Entity

Time filter

Source Type

Sausalito, CA, United States

Cook P.,University of California at Santa Cruz | Reichmuth C.,University of California at Santa Cruz | Gulland F.,Marine Mammal Center
Biology Letters | Year: 2011

Domoic acid is a neurotoxic metabolite of widely occurring algal blooms that has caused multiple marine animal stranding events. Exposure to high doses of domoic acid, a glutamate agonist, may lead to persistent medial temporal seizures and damage to the hippocampus. California sea lions (Zalophus californianus) are among the most visible and frequent mammalian victims of domoic acid poisoning, but rapid, reliable diagnosis in a clinical setting has proved difficult owing to the fast clearance of the toxin from the blood stream. Here, we show that the behavioural orienting responses of stranded sea lions diagnosed with domoic acid toxicosis habituate more slowly to a series of non-aversive auditory stimuli than do those of sea lions with no apparent neurological deficits. A signal detection analysis based on these habituation measures was able to correctly identify 50 per cent of subjects with domoic acid toxicosis while correctly rejecting approximately 93 per cent of controls, suggesting potential diagnostic merit. © 2011 The Royal Society. Source


Sedlak M.D.,San Francisco Estuary Institute | Greig D.J.,Marine Mammal Center
Journal of Environmental Monitoring | Year: 2012

Previous research has documented the bioaccumulation of perfluoroalkyl compounds (PFCs) in apex predators in remote locations but few studies have evaluated urban estuaries. To assess the importance of PFCs in San Francisco Bay, two apex predators in the San Francisco Bay, double-crested cormorants (Phalacrocorax auritus) and Pacific harbor seals (Phoca vitulina richardii), were sampled. Prey fish (Atherinops affinis and Menidia audens) were also evaluated to better understand potential sources of PFCs to the foodweb. Perfluorooctane sulfonate (PFOS) was the primary PFC detected in cormorant eggs, small fish and harbor seal serum. PFOS detected in San Francisco Bay seal serum was typically an order of magnitude higher than those at the reference site. PFOS concentrations were highest in seals and cormorant eggs from the highly urbanized southern portion of the Bay. PFOS in eggs from the southern part of the Bay remained relatively constant between 2006 and 2009 despite the phase-out of perfluorosulfonyl-based compounds nationally. In addition, these levels exceed the avian predicted no effects concentration of 1.0 μg mL -1. Concentrations of the remaining PFCs measured were substantially lower than those of PFOS. © 2012 The Royal Society of Chemistry. Source


Ramsdell J.S.,Center for Coastal Environmental Health and Biomolecular Research | Gulland F.M.,Marine Mammal Center
Marine Drugs | Year: 2014

Domoic acid epileptic disease is characterized by spontaneous recurrent seizures weeks to months after domoic acid exposure. The potential for this disease was first recognized in a human case study of temporal lobe epilepsy after the 1987 amnesic shellfish-poisoning event in Quebec, and was characterized as a chronic epileptic syndrome in California sea lions through investigation of a series of domoic acid poisoning cases between 1998 and 2006. The sea lion study provided a breadth of insight into clinical presentations, unusual behaviors, brain pathology, and epidemiology. A rat model that replicates key observations of the chronic epileptic syndrome in sea lions has been applied to identify the progression of the epileptic disease state, its relationship to behavioral manifestations, and to define the neural systems involved in these behavioral disorders. Here, we present the concept of domoic acid epileptic disease as a delayed manifestation of domoic acid poisoning and review the state of knowledge for this disease state in affected humans and sea lions. We discuss causative mechanisms and neural underpinnings of disease maturation revealed by the rat model to present the concept for olfactory origin of an epileptic disease; triggered in dendodendritic synapases of the olfactory bulb and maturing in the olfactory cortex. We conclude with updated information on populations at risk, medical diagnosis, treatment, and prognosis. © 2014 by the authors; licensee MDPI. Source


News Article
Site: http://www.biosciencetechnology.com/rss-feeds/all/rss.xml/all

California sea lions exposed to the algal toxin domoic acid can suffer brain damage that leads to significant deficits in spatial memory, according to a study to be published in the Dec. 18 issue of Science. The new findings suggest that chronic exposure to the toxin, produced by naturally occurring marine algae, causes impairments that are likely to affect sea lions' ability to navigate in their ocean habitat and survive in the wild. Domoic acid, a potent neurotoxin, captured headlines this year after it was detected in Dungeness crabs, prompting authorities to delay the opening of the crab season on the west coast. For California sea lions, however, the toxin has been causing problems for years. Hundreds of sea lions strand on California beaches every year with symptoms of domoic acid poisoning, including disorientation and seizures. Prior research has characterized the clinical effects of the toxin, but the behavioral effects of domoic acid poisoning in wild animals had not been assessed. A team led by scientists at the University of California, Santa Cruz, studied 30 California sea lions undergoing veterinary care and rehabilitation at the Marine Mammal Center in Sausalito. Researchers administered behavioral tests to assess spatial memory and performed brain imaging (MRI) to see the extent of brain lesions in the affected animals. Damage to the hippocampus, a part of the brain involved in memory, is often seen in sea lions with domoic acid poisoning, according to first author Peter Cook, who led the study as a graduate student at UC Santa Cruz and is now at Emory University. "In this study, we were able to correlate the extent of hippocampal damage to specific behavioral impairments relevant to the animals' survival in the wild," Cook said. The study documented impaired performance on short-and long-term spatial memory tasks in animals with hippocampal lesions. These deficits are likely to interfere with a sea lion's ability to find food and may also help explain anecdotal reports of sea lions showing up in unusual places far outside their normal range, either too far out at sea or inland far from the coast, according to coauthor Colleen Reichmuth, director of the Pinniped Cognition and Sensory Systems Laboratory at UC Santa Cruz where the behavioral tests were conducted. Domoic acid is produced by microscopic algae (diatoms in the genus Pseudo-nitzschia) that occur naturally in coastal waters. Blooms of the toxic algae along the California coast typically occur in the spring and fall and last just a few weeks, but they have been increasing in frequency and severity. This year's massive bloom, the largest ever recorded, lasted through the summer and extended from Santa Barbara to Alaska. During a Pseudo-nitzschia bloom, domoic acid accumulates in shellfish and small fish such as anchovies and sardines that feed on algae filtered from the water. Animals that feed on those fish, including sea lions and other marine mammals and seabirds, can be exposed to high levels of the toxin. The sea lion study was carried out over several years, and the researchers tested animals with and without symptoms of brain damage caused by exposure to domoic acid. Cook noted that during an algal bloom, sea lions brought to the Marine Mammal Center with acute domoic acid poisoning may not yet have permanent brain damage. Acute poisoning can cause seizures and disorientation, but brain lesions develop over time, likely as a result of a chronic epileptic condition caused by one or more exposures to the toxin, he said. Sea lions with symptoms of brain damage strand on beaches all year round, even when there is no active bloom of the toxic algae. "What isn't well understood yet is the dose response," Cook said. "We don't know how heavy the exposure needs to be, or how often repeated, to cause this kind of brain damage, and we don't know the effects of repeated low-dose exposure." In addition to assessing the behavioral effects of brain damage, the research team also used functional MRI to look at the effects of domoic acid exposure on important brain networks. They found that sea lions with symptoms of toxic exposure had greatly reduced connectivity between the hippocampus and the thalamus, a pathway known to be essential for the formation of episodic memory (memories of events or experiences) in rodents and humans. "This is the first evidence of changes to brain networks in exposed sea lions, and suggests that these animals may be suffering a broad disruption of memory, not just spatial memory deficits," Cook said. "It's rare to have this type of experimental evidence linking a naturally occurring neurotoxic effect to behavioral impairment in a wild animal. There are thousands of California sea lions with varying degrees of exposure to domoic acid out there. Sea lions navigate a complex and changing environment, and if their spatial memory is impaired it's bound to affect their ability to survive in the wild."


News Article
Site: http://phys.org/biology-news/

Domoic acid, a potent neurotoxin, captured headlines this year after it was detected in Dungeness crabs, prompting authorities to delay the opening of the crab season on the west coast. For California sea lions, however, the toxin has been causing problems for years. Hundreds of sea lions strand on California beaches every year with symptoms of domoic acid poisoning, including disorientation and seizures. Prior research has characterized the clinical effects of the toxin, but the behavioral effects of domoic acid poisoning in wild animals had not been assessed. A team led by scientists at the University of California, Santa Cruz, studied 30 California sea lions undergoing veterinary care and rehabilitation at the Marine Mammal Center in Sausalito. Researchers administered behavioral tests to assess spatial memory and performed brain imaging (MRI) to see the extent of brain lesions in the affected animals. Damage to the hippocampus, a part of the brain involved in memory, is often seen in sea lions with domoic acid poisoning, according to first author Peter Cook, who led the study as a graduate student at UC Santa Cruz and is now at Emory University. "In this study, we were able to correlate the extent of hippocampal damage to specific behavioral impairments relevant to the animals' survival in the wild," Cook said. The study documented impaired performance on short-and long-term spatial memory tasks in animals with hippocampal lesions. These deficits are likely to interfere with a sea lion's ability to find food and may also help explain anecdotal reports of sea lions showing up in unusual places far outside their normal range, either too far out at sea or inland far from the coast, according to coauthor Colleen Reichmuth, director of the Pinniped Cognition and Sensory Systems Laboratory at UC Santa Cruz where the behavioral tests were conducted. Domoic acid is produced by microscopic algae (diatoms in the genus Pseudo-nitzschia) that occur naturally in coastal waters. Blooms of the toxic algae along the California coast typically occur in the spring and fall and last just a few weeks, but they have been increasing in frequency and severity. This year's massive bloom, the largest ever recorded, lasted through the summer and extended from Santa Barbara to Alaska. During a Pseudo-nitzschia bloom, domoic acid accumulates in shellfish and small fish such as anchovies and sardines that feed on algae filtered from the water. Animals that feed on those fish, including sea lions and other marine mammals and seabirds, can be exposed to high levels of the toxin. The sea lion study was carried out over several years, and the researchers tested animals with and without symptoms of brain damage caused by exposure to domoic acid. Cook noted that during an algal bloom, sea lions brought to the Marine Mammal Center with acute domoic acid poisoning may not yet have permanent brain damage. Acute poisoning can cause seizures and disorientation, but brain lesions develop over time, likely as a result of a chronic epileptic condition caused by one or more exposures to the toxin, he said. Sea lions with symptoms of brain damage strand on beaches all year round, even when there is no active bloom of the toxic algae. "What isn't well understood yet is the dose response," Cook said. "We don't know how heavy the exposure needs to be, or how often repeated, to cause this kind of brain damage, and we don't know the effects of repeated low-dose exposure." In addition to assessing the behavioral effects of brain damage, the research team also used functional MRI to look at the effects of domoic acid exposure on important brain networks. They found that sea lions with symptoms of toxic exposure had greatly reduced connectivity between the hippocampus and the thalamus, a pathway known to be essential for the formation of episodic memory (memories of events or experiences) in rodents and humans. "This is the first evidence of changes to brain networks in exposed sea lions, and suggests that these animals may be suffering a broad disruption of memory, not just spatial memory deficits," Cook said. "It's rare to have this type of experimental evidence linking a naturally occurring neurotoxic effect to behavioral impairment in a wild animal. There are thousands of California sea lions with varying degrees of exposure to domoic acid out there. Sea lions navigate a complex and changing environment, and if their spatial memory is impaired it's bound to affect their ability to survive in the wild." Explore further: Domoic acid from toxic algal blooms may cause seizures in California sea lions More information: "Algal toxin impairs sea lion memory and hippocampal connectivity, with implications for strandings," Science, www.sciencemag.org/lookup/doi/10.1126/science.aac5675

Discover hidden collaborations