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Daniel E Crocker - One of the best experts on this subject based on the ideXlab platform.
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density dependent effects on reproductive output in a capital breeding carnivore the northern elephant seal Mirounga angustirostris
Proceedings of The Royal Society B: Biological Sciences, 2021Co-Authors: Rachel R Holser, Daniel E Crocker, Patrick W Robinson, Richard Condit, Daniel P. CostaAbstract:All organisms face resource limitations that will ultimately restrict population growth, but the controlling mechanisms vary across ecosystems, taxa, and reproductive strategies. Using four decades of data, we examine how variation in the environment and population density affect reproductive outcomes in a capital-breeding carnivore, the northern elephant seal (Mirounga angustirostris). This species provides a unique opportunity to examine the relative importance of resource acquisition and density-dependence on breeding success. Capital breeders accrue resources over large temporal and spatial scales for use during an abbreviated reproductive period. This strategy may have evolved, in part, to confer resilience to short-term environmental variability. We observed density-dependent effects on weaning mass, and maternal age (experience) was more important than oceanographic conditions or maternal mass in determining offspring weaning mass. Together these findings show that the mechanisms controlling reproductive output are conserved across terrestrial and marine systems and vary with population dynamics, an important consideration when assessing the effect of extrinsic changes, such as climate change, on a population.
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adipose transcriptome analysis provides novel insights into molecular regulation of prolonged fasting in northern elephant seal pups
Physiological Genomics, 2018Co-Authors: Bridget Martinez, Jane Khudyakov, Daniel E Crocker, Kim Rutherford, Neil J Gemmell, Rudy M. OrtizAbstract:The physiological and cellular adaptations to extreme fasting in northern elephant seals (Mirounga angustirostris, NES) are remarkable and may help to elucidate endocrine mechanisms that regulate l...
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variation in adrenal and thyroid hormones with life history stage in juvenile northern elephant seals Mirounga angustirostris
General and Comparative Endocrinology, 2017Co-Authors: J A Jelincic, Michael S Tift, Dorian S Houser, Daniel E CrockerAbstract:The classical approach to quantifying the impact of stressors on wildlife is through characterization of hormones associated with the generalized stress response. However, interpretation of hormone data can be difficult due to the range of natural variation within a species and potential confounds of individual and life-history variables. Blood adrenal and thyroid hormones were measured in 144 chemically immobilized yearling northern elephant seals (Mirounga angustirostris) to characterize variation between sexes and across semiannual haul-outs. There was no relationship between hormone concentrations and time needed for collecting blood nor evidence of diel patterns, suggesting that collection of samples for baseline values can be accomplished without bias due to handling artifacts or time of day. Serum cortisol concentrations did not vary with gender or across haul-out fasts but increased dramatically during molting. Cortisol was correlated with aldosterone across all measured life-history stages. Thyroid hormone levels were lower in females and decreased with fasting in both sexes during the fall haul-out. Cortisol concentrations were inversely associated with total triiodothyronine (T3) and positively associated with reverse T3 concentrations across all measured life-history stages suggesting an important impact of cortisol on deiodinase enzymes and thyroid function. Epinephrine concentrations increased across fasts and norepinephrine concentrations were higher in males than in females. Significant variation in stress hormone concentrations with gender and life-history stage emphasizes the importance of contextual variables when interpreting serum hormone concentrations.
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fasting increases the phosphorylation of ampk and expression of sirtuin1 in muscle of adult male northern elephant seals Mirounga angustirostris
Physiological Reports, 2017Co-Authors: Debby Lee, Bridget Martinez, Daniel E Crocker, Rudy M. OrtizAbstract:Fasting typically suppresses thyroid hormone (TH)-mediated cellular events and increases sirtuin 1 (SIRT1) activity. THs may regulate metabolism through nongenomic pathways and directly through activation of adenosine monophosphate-activated protein kinase (AMPK). Adult male elephant seals (Mirounga angustirostris) are active, hypermetabolic, and normothermic during their annual breeding fast, which is characterized by stable TH levels. However, the contribution of TH to maintenance of their fasting metabolism is unknown. To investigate the fasting effects on cellular TH-mediated events and its potential association with SIRT1 and AMPK, we quantified plasma TH levels, mRNA expressions of muscle SIRT1 and TH-associated genes as well as the phosphorylation of AMPK in adult, male northern elephant seals (n = 10/fasting period) over 8 weeks of fasting (early vs. late). Deiodinase type I (DI1) expression increased twofold with fasting duration suggesting that the potential for TH-mediated cellular signaling is increased. AMPK phosphorylation increased 61 ± 21% with fasting suggesting that cellular metabolism is increased. The mRNA expression of the TH transporter, monocarboxylate transporter 10 (MCT10), increased 2.4-fold and the TH receptor (THrβ-1) decreased 30-fold suggesting that cellular uptake of T4 is increased, but its subsequent cellular effects such as activation of AMPK are likely nongenomic. The up-regulation of SIRT1 mRNA expression (2.6-fold) likely contributes to the nongenomic activation of AMPK by TH, which may be necessary to maintain the expression of PGC-1α These coordinated changes likely contribute to the up-regulation of mitochondrial metabolism to support the energetic demands associated with prolonged fasting in adult seals.
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effects of environmental variables on surface temperature of breeding adult female northern elephant seals Mirounga angustirostris and pups
Journal of Thermal Biology, 2016Co-Authors: Sarah A Codde, Dorian S Houser, Sarah G Allen, Daniel E CrockerAbstract:Pinnipeds spend extended periods of time on shore during breeding, and some temperate species retreat to the water if exposed to high ambient temperatures. However, female northern elephant seals (Mirounga angustirostris) with pups generally avoid the water, presumably to minimize risks to pups or male harassment. Little is known about how ambient temperature affects thermoregulation of well insulated females while on shore. We used a thermographic camera to measure surface temperature (Ts) of 100 adult female elephant seals and their pups during the breeding season at Point Reyes National Seashore, yielding 782 thermograms. Environmental variables were measured by an onsite weather station. Environmental variables, especially solar radiation and ambient temperature, were the main determinants of mean and maximum Ts of both females and pups. An average of 16% of the visible surface of both females and pups was used as thermal windows to facilitate heat loss and, for pups, this area increased with solar radiation. Thermal window area of females increased with mean Ts until approximately 26°C and then declined. The Ts of both age classes were warmer than ambient temperature and had a large thermal gradient with the environment (female mean 11.2±0.2°C; pup mean 14.2±0.2°C). This large gradient suggests that circulatory adjustments to bypass blubber layers were sufficient to allow seals to dissipate heat under most environmental conditions. We observed the previously undescribed behavior of females and pups in the water and determined that solar radiation affected this behavior. This may have been possible due to the calm waters at the study site, which reduced the risk of neonates drowning. These results may predict important breeding habitat features for elephant seals as solar radiation and ambient temperatures change in response to changing climate.
Rudy M. Ortiz - One of the best experts on this subject based on the ideXlab platform.
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adipose transcriptome analysis provides novel insights into molecular regulation of prolonged fasting in northern elephant seal pups
Physiological Genomics, 2018Co-Authors: Bridget Martinez, Jane Khudyakov, Daniel E Crocker, Kim Rutherford, Neil J Gemmell, Rudy M. OrtizAbstract:The physiological and cellular adaptations to extreme fasting in northern elephant seals (Mirounga angustirostris, NES) are remarkable and may help to elucidate endocrine mechanisms that regulate l...
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fasting increases the phosphorylation of ampk and expression of sirtuin1 in muscle of adult male northern elephant seals Mirounga angustirostris
Physiological Reports, 2017Co-Authors: Debby Lee, Bridget Martinez, Daniel E Crocker, Rudy M. OrtizAbstract:Fasting typically suppresses thyroid hormone (TH)-mediated cellular events and increases sirtuin 1 (SIRT1) activity. THs may regulate metabolism through nongenomic pathways and directly through activation of adenosine monophosphate-activated protein kinase (AMPK). Adult male elephant seals (Mirounga angustirostris) are active, hypermetabolic, and normothermic during their annual breeding fast, which is characterized by stable TH levels. However, the contribution of TH to maintenance of their fasting metabolism is unknown. To investigate the fasting effects on cellular TH-mediated events and its potential association with SIRT1 and AMPK, we quantified plasma TH levels, mRNA expressions of muscle SIRT1 and TH-associated genes as well as the phosphorylation of AMPK in adult, male northern elephant seals (n = 10/fasting period) over 8 weeks of fasting (early vs. late). Deiodinase type I (DI1) expression increased twofold with fasting duration suggesting that the potential for TH-mediated cellular signaling is increased. AMPK phosphorylation increased 61 ± 21% with fasting suggesting that cellular metabolism is increased. The mRNA expression of the TH transporter, monocarboxylate transporter 10 (MCT10), increased 2.4-fold and the TH receptor (THrβ-1) decreased 30-fold suggesting that cellular uptake of T4 is increased, but its subsequent cellular effects such as activation of AMPK are likely nongenomic. The up-regulation of SIRT1 mRNA expression (2.6-fold) likely contributes to the nongenomic activation of AMPK by TH, which may be necessary to maintain the expression of PGC-1α These coordinated changes likely contribute to the up-regulation of mitochondrial metabolism to support the energetic demands associated with prolonged fasting in adult seals.
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transcriptome analysis of northern elephant seal Mirounga angustirostris muscle tissue provides a novel molecular resource and physiological insights
BMC Genomics, 2015Co-Authors: Jane Khudyakov, Likit Preeyanon, Rudy M. Ortiz, Cory D. Champagne, Daniel E CrockerAbstract:Background The northern elephant seal, Mirounga angustirostris, is a valuable animal model of fasting adaptation and hypoxic stress tolerance. However, no reference sequence is currently available for this and many other marine mammal study systems, hindering molecular understanding of marine adaptations and unique physiology.
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transcriptome analysis of northern elephant seal Mirounga angustirostris muscle tissue provides a novel molecular resource and physiological insights
BMC Genomics, 2015Co-Authors: Jane I Khudyakov, Likit Preeyanon, Rudy M. Ortiz, Cory D. Champagne, Daniel E CrockerAbstract:The northern elephant seal, Mirounga angustirostris, is a valuable animal model of fasting adaptation and hypoxic stress tolerance. However, no reference sequence is currently available for this and many other marine mammal study systems, hindering molecular understanding of marine adaptations and unique physiology. We sequenced a transcriptome of M. angustirostris derived from muscle sampled during an acute stress challenge experiment to identify species-specific markers of stress axis activation and recovery. De novo assembly generated 164,966 contigs and a total of 522,699 transcripts, of which 68.70% were annotated using mouse, human, and domestic dog reference protein sequences. To reduce transcript redundancy, we removed highly similar isoforms in large gene families and produced a filtered assembly containing 336,657 transcripts. We found that a large number of annotated genes are associated with metabolic signaling, immune and stress responses, and muscle function. Preliminary differential expression analysis suggests a limited transcriptional response to acute stress involving alterations in metabolic and immune pathways and muscle tissue maintenance, potentially driven by early response transcription factors such as Cebpd. We present the first reference sequence for Mirounga angustirostris produced by RNA sequencing of muscle tissue and cloud-based de novo transcriptome assembly. We annotated 395,102 transcripts, some of which may be novel isoforms, and have identified thousands of genes involved in key physiological processes. This resource provides elephant seal-specific gene sequences, complementing existing metabolite and protein expression studies and enabling future work on molecular pathways regulating adaptations such as fasting, hypoxia, and environmental stress responses in marine mammals.
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development enhances hypometabolism in northern elephant seal pups Mirounga angustirostris
Functional Ecology, 2013Co-Authors: Michael S Tift, Elizabeth C Ranalli, Rudy M. Ortiz, Dorian S Houser, Daniel E CrockerAbstract:Summary Investigation into the development of oxygen storage capacity in air-breathing marine predators has been performed, but little is known about the development of regulatory factors that influence oxygen utilization. Strategies for efficiently using oxygen stores should enable marine predators to optimize time spent foraging underwater. We describe the developmental patterns of oxygen use during voluntary breath-holds in northern elephant seals (Mirounga angustirostris) at 2 and 7 weeks postweaning. We measured (i) changes in oxygen consumption (VO2) and (ii) changes in venous pH, partial pressure of oxygen (pO2), haemoglobin saturation (sO2), oxygen content (O2ct), partial pressure of carbon dioxide (pCO2), haematocrit (Hct) and total haemoglobin (tHb). To examine the effect of the dive response on the development of oxygen utilization, voluntary breath-hold experiments were conducted in and out of water. Suppression of VO2 during voluntary breath-holds increased significantly between 2 and 7 weeks postweaning, reaching a maximum suppression of 53% below resting metabolic rate and 56% below Kleiber's standard metabolic rate. From 2 to 7 weeks postweaning, breath-hold VO2 was reduced by 52%. Between the two age classes, this equates to a mean breath-hold VO2 reduction of 16% from resting VO2. Breath-hold VO2 also declined with increasing breath-hold duration, but there was no direct effect of voluntary submergence on reducing VO2. Age did not influence rates of venous pO2 depletion during breath-holds. However, voluntary submergence did result in slower pO2 depletion rates when compared with voluntary terrestrial apnoeas. The differences in whole-body VO2 during breath-holds (measured at recovery) and venous pO2 (reflective of tissue O2-use measured during breath-holds) likely reflect metabolic suppression in hypoxic, vasoconstricted tissues. Consistent pCO2 values at the end of all voluntary breath-holds (59·0 ± 0·7 mmHg) suggest the physiological cue for stimulating respiration in northern elephant seal pups is the accumulation of CO2. Oxygen storage capacity and metabolic suppression directly limit diving capabilities and may influence foraging success in low-weaning weight seals forced to depart to sea prior to achieving full developmental diving capacity.
Michael S Tift - One of the best experts on this subject based on the ideXlab platform.
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variation in adrenal and thyroid hormones with life history stage in juvenile northern elephant seals Mirounga angustirostris
General and Comparative Endocrinology, 2017Co-Authors: J A Jelincic, Michael S Tift, Dorian S Houser, Daniel E CrockerAbstract:The classical approach to quantifying the impact of stressors on wildlife is through characterization of hormones associated with the generalized stress response. However, interpretation of hormone data can be difficult due to the range of natural variation within a species and potential confounds of individual and life-history variables. Blood adrenal and thyroid hormones were measured in 144 chemically immobilized yearling northern elephant seals (Mirounga angustirostris) to characterize variation between sexes and across semiannual haul-outs. There was no relationship between hormone concentrations and time needed for collecting blood nor evidence of diel patterns, suggesting that collection of samples for baseline values can be accomplished without bias due to handling artifacts or time of day. Serum cortisol concentrations did not vary with gender or across haul-out fasts but increased dramatically during molting. Cortisol was correlated with aldosterone across all measured life-history stages. Thyroid hormone levels were lower in females and decreased with fasting in both sexes during the fall haul-out. Cortisol concentrations were inversely associated with total triiodothyronine (T3) and positively associated with reverse T3 concentrations across all measured life-history stages suggesting an important impact of cortisol on deiodinase enzymes and thyroid function. Epinephrine concentrations increased across fasts and norepinephrine concentrations were higher in males than in females. Significant variation in stress hormone concentrations with gender and life-history stage emphasizes the importance of contextual variables when interpreting serum hormone concentrations.
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isolation of progenitor cells from the blubber of northern elephant seals Mirounga angustirostris in order to obtain an in vitro adipocyte model preliminary results
Marine Mammal Science, 2015Co-Authors: Caroline Louis, Michael S Tift, Daniel E Crocker, D M Alexander, Donald R Smith, Cathy DebierAbstract:Marine top predators are highly informative in understanding the quality and health of ocean habitats. Through bioamplification, they face a very large risk of exposure to toxic, persistent, and fat-soluble molecules such as polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), dichlorodimethyltrichloroethane (DDT), and methylmercury, which are preferentially stored in the adipose tissue. The life history of pinnipeds often includes extended periods of fasting on land. This is particularly true for phocid seals such as northern elephant seal (NES) (Mirounga angustirostris). This species indeed exhibits one of the most extreme terrestrial fasting durations (up to 3 mo) corresponding to breeding, lactation, and molting for females, postweaning development for pups, and maintaining a territory or competing for dominance rank on the breeding rookery for males (Le Boeuf et al. 1972). During such periods, individuals mobilize primarily lipids from their large adipose tissue stores (Costa et al. 1986, Noren et al. 2003). This mobilization of blubber lipids presents a risk through the release of environmental pollutants into the circulation. Previous studies in fasting NES pups and females elucidated the mobilization dynamics
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causes of death in preweaned northern elephant seal pups Mirounga angustirostris gill 1866 ano nuevo state reserve california 2012
Journal of Veterinary Diagnostic Investigation, 2014Co-Authors: Terry R Spraker, Michael S Tift, E T Lyons, T A Kuzmina, Stephen Raverty, Nicole Jaggi, Daniel E CrockerAbstract:During an ongoing physiological ecology study on pups and adult female northern elephant seals (Mirounga angustirostris, Gill, 1866) on the mainland rookery at Ano Nuevo State Reserve (California), an opportunity was afforded to collect fresh dead pups for parasitology and necropsy. The investigation was undertaken to delineate the causes of death of northern elephant seals recovered from Ano Nuevo State Reserve. Prior to this study, there was no evidence of increased mortality or health problems on this rookery. Necropsies, histology, and ancillary diagnostic studies were conducted on 21 fresh dead preweaned pups. Ages ranged from 1 stillbirth to pups approximately 2 weeks of age. Gross lesions included varying degrees of bruising, hemorrhage, lacerations, and fractures attributed to blunt force trauma to the head, chest, and/or abdomen in 16 pups; starvation in 6 pups; bite wounds in 2 pups; generalized icterus in 2 pups; presumptive drowning in 2 pups; and 1 stillbirth. Most pups had multiple gross lesions. Following light microscopic examination, pups could be assigned into 4 general diagnostic categories: 1) trauma, 2) nutritional status, 3) infectious conditions, and 4) congenital anomalies. This investigation of preweaned pup mortality of northern elephant seals in California further refines diagnostic categories for perinatal pup mortality.
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causes of death in preweaned northern elephant seal pups Mirounga angustirostris gill 1866 ano nuevo state reserve california 2012
Journal of Veterinary Diagnostic Investigation, 2014Co-Authors: Terry R Spraker, Michael S Tift, E T Lyons, T A Kuzmina, Stephen Raverty, Nicole Jaggi, Daniel E CrockerAbstract:During an ongoing physiological ecology study on pups and adult female northern elephant seals (Mirounga angustirostris, Gill, 1866) on the mainland rookery at Ano Nuevo State Reserve (California), an opportunity was afforded to collect fresh dead pups for parasitology and necropsy. The investigation was undertaken to delineate the causes of death of northern elephant seals recovered from Ano Nuevo State Reserve. Prior to this study, there was no evidence of increased mortality or health problems on this rookery. Necropsies, histology, and ancillary diagnostic studies were conducted on 21 fresh dead preweaned pups. Ages ranged from 1 stillbirth to pups approximately 2 weeks of age. Gross lesions included varying degrees of bruising, hemorrhage, lacerations, and fractures attributed to blunt force trauma to the head, chest, and/or abdomen in 16 pups; starvation in 6 pups; bite wounds in 2 pups; generalized icterus in 2 pups; presumptive drowning in 2 pups; and 1 stillbirth. Most pups had multiple gross les...
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development enhances hypometabolism in northern elephant seal pups Mirounga angustirostris
Functional Ecology, 2013Co-Authors: Michael S Tift, Elizabeth C Ranalli, Rudy M. Ortiz, Dorian S Houser, Daniel E CrockerAbstract:Summary Investigation into the development of oxygen storage capacity in air-breathing marine predators has been performed, but little is known about the development of regulatory factors that influence oxygen utilization. Strategies for efficiently using oxygen stores should enable marine predators to optimize time spent foraging underwater. We describe the developmental patterns of oxygen use during voluntary breath-holds in northern elephant seals (Mirounga angustirostris) at 2 and 7 weeks postweaning. We measured (i) changes in oxygen consumption (VO2) and (ii) changes in venous pH, partial pressure of oxygen (pO2), haemoglobin saturation (sO2), oxygen content (O2ct), partial pressure of carbon dioxide (pCO2), haematocrit (Hct) and total haemoglobin (tHb). To examine the effect of the dive response on the development of oxygen utilization, voluntary breath-hold experiments were conducted in and out of water. Suppression of VO2 during voluntary breath-holds increased significantly between 2 and 7 weeks postweaning, reaching a maximum suppression of 53% below resting metabolic rate and 56% below Kleiber's standard metabolic rate. From 2 to 7 weeks postweaning, breath-hold VO2 was reduced by 52%. Between the two age classes, this equates to a mean breath-hold VO2 reduction of 16% from resting VO2. Breath-hold VO2 also declined with increasing breath-hold duration, but there was no direct effect of voluntary submergence on reducing VO2. Age did not influence rates of venous pO2 depletion during breath-holds. However, voluntary submergence did result in slower pO2 depletion rates when compared with voluntary terrestrial apnoeas. The differences in whole-body VO2 during breath-holds (measured at recovery) and venous pO2 (reflective of tissue O2-use measured during breath-holds) likely reflect metabolic suppression in hypoxic, vasoconstricted tissues. Consistent pCO2 values at the end of all voluntary breath-holds (59·0 ± 0·7 mmHg) suggest the physiological cue for stimulating respiration in northern elephant seal pups is the accumulation of CO2. Oxygen storage capacity and metabolic suppression directly limit diving capabilities and may influence foraging success in low-weaning weight seals forced to depart to sea prior to achieving full developmental diving capacity.
Terry R Spraker - One of the best experts on this subject based on the ideXlab platform.
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causes of mortality in northern elephant seal pups on san miguel island california
Journal of Veterinary Diagnostic Investigation, 2020Co-Authors: Robert L Delong, Terry R Spraker, Tatiana A KuzminaAbstract:In February 2015, we conducted a field study of causes of mortality of northern elephant seal (Mirounga angustirostris) pups on San Miguel Island, California. Autopsies were performed on 18 freshly...
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multifocal necrotizing myopathy in northern elephant seal Mirounga angustirostris pups san miguel island california
Veterinary Pathology, 2019Co-Authors: Terry R Spraker, Robert L Delong, Claire Simeone, Tatiana A Kuzmina, D Rao N VeeramachaneniAbstract:A field study addressing causes of mortality in freshly dead northern elephant seals (Mirounga angustirostris, Gill, 1866) was conducted on San Miguel Island, California, in February 2015. Necropsies were performed on 18 pups ranging in age from stillbirths to approximately 7 to 8 weeks. The primary gross diagnoses in these pups included trauma, myopathy, starvation/emaciation, infections, congenital anomalies, and perinatal mortality. However, 6 (33%) had a previously unrecognized myopathy characterized by multiple white streaks that were most obvious within the inner layer of the abdominal wall and the small innermost ventral intercostal muscles. Following histological examination, 2 more pups from San Miguel Island and 6 pups from The Marine Mammal Center (Sausalito, California) were found to have similar lesions. Histologically, the lesions within the skeletal muscles were characterized by a multifocal polyphasic, mild to severe, acute to subacute necrotizing myopathy with mineralization. Acute necros...
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multifocal necrotizing myopathy in northern elephant seal Mirounga angustirostris pups san miguel island california
Veterinary Pathology, 2019Co-Authors: Terry R Spraker, Robert L Delong, Tatiana A Kuzmina, E T Lyons, Claire A Simeone, D Rao N VeeramachaneniAbstract:A field study addressing causes of mortality in freshly dead northern elephant seals ( Mirounga angustirostris, Gill, 1866) was conducted on San Miguel Island, California, in February 2015. Necropsies were performed on 18 pups ranging in age from stillbirths to approximately 7 to 8 weeks. The primary gross diagnoses in these pups included trauma, myopathy, starvation/emaciation, infections, congenital anomalies, and perinatal mortality. However, 6 (33%) had a previously unrecognized myopathy characterized by multiple white streaks that were most obvious within the inner layer of the abdominal wall and the small innermost ventral intercostal muscles. Following histological examination, 2 more pups from San Miguel Island and 6 pups from The Marine Mammal Center (Sausalito, California) were found to have similar lesions. Histologically, the lesions within the skeletal muscles were characterized by a multifocal polyphasic, mild to severe, acute to subacute necrotizing myopathy with mineralization. Acute necrosis and degeneration characterized by pyknotic nuclei, eosinophilic cytoplasm and cytoplasmic vacuolization were found in smooth muscle myocytes within the urinary bladder and digestive system. Degeneration of myocytes was present in the tunica media of a few small- to medium-sized vessels and was characterized by a vacuolar degeneration and occasionally necrosis. This condition has been termed multifocal necrotizing myopathy. A cause of this myopathy was not identified.
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isolation of leptospira from a phocid acute renal failure and mortality from leptospirosis in rehabilitated northern elephant seals Mirounga angustirostris california usa
Journal of Wildlife Diseases, 2014Co-Authors: Terry R Spraker, Martha A Delaney, Richard L Zuerner, Renee L GallowayAbstract:Abstract During rehabilitation, acute renal failure due to leptospirosis occurred in eight male northern elephant seals (Mirounga angustirostris) that stranded along the central California coast in 2011. Characteristic histologic lesions including renal tubular degeneration, necrosis, and mineralization, and mild lymphoplasmacytic interstitial nephritis were noted in the six animals examined. Immunohistochemistry, bacterial culture, and PCR were positive in 2/3, 2/3, and 3/4 seals, respectively, and 6/8 had high serum antibody titers to Leptospira interrogans serovar pomona. Pulsed-field gel electrophoresis confirmed one isolate as serovar pomona. Variable number tandem repeat (VNTR) analysis showed both elephant seal isolates were identical to each other but distinct from those isolated from California sea lions (Zalophus californianus). The time from stranding to onset of azotemia was 1 to 38 (median = 24) days, suggesting some seals were infected at the rehabilitation facility. Based on temporal and sp...
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causes of death in preweaned northern elephant seal pups Mirounga angustirostris gill 1866 ano nuevo state reserve california 2012
Journal of Veterinary Diagnostic Investigation, 2014Co-Authors: Terry R Spraker, Michael S Tift, E T Lyons, T A Kuzmina, Stephen Raverty, Nicole Jaggi, Daniel E CrockerAbstract:During an ongoing physiological ecology study on pups and adult female northern elephant seals (Mirounga angustirostris, Gill, 1866) on the mainland rookery at Ano Nuevo State Reserve (California), an opportunity was afforded to collect fresh dead pups for parasitology and necropsy. The investigation was undertaken to delineate the causes of death of northern elephant seals recovered from Ano Nuevo State Reserve. Prior to this study, there was no evidence of increased mortality or health problems on this rookery. Necropsies, histology, and ancillary diagnostic studies were conducted on 21 fresh dead preweaned pups. Ages ranged from 1 stillbirth to pups approximately 2 weeks of age. Gross lesions included varying degrees of bruising, hemorrhage, lacerations, and fractures attributed to blunt force trauma to the head, chest, and/or abdomen in 16 pups; starvation in 6 pups; bite wounds in 2 pups; generalized icterus in 2 pups; presumptive drowning in 2 pups; and 1 stillbirth. Most pups had multiple gross lesions. Following light microscopic examination, pups could be assigned into 4 general diagnostic categories: 1) trauma, 2) nutritional status, 3) infectious conditions, and 4) congenital anomalies. This investigation of preweaned pup mortality of northern elephant seals in California further refines diagnostic categories for perinatal pup mortality.
Daniel P. Costa - One of the best experts on this subject based on the ideXlab platform.
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density dependent effects on reproductive output in a capital breeding carnivore the northern elephant seal Mirounga angustirostris
Proceedings of The Royal Society B: Biological Sciences, 2021Co-Authors: Rachel R Holser, Daniel E Crocker, Patrick W Robinson, Richard Condit, Daniel P. CostaAbstract:All organisms face resource limitations that will ultimately restrict population growth, but the controlling mechanisms vary across ecosystems, taxa, and reproductive strategies. Using four decades of data, we examine how variation in the environment and population density affect reproductive outcomes in a capital-breeding carnivore, the northern elephant seal (Mirounga angustirostris). This species provides a unique opportunity to examine the relative importance of resource acquisition and density-dependence on breeding success. Capital breeders accrue resources over large temporal and spatial scales for use during an abbreviated reproductive period. This strategy may have evolved, in part, to confer resilience to short-term environmental variability. We observed density-dependent effects on weaning mass, and maternal age (experience) was more important than oceanographic conditions or maternal mass in determining offspring weaning mass. Together these findings show that the mechanisms controlling reproductive output are conserved across terrestrial and marine systems and vary with population dynamics, an important consideration when assessing the effect of extrinsic changes, such as climate change, on a population.
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terrestrial locomotion of the northern elephant seal Mirounga angustirostris limitation of large aquatically adapted seals on land
The Journal of Experimental Biology, 2018Co-Authors: Kelsey A Tennett, Anthony J Nicastro, Daniel P. Costa, Frank E. FishAbstract:ABSTRACT The aquatic specializations of phocid seals have restricted their ability to locomote on land. The amphibious northern elephant seal, Mirounga angustirostris , is the second largest phocid seal in the world, with males reaching 2700 kg. Although elephant seals are proficient swimmers and deep divers, their extreme size and aquatic specializations limit terrestrial movement. The kinematics of terrestrial locomotion in northern elephant seals were analyzed from video recordings of animals observed on the beach of Ano Nuevo State Reserve, CA, USA. The seals moved using a series of rhythmic undulations produced by dorsoventral spinal flexion. The traveling spinal wave moved anteriorly along the dorsal margin of the body with the chest, pelvic region and foreflippers serving as the main points of contact with the ground. The hindflippers were not used. The spinal wave and foreflippers were used to lift the chest off the ground as the body was pushed forward from the pelvis as the foreflippers were retracted to pull the body forward. Seals moved over land at 0.41–2.56 m s −1 (0.12–0.71 body lengths s −1 ). The frequency and amplitude of spinal flexions both displayed a direct increase with increasing speed. The duty factor for the pelvic region decreased with increasing velocity while the duty factor of the foreflipper remained constant. Kinematic data for elephant seals and other phocids were used in a biomechanical model to calculate the mechanical energy expended during terrestrial locomotion. The elephant seals were found to expend more energy when traveling over land for their size than smaller phocids. The unique method of terrestrial movement also exhibited greater energy expenditure on land than values for large quadrupeds. The trade-off for the northern elephant seal is that its massive size and morphology have well adapted it to an aquatic existence but limited its locomotor performance (i.e. speed, endurance) on land.
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adipose triglyceride lipase not hormone sensitive lipase is the primary lipolytic enzyme in fasting elephant seals Mirounga angustirostris
Physiological and Biochemical Zoology, 2015Co-Authors: Melinda A Fowler, Daniel P. Costa, Daniel E Crocker, Wenjun Shen, Fredric B KraemerAbstract:AbstractLittle is known about the mechanisms that allow capital breeders to rapidly mobilize large amounts of body reserves. Northern elephant seals (Mirounga angustirostris) utilize fat reserves for maternal metabolism and to create high fat milk for the pup. Hormone-sensitive lipase (HSL) has been hypothesized to be an important lipolytic enzyme in fasting seals, but the activity of HSL and adipose triglyceride lipase (ATGL) has not been quantified in fasting adult seals, nor has their relationship to milk lipid content been assessed. Blubber and milk samples were obtained from 18 early lactation and 19 late lactation females, as well as blubber from five early and five late molting female seals. Blubber lipolytic activity was assessed with radiometric assays. HSL activity was negligible in seal blubber at all fasting stages. Total triglyceride lipase activity was stable among early and late lactation and early molt but increased in late molting seals. Relative abundance of ATGL protein increased across...
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mobilisation of lipophilic pollutants from blubber in northern elephant seal pups Mirounga angustirostris during the post weaning fast
Environmental Research, 2014Co-Authors: Caroline Louis, Alin C Dirtu, Marie Stas, Govindan Malarvannan, Yves Guiot, Daniel P. Costa, Daniel E Crocker, Adrian Covaci, Cathy DebierAbstract:Northern elephant seals (NES) (Mirounga angustirostris) from the Ano Nuevo State Reserve (CA, USA) were longitudinally sampled during the post-weaning fast in order to study the mobilisation and redistribution of various classes of persistent organic pollutants (POPs), such as polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethylene (p,p′-DDE) and hexachlorobenzene (HCB) between blubber and blood. Inner and outer blubber layers were analysed separately. Organohalogenated compounds were detected in all blubber samples in the decreasing order of their concentrations: p,p′-DDE>PCBs⪢HCB>PBDEs. The concentrations of all studied compounds were homogeneously distributed in the blubber layer at early fast, since the concentrations of POPs were statistically not different in the inner and outer layers. With the progression of the fast, the concentrations of PBDEs, PCBs and p,p′-DDE increased more sharply in inner blubber than in outer blubber. As a result, their levels became significantly higher in inner blubber as compared to outer blubber at late fast. The rise of pollutant concentrations in blubber might result from a less efficient mobilisation than triglycerides and/or a reuptake by adipocytes of some of the pollutants released into the circulation. The mobilisation of pollutants from blubber was higher at late fast. An increase of pollutant concentrations was observed in serum between early and late fast. Lower halogenated congeners (i.e. tetra-CBs) were present in higher proportions in serum, whereas the higher halogenated congeners (i.e. hepta-CBs) were mainly found in the inner and outer blubber layers. The transfer ratios of both PBDEs and PCBs from inner blubber to serum decreased with the number of chlorine and bromine atoms. In addition, the distribution of both types of compounds between serum and blubber was strongly influenced by their lipophilic character (log Kow values), with more lipophilic compounds being less efficiently released from blubber to serum.
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Parasitological examination for presence of hookworms ( Uncinaria spp.) in northern elephant seals ( Mirounga angustirostris ) at Año Nuevo State Reserve, California (2012)
Parasitology Research, 2012Co-Authors: Eugene T. Lyons, Terry R Spraker, Tatiana A Kuzmina, Daniel P. Costa, Daniel E Crocker, N. Jaggi, Sharon C. Tolliver, Michael S TiftAbstract:Northern elephant seals (Mirounga angustirostris Gill, 1866), inhabiting rookeries on the mainland of Ano Nuevo State Reserve in central California, were investigated in 2012 for presence of hookworms (Uncinaria spp.). Material collected and examined for hookworms included: blubber (n = 15), stomach and intestines (n = 21) from dead pups; feces from the rectum of weaned pups (n = 23); sand containing apparent feces in areas of weaned pups (n = 28) and sand without apparent feces in areas of weaned pups (n = 54); milk from females (n =23) at 5 days and about 23 to 26 days postpartum; and placenta from one female. Evidence of hookworm presence was not detected in any of the samples examined. Possible reasons why hookworms were not found in northern elephant seals on the mainland of Ano Nuevo State Reserve are discussed.