney, Elizabeth A Wheeler, Kathleen M. Colegrove, Xutao Deng, Yanpeng Li
    Abstract:

    An emaciated subadult free-ranging California sea lion (Csl or Zalophus californianus) died following stranding with lesions similar to 11 other stranded animals characterized by chronic disseminated granulomatous inflammation with necrotizing steatitis and vasculitis, involving visceral adipose tissues in the thoracic and peritoneal cavities. Histologically, affected tissues had extensive accumulations of macrophages with perivascular lymphocytes, plasma cells, and fewer neutrophils. Using viral metagenomics on a mesenteric lymph node six mammalian viruses were identified consisting of novel parvovirus, polyomavirus, rotavirus, anellovirus, and previously described Csl adenovirus 1 and Csl bocavirus 4. The causal or contributory role of these viruses to the gross and histologic lesions of this sea lion remains to be determined.

  • cryptococcus albidus infection in a california sea lion Zalophus californianus
    Journal of Wildlife Diseases, 2012
    Co-Authors: Shannon Mcleland, Colleen Duncan, Elizabeth Wheeler, Terry R Spraker, Shawn R. Lockhart
    Abstract:

    Sporadic cases of cryptococcosis have been reported in marine mammals, typically due to Cryptococcus neoformans and, more recently, to Cryptococcus gattii in cetaceans. Cryptococcus albidus, a ubiquitous fungal species not typically considered to be pathogenic, was recovered from a juvenile California sea lion (Zalophus californianus) rescued near San Francisco Bay, California. Yeast morphologically consistent with a Cryp-tococcus sp. was identified histologically in a lymph node and C. albidus was identified by an rDNA sequence from the lung. Infection with C. albidus was thought to have contributed to mortality in this sea lion, along with concurrent bacterial pneumonia. Cryptococcus albidus should be considered as a potential pathogen with a role in marine mammal morbidity and mortality.

  • antemortem diagnosis of a ventricular septal defect in a california sea lion Zalophus californianus
    Diseases of Aquatic Organisms, 2011
    Co-Authors: Sophie Dennison, Terry R Spraker, Nicola Pussini, W. Van Bonn, Marjorie Boor, James Adams, Frances M. D. Gulland
    Abstract:

    A yearling California sea lion Zalophus californianus stranded in poor body condition, and on physical examination a heart murmur was audible bilaterally. The sea lion was diagnosed with a left-to-right shunting membranous ventricular septal defect (VSD) using B-mode, color-flow Doppler and continuous-wave Doppler echocardiography. A left-to-right intracardiac shunting lesion was confirmed during cardiac angiographic computed tomography. The VSD defect was verified during the necropsy examination. On histologic examination concurrent mild multifocal myocarditis with focal mild ventricular free-wall myocardial necrosis were identified. A specific cause for the myocarditis and myocardial necrosis was not found, and association with the VSD and resultant myocardial dysfunction was presumed. This is the first report of the antemortem diagnosis of a VSD in a marine mammal and the first report of a VSD in a California sea lion.

  • hookworm enteritis with bacteremia in california sea lion pups on san miguel island
    Journal of Wildlife Diseases, 2007
    Co-Authors: Terry R Spraker, Robert L Delong, E T Lyons, Sharon R. Melin
    Abstract:

    Large breeding populations of California sea lions (Zalophus californianus) are located on San Miguel and San Nicolas Islands in the Southern California Bight. In 2001, there was a substantial increase in pup mortality in late summer and fall. From June 2002 to January 2003, 208 freshly dead pups were examined on San Miguel Island, the most western of the Channel Islands off the coast of southern California. Tissues from 186 of these pups were examined histologically. The primary lesions in 133 (72%) of the pups were an enteritis associated with hookworms and infections in major organs. Emaciation/starvation in 43 pups (26%) was the second most important cause of death.

  • pathology of domoic acid toxicity in california sea lions Zalophus californianus
    Veterinary Pathology, 2005
    Co-Authors: Paul Silvagni, Terry R Spraker, Linda J. Lowenstine, Thomas P Lipscomb, Frances M. D. Gulland
    Abstract:

    Over 100 free-ranging adult California sea lions (Zalophus californianus) and one Northern fur seal (Callorhinus ursinus), predominantly adult females, were intoxicated by domoic acid (DA) during three harmful algal blooms between 1998 and 2000 in central and northern California coastal waters. The vector prey item was Northern anchovy (Engraulis mordax) and the primary DA-producing algal diatom was Psuedo- nitzschia australis. Postmortem examination revealed gross and histologic findings that were distinctive and aided in diagnosis. A total of 109 sea lions were examined, dying between 1 day and 10 months after admission to a marine mammal rehabilitation center. Persistent seizures with obtundation were the main clinical findings. Frequent gross findings in animals dying acutely consisted of piriform lobe malacia, myocardial pallor, bron- chopneumonia, and complications related to pregnancy. Gross findings in animals dying months after intoxi- cation included bilateral hippocampal atrophy. Histologic observations implicated limbic system seizure injury consistent with excitotoxin exposure. Peracutely, there was microvesicular hydropic degeneration within the neuropil of the hippocampus, amygdala, pyriform lobe, and other limbic structures. Acutely, there was ischemic neuronal necrosis, particularly apparent in the granular cells of the dentate gyrus and the pyramidal cells within the hippocampus cornu ammonis (CA) sectors CA4, CA3, and CA1. Dentate granular cell necrosis has not been reported in human or experimental animal DA toxicity and may be unique to sea lions. Chronically, there was gliosis, mild nonsuppurative inflammation, and loss of laminar organization in affected areas.