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Rollwitz E, Jastroch M. Plate-Based Respirometry to Assess Thermal Sensitivity of Zebrafish Embryo Bioenergetics in situ. Front Physiol 2021; 12:746367. [PMID: 34621190 PMCID: PMC8491625 DOI: 10.3389/fphys.2021.746367] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Accepted: 08/24/2021] [Indexed: 11/19/2022] Open
Abstract
Oxygen consumption allows measuring the metabolic activity of organisms. Here, we adopted the multi-well plate-based respirometry of the extracellular flux analyzer (Seahorse XF96) to investigate the effect of temperature on the bioenergetics of zebrafish embryos (Danio rerio) in situ. We show that the removal of the embryonic chorion is beneficial for oxygen consumption rates (OCR) and penetration of various mitochondrial inhibitors, and confirm that sedation reduces the variability of OCR. At 48h post-fertilization, embryos (maintained at a routine temperature of 28°C) were exposed to different medium temperatures ranging from 18°C to 37°C for 20h prior OCR measurement. Measurement temperatures from 18°C to 45°C in the XF96 were achieved by lowering the room temperature and active in-built heating. At 18°C assay temperature, basal OCR was low due to decreased ATP-linked respiration, which was not limited by mitochondrial power, as seen in substantial spare respiratory capacity. Basal OCR of the embryos increased with assay temperature and were stable up to 37°C assay temperature, with pre-exposure of 37°C resulting in more thermo-resistant basal OCR measured at 41°C. Adverse effects of the mitochondrial inhibitor oligomycin were seen at 37°C and chemical uncouplers disrupted substrate oxidation gradually with increasing assay temperature. Proton leak respiration increased at assay temperatures above 28°C and compromised the efficiency of ATP production, calculated as coupling efficiency. Thus, temperature impacts mitochondrial respiration by reduced cellular ATP turnover at lower temperatures and by increased proton leak at higher temperatures. This conclusion is coherent with the assessment of heart rate, an independent indicator of systemic metabolic rate, which increased with exposure temperature, peaking at 28°C, and decreased at higher temperatures. Collectively, plate-based respirometry allows assessing distinct parts of mitochondrial energy transduction in zebrafish embryos and investigating the effect of temperature and temperature acclimation on mitochondrial bioenergetics in situ.
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Affiliation(s)
- Erik Rollwitz
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Martin Jastroch
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
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Maus B, Gutsfeld S, Bock C, Pörtner HO. Non-invasive MRI Studies of Ventilatory and Cardiovascular Performance in Edible Crabs Cancer pagurus During Warming Under Elevated CO 2 Levels. Front Physiol 2021; 11:596529. [PMID: 33505316 PMCID: PMC7831881 DOI: 10.3389/fphys.2020.596529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Accepted: 12/04/2020] [Indexed: 11/13/2022] Open
Abstract
The thermal tolerance of marine decapod crustacea is defined through their capacities for oxygen uptake and distribution. High ambient CO2 levels were previously shown to reduce hemolymph oxygen levels at enhanced cardiac performance during warming. This study investigated the impacts of warming under two CO2 levels on ventilation and hemolymph circulation in edible crabs Cancer pagurus. It also highlights changes in the ventilatory and cardiac pauses displayed by Decapoda under routine metabolism. Animals were exposed to step-wise, sub-critical warming (12–20°C over 5 days) under control (470 μatm) and high (1,350 μatm) water PCO2. Flow-through respirometry was combined with magnetic resonance imaging and infra-red photoplethysmography to allow for simultaneous, non-invasive measurements of metabolic rates (M˙O2), ventilation and cardiovascular performance. Crabs spent significantly more time in a low M˙O2 state (metabolic pause), when experiencing high CO2 conditions above 16°C, compared to normocapnic warming. Heart rates leveled off beyond 18°C at any CO2 level. Cardiac output continued to increase with high-CO2-warming, due to elevated cardiac stroke volumes. Consequently, temperature-dependent branchial hemolymph flow remained unaffected by CO2. Instead, a suppressing effect of CO2 on ventilation was found beyond 16°C. These results indicate constrained oxygen uptake at stable cardiovascular performance in a decapod crustacean. Cancer pagurus: urn:lsid:zoobank.org:act:B750F89A-84B5-448B-8D80-EBD724A1C9D4
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Affiliation(s)
- Bastian Maus
- Integrative Ecophysiology, Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.,Department of Biology and Chemistry, University of Bremen, Bremen, Germany
| | - Sebastian Gutsfeld
- Integrative Ecophysiology, Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Christian Bock
- Integrative Ecophysiology, Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Hans-Otto Pörtner
- Integrative Ecophysiology, Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.,Department of Biology and Chemistry, University of Bremen, Bremen, Germany
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Non-invasive quantification of cardiac stroke volume in the edible crab Cancer pagurus. Front Zool 2020; 16:46. [PMID: 31889965 PMCID: PMC6909657 DOI: 10.1186/s12983-019-0344-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Accepted: 11/29/2019] [Indexed: 12/02/2022] Open
Abstract
Background Brachyuran crabs can effectively modulate cardiac stroke volume independently of heart rate in response to abiotic drivers. Non-invasive techniques can help to improve the understanding of cardiac performance parameters of these animals. This study demonstrates the in vivo quantification of cardiac performance parameters through magnetic resonance imaging (MRI) on the edible crab Cancer pagurus. Furthermore, the suitability of signal integrals of infra-red photoplethysmographs as a qualitative tool is assessed under severe hypoxia. Results Multi-slice self-gated cardiac cinematic (CINE) MRI revealed the structure and motion of the ventricle to quantify heart rates, end-diastolic volume, end-systolic volume, stroke volume and ejection fraction. CINE MRI showed that stroke volumes increased under hypoxia because of a reduction of end-systolic volumes at constant end-diastolic volumes. Plethysmograph recordings allowed for automated heart rate measurements but determination of a qualitative stroke volume proxy strongly depended on the position of the sensor on the animal. Both techniques revealed a doubling in stroke volumes after 6 h under severe hypoxia (water PO2 = 15% air saturation). Conclusions MRI has allowed for detailed descriptions of cardiac performance in intact animals under hypoxia. The temporal resolution of quantitative non-invasive CINE MRI is limited but should encourage further refining. The stroke volume proxy based on plethysmograph recordings is feasible to complement other cardiac measurements over time. The presented methods allow for non-destructive in vivo determinations of multiple cardiac performance parameters, with the possibility to study neuro-hormonal or environmental effects on decapod cardio physiology.
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Studying the cardiovascular system of a marine crustacean with magnetic resonance imaging at 9.4 T. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2019; 32:567-579. [PMID: 31124010 DOI: 10.1007/s10334-019-00752-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 04/29/2019] [Accepted: 05/07/2019] [Indexed: 10/26/2022]
Abstract
OBJECTIVES An approach is presented for high-field MRI studies of the cardiovascular system (CVS) of a marine crustacean, the edible crab Cancer pagurus, submerged in highly conductive seawater. MATERIALS AND METHODS Structure and function of the CVS were investigated at 9.4 T. Cardiac motion was studied using self-gated CINE MRI. Imaging protocols and radio-frequency coil arrangements were tested for anatomical imaging. Haemolymph flow was quantified using phase-contrast angiography. Signal-to-noise-ratios and flow velocities in afferent and efferent branchial veins were compared with Student's t test (n = 5). RESULTS Seawater induced signal losses were dependent on imaging protocols and RF coil setup. Internal cardiac structures could be visualized with high spatial resolution within 8 min using a gradient-echo technique. Variations in haemolymph flow in different vessels could be determined over time. Maximum flow was similar within individual vessels and corresponded to literature values from Doppler measurements. Heart contractions were more pronounced in lateral and dorso-ventral directions than in the anterior-posterior direction. DISCUSSION Choosing adequate imaging protocols in combination with a specific RF coil arrangement allows to monitor various parts of the crustacean CVS with exceptionally high spatial resolution despite the adverse effects of seawater at 9.4 T.
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Crossley DA, Burggren WW, Reiber CL, Altimiras J, Rodnick KJ. Mass Transport: Circulatory System with Emphasis on Nonendothermic Species. Compr Physiol 2016; 7:17-66. [PMID: 28134997 DOI: 10.1002/cphy.c150010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Mass transport can be generally defined as movement of material matter. The circulatory system then is a biological example given its role in the movement in transporting gases, nutrients, wastes, and chemical signals. Comparative physiology has a long history of providing new insights and advancing our understanding of circulatory mass transport across a wide array of circulatory systems. Here we focus on circulatory function of nonmodel species. Invertebrates possess diverse convection systems; that at the most complex generate pressures and perform at a level comparable to vertebrates. Many invertebrates actively modulate cardiovascular function using neuronal, neurohormonal, and skeletal muscle activity. In vertebrates, our understanding of cardiac morphology, cardiomyocyte function, and contractile protein regulation by Ca2+ highlights a high degree of conservation, but differences between species exist and are coupled to variable environments and body temperatures. Key regulators of vertebrate cardiac function and systemic blood pressure include the autonomic nervous system, hormones, and ventricular filling. Further chemical factors regulating cardiovascular function include adenosine, natriuretic peptides, arginine vasotocin, endothelin 1, bradykinin, histamine, nitric oxide, and hydrogen sulfide, to name but a few. Diverse vascular morphologies and the regulation of blood flow in the coronary and cerebral circulations are also apparent in nonmammalian species. Dynamic adjustments of cardiovascular function are associated with exercise on land, flying at high altitude, prolonged dives by marine mammals, and unique morphology, such as the giraffe. Future studies should address limits of gas exchange and convective transport, the evolution of high arterial pressure across diverse taxa, and the importance of the cardiovascular system adaptations to extreme environments. © 2017 American Physiological Society. Compr Physiol 7:17-66, 2017.
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Affiliation(s)
- Dane A Crossley
- Department of Biological Sciences, University of North Texas, Denton, Texas, USA
| | - Warren W Burggren
- Department of Biological Sciences, University of North Texas, Denton, Texas, USA
| | - Carl L Reiber
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, Nevada, USA
| | - Jordi Altimiras
- AVIAN Behavioral Genomics and Physiology, IFM Biology, Linköping University, Linköping, Sweden
| | - Kenneth J Rodnick
- Department of Biological Sciences, Idaho State University, Pocatello, Idaho, USA
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Wittmann AC, Pörtner HO, Sartoris FJ. A role for oxygen delivery and extracellular magnesium in limiting cold tolerance of the sub-antarctic stone crab Paralomis granulosa? Physiol Biochem Zool 2012; 85:285-98. [PMID: 22494984 DOI: 10.1086/665328] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
A low capacity for regulation of extracellular Mg(2+) has been proposed to exclude reptant marine decapod crustaceans from temperatures below 0°C and thus to exclude them from the high Antarctic. To test this hypothesis and to elaborate the underlying mechanisms in the most cold-tolerant reptant decapod family of the sub-Antarctic, the Lithodidae, thermal tolerance was determined in the crab Paralomis granulosa (Decapoda, Anomura, Lithodidae) using an acute stepwise temperature protocol (-1°, 1°, 4°, 7°, 10°, and 13°C). Arterial and venous oxygen partial pressures (Po(2)) in hemolymph, heartbeat and ventilation beat frequencies, and hemolymph cation composition were measured at rest and after a forced activity (righting) trial. Scopes for heartbeat and ventilation beat frequencies and intermittent heartbeat and scaphognathite beat rates at rest were evaluated. Hemolymph [Mg(2+)] was experimentally reduced from 30 mmol L(-1) to a level naturally observed in Antarctic caridean shrimps (12 mmol L(-1)) to investigate whether the animals remain more active and tolerant to cold (-1°, 1°, and 4°C). In natural seawater, righting speed was significantly slower at -1° and 13°C, compared with acclimation temperature (4°C). Arterial and venous hemolymph Po(2) increased in response to cooling even though heartbeat and ventilation beat frequencies as well as scopes decreased. At rest, ionic composition of the hemolymph was not affected by temperature. Activity induced a significant increase in hemolymph [K(+)] at -1° and 1°C. Reduction of hemolymph [Mg(2+)] did not result in an increase in activity, an increase in heartbeat and ventilation beat frequencies, or a shift in thermal tolerance to lower temperatures. In conclusion, oxygen delivery in this cold-water crustacean was not acutely limiting cold tolerance, and animals may have been constrained more by their functional capacity and motility. In contrast to earlier findings in temperate and subpolar brachyuran crabs, these constraints remained insensitive to changing Mg(2+) levels.
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Affiliation(s)
- Astrid C Wittmann
- Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany.
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Pattern and causes of a temperature-dependent gradient of size at terminal moult in snow crab (Chionoecetes opilio) along West Greenland. Polar Biol 2010. [DOI: 10.1007/s00300-009-0755-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Mowles SL, Briffa M, Cotton PA, Spicer JI. The Role of Circulating Metal Ions During Shell Fights in the Hermit CrabPagurus bernhardus. Ethology 2008. [DOI: 10.1111/j.1439-0310.2008.01542.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Goudkamp JE, Seebacher F, Ahern M, Franklin CE. Physiological thermoregulation in a crustacean? Heart rate hysteresis in the freshwater crayfish Cherax destructor. Comp Biochem Physiol A Mol Integr Physiol 2004; 138:399-403. [PMID: 15313496 DOI: 10.1016/j.cbpb.2004.06.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2004] [Revised: 06/02/2004] [Accepted: 06/03/2004] [Indexed: 11/18/2022]
Abstract
Differential heart rates during heating and cooling (heart rate hysteresis) are an important thermoregulatory mechanism in ectothermic reptiles. We speculate that heart rate hysteresis has evolved alongside vascularisation, and to determine whether this phenomenon occurs in a lineage with vascularised circulatory systems that is phylogenetically distant from reptiles, we measured the response of heart rate to convective heat transfer in the Australian freshwater crayfish, Cherax destructor. Heart rate during convective heating (from 20 to 30 degrees C) was significantly faster than during cooling for any given body temperature. Heart rate declined rapidly immediately following the removal of the heat source, despite only negligible losses in body temperature. This heart rate 'hysteresis' is similar to the pattern reported in many reptiles and, by varying peripheral blood flow, it is presumed to confer thermoregulatory benefits particularly given the thermal sensitivity of many physiological rate functions in crustaceans.
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McGaw IJ. Behavioral thermoregulation in Hemigrapsus nudus, the amphibious purple shore crab. THE BIOLOGICAL BULLETIN 2003; 204:38-49. [PMID: 12588743 DOI: 10.2307/1543494] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The thermoregulatory behavior of Hemigrapsus nudus, the amphibious purple shore crab, was examined in both aquatic and aerial environments. Crabs warmed and cooled more rapidly in water than in air. Acclimation in water of 16 degrees C (summer temperatures) raised the critical thermal maximum temperature (CTMax); acclimation in water of 10 degrees C (winter temperatures) lowered the critical thermal minimum temperature (CTMin). The changes occurred in both water and air. However, these survival regimes did not reflect the thermal preferences of the animals. In water, the thermal preference of crabs acclimated to 16 degrees C was 14.6 degrees C, and they avoided water warmer than 25.5 degrees C. These values were significantly lower than those of the crabs acclimated to 10 degrees C; these animals demonstrated temperature preferences for water that was 17 degrees C, and they avoided water that was warmer than 26.9 degrees C. This temperature preference was also exhibited in air, where 10 degrees C acclimated crabs exited from under rocks at a temperature that was 3.2 degrees C higher than that at which the 16 degrees C acclimated animals responded. This behavioral pattern was possibly due to a decreased thermal tolerance of 16 degrees C acclimated crabs, related with the molting process. H. nudus was better able to survive prolonged exposure to cold temperatures than to warm temperatures, and there was a trend towards lower exit temperatures with the lower acclimation (10 degrees C) temperature. Using a complex series of behaviors, the crabs were able to precisely control body temperature independent of the medium, by shuttling between air and water. The time spent in either air or water was influenced more strongly by the temperature than by the medium. In the field, this species may experience ranges in temperatures of up to 20 degrees C; however, it is able to utilize thermal microhabitats underneath rocks to maintain its body temperature within fairly narrow limits.
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Affiliation(s)
- I J McGaw
- Department of Biological Sciences, University of Nevada Las Vegas, 4505 Maryland Parkway, Las Vegas, Nevada 89154-4004, USA.
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Pörtner HO. Climate variations and the physiological basis of temperature dependent biogeography: systemic to molecular hierarchy of thermal tolerance in animals. Comp Biochem Physiol A Mol Integr Physiol 2002; 132:739-61. [PMID: 12095860 DOI: 10.1016/s1095-6433(02)00045-4] [Citation(s) in RCA: 712] [Impact Index Per Article: 32.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The physiological mechanisms limiting and adjusting cold and heat tolerance have regained interest in the light of global warming and associated shifts in the geographical distribution of ectothermic animals. Recent comparative studies, largely carried out on marine ectotherms, indicate that the processes and limits of thermal tolerance are linked with the adjustment of aerobic scope and capacity of the whole animal as a crucial step in thermal adaptation on top of parallel adjustments at the molecular or membrane level. In accordance with Shelford's law of tolerance decreasing whole animal aerobic scope characterises the onset of thermal limitation at low and high pejus thresholds (pejus=getting worse). The drop in aerobic scope of an animal indicated by falling oxygen levels in the body fluids and or the progressively limited capacity of circulatory and ventilatory mechanisms. At high temperatures, excessive oxygen demand causes insufficient oxygen levels in the body fluids, whereas at low temperatures the aerobic capacity of mitochondria may become limiting for ventilation and circulation. Further cooling or warming beyond these limits leads to low or high critical threshold temperatures (T(c)) where aerobic scope disappears and transition to an anaerobic mode of mitochondrial metabolism and progressive insufficiency of cellular energy levels occurs. The adjustments of mitochondrial densities and their functional properties appear as a critical process in defining and shifting thermal tolerance windows. The finding of an oxygen limited thermal tolerance owing to loss of aerobic scope is in line with Taylor's and Weibel's concept of symmorphosis, which implies that excess capacity of any component of the oxygen delivery system is avoided. The present study suggests that the capacity of oxygen delivery is set to a level just sufficient to meet maximum oxygen demand between the average highs and lows of environmental temperatures. At more extreme temperatures only time limited passive survival is supported by anaerobic metabolism or the protection of molecular functions by heat shock proteins and antioxidative defence. As a corollary, the first line of thermal sensitivity is due to capacity limitations at a high level of organisational complexity, i.e. the integrated function of the oxygen delivery system, before individual, molecular or membrane functions become disturbed. These interpretations are in line with the more general consideration that, as a result of the high level of complexity of metazoan organisms compared with simple eukaryotes and then prokaryotes, thermal tolerance is reduced in metazoans. A similar sequence of sensitivities prevails within the metazoan organism, with the highest sensitivity at the organismic level and wider tolerance windows at lower levels of complexity. However, the situation is different in that loss in aerobic scope and progressive hypoxia at the organismic level define the onset of thermal limitation which then transfers to lower hierarchical levels and causes cellular and molecular disturbances. Oxygen limitation contributes to oxidative stress and, finally, denaturation or malfunction of molecular repair, e.g. during suspension of protein synthesis. The sequence of thermal tolerance limits turns into a hierarchy, ranging from systemic to cellular to molecular levels.
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Affiliation(s)
- H O Pörtner
- Alfred-Wegener-Institut für Polar- und Meeresforschung, Okophysiologie, Postfach 12 01 61, D-27515 Bremerhaven, Germany.
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Bock C, Frederich M, Wittig RM, Pörtner HO. Simultaneous observations of haemolymph flow and ventilation in marine spider crabs at different temperatures: a flow weighted MRI study. Magn Reson Imaging 2001; 19:1113-24. [PMID: 11711236 DOI: 10.1016/s0730-725x(01)00414-3] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In vivo magnetic resonance imaging (MRI) and angiography were applied to the marine spider crab Maja squinado for a study of temperature effects and thermal tolerance. Ventilation and haemolymph circulation were investigated during progressive cooling from 12 degrees C to 2 degrees C. The anatomical resolution of MR images from Maja squinado obtained with a standard spin echo sequence were suitable to resolve the structures of various internal organs. The heart of the animal could be depicted without movement artifacts. The use of a flow compensated gradient echo sequence allowed simultaneous observations of ventilation, reflected by water flow through the gill chambers as well as of haemolymph flow. Simultaneous investigation of various arteries was possible by use of flow weighted MRI. In addition to those accessible by standard invasive flow sensitive doppler sensors, flow changes in gill, leg arteries and the venous return could be observed. Both ventilation and haemolymph flow decreased during progressive cooling and changes in haemolymph flow varied between arteries. Haemolymph flow through the Arteria sternalis, some gill and leg arteries was maintained at low temperatures indicating a reduced thermal sensitivity of flow in selected vessels. In support of previous invasive studies of haemolymph flow as well as heart and ventilation rates, the results demonstrate that the operation of gills and the maintenance of locomotor activity are critical for cold tolerance. A shift in haemolymph flow between arteries likely occurs to ensure the functioning of locomotion and ventilation in the cold.
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Affiliation(s)
- C Bock
- Alfred-Wegener-Institute for Polar and Marine Research, Columbusstrasse, 27568 Bremerhaven, Germany.
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