Thyroid hormone concentrations in captive and free-ranging West Indian manatees (Trichechus manatus)

2000 ◽  
Vol 203 (23) ◽  
pp. 3631-3637 ◽  
Author(s):  
R.M. Ortiz ◽  
D.S. MacKenzie ◽  
G.A. Worthy
Keyword(s):  
Thyroid Hormone ◽  
Food Consumption ◽  
Marine Mammals ◽  
Critical Role ◽  
West Indian ◽  
Water Salinity ◽  
Metabolic Rates ◽  
Trichechus Manatus ◽  
Total Thyroxine ◽  
Free Ranging

Because thyroid hormones play a critical role in the regulation of metabolism, the low metabolic rates reported for manatees suggest that thyroid hormone concentrations in these animals may also be reduced. However, thyroid hormone concentrations have yet to be examined in manatees. The effects of captivity, diet and water salinity on plasma total triiodothyronine (tT(3)), total thyroxine (tT(4)) and free thyroxine (fT(4)) concentrations were assessed in adult West Indian manatees (Trichechus manatus). Free-ranging manatees exhibited significantly greater tT(4) and fT(4) concentrations than captive adults, regardless of diet, indicating that some aspect of a captive existence results in reduced T(4) concentrations. To determine whether this reduction might be related to feeding, captive adults fed on a mixed vegetable diet were switched to a strictly sea grass diet, resulting in decreased food consumption and a decrease in body mass. However, tT(4) and fT(4) concentrations were significantly elevated over initial values for 19 days. This may indicate that during periods of reduced food consumption manatees activate thyroid-hormone-promoted lipolysis to meet water and energetic requirements. Alterations in water salinity for captive animals did not induce significant changes in thyroid hormone concentrations. In spite of lower metabolic rates, thyroid hormone concentrations in captive manatees were comparable with those for other terrestrial and marine mammals, suggesting that the low metabolic rate in manatees is not attributable to reduced circulating thyroid hormone concentrations.

scholarly journals Activity-specific metabolic rates for diving, transiting, and resting at sea can be estimated from time-activity budgets in free-ranging marine mammals

2017 ◽  
Vol 7 (9) ◽  
pp. 2969-2976 ◽  
Author(s):  
Tiphaine Jeanniard-du-Dot ◽  
Andrew W. Trites ◽  
John P. Y. Arnould ◽  
John R. Speakman ◽  
Christophe Guinet
Keyword(s):  
Marine Mammals ◽  
Metabolic Rates ◽  
Activity Budgets ◽  
Time Activity ◽  
Free Ranging

Metabolic rates of seals and whales

1986 ◽  
Vol 64 (2) ◽  
pp. 279-284 ◽  
Author(s):  
D. M. Lavigne ◽  
S. Innes ◽  
G. A. J. Worthy ◽  
K. M. Kovacs ◽  
O. J. Schmitz ◽  
...  
Keyword(s):  
Metabolic Rate ◽  
Food Consumption ◽  
Marine Mammal ◽  
Critical Review ◽  
Comparative Studies ◽  
Marine Mammals ◽  
Metabolic Rates ◽  
Sea Lions ◽  
Terrestrial Mammals ◽  
Fur Seals

A critical review of metabolic rate determinations for pinnipeds (seals, sea lions, fur seals, and walrus) and cetaceans (whales, dolphins, and porpoises) does not support the widely accepted generalization that they have higher metabolic rates than terrestrial mammals of similar size. This finding necessitates a rethinking of the thermoregulatory adaptations of these marine mammals for an aquatic existence and has important implications in comparative studies of mammals, which frequently omit marine forms because they are perceived to be "different" from other mammals. It also suggests that numerous studies have overestimated food consumption by marine mammal populations.

scholarly journals A blubber gene expression index for evaluating stress in marine mammals

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Laura Pujade Busqueta ◽  
Daniel E Crocker ◽  
Cory D Champagne ◽  
Molly C McCormley ◽  
Jared S Deyarmin ◽  
...  
Keyword(s):  
Gene Expression ◽  
Thyroid Hormone ◽  
Marine Mammal ◽  
Marine Mammals ◽  
Elephant Seals ◽  
Hormone Levels ◽  
Stress Markers ◽  
Thyroid Hormone Levels ◽  
Species Specific ◽  
Free Ranging

Abstract Evaluating the impacts of anthropogenic disturbance on free-ranging marine mammal populations, many of which are in decline, requires robust diagnostic markers of physiological stress and health. However, circulating levels of canonical ‘stress hormones’ such as glucocorticoids, which are commonly used to evaluate animal health, do not capture the complexity of species-specific responses and cannot be easily measured in large, fully aquatic marine mammals. Alternatively, expression of stress-responsive genes in hormone target tissues such as blubber, the specialized subcutaneous adipose tissue that can be manually or remotely sampled from many marine mammals, may be a more informative and sensitive indicator of recent (within 24 h) exposure to stressors. We previously identified genes that were upregulated in the inner blubber of juvenile northern elephant seals during experimental stimulation of the hypothalamic–pituitary–adrenal axis. In this study, we measured baseline expression levels of a subset of these genes in inner blubber of unmanipulated juvenile elephant seals of varying physiological states and correlated them with other stress markers (body condition index, corticosteroid and thyroid hormone levels). Expression of 10 genes, including those associated with lipid metabolism (ACSL1, HMGCS2, CDO1), redox homeostasis (GPX3), adipokine signaling (ADIPOQ), lipid droplet formation (PLIN1, CIDEA) and adipogenesis (DKK1, AZGP1, TGFBI), was described by three principal components and was associated with cortisol and thyroid hormone levels. Significantly, baseline gene expression levels were predictive of circulating hormone levels, suggesting that these markers may be potential indicators of exposure to stressors in marine mammal species that are inaccessible for blood sampling. A similar approach may be used to identify species-specific stress markers in other tissues that can be sampled by remote biopsy dart from free-ranging marine mammals, such as outer blubber and skin.

scholarly journals Subsurface swimming and stationary diving are metabolically cheap in adult Pacific walruses (Odobenus rosmarus divergens)

2021 ◽  
Author(s):  
Alicia Borque-Espinosa ◽  
Karyn D. Rode ◽  
Diana Ferrero-Fernández ◽  
Anabel Forte ◽  
Romana Capaccioni-Azzati ◽  
...  
Keyword(s):  
Sea Ice ◽  
Water Surface ◽  
Marine Mammals ◽  
Benthic Habitat ◽  
Metabolic Rates ◽  
Energetic Costs ◽  
Odobenus Rosmarus Divergens ◽  
Odobenus Rosmarus ◽  
Free Ranging ◽  
The Impact

Walruses rely on sea-ice to efficiently forage and rest between diving bouts while maintaining proximity to prime foraging habitat. Recent declines in summer sea ice have resulted in walruses hauling out on land where they have to travel farther to access productive benthic habitat while potentially increasing energetic costs. Despite the need to better understand the impact of sea ice loss on energy expenditure, knowledge about metabolic demands of specific behaviours in walruses is scarce. In the present study, 3 adult female Pacific walruses (Odobenus rosmarus divergens) participated in flow-through respirometry trials to measure metabolic rates while floating inactive at the water surface during a minimum of 5 min, during a 180-second stationary dive, and while swimming horizontally underwater for ∼90 m. Metabolic rates during stationary dives (3.82±0.56 l O2 min−1) were lower than those measured at the water surface (4.64±1.04 l O2 min−1), which did not differ from rates measured during subsurface swimming (4.91±0.77 l O2 min−1). Thus, neither stationary diving nor subsurface swimming resulted in metabolic rates above those exhibited by walruses at the water surface. These results suggest that walruses minimize their energetic investment during underwater behaviours as reported for other marine mammals. Although environmental factors experienced by free-ranging walruses (e.g., winds or currents) likely affect metabolic rates, our results provide important information for understanding how behavioural changes affect energetic costs and can be used to improve bioenergetics models aimed at predicting the metabolic consequences of climate change on walruses.

scholarly journals Detection of free-ranging West Indian manatees Trichechus manatus using side-scan sonar

2009 ◽  
Vol 8 ◽  
pp. 249-257 ◽  
Author(s):  
D Gonzalez-Socoloske ◽  
LD Olivera-Gomez ◽  
RE Ford
Keyword(s):  
West Indian ◽  
Trichechus Manatus ◽  
Side Scan Sonar ◽  
Free Ranging

Response to Conditioned Stimuli by Two Rehabilitated and Released West Indian Manatees (Trichechus manatus latirostris)

2006 ◽  
Vol 32 (1) ◽  
pp. 66-74 ◽  
Author(s):  
Wendi Fellner ◽  
Kim Odell ◽  
Allison Corwin ◽  
Lisa Davis ◽  
Cathy Goonen ◽  
...  
Keyword(s):  
West Indian ◽  
Conditioned Stimuli ◽  
Trichechus Manatus ◽  
Trichechus Manatus Latirostris

scholarly journals PCB-Related Alteration of Thyroid Hormones and Thyroid Hormone ReceptorGene Expression in Free-Ranging Harbor Seals (Phoca vitulina)

2006 ◽  
Vol 114 (7) ◽  
pp. 1024-1031 ◽  
Author(s):  
Maki Tabuchi ◽  
Nik Veldhoen ◽  
Neil Dangerfield ◽  
Steven Jeffries ◽  
Caren C. Helbing ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Hormones ◽  
Phoca Vitulina ◽  
Harbor Seals ◽  
Free Ranging

Thyroid hormones regulate phosphate homoeostasis through transcriptional control of the renal type IIa sodium-dependent phosphate co-transporter (Npt2a) gene

2010 ◽  
Vol 427 (1) ◽  
pp. 161-169 ◽  
Author(s):  
Mariko Ishiguro ◽  
Hironori Yamamoto ◽  
Masashi Masuda ◽  
Mina Kozai ◽  
Yuichiro Takei ◽  
...  
Keyword(s):  
Thyroid Hormone ◽  
Thyroid Hormones ◽  
Molecular Mechanisms ◽  
Hormone Receptors ◽  
Critical Role ◽  
Serum Phosphate ◽  
Luciferase Assay ◽  
Mobility Shift ◽  
Intron 1 ◽  
Sodium Dependent

The type IIa renal sodium-dependent phosphate (Na/Pi) co-transporter Npt2a is implicated in the control of serum phosphate levels. It has been demonstrated previously that renal Npt2a protein and its mRNA expression are both up-regulated by the thyroid hormone T3 (3,3′,5-tri-iodothyronine) in rats. However, it has never been established whether the induction was mediated by a direct effect of thyroid hormones on the Npt2a promoter. To address the role of Npt2a in T3-dependent regulation of phosphate homoeostasis and to identify the molecular mechanisms by which thyroid hormones modulate Npt2a gene expression, mice were rendered pharmacologically hypo- and hyper-thyroid. Hypothyroid mice showed low levels of serum phosphate and a marked decrease in renal Npt2a protein abundance. Importantly, we also showed that Npt2a-deficient mice had impaired serum phosphate responsiveness to T3 compared with wild-type mice. Promoter analysis with a luciferase assay revealed that the transcriptional activity of a reporter gene containing the Npt2a promoter and intron 1 was dependent upon TRs (thyroid hormone receptors) and specifically increased by T3 in renal cells. Deletion analysis and EMSAs (electrophoretic mobility-shift assays) determined that there were unique TREs (thyroid-hormone-responsive elements) within intron 1 of the Npt2a gene. These results suggest that Npt2a plays a critical role as a T3-target gene, to control phosphate homoeostasis, and that T3 transcriptionally activates the Npt2a gene via TRs in a renal cell-specific manner.

Sign in / Sign up

Export Citation Format

Share Document