Abstract
BackgroundBrachyuran 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.ResultsMulti-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).ConclusionsMRI 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.
Highlights
Brachyuran crabs can effectively modulate cardiac stroke volume independently of heart rate in response to abiotic drivers
MR imaging Combining gap-less 2D single-slice anatomical magnetic resonance imaging (MRI) scans of the heart into a volumetric stack allowed for reconstructions of 3D surface renders of pericardial sinus, myocardium and ventricular cavities (Fig. 1)
Our observations indicate that the smaller secondary peak sequence in the infra-red photoplethysmographs (IR-PPG) signal is not caused by the contraction of the heart, but rather the blood flowing through the arteria sternalis, which shows pulsatile behavior delayed from the cardiac motion [16]
Summary
Brachyuran crabs can effectively modulate cardiac stroke volume independently of heart rate in response to abiotic drivers. Brachyuran crustaceans are one of the most thoroughly studied groups, concerning their responses and vulnerability to future climate change [1]. Their importance at a global level is characterized by their abundance in benthic ecosystems, as well as the high invasive potential and the economic value of some species. Crustaceans are able to adjust their cardiac output through independently modulating HR and SV [11] This is evidenced by constant stroke volumes with increasing heart rates above certain, species-specific
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